Cam Sensor Position Module?? Hmmm, sounds fancy. I referred to it as the Cam sensor. I assume we're talking about the same thing. Small part, about 2 by 1 inches, around $25 or so. If this doesn't answer your question, send me an e-mail.

Having problems sending u an email. But, the part sits on top of the distributor and has a three (3) pronged plug (female I believe). A picture of the part can be found at the following link: http://www.rockauto.com/ref/ACDelco/Detail.html?213-920.jpg.

Is this what you had changed?

Thanks.

Yup, that's the part. After all it put me through, I thought about hanging it from the rear view mirror!

Yup, that's the part. After all it put me through, I thought about hanging it from the rear view mirror!

Well, I had the "knock sensor" changed and it seems to have helped. I can pull my 27' StarCraft Travle Trailer (4,050lbs) up a small hill, and no misfiring, shaking or pinging. BTW, I also had a terrible time with pinging; sounded like a bunch of monkeys with ball peen(spelling??) hammers inside banging away.

Anyways, my mechanic has the camshaft sensor, but I am going to wait for a couple more days and see.

Well after reading all of the threads I changed the Cam Sensor Position Module this weekend and so far no shake rattle and roll when underload and shifting into overdrive. I will add this good luck lineing up the notch on the dist. plate.

I just discovered this forum, and this thread, so I guess I'll throw my hat into the ring as well.

We too have a '99 suburban with the 5.7. Bought the truck from a used car lot with 50K on the clock, so I don't know what was done before that, but it was pretty much a cream puff. We've had the truck about three years, and noticed the mis-firing problem pulling a camper on a trip out West the first summer we had it. First sign of trouble was a check-engine light that came on during a long easy hill at speed. Next day the light had gone off again, but it did this several more times. Finally on a really strenuous grade on I-70 in the Rockies, I got the blinking check-engine light and the shuddering. Slowing down cured the problem.

After arriving home, we continued to have problems even when not pulling a trailer. Exactly as the OP described, it would start shaking badly when cresting a hill. At first I thought it might have to do with what gear it was in, i.e. an RPM related problem. The local dealer checked the codes and detected a misfire (don't remember what cylinder), and a slipping transmission. They serviced and adjusted the tranny, and recommended I change out the cap, rotor, and plugs for the misfire. I did that, but didn't use GM parts. The problem continued. I had another dealership check it out: misfire diagnosis again. I replaced the cap, rotor, and plugs again using all GM parts this time, to eliminate that as a possibility. Since then we moved, and I haven't had it back to a dealer. The problem seemed to have lessened, but then where we live now doesn't require as much hiway driving. Recently we noticed the misfire problem is still there when nearing the top of a long hill.

Separately, we took the Burb in to an independent mechanic for what I thought was going to be a water pump, but turned out to be the intake manifold gasket. They also diagnosed a misfire, but I didn't ask them to check into it. The misfire is still there after the new gasket, same as it was before, so in this case they don't appear to be related. OTOH, perhaps whoever owned it before us already had the gasket replaced . . .

So after reading through this thread, the possibilities seem to be the cam sensor module, a sticky EGR, injectors, or carbon buildup in the intake. Is there any follow-up information that previous posters would care to add?

Oh great! Something else to look forward to with my '99 Suburban! I just had the intake manifold gasket replaced 2 weeks ago and I have noticed that it seems to be skipping at idle. We are suppose to drive it to the mountains at Thanksgiving so I guess I'll get to see if I am having the same problem everyone is describing with it missing at load going uphill. Let's see, it has 65,000 miles on it and so far I have had to replace the transmission at 60,000 miles to the tune of 2600.00. The old transmission was serviced per GM instruction. The intake manifold went out at 65,000 miles to the tune of 504.00. That is a bunch of coin!!

This is the nicest car I have ever owned from the heated leather seats to the self-dimming rear view mirror. It rides and drives great and the MPG is not bad for the size vehicle--actually got 19 on last trip. But if this thing keeps busting my chops I am going to have to unload it! I have an 88 Silverado with the old TBI 350 and it has 205,000 hard miles on it and none of the problems the Suburban has presented. It still has the original engine and transmission.

