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

[userpete1037]

I will definitely look into that. Thanks a lot.

[userpete1037]

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]

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]

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]

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]

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]

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]

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]

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]

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]

Originally Posted by userpete1037

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.

[777stickman]

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.

[ShadeTreeNewbie l]

Originally Posted by 777stickman

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.

[Schurkey]

Originally Posted by ShadeTreeNewbie l

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.

[j cAT]

Originally Posted by ShadeTreeNewbie l

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.