1995 Chevy 1500 1/2 Ton Truck (350, 5.7L)

Ok,

Last week my truck started to stall a little bit. As I drove it a little longer, it stalled all the way out. It started back up fine but when I gave it some gas, it cut off. This happened several times. I popped the hood and noticed the throttle body was a little loose. Thinking air may have gotten into the system,I tightened it back up. I started it up,put it in gear and it seemed to drive fine and it started stalling again. While I was on the interstate, it would cut off, cut back on,cut off and then cut back on. Finally it completely stalled out. I had to have it towed to my house. I hooked my code scanner up to it and it through code 44 (O2 sensor) and code 54 (Fuel pump relay or something like that). I have no idea what could be causing my truck to run this way. Does anyone have any suggestion as to what it might be causing this problem?

What is the engine code?

02 sensor is not you main problem.
Have you got good spark and fuel pressure when it acts up or quits?
Is it dead now or just acting up?

Pull the throtle body and replace the base gasket to start with.
Clear codes and see what comes back.

Check fuel pressure when it quits.
Post back fuel pressure readings.

Get some good repair info on the code for fuel pump relay and fuel pump and fuel pressure.
Let us know how it goes.

It's not dead. It actually starts up. As a matter of fact, I started it up yesterday and it ran fine. I gave it gas and it idled up with no problems. After about 15 min of running, I gave it some more gas it acted like it wanted to cut off when I gave it gas. Other than that, it runs fine when it idles by itself it's just when I press the accelerator,it wants to shut off.

Engine code?

Check the fuel pressure when it quits for being up to specs.

IT's been a while guys and I apologize for not getting back to with. Work has allowed me little time to troubleshoot my truck. Anyway, I tested the pressure and it was around 7-8lbs. I thought I might have a faulty fuel pump so I replaced it along with a sending unit and it still is doing the same thing. I've needed a new knock sensor for a couple of years but I know that isn't the problem. I think I will try replacing the MAP SENSOR unless anyone has anymore suggestions.

Proper testing before throwing parts at it.

What is your engine code? The 8th diget in vin?

What is the fuel pressure reading when it quits?
When it quits is it losing spark or fuel pressure or both or someting else?

The 8th digit is K. When it quits, it's loosing fuel pressure not spark.

The 8th digit is K. When it quits, it's loosing fuel pressure not spark.

What is the fuel pressure reading when it quits?
When it quits is it losing spark or fuel pressure or both or someting else?

the reading is about a constant 8psi. What's happening is when I press the gas pedal very quickly, it stalls for a split second and idles back into place. If I press the pedal gently it idles fine without stalling. This is weird. I have no idea what's going on.

the reading is about a constant 8psi. What's happening is when I press the gas pedal very quickly, it stalls for a split second and idles back into place. If I press the pedal gently it idles fine without stalling. This is weird. I have no idea what's going on.

8 lbs is low pressure.
Are you sure it is not losing fuel when it stalls?
Watch the gauge when it stalls or quits.

Any check engine lights or codes?

8 psi is definitely low. Should be 11-15 psi. I'd check the fuel pressure regulator...IAC, PCV, and EGR valves also while you're under there.

I got a t-fitting made that fits where the fuel filter goes and I'm getting a constant 13psi now. My truck will start with no problem but the problem I'm having now is that it's starting to idle rough and backfire. I changed the spark plugs because they were corroded some with what appears to be carbon deposits. Still doing the same thing. I took off the distributor cap and rotor button and it appears they need replacing but not sure if that will do the trick. I hooked my Actron Code Scanner up to it and it though a code 34 which references the MAss Air Flow (MAF) Sensor and Manifold Absolute Pressure (MAP) Sensor. I know mine doesn't have an MAF.

Check the vacuum hose to the MAP sensor which is at the back of the TBI and goes to the MAP sensor. If hose is bad or if the MAP sensor will not hold a vacuum, a code 34 will be set.

//2000CAYukon

I will check the hose and I believe I can perform a vacuum test on the MAP sensor. I be sort of busy through the week so it may take me a couple of days before I can respond. Thanks for the insight.

Try a known good throttlebody on it... Here lately I have seen quite a few fuel pump and TBI failures. Which I believe is caused by the ethanol/ gas mixture deteriorating the fuel systems. As far as the TBIs go in the last 3 months I've had a 94 4.3L TBI, a 91 305 TBI, and a 94 350 TBI. All three developed internal vacuum leaks in the units themselves. This is evident from your code 34 MAP sensor stored. If the TBI can not hold a steady vacuum without it leaking off then the ECM will become aware of the vacuum loss by monitoring the MAP (manifold absolute pressure) sensor and seeing a gradual bleed off at that point it codes 34 thinking the Map is not holding the vacuum when infact it is it's vacuum source that is failing to hold the vacuum. Your original code 44 O2 sensor code was probaly triggered by extremely lean exhaust caused by airleaking around the TBI base gasket when it was loose. If you have been burning alot of ethanol/gas definately look hard at the throttlebody.

