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1995 Running Really Rough



hI THERE i NEED help!!!!!!!!!!!! :confused

I have a 1995 vette c4 with automatic.. I thought I was getting water in the gas yet after snaking my drain and replacing my gas cap I am still having worsening problems.. It seem as though the right side of my engine is not firing regularly.. the car runs fine when coold.. but upon hard acceleration or running it begins to miss and i get big puffs of black smoke out the right tailpipe.. I replaced spark plugs.. all right side plugs were completely carbonized.... yet this did little to solve the problem. The local chevy dealer I distrust with my vette (they broke it last time when it was in for an oil change)... It must be some sensor... yet i cannot diagnose it by myself... ANY SUGGESTIONS WOULD BE GR8LY appreciated!!

Thaks TOM :confused
I guess no one has a clue, which is maybe the reason that no one responded.

There are evidently to many variables to diagnose this problem without looking at the motor. Have you checked compression on those 4 cylinders? Maybe you've lost compression..ie a crack in the cylinder which maybe leaking oil into the cylinder creating the smoke out your tailpipe.

I wish I could be more help.

good luck

Tom, are you getting any codes? It sounds like you should be. Wish I were able to help you out. Have you considered taking it to a speedshop rather than the Chevy dealer?

Best of luck,

Workin on getting codes

I will post the codes this weekend... I am a single dad (2 kids) and work full time.. I hope to get enough time to play with my Vette this weekend.. THANKS FOR THE POSTS!! I WILL KEEP UPDATING :)
Hi there,
It sounds like something is not right, as I would check also, and please tell us if the plugs were wet or dry upon removal??
Please keep us posted, c4c5
plug condition

When I pulled the plugs (bought new ones ...8$ a piece) the ones on the passenger side were dry but COMPLETELY black with carbon... (otherwise show no wear) Drivers side were dry and slightly brown but looked the way they should. The car has 37k on it. Again I am gonna get codes off of it ASAP and post them. I disconnected the battery to clear the computer and drove the car for about an hour or so.. Whatever is failing the service engine soon light is coming on and staying on for longer periods of time.. (when the light is on the car runs better).. it tends to go off after extended (5 or 10 minutes) running at speed (highway)..

Okay i dunno if this would be the same on corvettes.....

But my mom had a 92 GMC Sonoma with the 4.3 in it.

it was doing the same thing.....after painfull hours of trying to figure it out....(along with BAAADDD vibrations and hesitations)

It tured out to be the computer.......we got the computer replaced and bam....ran like new.

i dunno...its worth a shot
well the 'puter is an expensive box for a 95 vette... I am guessing fuel pressure or something.. I initially though I had gotten bad gas or something. I PRAY I DO NOT NEED TO BUY A NEW BOX!!!! This weekend (along with running the codes) I am going to replace the fuel filter (its 3 years old).. see what kinda crap is in there..(any one got any pointers on swapping out the fuel filter??)

thanks for the respnses~:confused :Twist

Hi there,
Wear safety glasses, and take it slow.
Change the filter when it is cold, you will need a 16.. and a 20mm wrench.
A 10 mm will hold the filter in place with a bracket.
Remove the gas cap, as pressure within the tank will push out fuel.
As for the rest, have a drain pan ready, as when you remove the first line, it could spray a little, than it will start to drain, about a pint.
Then, be aware that there is a flow direction that must be followed. It will be stamped on the filter, the arrow goes toward the front.
Let us know how you do, c4c5

Ok I got out to check code this morning.. I only seem to have the instructions for checking them up to a 93.. I have a 95 with 16 pin connector... which 2 pins should I short (A & B) are they still the 2 at the top right hand portion of the connector??

I just do not want to short the 'puter out!! Thanks!!!

You cannot extract codes

Hi there,
Well, you cannot read codes off of that connector, in that fashion.
However, if you feel a challenge, start by doing the following.
If you can, ground out terminal 12 of the Diagnostic connector, to pin 4, which is directly above the pin 12.
Then, turn the ignition on, and focus on the digital display, where your odometer will be located. Have a pen and paper ready.
You will see codes displayed for each and every module, depending on what options you have on your car.
You will see the top 3 large digits, and one small digit, on the left middle location.
They will come as follows, 1 is the CCM
4 is the PCM, this is what you want
FX3/F45 is #7, if equipped,
#9 is the ASB/ASR
Then post the codes, and we can help.
Please keep us posted, c4c5


I don't think I have any answers here...

Module 1 c 12 ????

module 9 h 37 - once the asr/abr light stayed on

any suggestions??

It is so frustrating to own a 28 year old vette that runs like old faithfull, and have a newer beautiful c4 with 37K that is finicky!!

The PKE system has backfired too! I was driving and it popped the hatch open.. Thats it since.. sometime the PKE light comes on yet I cannot reset the system.. Key fobs (i have 2) do not work and doors do not lock automatically... I will get into this bug later... I really would like to solve the drivability issue before i put the car to bed for the winter!!!

Thanks again for everyones reply!!:beer

What about 4??

Hi Tom,
Well, your 12 code in the ccm, thats ok, and normal when you are retrieving diagnostics.
As for the ABS, the 37, left rear wheel speed sensor malfunction.
Was there anything displayed for the #4 module??
Please let me know, c4c5
module 4 was clear.....

I have yet to switch fuel filter.. I understand that if fuel pressure is low.. it may cause the engine to run rich (sounds like just the opposite should happen)... any guesses?
fuel pressure & spark quality

What is the best way to check fuel pressure??? I figured I would change the filter and see if my problem improved.. as far as spark goes... it only seems to run rough when warmed up... replascing the plugs i did check that all wires were firing....yet I can not even find a traditional distributor on this car!!

You will need a fuel pressure gauge, and a spark voltage oscilloscope.
This is really some thing that a professional should do at this point.
I am going to do a bulletin search in the GM data base, and see if I could come up with something else in the meantime.
If this car had a problem with water in the fuel and now has a problem with one or more cylinders running very rich, without actually seeing this car myself; I'd say there's a fair chance the engine has one or more leaking injectors.

OE injectors have mild steel internals and any period of time with moisture in the fuel with the engine not running, allows rust to form inside the injector. Once that rust begins, the injector eventually begins to leak.

Best way to diagnose an injector problem is to use the fuel pressure tests listed in the factory service manual. Those instructions will explain how to test for leaking injectors.

You need both the factory manual and the fuel pressure gauge mentioned by c4c5specialist.

I got lucky and broght the car to a friends garage (to test his new snap on diag unit).. right O2 sensor... we checked the wiring and bought a new one (from gm dealer).. ALL SEEMS WELL NOW !

I wanted to thank you all for the info along the way and all of your responses!

I will try to post pictures soon!!


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