Suburban miss fires after going up a hill?

[markdpro]

Originally Posted by frootl00p3

Um, mine does it and I have not had the gasket job done. My suburban has 90K miles on it. Haven't put any money into it yet. Love my truck wouldn't sell it, just want to fix it. think there might be something to the fuel system cleaning idea. Had a 77 chevy, put bad gas into it one time, it ran like crap for months. I went through 30 plus fuel filters, and it always misfired until it eventually stalled, at which time (rain, hail, snow or never sun) I had to replace that darn fuel filter on the side of the road.
Jodi

Well - I don't usually go for better living through chemistry - but I blew a can of intake cleaner - cat converter safe - through the open throttle body after removing the zip tube/ resonator box (the box on top of the engine, comes off with the thumb screw) and my problem has gone into hiding. There was a film of carbon in the plenum and I believe that indicates some backfire condition and the cleaner dissolved it. There is a post in this thread where a guy used "Seafoam" whatever that is and got some positive results. Nobody else has. I don't like it because I have no idea what I changed but yeasterday I climbed "the hill" at full throttle full load and I did not get the miss.

[myname]

What type of cleaner did you use? After reading this thread, I to may be having this same type of problem.....has any one noticed if the problem gets worse if you take a hard left under heavy exceleration?

[markdpro]

Originally Posted by myname

What type of cleaner did you use? After reading this thread, I to may be having this same type of problem.....has any one noticed if the problem gets worse if you take a hard left under heavy exceleration?

I used a Solder Seal/Gunk spray called INTAKE MEDIC

[frootl00p3]

My father is an old time mechanic and used to work on cars, before they became computerized. He is pretty knowledgeable and I get 99% of my information from him. From what he has always taught me, I don't think it is a good idea to stick anything in your engine that is a sealant. I could be wrong, but I would be leary since you don't really know what it will choose to seal and how dearly you will have to pay in the long run.

[myname]

Solder Seal/Gunk is a brand name, and yes, they do make a sealer for your radiator! Intake Medic is an entirely different product however!

[GrandmaK]

We have had misfire problems with our 1999 Suburban for quite some time. It usually showed up when going up a hill. The 'service engine light' would come on but when the codes were checked by a dealer or our mechanic there was only a 'random misfire' listed. I came to this site to because I was interested to see what other people had to say about what seems to be a chronic problem.

We purchased our 1999 in 2000. It was previously owned by a GMC sales manager. The first time we had problems was in 2002. At that time we replaced the plug wire set and the platinum plugs.

In 2003 we replaced the fuel pump.

In 2004 we replaced the distributor cap and the rotor. We replaced the platinum plugs again.

Later in 2004 we had the fuel injectors cleaned and the gas filter replaced and had the codes set by a dealer.

We had put on an after-market K&N airfilter. The beginning of 2005,we replaced the air filter and it ran fairly well for a few months.

But this month the 'service engine' light came on again. When we took it in the 'recommended fix' was to replace the CSFI fuel injection system with MFI injectors which we did. The water pump was leaking and had to be replaced also. When the suburban was taken for a test drive before we took it home, they checked for misfires and found that the #3 & #4 cylinder had a few misfires but cylinder #5 had 500 misfires on the test drive. So obviously changing to the MFI fuel injection was not the fix for us. We trust our mechanic and he has tried to fix the problem but it is ellusive!

The next suggestion was to replace the air sensor or replace the manifold intake gasket. We're not sure if we should or want to try this next.

My husband is just about ready to take JeffV's out and sell it, but I like the suburban and would like to fix the problem.

Any new suggestions?? Has anyone else who has had this problem been able to find a fix that has lasted??

The posts here have given us some additional things to consider and I appreciate the information.

[GrandmaK]

Did anyone find a permanent solution to the misfire problem?

[suburban_lee]

Originally Posted by GrandmaK

Did anyone find a permanent solution to the misfire problem?

Yes. It took some time - a lot of time, and on a whim, we changed the cam sensor. The misfire has gone away and I can now pull a nice steep hill going 70 or so MPH in all of the 4 miles per gallon glory that a Burb has when pushing it like that!

