1999 Q45 Intermittet Hesitation MAF, BAD ECU/PCM?

[allerickb]

Hello, I'm new two this forum, and I'm sure somewhere buried this topic has been covered, but I can't find it.

My Q has terrible intermittent hesitation when taken off between idle and about 2800 rpm. From there it takes off. I recently replaced the MAF with a new (but generic) MAF, but it didn't seem to solve the problem. I know that these symptoms can be caused by a bad MAF, but at this point I'm beating my head against the dash trying to figure this out. Should I have spend the money for a genuine MAF, or could it possibly be a bad PCM/ECU. Like I mentioned, the its only in the rpm range from take off to 2800, which leads me to believe that it's not a mechanical problem, but a sensor/communication problem between motor and PCM/ECU. I have tried unplugging the MAF, which leads to HORRIBLE running conditions of the motor, but I don't understand why I'm having so much trouble under 2800 rpms, which in my mind, rules out the plugs, injectors, and coil packs. Could it be the PCM? Any help or advice would be greatly appreciated!

[Q451990]

If I had to guess, I would say MAF. ECU failures are extremely rare. Have you looked for stored codes?

Check out the FSM (Factory service manual) here for the procedure. http://www.nicoclub.com/FSM/

Welcome to NICO!

Heath

[JOHNQ]

dont rule out coilpacks!

[allerickb]

So what plugs do you guys run in your Q's? Should I go back with the OEM recommended NGK PFG5G11? I'm going to start with the plugs and If that isn't the issues, I'll start looking at the coil packs.

JohnQ, were you having an issues similar to this?

[NightRiderQ45]

That is a start. You should run this plug in our car. I hope you are not running any "american" plugs in your car....autolite, bosh. From what I've read before, I thought the coil packs (all 8) would need to be changed if you are having issues that you stated.

[allerickb]

Honestly I don't remember, we changed the plugs about 20K miles ago, but I don't think we spending the money for these OEM plugs. I'd much rather it be an $80 set of plugs than possibly $600+ in coil packs! My Q has about the same amount of miles as yours NightRider. It had about 76K on it when we bought it an it has been a great car since then needing nothing but a few sets of tires over the years, but then this issues started creeping up on us. I'm going to also check the EGR valve/solenoid system to see if there are any problems there too. But this has been very difficult for us because the ECU isn't giving us any trouble codes whatsoever. The Service Engine light had been coming on for O2 sensors that needed replacing, but its all been fixed, but the stumbling at take off is still there.

Do you have any experience with one of those OBD-II coder readers? I'm think of investing in one. I've seen some of the CONSULT readers on ebay, but from what I heard they might not be worth the trouble.

[loystock]

Non-OEM plugs are known to cause performance issues and even engine damage on Q45b engines. Avoid Bosch plugs at all cost.

An OBD scanner is one of the best investments you can make. Aside from giving you fault codes, it will also tell you whether your car is ready for SMOG check (System Readiness Test status). Nowadays, you can get a good one for @ $60. Some advanced scanners can give you real-time engine parameters. Of course you can always go to AutyoZone for a free scan.

Problem with the Knock Sensor (KS) are more pronounced in the lower RPM range, as in your case. A failing KS will store a code but will not turn on the CEL. Check the resistance, must be @ 550K-ohm, KS pin to negative battery terminal. If I remember correctly, the Y33 KS sensor has a 2-pin connector only one of which is used, with the engine used as ground. A KS sensor may pass the resistance check but it may have cracks on the housing which may adversely affect the signal to the ECM..

Paranoidjack has a very good write up on intake plenum removal to access the KS.

zer...s-now

[Mopar]

I have a 98 Q and I would say your problem is 98 percent coil packs. I know you don't want to hear this, but I had the same problem, changed my plugs (use ONLY NKG nothing else!) and the coil packs and problem went away.

[bullittandy]

Coils.

I know-trust me.

[paranoidjack]

Coils, for sure.

[allerickb]

I appreciate all the help guys! I managed over yesterday and today to get back in there and replace those plugs with the OEM NGK's. Come to find out that Bosch Platinum 2+ where put in the car, I guess that was my first mistake. Also replaced the radiator which was progressively failing. Spend the majority of my time replacing the valve cover gasket on the driver side. It's a pain in the a**, but needed to be done, both sides were blowing by oil, but the driver side was the worse. I hope to get the other side in the near future.

Great news though! The stumbling is gone!! I'm keeping my fingers crossed though, I really haven't had much of chance to get her back in the road and open her up yet, but so far so good!

I read through the FSM and did the ohm testing procedure on all the coil packs. They were all reading within 150 ohms of each other, but there nothing definitive that determines a bad coil besides infinite resistance. All 8 of mine were between 1450-1600 ohms, however I don't know what new coils would spec out against them.

Do have a new issue though, My Slip and TCS lights are coming on now. I was in a hurry to get into work and haven't had a chance to diagnosis it, but I guess is that I left something unplugged after working on that valve cover gasket, everything on that sided (literally EVERYTHING) has to be unplugged to get it off............

Thanks for your help.

[bullittandy]

Coils, trust me. start saving your money for new ones.

The slip/TCS light is the ABS relay but I don't know where it is on a 99, on a 97 its mounted to the ABS module.