:lol: :rofl: :lol: :rofl: :iceslolan
I have to laugh at this thread...I have posted the fix for this concern many times here in the forum and it appears that no one has bothered doing a search to find the answer.

Misfires on these engines that occur under load (climbing hills or cruising at highway speeds) are usually caused by the valves sticking in the guides (after proper diagnosis of the fuel and ignition system rules out fuel or spark).
The cause is carbon buildup on the valve stems that cause the valves to stick in the guides under higher RPM (acts like valve float)
There are a couple paths to follow here.
You can use a product such as Seafoam in the oil and gas to help with lubercation of the valve stems.
Decarbonizing of your engine with GM Top engine cleaner will help.
Or if one of those 2 don't work the next thing is to remove the heads and have them professionally cleaned and the guides replaced.

Laugh all you want, assuming that each and every problem with a similar sympton has the same cause is narrow minded. There are many causes that could contribute to a misfire condition, from as simple as bad ignition wires to your carbon-sticky valve issue. Truth is, it may not be a valve problem (something that we explored while diagnosing my same issue).

In your case, it was sticky valves, in my case it happened to be the CAM position sensor. How about we just pass the information and let those searching for it make the decision as to what to fix?

I know I'll be starting with the cheapest solution, then working my way up :)

Laugh all you want, assuming that each and every problem with a similar sympton has the same cause is narrow minded. There are many causes that could contribute to a misfire condition, from as simple as bad ignition wires to your carbon-sticky valve issue. Truth is, it may not be a valve problem (something that we explored while diagnosing my same issue).

In your case, it was sticky valves, in my case it happened to be the CAM position sensor. How about we just pass the information and let those searching for it make the decision as to what to fix?
Once again someone reads half of what is written and jumps to a conclusion.
Go back and read ALL of my post..including this part
“Misfires on these engines that occur under load (climbing hills or cruising at highway speeds) are usually caused by the valves sticking in the guides (after proper diagnosis of the fuel and ignition system rules out fuel or spark).”
How can this be an “assumption that each and every problem with a similar sympton has the same cause”.
After ruling out the obvious (fuel and spark), an often overlooked area is the valvetrain, especially on these engines.
I personally have never seen a CMP sensor on these vehicle cause a misfire at highway speeds.
Usually any concerns related to the CMP sensor that I have seen revolve around worn Dist housing bushings or worn Dist driven gears.

The VCM uses the CMP signal to determine the position of the #1 piston during its power stroke. This signal is used by the VCM to calculate fuel injection mode of operation.
If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The engine can be restarted and will run in the calculated mode as long as the fault is present .

So where your misfire and change in engine performance comes from is the change from a individual injector firing strategy to an all fire injector strategy.

Guys,

I don't have the technicals knowledge on car engines but I was a mecanic on jets for 6 years.
What I learned was mostly that carbone deposit can be removed with the good chimical.
I've been struggling with my GMC Yukon for 6 months and spent $700 trying to fix all of the above.
Tired of the bad advices I decided to buy a quarter of SEA FOAM (2 bottles of 433 cl) at Autozone for $13.
Engine running with a gas tank almost dryed ( 2 gallons remaining) I poored the 2 bottles in my tank.
After 15 minutes at iddle speed my engine caughed and stoped.
Then I poored 5 gallons of fresh gas and crancked the baby.
After 10 second of caughing black smoke, my V8 sounded like a brand new one.
Some will tell me that there is a risk of destroying my fuel pump with that much SEA FOAM concentrated in only 2 gallons of fuel.
Maybe, but it worked better than anything I did before and cost only 13 bucks without destrying anything.
I dont say it will work for you but it worked for me