I will definitely look into that. Thanks a lot.

I believe I'm about to give up on this. I have replaced the MAP sensor, plugs, distributor cap,rotor button, TBI Unit gasket, fuel pump and sending unit. Still is backfiring when I get up to speed. I didn't replace the plugs although I probably should have. I'm at a lost and I don't have the money right now to buy a new TBI. I did notice when I pulled the wire off the ignition coil, the post on the ignition coil had a white powdery substance on it. Don't quite know what that means but I'm at a lost right now. I was thinking it might be the pickup coil but still that's just me guessing. Later.

I am trying to remember what I did to fix the exact same problem when I first got my truck, minus the backfiring. I recall replacing the spark plugs (they were worn down to the nubs), TBI gasket sets and o-rings, replacing the coolant temp sensor, and cleaning the IAC and EGR valves. I also ran some seafoam through the engine oil, fuel, and intake. I rerouted the spark plug wires so they were not crossed, cleaned the cap & rotor terminals, and cleaned the ignition coil secondary terminal. That white stuff could be oxidation or very old dielectric grease...my bet's on the former. A scotch-brite pad will shine that up, but getting the oxidation inside the plug wire boot will take a small knife and some patience.

You or someone mentioned a code 44 (faulty O2 sensor)...was that code stored as well? I did not read anywhere above that you had replaced the sensor. If it is failing, it can cause the engine to run rich by default (open-loop) which would explain the bogging down when warm and the backfiring due excessive fuel.

Don't buy a new TBI , buy 2 new gaskets... 1 incase you tear yours getting the TBI off and the 2nd to send back with the known good TBI you BORROW... If it fixes your truck go buy one from a salvage yard they usually cost $30-$50.

As for the white powder on the coil.... That very well could be the entire problem. If it is on the main body of the coil then the coil is cracked and needs to be replaced,.. if it is only on the tip of the tower than you have extremely high resistance in the sparkplugs and wires and replacing them should fix it. ( unburnt fuel in the exhaust followed immedialely by hot burnt fuel equals backfire)

If that white substance is either pasty or dried and flaky it's dielectric grease, if it is a thin powdery film coating then it is actually a residue smoke trail left by spark arcing off of the coil tower instead of going down the wire to the distributor cap. it can be caused by any of the following : used up plugs, brokedown ignition wires, corroded distr cap or rotor, wore out distrib shaft bearings (allowing rotor to flop side to side), weak or cracked coil, or weak pickup coil. In the later 3 conditions they are usually accompanied with a rough idle and frequent stalling.

Ok guys, Friday I purchased an ignition coil and pickup coil. I installed the ignition coil first. Test drove it to see if that would fix it an it did not. Barely made it back home. Friday night, I took out the distributor so I could install the pickup coil. I had trouble trying to knock out the pin at the end of the gear, in fact, I was unsuccessful in taking it out. I broke the tip twice on the pin remover in both sides of the gear. So Saturday, I returned the pickup coil and bought a new distributor. That did the trick. So I'm guessing the pickup coil was bad. The only thing I haven't replaced are the wires which I purchased a couple of years ago. I guess I should replace those. They don't look bad but who knows. Thank all of you for your input. I greatly appreciate it.

hey guys, ok well i know this topic is old, but i am having sorta the same problem, except on my truck it is a 5 spd so when i first start it up, it will idle just fine for about 3 to 5 min then it will start to cut out and die out, but it will start right back up as long as i keep my foot on the throd. when i go to take off, the truck hesitates and jurks with little to no power. if i put it in neutral and gas it, it will idle just fine but a little rough. could my truck be having the same proble as this other guys? my OB1 code came out as 44 (O2) could this problem be my Dist? please help !

What is the fuel pressure?

Have you inspected spark plugs, plug wires, Cap 'n' rotor?

EGR works?

Vacuum hoses not rotted or fallen off?

Shine a timing light at the fuel injectors with the engine idling. Nice, cone-shaped fuel spray?





My '88 VIN K needed a distributor mainshaft to correct a misfire at high speed that eventually degraded to misfire at high and low speed, and finally stalling at idle. A replacement distributor would be essentially the same "fix".

