95 5.7 Problems

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ptrac

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Hey guys,
I am new to your fourm so bear with me please. I am having some major problems with my 95, let me start by telling you it has a random miss. some time 1 cyl. some times it feels like 4. Ihave replaced withinlast year, cat.conv. maps,egr.wires.plugs,tps.intake temp sensor. o2, fuel pressure reg. I am at a loss, after 35 plus years of working on Chevys I am wooped with this one. The miss is so random that if fools me to thinking its fixed......Any feed back is welcomed.
 

95slowhoe

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Have you checked the timing. The tbi 350 will miss fire randomly if it is to far advanced.
 

ezdaar

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What is your plug gap?
A weak coil and improperly gapped plugs is #1 reason for random missfire..

On ALL of my "legacy" Chevy motors I instantly replace the pickup coil in distributor, primary coil, and wires with MSD parts. along with standard copper NGK plugs gapped at 40.
 
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ptrac

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Have you checked the timing. The tbi 350 will miss fire randomly if it is to far advanced.

Thanks, timing seams to be ok but I will check again.

---------- Post added at 07:27 PM ---------- Previous post was at 07:24 PM ----------

What is your plug gap?
A weak coil and improperly gapped plugs is #1 reason for random missfire..

On ALL of my "legacy" Chevy motors I instantly replace the pickup coil in distributor, primary coil, and wires with MSD parts. along with standard copper NGK plugs gapped at 40.

i will try the coils, plugs are e3's gaped at .40....Thanks
 

retorq

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When it's missing is it throwing a code?? I don't see a TPS sensor on that list of stuff that was swapped. That was one of the first things that went on mine ... WAY before I changed many of those other things you listed.
 
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SunlitComet

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get yourself a obdI code reader, plug it in, it will trigger your dash light to help narrow thing down could also use the key method too with a jumper wire. Lots of help from everyone here.

In the meantime here is something to add from the others:

Cuts Out, Misses


SYMPTOM DEFINITION:
Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases. The exhaust has a steady spitting sound at idle or low speed.

PRELIMINARY CHECKS

* Refer to Diagnostic Notes. See: Computers and Control Systems\Testing and Inspection\Flow of Diagnosis\Diagnostic Notes
* If there is spray from only one injector on a TBI system, then, there may be a malfunctioning injector assembly, or in the signal to the injector assembly. The malfunction can be isolated, by switching the injector connectors. If the problem remains with the original injector, after switching the connector, the injector is defective. Replace the injector. If the problem moves with the injector connector, the problem is an improper signal in the injector circuits. Refer to "Chart A-3." See: Computers and Control Systems\Testing and Inspection\Diagnostic Trouble Code Tests and Associated Procedures\Related Tests and Information

IGNITION SYSTEM
Check:

* For cylinder miss by:

1. Start engine, allow engine to stabilize then disconnect IAC motor. Remove one spark plug wire at a time, using insulated pliers. NOTE: Do not perform this test for more than 2 minutes, as this may cause damage to the catalytic converter.
2. If there is a rpm drop, on all cylinders, (equal to within 50 rpm), go to "Rough, Unstable Or Incorrect Idle, Stalling" symptom. Reconnect IAC motor with ignition "OFF."
3. If there is no rpm drop on one or more cylinders, or excessive variation in drop, check for spark, on the suspected cylinder(s) with J 26792 (ST 125) Spark Tester or equivalent.
4. If no spark, refer to Ignition System.
5. If there is spark, remove spark plug(s) in these cylinders and check for:

o Insulation cracks.
o Wear.
o Improper gap.
o Burned electrodes.
o Heavy deposits.
o Spark plug wire resistance (should not exceed 30,000 ohms), also, check rotor and distributor cap.
o If the previous checks did not find the problem:
o Visually inspect ignition system for moisture, dust, cracks, burns, etc. With engine running, spray plug wires with fine water mist to check for shorts.