I had a similar problem, this might be another solution. But it is an expensive one!
The Problem:
99 Suburban Big Block- purchased with 59,000 miles and driven 500 miles no problems. First towing trip, towing a car trailer, first long steep hill, it feels like the transmission is slipping or someone unplugged 5 spark plug wires. Check engine light is on. After turning off the motor and turning it back on, it seems fine. Next hill same problem. Good news- it is under a used vehicle warranty. Bad news- when I took it to the dealer, since the check engine light was not on, they could not diagnose.
The Solution:
Long story short, I couldn't duplicate it except to hook up the trailer and tow up a long steep hill. I then drove to the dealer, with very little power, and did not turn it off. They connected their scanner- here's where my memory goes fuzzy- and they adjust some things. No change. He disconnects the connector (electrical) on the Mass Airflow Sensor and likes what he sees.
What Filter do you use?
He asks a question that surprised me.. Did I use a K&N Filter? The oil from those causes problems with the MAS. In my case no. They replaced the MAS and I have had no problems since.
Now I know why the original owner traded it in!!
The symptoms I had don't sound exactly like some who have posted here, but they do a little. Sorry I wasn't real detailed on the dealer troubleshooting. That was two years ago.

I have had the same misfiring problems on my 99 Chevy Suburban (143,000 Km). Everytime I went up a hill and the rpm's were sustained between 2500 and 3000, the engine would noticably misfire and the codes consistently reported it was cylinder #6. I have replaced sparkplugs/wires, distributor, #6 fuel injector, flushed the engine to unstick valves, and I still experienced misfiring and codes. Finally, I pulled the pre-cat O2 sensor and took my burb for several test drives up and down some steep hills. No misfiring and no codes! I had a bad cat converter. Temporarily pulling the O2 sensor and taking a test drive might be a useful step in the process of helping to diagnose other engine misfiring problems. I wish I had done this before replacing the injector.

After reading this thread and one titled "99 suburban wont start" I realized that the problems are fairly similar and require aproximatley the same repair. My 99 suburban wouldnt start one day and the next it did. I found this thread very informative and wanted to let anyone with these same issues know that after only one year of just having a complete tune-up I took my suburban (that wouldnt start) to the mechanic only for them to tell me that I needed yet another $424 tune-up! Theres no way! Turnes out the spark plugs did not need to be replaced, nor did the distrubutor cap, nor the wires. BUT the rotor button was a little burnt up. After buying a new one, a Haynes Manual, replacing the cam sensor, and feeding it some sea foam, my suburban starts up without any hesiatation, purrs like a kitten, and seems to have a little more pep. This was my fix....so far, so good.

Well after reading all of the threads I changed the Cam Sensor Position Module this weekend and so far no shake rattle and roll when underload and shifting into overdrive. I will add this good luck lineing up the notch on the dist. plate.I am having similar probs in my 97 suburban 4x4 with 33's and the hyperdyne programmer installed-with k&n filter. All the way up to like a month ago I could pull my 30' boat up ridiculous hills with that little small block and have no probs reving up to 5k etc. Now Im fighting with the dreaded po300 code but only under a load . the truck will kick down at speed to 5k then shift to o/d after that "stumble" and codes if I stay in the throttle. I have to let off for about 15 sec for it to run right again. Replaced plugs, wires, cap, rotor, fuel filter, cam sensor, fuel pres test 55@idle 65@load. Ran injector test thru scan tool . The dealer said I had a clogged cat, but I took it to a exhaust shop and that wasn't the case--pissing me off considering I work on blower motors and outdrives all day but can't fix my little sm. block!

:lol: :rofl: :lol: :rofl: :iceslolan
I have to laugh at this thread...I have posted the fix for this concern many times here in the forum and it appears that no one has bothered doing a search to find the answer.

Misfires on these engines that occur under load (climbing hills or cruising at highway speeds) are usually caused by the valves sticking in the guides (after proper diagnosis of the fuel and ignition system rules out fuel or spark).
The cause is carbon buildup on the valve stems that cause the valves to stick in the guides under higher RPM (acts like valve float)
There are a couple paths to follow here.
You can use a product such as Seafoam in the oil and gas to help with lubercation of the valve stems.
Decarbonizing of your engine with GM Top engine cleaner will help.
Or if one of those 2 don't work the next thing is to remove the heads and have them professionally cleaned and the guides replaced.
My 98 Suburban had all the symptoms, going up the hill miss when pulling a trailer. New original cap, wires, cam sensor & two mechanics both reported # 5 Miss. but no solution. Guess what. The seafoam guy had my answer. One can in the tank, one can in the oil, and one down the brake vacum line (actually did this twice) and up the hill we went with no knock and no miss. Thanks.