Schurkey,
yes i replaced the plugs, wires, cap and rotor. my cap when i took it off had blue corrision on all 6 points of the cap. i have not checked my fuel pressure yet, but i do have a nice cone spray of fuel, kinda sputters a bit durring rough idle after about 5 min or so. all the vacuum lines are fine but unsure about the EGR valve. any ideas ? BtW my truck is a 4.3L v-6
thank you, Todd

Well well it has been sometime since I thought about this and if you read all the threads you will see I tried just about everything before I figured it out that it was the distributor. It was a good experience with great people helping me. As far as my symptoms, my truck would start up fine with no problem and run fine with no problem. It even would drive fine was in got out of the driveway but once I got down the road it would backfire and shutoff. I would have to sit for a while and drive about 2mph literally to get back home because it would just about shutoff. So as a result after all of the parts I threw at it, the distributor was the last resort and it was the culprit all along. Hope this helps.

Well well it has been sometime since I thought about this and if you read all the threads you will see I tried just about everything before I figured it out that it was the distributor. It was a good experience with great people helping me. As far as my symptoms, my truck would start up fine with no problem and run fine with no problem. It even would drive fine was in got out of the driveway but once I got down the road it would backfire and shutoff. I would have to sit for a while and drive about 2mph literally to get back home because it would just about shutoff. So as a result after all of the parts I threw at it, the distributor was the last resort and it was the culprit all along. Hope this helps.
Thanks a ton for posting!! I am in the same boat. I threw a bunch of parts at my truck trying to eliminate the problem. My truck is running great and I get running down the road about 1/2 to 3/4 of mile away from home and it just acts like a little gremlin is under my hood screwing around with my motor. I'm going for the distributor next and hopefully this will fix this green monster of mine. Thanks everyone on this forum for input, excellent advise to follow from all of us sharing the experience of owning an older truck and troubleshooting ourselves.

A couple of things I noticed.

1. You've replaced everything but the distributor itself, as the O.P. did to cure his issue.

Check for wear by holding slight down press on the rotor and turning left to right. No rotational movement is allowed. Also no side to side movement is allowed at the rotor.

2. Your 5.7 truck needs a 195* t-stat. Running at 185 may be keeping it in the "enrichment" mode, like the choke is stuck on.

A couple of things I noticed.

1. You've replaced everything but the distributor itself, as the O.P. did to cure his issue.

Check for wear by holding slight down press on the rotor and turning left to right. No rotational movement is allowed. Also no side to side movement is allowed at the rotor.

2. Your 5.7 truck needs a 195* t-stat. Running at 185 may be keeping it in the "enrichment" mode, like the chock is stuck on.

1. I'll try your rotor test. I've avoided the distributor for fear I'm not skilled enough to replace it, though it's been on my suspect list for a couple weeks.

2. Interesting thing about that thermostat, I did purchase a 195 degree version and twice in the first week it hasn't opened until about 230 degrees. Both times the temp settled down after popping. Love these "new" parts that perform worse than the old ones...

Thanks for inputs.

Checked 8 spark plugs; showing chocolate-colored markings, indicating no lean/rich conditions.
Ummmm...NO.

Those plugs should be WHITE, or there's excess fuel, excess oil, or misfire.

What does the data stream (on the scan tool) show?

You've spent a pile of money and done zero diagnosis. Might as well start putting parts on some other car, hoping to fix this one.

Wow, that's really helpful, a$$hole...

OBD1 isn't available near me. Why do you assume "no diagnosis?"

You fix cars for a living, loser? Stick with that. Being helpful to others is not your forte.

And I don't know much, but I know you're wrong about the spark plugs.

They just let idiots post in here?

No help from you is needed or wanted. Now, shoo! Go away.

YOU did or had someone replace lots of parts . now you come here to get some help.

If you looked on these internet forums first , you would have saved a lot of effort and cash. This posting was addressing your type failure ,, jumping in to this old post of another ,, does add confusion on helping vehicle owners with their problem.

the people that you went to are idiots , on the repair/help of your vehicle,, I would go to a repair shop that has good trained auto tech's.the repair shop just gave you bad info to screw with you , because they were not getting the work.

since this is a 95 350CU and with your problem the , distributor is defective. these do not last when they are over 10 years old and have 175K plus miles on them.
with a manual follow the instructions on replacement. the timing is very important and may require a GM timing tool to set at the proper point. marking the old and installing the new to have the distributor in the same point will get it to run but maybe slightly off , causing the engine to be running with low power or detonation.I would also check the distributor cam gear for wear since this with lots of use , is sometimes a problem with poor maintenance...

on the engine temp. 195 deg f is where the temp should be . if you put in many thermostats and the temp still goes above 195F then you have a coolant leak. make sure the system is with pressure. change the pressure cap if old. no pressure the coolant will boil then it will run hot ..the pressure keeps the coolant from boiling. the pump pumps water not air bubbles no boiling is allowed.

