[Bob Dillon]

Originally Posted by Hillard

Old thread, new problem. Car was running rough and even died a few times. Put a scanner on it and it said Mass Air Flow Sensor. So I replaced it. Now it runs down the road ok, but idles rough. Doesn't die but will act like it's going to and the idle will fluctuate from 600 to 1100. Scanner just says idle rpm unusually high detected. But doesn't say why. Any ideas?

Remove and clean the throttle body thoroughly, paying special attention to the throttle blade. And make sure you have no leaks in vacuum hoses.

[mgarblik]

If your model has the PVC valve in a pocket in the plastic intake manifold? If it does, carefully turn the plastic cap that holds it in and remove the PCV valve and check the O-ring that goes around it. Those were problem areas for vacuum leaks. Also if this model has the plastic intake manifold they were famous for a melt through where the EGR tube sends the exhaust gas back into the intake near the throttle body. Famous for water leaks, vacuum leaks and other chaos where the pipe attaches. Dorman sells an improved replacement intake. Finally, the EGR valve could be sticking slightly open, another common problem. Check the pintle position with a scan tool. Should be 0 +_ 2% at idle. Desired vs actual position should track +- 2%. It's always possible the "new MAF" sensor is defective. Should pass 6-8 grams per sec at a hot curb idle. Hope this helps.

[Hillard]

Thanks guys. Gives me at least some direction. I would love to just stick a Q-jet on this and be done. lol

[Bob Dillon]

"Also if this model has the plastic intake manifold they were famous for a melt through where the EGR tube sends the exhaust gas back into the intake near the throttle body."


If this were so, it would be eating coolant like crazy.


There are aftermarket intake manifolds where they are "sleeved" with metal to prevent this. They run around $125, and it's an easy swap, too.

[jerry455]

Check and see where the IAC, Idle Air Control number is at idle. This is the bypass when the throttle is closed. It should be around 10. If it is at zero, then you have a vacuum leak. At 0 it is all the way closed and if it is still running, then air is getting in somewhere else.

[Hillard]

Originally Posted by mgarblik

If your model has the PVC valve in a pocket in the plastic intake manifold? If it does, carefully turn the plastic cap that holds it in and remove the PCV valve and check the O-ring that goes around it. Those were problem areas for vacuum leaks. Also if this model has the plastic intake manifold they were famous for a melt through where the EGR tube sends the exhaust gas back into the intake near the throttle body. Famous for water leaks, vacuum leaks and other chaos where the pipe attaches. Dorman sells an improved replacement intake. Finally, the EGR valve could be sticking slightly open, another common problem. Check the pintle position with a scan tool. Should be 0 +_ 2% at idle. Desired vs actual position should track +- 2%. It's always possible the "new MAF" sensor is defective. Should pass 6-8 grams per sec at a hot curb idle. Hope this helps.

Mike, you were right. I just went and purchased another MAF sensor and now it's running fine. It's sad that you can't always trust new parts. Thanks.

[mgarblik]

Glad you have it running good again! Couple little things I always try to remember from my mentor, James Halderman. You may remember him from Sinclair College and he is the author of dozens of automotive textbooks. 1. "New doesn't mean good", (just means it is clean and in a box) 2. "When in doubt, take it out". This means the computer has a back-up system for most of the sensors. If you think a sensor is defective, un-plug it and try to drive the car. If it runs better without that sensor, the problem is the sensor. It's a good test for O2 sensors, MAP, TPS, IAT, ECT.

[Mr Anonymous]

The Dorman replacement intakes were pretty good for a long time, then went to hell. The last one I did (for my 99 bonneville), was so malformed inside that I used a heat gun and wood scraps to "re-form" the damn thing to where it would fit. It was a train wreck. I was just gonna order another and then I heard from someone that they were ALL bad.

[Bob Dillon]

Originally Posted by Mr Anonymous

The Dorman replacement intakes were pretty good for a long time, then went to hell. The last one I did (for my 99 bonneville), was so malformed inside that I used a heat gun and wood scraps to "re-form" the damn thing to where it would fit. It was a train wreck. I was just gonna order another and then I heard from someone that they were ALL bad.

I made my own. Took another dead manifold, drilled the hole out to 7/8" and sleeved it with 7/8" stainless steel tubing and fixed it in place with JB weld. Held for 90K and was still OK when I sold the car.