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


userpete1037
06-19-2009, 09:32 PM
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?

MT-2500
06-20-2009, 06:16 AM
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.

userpete1037
06-20-2009, 06:28 AM
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.

MT-2500
06-20-2009, 06:44 AM
Engine code?

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

userpete1037
07-17-2009, 11:24 PM
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.

MT-2500
07-18-2009, 08:50 AM
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?

userpete1037
07-18-2009, 11:21 AM
The 8th digit is K. When it quits, it's loosing fuel pressure not spark.

MT-2500
07-18-2009, 11:52 AM
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?

userpete1037
07-18-2009, 12:19 PM
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.

MT-2500
07-18-2009, 12:37 PM
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?

jdmccright
07-20-2009, 03:17 PM
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.

userpete1037
07-20-2009, 11:01 PM
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.

2000CAYukon
07-21-2009, 02:12 AM
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

userpete1037
07-21-2009, 09:48 AM
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.

CalifOkie
07-22-2009, 03:59 AM
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.

userpete1037
07-23-2009, 12:54 AM
I will definitely look into that. Thanks a lot.

userpete1037
07-23-2009, 09:59 PM
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.

jdmccright
07-24-2009, 12:53 AM
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.

CalifOkie
07-24-2009, 02:23 PM
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)

CalifOkie
07-24-2009, 03:31 PM
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.

userpete1037
07-25-2009, 09:52 PM
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.

wtodd70
03-06-2012, 05:06 PM
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 !

Schurkey
03-07-2012, 12:29 PM
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".

wtodd70
03-07-2012, 05:51 PM
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

userpete1037
03-07-2012, 07:49 PM
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.

DoubleZs
02-17-2014, 09:55 PM
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.

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