OBD1 isn't available near me.
Of course it is. OBD 1 scan tools are...well...everywhere. You just haven't looked hard enough, or you're not committed enough to buy proper tools. I'm not asking you to buy a scan tool, although if you plan to work on OBD 1 vehicles, it just makes sense. All you need to do is borrow or rent one; and perhaps you'll rent the guy who owns it, too.

Gotta be cheaper than throwing parts at it like you have been.

Why do you assume "no diagnosis?"
Obvious. You've replaced an armload of parts, but you haven't fixed anything. You (or the shops you've paid to fix this thing) didn't diagnose the REAL cause before you (they) started slapping parts on the truck.

You fix cars for a living, loser? Stick with that. Being helpful to others is not your forte. And I don't know much, but I know you're wrong about the spark plugs.
I'm very helpful to others, when they're mature enough to accept suggestions. That you don't like my style doesn't bother me too much. MY TBI vehicle runs just fine, and has nice white spark plugs, too. It takes tens of thousands of miles to put color on the plugs of vehicles with feedback fuel injection. The days of choclolate-brown plugs went away when the lead in gasoline went away. With feedback fuel injection and overdrive transmissions, it takes a bazillion miles to see color on the plugs--unless there's oil burning, coolant leaks into the chamber, or the gasoline has certain additives that promote green or orange tint. Given enough miles and a properly-operating engine, plugs might go greyish-tan. You said the first shop replaced the plugs, and the second shop says they're chocolate-colored. How many miles do they have on them?

They just let idiots post in here?
Did YOU pass any sort of test when you showed up here?







If this vehicle parked in my driveway, I'd be looking at why the cranking compression varies by more than 50% (60 psi), from a high of 160 to low of 100. A leakdown test is indicated to see if you've got worn valves or worn rings. While I was in there, I'd perform a cylinder-balance test on general principles. That much compression variation has to affect engine operation. I have my doubts about both the O2 sensor and the catalytic converter--what "test" did the shop perform to claim that it's OK?

Yes, the distributor could easily be the cause of your current driveability problem (It was with my truck, when I had misfire and stalling problems) but as I said, I'd do diagnosis first.

WOW!! What a story. I was 50 years old 22 years ago and had a similar attitude as you do now. I no longer have that attitude as age has mellowed me.

You say the we (as repliers) don't have any vested interest. why would you feel the need to chastise me for things I did for which you had no vesting...?.

Problem with that statement is that we have all spent time (45 mins for me) reading your diatribes, trying to digest and come up with some helpful suggestions. AKA vested interest.

Sure j Cat is a "fanatic" but he has great info and experience. Schurkey, if you read his signature, is a certified "dumbass", but he also has great info and experience.

So please get rid of your 50"s attitude and respond back with what you've done with our responses to your "mechanical issues".

Thank You.

Crap: Just realized I'm adding to a 6 year old original post. Sorry Mods!!

the distributor is bad worn bearings replace it. this is when they fail 175K miles with good maintenance... if you continue to run it like this with the miss fires your cats will be cooked !!

[QUOTE=777stickman;7168678]WOW!! What a story. I was 50 years old 22 years ago and had a similar attitude as you do now. I no longer have that attitude as age has mellowed me.

Problem with that statement is that we have all spent time (45 mins for me) reading your diatribes, trying to digest and come up with some helpful suggestions. AKA vested interest.

Sure j Cat is a "fanatic" but he has great info and experience. Schurkey, if you read his signature, is a certified "dumbass", but he also has great info and experience.

So please get rid of your 50"s attitude and respond back with what you've done with our responses to your "mechanical issues."
_________
Um, you're saying I have an attitude, stickman? That's hilarious. The depth of attitude I've seen here from you lot is unbelievable. If it took you 45 minutes to read what I wrote, you're dumber than you sound.
No, thank you. I'll pass on this forum. I don't have time for judgmental fanatics, dumbasses and geezers. You guys are waaaaày too uptight.

Well Darn Ol' Son. Sorry to hear your leaving us and just when it was gettin' fun.

Best to you............The Geezer?

Shucks.

Not only did he leave, he felt so guilty that he removed his incriminating posts!