FUEL SYSTEM
Check:

* Fuel pressure. Refer to "Chart A-6." See: Computers and Control Systems\Testing and Inspection\Diagnostic Trouble Code Tests and Associated Procedures\Related Tests and Information\Chart A-6 Fuel System Diagnosis
* For contaminated fuel or restricted fuel filter.

ENGINE MECHANICAL
Check:

* For proper valve timing, low compression, bent pushrods, worn rocker arms, broken or weak valve springs, worn camshaft lobes.
* Intake and exhaust manifold passages for casting flash.
 

gulleyman

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x's 2 on checking the compression, that's what my random misfire turned out to be. I replaced a LOT of parts trying to figure it out, it would misfire on 5 and 7, then after the RPM's were over 1500 they would come back and I would lose 6.
Two mechanics looked at it and said the compression was fine, then a third found zero compression on 6. Suspected cause is a burnt exhaust valve, but we'll find out for sure when it get's rebuilt, hopefully this week.
There's a great deal of help on this forum, good luck with yours :D
 
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ptrac

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When it's missing is it throwing a code?? I don't see a TPS sensor on that list of stuff that was swapped. That was one of the first things that went on mine ... WAY before I changed many of those other things you listed.

No code, that is what is blowing my mind, I was told today that e3 plugs are great but have been having a lot of issues.
 

96ProCompTahoe

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No code, that is what is blowing my mind, I was told today that e3 plugs are great but have been having a lot of issues.


I've heard both ways with the E3's. i just use the AC delco plugs in mine.
 

SunlitComet

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if your the rest of the ignition is stock switch back to the ac delco plugs and make sure your cap and rotor are correct. A lot of stuff slips by OBDI systems. They were not really designed to identify misfires or their direct cause.
 

TORONTO 95 GT

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Had the same problem that returned after the standard tune up with non delco parts. Replaced all with Delco parts, misfire gone. Also never had the CEL with the misfire and when the TPS went it tripped my CEL randomly but the thing would feel like the trans was slipping when it was on.

Good luck
 

96Tahoe4x4

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Timing off, pulsating excelaration....

I read through all of these threads. What I didn't see any mention of was the cap and rotor. They have a history of corroding and gumming up. This causes all of the mechanical failures that were mentioned.

I hope that helps.

FYI...These are GREAT trucks!

I am two days away from installing (front to rear) the High Performance polyurethane (red) bushing kit on mine! :shocked: :hands:
 

kelly1

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I agree on running stock ac delco plugs. I've had lots of tbi trucks and love them but they do lack the diagnostic capability of today's vehicle.

On the timing, make sure you disconnecting the brown with black stripe wire before checking or setting timing. Someone can correct me if I'm wrong but timing with the wire disconnected should be a zero I believe. I used to run all of mine at 2 degrees btdc. Got a little extra pep and no real drop in fuel mileage.

good luck.
 

95BlackTahoe

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My 95 tahoe did the same thing...hard to start, had a miss occasionally...turned out the timing was 18* off to the negative. I timed it and the miss went away, also helped I'm sure with the new msd wires, coil, cap and rotor...lol. Either way, she runs great now.

Now I have to fix the fuel pump issue. It was a no start yesterday, and the pump wouldn't even prime. My friend reached in in the front of the drivers side rear wheel, and wiggled some wires, and it primed and ran...lol...another project...

Shawn
 

retorq

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Probably not, all 95s need to be lit on fire and pushed it off a cliff ...
 

TORONTO 95 GT

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Hey, thats not fair!!!

I think my 95 runs pretty good for its age and milage all though I swear I could out run it in a 1/4 mile race. It takes forever to get up to speed. I am slowly fixing up things as I go. I have not been driving it since October but getting ready to drive it a bit this summer up north a few times.
 

19992dr4x4

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I had a miss or sputter like feel on my on my 99 tahoe and replaced plugs,wires,cats,cleaned the EGR valve and no fix. So I replaced my fuel pump...no more miss or sputter.
 

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