I've got a problem with my LB9 that hopefully someone can help me out with. Last Friday on the last straight before I got home, I goosed it down the road. When my RPMs came down I immediately had a hesitation and sputter at low speeds and idle. The car died pulling into my driveway.

I had a suspicion about my EGR valve anyway, so I replaced it. it didn't help. The car absolutely will not idle or run below full throttle when its cold. In the afternoons it is hit or miss, it may start crappy and after a rev it wants to idle and run normal.

I am currently at work, I tried checking for a code this morning but apparently my bulb for my service engine light is out.

Can anyone help?

 

I'm trying to think of what might have been affected by the full throttle acceleration event. You may have sucked a gasket somewhere in the induction system. You may have damaged the distributor cap and rotor somehow, or perhaps the pole piece and timing core in the distributor may have taken a dump. There is a method for checking codes without the check engine light. Terminal D of the ALDL is the check engine light driver circuit and by holding a 12V test light to this terminal while performing the code check, the test light will flash codes.

I think I would start my diagnosis by using brake cleaner to spray around the intake, looking for a response. This will help you find a sucked gasket.

 

Thank you, I will start checking it out if I can make it home this afternoon. earlier this week, when the engine gets warm or in the afternoon when the temperature is higher, the car runs fine. based on that, do you still think distributor is suspect?

I just got off work and attempting to get it to idle, no dice.

EDIT: Fighting with the crappy idle for about 5 minutes, I turned the ignition off and attempted to start it again. Its idling fine now. I am thoroughly confused.

 

Maybe you have an issue with the coolant temp sensor. It might think its alot warmer outside than it is. Or the IAC valve is broken.

 

Worth checking. I replaced my IAC in February, but who knows. I'm on the way to the auto parts store to pick a bulb up for my check engine light right now.

 

I didn't even think of the ECT sensor. Maybe look for a poor connection at the sensor. That would explain it running fine sometimes. I got caught up in thinking of a connection between a hard pull and the sudden onset of the problem. You can also use a DVOM on the ohms scale to test the ECT sensor. It should read about 3,400 ohms at 70 degrees(full cold) and about 180 ohms at 200 degrees.

 

The only code I'm showing is 34 which could be a slew of things.

 

Code 34 is MAF sensor voltage low. It can't really be a slew of things. It simply means that the MAF is reading low. You need to complete the trouble tree for this code. This basically means verifying power and ground to the sensor then monitoring sensor signal voltage to look for it being lower that it should be. The one thing that does complicate things is the burn off system, which powers up on key off to burn any dirt build up off of the sensor wire. Find the trouble tree by searching here on TGO.

 

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Thanks, I do have to troubleshoot and I appreciate the input.

I've confirmed this at a couple of different times since my last post, but when I shut the ignition off and then install a jumper in my ALDL, then try to start the car, it fires and idles. What in the world could this be?

 

I used the TPI code troubleshooting manual and for a code 34, it tells you to disconnect the MAF. If doing so causes the engine idling problem to go away, it says to replace the MAF. Disconnecting the sensor appears, at least for this start-up, to have fixed the issue. We'll see tomorrow morning.

 

That's funny. I just told another member to use that test. I didn't have time to look at the trouble tree yesterday myself. That's an old test used on almost every MAF vehicle. The only thing is, that yours does have a MAF relay and a burnoff relay. If either relay or the circuits have issues, it can cause that code and your drivability problem to return. Even with a new MAF sensor. And these MAFs aren't cheap, so verifying that all the circuits and relays are okay is valuable.

 

I just wanted to add what is hopefully some closure to this thread I started. I tried swapping both of my MAF relays with no improvement in the way the car was running. Like ASE doc said, there still could have possibly been a problem with wiring. A few months ago when I first bought this particular third gen, I had a code 33 which I believe is a high voltage at the MAF as well. I figured I'd just try to replace the MAF sensor and it is running extremely well. I'm going to clear my codes and put some miles on it this weekend, but all seems well.