i have 97 tahoe 5.7,havin a problem goin up hill, feels like im losin power,petal to the floor ,but still,no power,does anyone know of problem

Hello all I have a 1998 GMC 1500 truck with the 5.7L engine. It has about 85,000 miles on it. I first noticed the misfire problem after we bought a travel trailer and pulled it up a pass to go camping. The light came on and it was a random misfire under load. I started with the tune up, plugs, wires, cap, roter. And I had an injection cleaning and new fuel filter. Well the problem was still there and it started doing it without the trailer at the top of a long hill we live on. Just as I would get to the top and start to let off the gas it would start shaking really bad but it would go away after taping the gas a few times.(not enought to make the light come on) Right before a camping trip last fall it did it again with the trailer on a slight incline on the freeway. We turned around and headed back to the shop. They thought maybe they would try the EGR valve and that did the trick! We pulled over a 5000 foot pass both ways and not a problem. Well a month ago (4 mo. after the EGR) it started missing again!!! So then I tried the seafoam in the pcv line but I'm not sure it got to all the cylinders? The pcv enters on the side of the intake so I'm not sure if its one big cavity under there or not. I also put the seafoam in the gas and I will put some in the oil today. The seafoam in the intake didn't do the trick so I might try the egr again, but I'm not sure why the egr would work for 4 months and then start missing again ? Poor quality EGR ?? I can't afford a new truck but this misfire thing is really pissing me off!! It takes the fun out of camping because I worry the whole time if we'll make it there. I did put a K&N filter in last year and I thought I read someone posted about it could foul up the Mass airflow sensor?? I just don't know what to do.

I have a 99 chevy k1500 truck it was doing the same thing on misfiring going uphill or under a load. We changed everything Injectors, wire, plugs.sensor..etc. over 2000.00 worth of parts STILL NOT FIXED.
I changed the fuel cap with a factory one perfect now!!!! 10.00 FUEL CAP Make sure factory though.
Thought I would share my fix.
Lisa

I'm having similar problems but for some reason the plug in cylinder four keeps fouling out. About every two weeks it will start to idle rough and the check engine light comes on after each cleaning. Any ideas as to why this keeps happening?

Same problem, misfiring, 5.7 vortec, 140k miles. Just installed NEW heads (old ones cracked), polished rough edges in heads, cleaned piston tops like new, NEW fuel injection with electronic injectors, plugs, wires, distributor cap, rotor (all Delco or better, no crap), new thrust bushing in distributor, new crank sensor. no codes, cam retard ok, ran with GM Tech 2 scanner, everything normal. Popping is now WORSE with everything in great shape. disconnected EGR, no help. Can't drive over 60 without serious popping/misfire. Ran on ignition scanner..trace on primary side was perfect. Fuel pressure 55+ lbs. Replaced new injector system with old poppet valve injection unit..no difference. Really frustrated. Cam sensor in distributor just tells brain which cycle crank sensor is reading..at 2500 rpm shouldn't make much difference in injector pattern. TPS? Looked ok on Tech2. O2's were banging away. Short/long term fuel trim were ok. Cleaned Mass airflow sensor, no vacuum leaks, no slop in timing chain, distributor gear like new.

Frustrated as hell. It really feels like ignition problem, but nothing apparent. It's a small block Chebby..ain't new stuff. Someone out there MUST have figgered this out..talk to me!

Just read the fuel cap post again..I have disconnected the evap cannister and run it,,no help. There IS a breather on the top of the cannister..pulled up the plactic cover and cleaned the leaves out. No difference. The evap pipe goes across the motor and is connected to the purge valve on the passenger side of the upper manifold. It then breathes into a pipe that sticks up under the throttle body. BTW, cleaned the throttle body and IAC passage. No help.

