97venom

I have not had many posts here, but I do visit from time to time. I have really hit a brick wall here and am in need of some help. OK, first general info on my car. It's a 97 Z28 LE Anniversary T56. Mostly stock except for k&n cold air, catco highflow cats, flowmaster catback, ngk iridium plugs, accell 9000 wires centerforce dual friction clutch and b&m ripper shifter. It has about 100,000 miles but does not use a drop of oil between changes (5,000 miles since I only use Mobil One full synthetic).

Here is the problem, I got home the other day and right when I pulled into the garage, it started to run really rough and the ses light came on, then it died. I pulled the codes and got p0171 and p0174 (p0174 was listed twice) Lean on both banks. I cleared the codes. Since it died it has not started. My buddy Dave has a 97 z with automatic so he came over to help. here is what we have done so far with absolutly no results. checked fuel pressure, goes up to 45 and over about 15 to 20 mins goes down to about 30, off of Dave's car we swapped out the MAF, fuel pressure regulator, and fuel rail. We are getting spark at the coil and the #1 cylinder. The opti is a Delco only about 7 months old, same age on the plugs and wires. We thought about swapping pcms but his is an auto and mine a 6 speed and I was told the nuetral safety was a different pin on the two.

Anybody know how to check the PCM without the car running?? Or any other ideas???

Sorry this is such a long post and I appreciate any help anyone can give.

Injuneer

What happens to the fuel pressure when you try and start it?

Did you check for a tear in the inlet elbow?

Check the fuses for the injectors?

Check for +12V at the pink wire for each injector harness plug?

Check for 12V between the pink wire and the black/white wire in the MAF harness connector.

Have you scanned it since you found the first tow codes?

97venom

First off, Thank You very much for the reply!!

1 fuel pressure jumps to about 50 when I turn it over

2 no tears in the elbow (I just double checked it) we have been looking for a vacume leak and can find none anywhere

3 injector fuses good

4 voltage at +12v at each injector with key in run position

5 volts at maf connector 5.08, My haynes said it should be at 5.0?? Is that correct? We have also tried to start with known working maf and the maf unplugged

6 i cleared codes with the scanner and have had the battery disconnected several times when doing things and if I scan for codes now, it gives me "no codes"

I am starting to think PCM or something spark related. I am getting spark, but is it at the right time? I don't know, I am just lost right now.

Any other suggestions??

97venom

One other thing, it does spit sputter and pop a little when you release the ignition key from the start position.

97venom

Anyone???? I guess tomorrow I am going to take everything down to the opti and look there. It sure does act like it did when my waterpump filled it before. the codes are what has me stumped. I wouldn't think that a bad opt would throw lean codes, or am I wrong?

Injuneer

Misfires cause lean codes.

You should have a 12V power supply to the pink wire on the MAF connector. You should have a 5V reference signal on the yellow signal wire, without the engine running. When the engine runs, the voltage on the yellow wire will be pulled down to ~4.3V. The variable frequency signal from the MAF sensor "rides" on that DC voltage, so the voltage will vary. The difference between 5.00 and 5.08V at the yellow wire on the MAF connector is insignificant. But I suggested you check the pink wire.

97venom

OK, I finally got some time to work on it some more. Yellow wire is 5.08 v and the pink wire is 11.46v. Is that 11.46 suffecent?

97WS6

It could be a bad PCM.
It could be the fuel pump though from your post it is probably ok.
It could be bad fuel, or something, like water, in the system.
It could be a faulty ignition coil or the wiring to it.
It could be the OptiSpark.
It could be incorrect valve timing caused by a slipped timing chain.
I would start with things I could check and eliminate, after that start with the cheapest component, the coil, then the opti and PCM, If you're still not going anywhere you'll need to check the valve timing.
Good Luck.
What a bummer, summer just starts and your ride won't.
97WS6

97venom

I am getting what seems to good spark from the coil to the opti (put a timing light on the coil wire and it lit up strong). I then put it on the #1 plug wire and got just a flicker when it was turned over. Lookin like the opti huh? If I had bad gas or water in the fuel, wouldn't starting fluid sprayed in the intake have gotten it to start??

97WS6

The weak spark at the output of the Opti certainly makes it suspect.
I had that problem once and it turned out to be water had gotten into the Opti somehow while I was cleaning the motor. Also, I know you didn't throw any codes for the CKP sensor(PO335,PO336, P1336) but you may want to check the connector while your getting into the Opti.
Are we having fun yet?

97venom

All part of it I guess. As long as I don't have to replace the plugs and wires again, I'll be OK.

94SLUG

I have the same problem!! I have tried just about everything as well. I have new AC- Delco opti, new plugs, wires, ICM, coil, put another ecm just to see, same with MAF, and still no love. I have never been so stuck since I have owned this car. It ran great died as I was driving, does the same thing as yours now, try to start it wants to and no...............

97venom

Hey 94Slug, follow this link http://www.mainstreamtopics.com/foru...p?showtopic=78

I was doing some searches here and was reading one post that had this link in it. I followed the instructions and it took me right to the problem...... bad rotor putting in new cap and rotor tomorrow or the next day. I will post the results. Seriously, this is a good walkthrough. Hopefully it will help you. Let me know if it does I am curious as to your problem.

Thanks for the help everyone, I will post when it is done

97venom

Well, cap and rotor did not do it, neither did a brand new opti. I really hate to say this, but I guess it is going in the...........gulp...............shop. I have never not been able to fix my own car, ever. This really sux. I will post the results when I find out what the issue is. Thankx for everyones input. I appreciate it.

97venom

Well she's fixed!!!

Much to my embarrassment, it was the coil. I ohmed it out and it checked out fine and was throwing a decent blue spark, but the shop owner said it wasn't throwing far enough.

It figures, I finally get it up and running after 4th of July weekend(I live in Panama City Beach Fl). I am just glad she's goin again!!

Thanks for everyones help on this.