Hi All, please excuse me if my topic is covered elsewhere but I've pretty much exhasted the knowledge base here in Australia..

My 88 GTA (L98) has developed a severe idle and drivability problem that has the car backfiring and running as though its running on only 7 cylinders (although all eight are firing)

I have found the car is running extremely rich with heavy oil contamination and checking the new plugs today they are all covered in equal amounts of fuel and oil.

Normal checks I have done are:

Base timing at 6 degrees BTDC
New plug leads
New distributor cap
New Ignition module
PCV works well with strong vacuum

Ran a Win ALDL scan with the car at 180,idle,in park, indicating closed loop and got:

Idle speed 1000 rpm (manual says this is a default with a scanner attached)
MAF - 10 gm/sec
BLM - 108
TPS - rigth on .55v
IAC counts between 20 and 40
o2 sensor is erratic ranging from .25 to .8
Temp is correct both at the gauge and the ECM

The car displays no codes, but recently I repaired a 42 EST (bad connections at module), and 36 (bad relay)

I cleaned the cold start injector (was not dirty)
My manual says to check to see if idle improved by dis connecting the MAF but it simply dies.

Any ideas guys? I don't know where to go from here?

 

Are you sure it's OIL on the plugs?? Or are they just black and sooty?

If oil, no "tune up" will fix it, unless you call valve seals or piston rings a tune-up. PCV at idle shouldn't be sucking a terribly high amount of Oil at idle, even if it's broken.

O2 sensor is supposed to be "erratic" like that when in closed loop. It means the ECU thinks it's found 14.7:1 A/F. But that can be wrong if the O2 sensor is seeing misfires. The misfires could be rich misfire.

I'd first check the fuel pressure. Could be a stuck fuel pressure regulator or something like that. Maybe a pinched return line.

Is it blowing a lot of smoke? Does the smoke look black, or does it have a lot of blue? Ignore any white steam for now.

Is it a stock engine with stock injectors and other parts?

 

[size=large]Rose[/size],

Have you tested the fuel pressure? As part of this test, you should monitor fuel pressure after the pump is shut off to help identify injector or pressure regulator leakage.

You can also check the vacuum pilot hose on the pressure regulator for the presence of raw fuel. A ruptured regulator diaphragm can dump large amounts of raw fuel into the plenum.

Any indication of vacuum leaks? A quick test if idle vacuum might help identify this.

 

Okay, seems my old Yankeerose username has been reallocated or something as I sure aint the guy in that profile.....


Anyway, the car has a stock motor but the injectors were replaced in 2001.

I agree that the first point of call should be fuel pressure, and I will look into this.

The plugs were coated in fuel, but because of the massive amount of fuel contamination in the oil ...it is getting everywhere even now to the plugs. However the deposits were mostly fuel (burnt)..

I will update progress, this could be an expensive fix so I'll go one step at a time.

Many Thanks for the help

 

It doesn't have to be expensive it you're doing the work yourself. I'm not sure if there is an injector service on the island, but suspect there is someone that might have the equipment and ability. If not, you could ship your set back to the States for the service, but that may not be cost effective.

NOTE: A quick search shows at least two places in Sydney and one in Brisbane that perform off-vehicle injector cleaning and flow-matching - Allen, Collier's, G&A.

If you discover low pressure, the problem may only be a filter or regulator. New filters are inexpensive, and regulators repairs aren't too expensive. Finding a diaphragm kit might be the trick, however.

Perhaps you'll be lucky and find only vacuum leaks, but that wouldn't explain the raw fuel in the oil. That's more likely the FPR or injector(s).

 

No probems, and thankyou for your help..

Between the workshop manual and an ALDL cable , and a knowledgable little club www.camaro-firebird.org we can get around most problems....

We have excellent part supplies as well, but just sometimes a problem arises where you want to check with US enthuiasts to save the local mechanics stitching us up.....We would love to have some posters like yourself visit our boards from time to time just to offer that little bit extra to the hobby in Australia...

I've organised a fuel pressure test and will advise of the out come...

MANY THANKS!!