Hi Guys!

I have a 1997 Z28 with 82K miles on the clock! The Car Sputters from idle to about 1500 Rpms!

Here is a list of the Parts Replaced:

Optispark, Plugs and Wires, EGR Valve, IAT sensor, Map Sensor, New Fuel Pump and Fuel Filter, Cleaned Throttle Body and Replaced top gasket in Throttle Body.

All parts AC Delco!

Here is a list of what show up on scanner at Idling!

Fuel Cell 16

Long Term Fuel Left 133
Long Term Fuel Right 131
Map Sensor 27.28 HG
IAC Counts 11
Engine Coolant Temp 175 Degrees
Short Term Fuel Left 127Short Term Fuel Right 126
Knock was 15 then moved to 26
Knock Retard was 0 Degrees
IAT Temp 123 Degrees
Mass Air Flow 6GR
Map Sensor Volts 1.14 Volts
O2 Sensors were switching back and fourth from 89 to 900 milivolts, however, the right side was not going up to 700-900 milivolts as much as the Left side did.

Spark Advance at Idle was 26-28 DegreesThrottle Position Sensor Volts .65 and Throttle open %=0

Thanks Guys! Sorry for it being so long but I have been tracking this problem for over a year now!

Any Help Greatly appreciated! Lee!

 

you check the intake boots after the MAf for leaks? sounds like an air / vacumm leak to me.

 

Anyone else want to give input?

 

Have you cleaned your IAC?

 

Yep! I did and replaced the Gaskets. Keep the suggestions rolling.

Thanks Lee!

 

sounds like an EGR problem. Now since you replaced your EGR valve, I have heard of cases where the manifold hole is gunked up too and causes problems. Probably wouldn't hurt to poke around back there with a bent screwdriver or something.

 

IAC counts are kinda low. Might mean you are picking up air from somewhere else, like a vacuum leak. Just for grins, remove the hose going to the HVAC system and plug the manifold side. See if your IAC counts change. If that does nothing, check your other vacuum hoses.

 

New AC Delco fuel pump installed 1 month ago and new fuel filter!What do you guys think the chances of either a fuel injectors stopping up or an air leak in the intake would be.

My car doesn't use any oil between changes.

It does take about 3 or 4 whirls of the starter to start of the morning or if it has sat all day.

No Black smoke though when I start it. I checked fuel pressure regulator for leaking. It didn't leak when I removed the vacuum line. Could it be bad and cause this to happen anyway?

Thanks Lee!

 

anyone else have any ideas

 

Just for the heck of it, did you try checking the pcm harness that goes to the opti?

 

Thats a good idea I'll check to see if it helps! I'll let everyone know what happens!

I sure would love to fix this problem. The dealer told me I should just live with it that they have seen lots of these cars do it.

Thanks Lee!

 

Check your fuel pressure. While idleing try unhooking VAC line from FPR - that will give you better understanding that FPR works.

 

I am trying to diagnose this problem on my own car, though my problem doesn't sound as bad as yours yet. It may be caused by the same thing and only the level of degredation of the part(s) responsible is differentiating the severity of our issues.
That said, I have done some fairly extensive datamaster logging on my car and found that I got some noticable surging during part throttle accel through the idle to 2000rpm range. Looking at the EGR DC readout, I noticed it's at 100% during this. Soon, I will temporarily disable EGR in the PCM to see if that helps my part throttle surging. I also have a WOT hesitation and surge in this rpm range (worse when hot), but I'm beginning to wonder if I am actually chasing two different problems in the same rpm range.

Have you considered replacing the coil and ICM?

I bought a gallon of a fuel additive called Fuel Power, by Lube Control, and I'll report results as I get through a few tanks with the additive. I am basically trying to eliminate causes. With the Fuel Power, if no change is felt after a few tanks, I can eliminate injector/intake/valve/combustion chamber deposits as the culprit. I am going to do the fuel filter this weekend but only as preventative maintenance (not chasing this problem).
Just search the board for "hesitation" and you'll VERY quickly learn that you are not alone. Over the past few years there have been countless threads trying to chase this problem, and similar problems. It's a shame really. I hear about this type of problem very infrequently on the Impala SS forum. I suspect M6 cars are more sensitive to the problem, where the torque converter in the A4 car would tend to cover up and mask unsmooth power delivery, especially off idle, where it's slipping quite a bit.