stalling problems

[rdybala]

My 94 Q began stumbling at 70 - 80 mph approx. 2 months ago [maybe once an hour]. That progressed to stumbe close to four times an hour. Also, the car presently starts well and drives well for the first one eight of a mile, then it lacks power and stalls almost as soon as restarted, put into drive and the gas pedal is stepped on. I am not getting any codes even though I saw the check engine light flash momentarily. So I pulled out the ECU to perform test mode 11 diagnostics and discovered the red led light was on even though I did not have the key in the ignition. When I put the key in and an turned it to the on position and run position no check engine light came on the dash. The red led stayed on but did not flash. However when I did the level two the led went off and stayed off showing no codes. I wonder if I have an ECU problem and/or fuel injector problem. I think the Q is running decent in open loop but acts up big time in closed. Also I put a fuel pressure gauge in the fuel line right after the filter and was surprised to see zero fuel pressure when I turned the key to the on position even though I could hear the fuel pump running. As soon as as I engaged the starter, the fuel pressure gauge showed normal pressure both at idle and accelerating. Is this normal for a Q? Thanks for any advice you may offer.Rich

[goody90q45]

You have plenty of easy things that can be done to get to the bottom of your engine stumbling issues so I guess checking ECU codes is as good a place as any to start.

Remember that not all ECU codes activate the CEL (i.e. knock sensors) so you need to follow the specific sequence to pull the codes from the ECU. By your description you may have erased the codes and not known it or never activated it in the first place.

Here's what you need to do:

* Since the codes may be gone you need to drive around for about 30 minutes and recreate the conditions where you think you are having issues.* With your key off, remove the ECU from behind the right footwell and plug it back in letting it lay on the floormat.* You already know where the LED is so the screw you need to turn is adjacent to it. It will be the one with the instructions around it.* Turn the ignition to the start position. The LED should be solid red.* Turn the screw completely clockwise (CW), wait at least 2 seconds, and turn it completely counterclockwise (CCW).* Read the codes. Long flashes are the tens digit and short flashes are the ones digits. The codes will repeat until you do the next step.* To clear all codes repeat: Turn the screw completely clockwise (CW), wait at least 2 seconds, and turn it completely counterclockwise (CCW). You will get a solid light again.

* If you do the above step (CW / CCW) a 3rd time you will get code 55 (no errors). * And if you do it a 4th time you'll be back to the solid red light.

Don't bother putting the ECU away behind the footwell as you may be needing it soon for other troubleshooting. Let us know what codes you get. Good luck.

[rdybala]

Fortunately, I did not erase the code. Your instructions are very precise. Even though I followed the service manual instructions yesterday, I could not retrive any codes or get the LED to saty on. Today the gods smiled and the #12 code was displayed. According to the manual somethings wrong with the mass air flow sensor. Do you have any suggestions that would help me with this culprit?

[goody90q45]

Try cleaning it first following these instructions from Q45.org.:

http://www.q45.org/maf.html

At the same time clean the connector. If it shows any corrosion then all the rest of your electrical connections are also suspect and should be inspected and cleaned as needed.

If the MAF cleaning doesn't work then you have options:* Swap in a known good MAF from another Q (easiest option)* Electrically troubleshoot following the FSM and NICO posts (PITA)* Buy a used MAF (Risky and cheap)* Buy a new MAF (expensive, $300+)

Now that you've read the codes and left it laying on the floormat, reset it and drive around for a while to verify that is the only code coming up. Good luck.

[96Qowner]

Your symptoms match a misbehaving MAF. You can try cleaning it. There are instructions at Q45.org:

http://www.q45.org/maf.html

If the symptoms reappear, you should start looking for a replacement. This is a common issue for that series Q45.

[rdybala]

Good advice can be hard to get, but not at the Nico forum. I plan to start the clean up Wednesday. Hope that is all it needs. But whatever it takes I will do since I really enjoy the Q. Thanks again Mike and 96 Owner.

[96Qowner]

Here's my history on a failing MAF and its symptoms:

zerothread?id=81759

[rdybala]

Thanks for sharing your miseries. It can be very aggravating and humbling when you experience intermitent prblems like we both have. It is great to go to school on the Nice forum.

[Q45tech]

Also consider that FPCU may have heat intermintent in one of the 3 circuits that provide different voltages [rpms] to fuel pump.

If a new MAF doesn't fix it, a NEW [not used] FPCU might -- sometimes some of each............plus intermittent KS [test ok at start up but becomes intermittent as the heads heats up----------won't show a code if it test ok at start up!

When things get over 100-120k 7-10 years you just have to expect to renew them for another 7 years! These <$2000 worth of components are rarely changed in a used car for sale why we point out the need for rehabilitation just after a used purchase.

[rdybala]

I cleand the sensor, but I could not get all the black film off the outside of the screen. The inside of the screen came out nice and shiney. Is the screen an important element of the MAF or just to protect the sensor? If it is important, could I use a soft bristle toothbrush on the screen since sprayng alone is not effective?

[goody90q45]

It's the wire elements inside the MAF tube that are important to keep clean. It sounds like you've cleaned up any loose debris / oil that may have been on the screen so that's good. Don't forget to clean up any corrosion from the connector and liberally coat male and female ends with dielectric grease. Let us know if you see any improvement.

[rdybala]

Well I cleaned the Maf sensor and connectors. Reinstalled it and saw no improvement at all. In fact, now the car stalls right after I start it and put the car in gear with my foot on the brake. I checked for codes and found #12 again. It appears the Maf is virtually dead. Mike and 96 owner, I plan to order a new Maf tomorrow. Do you agree?

[rdybala]

I repaced the MAP sensor today and like magic the Q is running very well. Thanks for your interest and help. It ames working on a Q feasible.