I don't have time to read all the replys to see if this was solved. I had same problem with 99 5.7 vortec in Van. After a year of looking for a solution to no avail, I went to dealer and they diagnosed as worn distributor shaft bushing or distributor shaft gear can't remember which. That fixed it. It was not the tranny, fuel injectors, tune up, wires, torque converter,intake manifold gasket etc. that was suspected by other mechanics. Hope this helps someone because it drove me crazy. Dale

Hello all ,I had the same problem you all do , first I replaced the cap ,rotor ,pluges ,platinum # 2 plugs ,coil and ignition module , still no good. Then I ran into a old mechanic and he told me to put Sea Foam in my gas tank and in my oil to. Advance Auto sell's it $6.97 a can . Well I did it and 2 tank fulls later no more miss fires , it;s the motor that is gumed up from the gas . BigNed

I have come to believe that this is a sensor induced problem. It could be ice forming in the intake, seeded by carbon (soot) bits. Spraying or adding cleaner to the fuel/induction system seems to fix it.

I don't think its sticking valves or some mechanical gremlin.

It can be a bad sensor by itself but trying cleaner is cheap and a quick fix if it works.

We too have a '99 suburban with the 5.7. Bought the truck from a used car lot with 50K on the clock, so I don't know what was done before that, but it was pretty much a cream puff. We've had the truck about three years, and noticed the mis-firing problem pulling a camper on a trip out West the first summer we had it. First sign of trouble was a check-engine light that came on during a long easy hill at speed. Next day the light had gone off again, but it did this several more times. Finally on a really strenuous grade on I-70 in the Rockies, I got the blinking check-engine light and the shuddering. Slowing down cured the problem.

After arriving home, we continued to have problems even when not pulling a trailer. Exactly as the OP described, it would start shaking badly when cresting a hill. At first I thought it might have to do with what gear it was in, i.e. an RPM related problem. The local dealer checked the codes and detected a misfire (don't remember what cylinder), and a slipping transmission. They serviced and adjusted the tranny, and recommended I change out the cap, rotor, and plugs for the misfire. I did that, but didn't use GM parts. The problem continued. I had another dealership check it out: misfire diagnosis again. I replaced the cap, rotor, and plugs again using all GM parts this time, to eliminate that as a possibility. Since then we moved, and I haven't had it back to a dealer. The problem seemed to have lessened, but then where we live now doesn't require as much hiway driving. Recently we noticed the misfire problem is still there when nearing the top of a long hill.

Separately, we took the Burb in to an independent mechanic for what I thought was going to be a water pump, but turned out to be the intake manifold gasket. They also diagnosed a misfire, but I didn't ask them to check into it. The misfire is still there after the new gasket, same as it was before, so in this case they don't appear to be related. OTOH, perhaps whoever owned it before us already had the gasket replaced . . .


Update to my own post: The Sub now has 160K on it, and still runs like a dream except for the misfire problem. Amazingly, I still have not tried SeaFoam, though I intend to do so finally this weekend. Since the last post, I replaced the fuel filter, the CMP sensor in the distributor, the fuel pump (it failed), and both cats (one was dead/clogged). 02 sensors tested fine. I also had the transmission flushed and serviced, since it was due, and I wanted to check for any possibly related problems. There were none.

Just returned from a trip through the Ozarks and Appalachians, misfire problem is as bad as ever, and I wasn't towing anything. Seems as long as I keep it in 3rd and under 65mph, the problem goes away. I have high hopes for the SeaFoam, because if that doesn't do the trick the next step is tearing into the intake and heads......

I still want to know why this problem seems to affect the '99s. What changed?

I replaced my Crank sensor, problem solved.

99 suburban here and same problem! 128,000 miles

Started doing this a couple of years ago when pulling the boat but got so it would missfire without pulling the boat but only when going up a hill. Premium fuel helped reduce the problem.

My mechanic cleaned the popet valves last week and my family took it on a road trip this weekend running regular unleaded. No missfires, no shakes but I am getting a knocking (rattling) sound when accelerating. I don't know whats going on but its back to the mechanic. $$$$.$$ :banghead:

Anyone ever come up with a solution to this? My mechanic and I suspect the problem is carbon buildup.

P0305 code on a 99 suburban.

