MikeC4

ok, tested the MAP sensor and it appears to be operational:
Idle => 1.45V
High RPM constant => 0.9V
idle to WOT => jumps from 1.45V to more than 4V

Observations made tonight:
-no noticable arching from plug wires in dark. No strange clicking sounds which may indicate a jumping voltage.

Checked all 8 FI's again, by disconnecting each connector while listening for slight drop in RPM:

Results from initial startup of cold engine, and before engine starts stumbling and spewing black smoke from right exhaust:
- When FI connector to Cylinder #2 removed, RPM's drop

Results after about 20 minutes of idleing, engine begins to stumble and exhaust fumes stink to high heaven:
- When FI connector to Cylindar #2 removed, no change in RPM's

Have I found the problem? Can a faulty FI be more sensitive to heat ?Or maybe a poor spray pattern or atomization which eventually saturates the plug to where it stops throwing a spark?

Any recommendations on reasonably priced new or refurbed "plug and play" FI's for a bone stock '95 LT1??

Thanks in advance folks....

REDC4CORVETTE

Most forget that a rich condition out the exaust is NOT a rich engine.
The motor is LEAN and the computer is pouring more fuel in it to compensate.
Have you cleaned the throttle body?
Try disconecting the EGR vaccum line and see if the engine improves EGR located at the back of the engine intake .
Is your air pump at the left front of the car running all the time?
Injectors will not cause this many fuel problems at the engine.
I hope when you cleaned the O2 sensors you did not spray anything into them ,otherwise you killed them.
Most likely all 3.

MikeC4

REDC4CORVETTE Most forget that a rich condition out the exaust is NOT a rich engine.
The motor is LEAN and the computer is pouring more fuel in it to compensate.
[MikeC4] ..but the result of the computer pouring more fuel is a Rich engine
Have you cleaned the throttle body?
[MikeC4] Yes, about 1 year ago, I will check again and clean. Also new TPS and IAC.
Try disconecting the EGR vaccum line and see if the engine improves EGR located at the back of the engine intake.
[MikeC4] Replaced EGR last week, old one was in real bad shape
Is your air pump at the left front of the car running all the time?
[MikeC4] there is no air pump on my '95
Injectors will not cause this many fuel problems at the engine.
[MikeC4] I would beg to differ, if 1 injector is not working, this could cause all sorts of problems, one being a Rich condition if injector leaking
I hope when you cleaned the O2 sensors you did not spray anything into them ,otherwise you killed them.
[MikeC4] noe chemicals used, just wiped them carefully with towel
Most likely all 3.

REDC4CORVETTE

This Blank computer.

REDC4CORVETTE

Hum?
If you have an LT1 it should have an air pump in the left fender well?
Oh well.
When you accelerate does the car get up to a certan speed and start to speed up or does the engine just humm and no more acceleration?
If you put your hand back at the exaust sitting still and have someone rev up the engine does it blow your hand out of the way?
Does the trans shift ok?
How old is the fuel presure regulator?

MikeC4

REDC4CORVETTEHum?
If you have an LT1 it should have an air pump in the left fender well?
no kidding!? I thought I would be looking for a belt driven air pump...I will check on this...What is the purpose of this air pump anyway???
Oh well.
When you accelerate does the car get up to a certan speed and start to speed up or does the engine just humm and no more acceleration?
it bogs down at first and slowly accelerates. My problem has also definately confused the transmission too....shifts at odd times
If you put your hand back at the exaust sitting still and have someone rev up the engine does it blow your hand out of the way?
I just had new cats installed, so exhaust is not a problem... I know if I continue to run car in current condition, I will probably ruin these cats.
Does the trans shift ok?
when the engine starts running rich and stumbly, the transmission seems to get confused, especially during heavy acceleration..
How old is the fuel presure regulator?
looks like original...

also, today I pulled fuel rail, put construction paper under each one, turned on ignition to pressurize fuel rail...no leaky injectors..I swapped #2 FI with #4 FI....no change...I think you were right about the FI NOT being the problem...pulled all 4 plugs from passenger side, and they were all heavily carbonized with black crud, but they all appear to be firing(since I had them all out, I went ahead and replaced them. Will do the drivers side tommorow...

After about 10 minutes of normal driving, the car runs poorly until the SES light illuminates and then it appears to idle better. I think the ECM/PCM is bypassing the O2 sensor's at this point. I replaced both O2 sensors less than a year ago...I am thouroughly stumped at this point..

Can you tell me more about the air pump please???

Thanks for stickin with me on this...

MikeC4

pulled my plugs today(Bosch Platinums), and noticed big difference between driver side plugs and passenger side plugs.

could this be as simple as an inoperative O2 sensor on passenger side? The right exhaust is the one spewing out all the black smoke..

REDC4CORVETTE

So the one side is lean and the other is rich.
You have 3 O2 sensors I would replace the sensor on the side that is rich.

K45_vette

One easy test you might try is to use a mechanics stethescope and touch the top of each injector (after taking off the covers). I did this and it pin pointed two bad injectors even though they all matched in resistance and the cardboard test showed non leaking. You can also apply 12V to the two leads to fire a suspect injector when doing the cardboard test.
It almost seems like you may have cut a wire or something to one of the injector banks when you replaced the EGR.

MikeC4

thanks K45.....that is exactly what happened, sort of. When my muffler shop replaced my O2 sensors, they bent one connector pin which killed that O2 sensor....car ran like ****e!!! Replaced with new O2 sensor and all is well now.

Thanks for the Injector info. I like the stethoscope idea!!!

onedef92

It sure can. And without warning, too. If you do replace your ignition module, use the thermal-transfer grease compound that should come with your new module.

It should be applied to the pad in the housing where the module rests. This thin layer of grease improves the transfer of heat produced by the module to the housing and is very important to the life of the module. (Do not confuse common dielectric grease with this thermal-transfer grease. They’re completely different.)

95BlkVader

Hi Mike, my name is Ray and currently have the same issues minus the black smoke on right side exhaust. I had a vacuum, leak on my evap sensor and on my throttle body boot both replaced & EGR valve.Car runs good initially then at a stop, idle will surge up & down. Changes in RPM & battery voltage noted. Replaced original MAP Sensor & it's rubber grommet. Now at stop does not lobe left to right as much, but after a while will start to surge up again and sometimes will stall. I will appreciate any suggestions to solve this problem, it's been a hit and miss for me? Have not looked at my O2 SENSORS yet. Thanks ray

pcolt94

You need to look at the dates of the threads. This thread is 13 years old and mike has not posted since 2009. I think he has more than "left the building".

He is not going to answer. Start a new thread and you will get some answers for your problems.