Up until that point, here's what was done, all of which did NOT resolve the problem:

New plugs
New wires
New cap and rotor
New fuel injector (#4 was the initial cylinder)
New intake manifold gasket
Crank sensor
Checked fuel pressure and cylinder compression (again #4)

[GrandmaK]

Thanks Suburban Lee,
I'll pass on the information to our mechanic about the cam sensor.

Our suburban is scheduled to go in on Tues for intake manifold gasket replacement and some kind of air sensor.

Has anyone contacted GMC about the numerous problems that some of us have had with the misfire and rough running problems of this model?

[dwallace1234]

Originally Posted by GrandmaK

Thanks Suburban Lee,
I'll pass on the information to our mechanic about the cam sensor.

Our suburban is scheduled to go in on Tues for intake manifold gasket replacement and some kind of air sensor.

Has anyone contacted GMC about the numerous problems that some of us have had with the misfire and rough running problems of this model?

I have read a lot of threads about this. I also have a 1999 C1500 Suburban. Same problem as everyone. Except I had to have the lifters replaced at about 85,000 miles. But when the lifters were replaced, of course the intake gasket was also replaced. The misfiring and shaking stopped or about 15,000 miles. But, IT's BACK!!!! One thing I have noticed is that when I run Super Unleaded gas, the misfiring is almost not there! I also have changed:

Distributor
Plugs (3 times; always using Platinum)
Plug wires
Fuel Filter
Coil
Distributor cap
Rotor
And, of course lifters!!!

Any ideas on why running hi-octane gas helps the misfiring not is so apparent?

[dwallace1234]

Originally Posted by dwallace1234

I have read a lot of threads about this. I also have a 1999 C1500 Suburban. Same problem as everyone. Except I had to have the lifters replaced at about 85,000 miles. But when the lifters were replaced, of course the intake gasket was also replaced. The misfiring and shaking stopped or about 15,000 miles. But, IT's BACK!!!! One thing I have noticed is that when I run Super Unleaded gas, the misfiring is almost not there! I also have changed:

Distributor
Plugs (3 times; always using Platinum)
Plug wires
Fuel Filter
Coil
Distributor cap
Rotor
And, of course lifters!!!

Any ideas on why running hi-octane gas helps the misfiring not is so apparent?

Also, there has been some posting on other forums regarding a HSTSA Bulletin # 3081. It talks about replacing the EVAP Canister Vent Hose Assembly. Anyone try that?

[suburban_lee]

Originally Posted by dwallace1234

I have read a lot of threads about this. I also have a 1999 C1500 Suburban. Same problem as everyone. Except I had to have the lifters replaced at about 85,000 miles. But when the lifters were replaced, of course the intake gasket was also replaced. The misfiring and shaking stopped or about 15,000 miles. But, IT's BACK!!!! One thing I have noticed is that when I run Super Unleaded gas, the misfiring is almost not there! I also have changed:

Distributor
Plugs (3 times; always using Platinum)
Plug wires
Fuel Filter
Coil
Distributor cap
Rotor
And, of course lifters!!!

Any ideas on why running hi-octane gas helps the misfiring not is so apparent?

This is my second burb. In total, I've put about 150K miles on these vehicles and I've never run high octane gasoline. Just me, but I think almost not there is not a qualifier. If there's a misfire, there's something wrong. If there's nothing wrong, then I don't care what kind of fuel you run through these vehicles.

I'm curious to hear from GrandmaK as to whether the CAM sensor proved to be a solution to the problem.

[markdpro]

Originally Posted by Luis100

OK, after taking back the truck to the shop we discover a engine code showing problems with the Camshaft Position Sensor we unplug the sensor and start the engine and the problems was there like if the sensor was dead, so we repace the sensor and the problem disapear, so I'm very happy!!!!
The check engine light never came up so we didn't know about any codes, we just plug in the scanner and magic the code came and the poblem faound. Just want averybody to know the end of my problem to try to help some.Good Luck!!!!!!

Luis
10 years working on computers
0 years working on cars

I wonder if the intake could be icing??????

[dwallace1234]

Suburban Lee: Did you replace the Cam Sensor Position Module? Thanks.

[suburban_lee]

Originally Posted by dwallace1234

Suburban Lee: Did you replace the Cam Sensor Position Module? Thanks.

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.