I have the same problem with my Suburban. SVS Engine soon goes on when going on a uphill. Changed all plugs and wires. I was told to change the coil by another mechanic. Can you tll me with your experiences what did you do to fix the problem. Truck is well maintained but running out of ideas. I reside in Escondido. Please email me if you have an idea or remedy to the problem I am having. It would be greatly appreciate it.

Thanks...

Welcome to AF, this also can be caused by carbon deposits on the valve stems causing the valves to hang up in the guides, GM has a TSB on this issue covering your year I believe, the problem is pinpointing this as the issue, a top engine decarbonizing treatment is performed and if the condition clears up this indicates that is the problem, but this is a temp. repair, the heads would have to come off.

I thank you very much for your advise. I try it out.

thanks,

I have a 99 chevy sub with the 5.7 and I had the seal replaced under the intake manifold and now it miss fires when I climb a hill and get to peak it will missfire badly. It will never do it when your climbing the hill or on flat ground but only when the engine has been enganged on the hill and then comes off of a little. It only happens at speeds over 50 MPH. I have replaced the plugs, wires, cap & rotor, and the fuel filter. The dealer wants to replace all these parts again and charge me 500 for it. I need some Ideas. I took it to another mechanic and he sees it misfire with the scope while driving but can't pinpoint it.

Thanks

Tony
I have a 99 chevy had the same problem one of the valves in the transmission was blocked have a transmission anaylisis done

Can someone explain how cam position sensor helps this condition? It's about the only part I haven't changed on my '99 Tahoe 5.7 to try to cure this poblem. I have done plugs, wires, EGR, Dist cap, rotor, Seafoam, cleaned mass airflow, still no cure.:banghead:

guys same problem misfire codes and problem here. Car misfires heavily at idle lots of black smoke poor MPG. We replaced rotor, cap, wires, a lot of plugs, coil, coil module, inatake valve seals, crank position sensor, and still the same problem. Intake gasket has been replaced 5 times. We tried the GM OEM twice one the autozone one the advance auto parts one, even a home made one out of gasket material. The car will run fine upon the change of the intake gasket (it even clears codes automatically) but within 24 to 72 hrs it will end up in the same condition.

guys same problem misfire codes and problem here. Car misfires heavily at idle lots of black smoke poor MPG. We replaced rotor, cap, wires, a lot of plugs, coil, coil module, inatake valve seals, crank position sensor, and still the same problem. Intake gasket has been replaced 5 times. We tried the GM OEM twice one the autozone one the advance auto parts one, even a home made one out of gasket material. The car will run fine upon the change of the intake gasket (it even clears codes automatically) but within 24 to 72 hrs it will end up in the same condition.

Dead thread. But, have you checked the O2 sensor(s) and the fuel pressure regulator?

Yes fuel pressure is good and 02 are good too. The problem obviously is the intake gasket when we replace it the problems goes away then it returns as the days go past. Why this happens beats me. Why do you say the thread is dead?



Dead thread. But, have you checked the O2 sensor(s) and the fuel pressure regulator?

I have fixed the problem. Thanks for the SeaFoam advise. I have poured Seafoam in my crankcase and fuel tank and fixed the problem overnight. I even passed my CA smog with flying colors. I highly recommend Seafoam to everyone who has been having the same problems with their Suburban.

Thanks again.

Yes fuel pressure is good and 02 are good too. The problem obviously is the intake gasket when we replace it the problems goes away then it returns as the days go past. Why this happens beats me. Why do you say the thread is dead?

The thread was dead because it was over a month old. When a thread is dead, start a new one.

The problem will come back. Sticking valve guides in the heads is most likely your problem. Seafoam will free it up for awhile but be ready for the return of the miss or as I call it the 1500-2000 RPM Shake:grinyes:

We discourage continuing a thread for more than 3 months, all the topics/possibilities have been thrashed over sufficiently at this point.

Hello all I just joined here, but have read the post's. I have a 99 suburban 5.7 also. I have this problem for over a year now I have allmost tried every from Seafoam to changeing the sensor's in my throttle body to new distributor. I will try the cam sensor this weekend ,hope it works also i use Royal purple oil in my truck .:evillol: