Info:

2000 Max GLE
3.0L
218,XXX miles

I've searched.....and searched...and I have ideas on what to tackle, but my question here is the order you would suggest.

Background: Car hasn't been idling well lately. Sometimes ok, usually after warm, sometimes not good even if it was warm. The RPM's wouldn't change, it'd sit at 750 all day, but it would idle rough. So, I decided to start tackling problems one by one. I started by cleaning the MAF...that changed nothing. I proceeded on to cleaning the TB, that changed nothing. I next proceeded to clean the EGR tube...thinking maybe it was clogged. The tube itself wasn't clogged at all at the bottom and probably around 1/4 clogged at the top....significantly less than I expected. Threw it all back together and things went down hill. She'll start, rev high, stumble, then die. Only way to keep her running is to stay on the gas, and then she definitely smells of gas. There is a hissing/sucking sound after I let off the gas. I can't assume this had anything to do with the cleaning of the EGR, maybe vacuum line? I was wanting to buy a code reader...this gave me an excuse....it comes back with no codes whatsoever.

Search: I knew going into my EGR tube cleaning that my ECU was probably fried...I hadn't gotten codes the whole time she idled like crap. My motor mounts went out long ago, and the IACV and TBS have not been replaced. I have both purchased and in the garage for install. Unplugging my motor mounts is the next order of business.

Recommendation on Procedure: Based off what I've read my thinking is to send the ECU to be repaired. While it's gone, unplug the motor mounts and replace the IACV & TPS, which I was planning to do before the EGR tube incident. I can't help but think maybe it's vacuum related, but I can't find anything. Anyway, I hate reading posts about how someone did a whole lot of crap to find out it was something else. I wanted to ask you all if you'd proceed any differently than I am.

Thanks in advance.

 

Try cleaning your IACV before doing anything else.

 

It's the IACV that will fry your ECU, not the EGR. Clean it, if that doesn't work, probably wouldn't hurt to replace it. It's a lot cheaper than a new ECU.

 

Ok, replaced the IACV with new (and TPS for good measure), and had cleaned the MAF well before all this happened, and still the same problem....maybe slightly less bad. I also took the ECU out to check for the dreaded burnt chip...but everything looks fine. I took a video, here's the link. First start is the car by itself (i might have given it a little gas at the start...can't remember, the second is the car with me keeping on the gas to keep it running. Any ideas? Bad MAF, vacuum leak???

http://www.youtube.com/watch?v=TcoNagg6_5E

 

maybe one of your vacuum hoses may be cracked because that vacuum suction i hear is rather loud and could be your issue. try getting a friend to help you keep it running while you pinpoint where that vacuum is coming from. good luck

 

Did you check fuel pressure? That would be my first place to look also just simply unplug the maf. Will put car on base a/f parameters and should idle out smooth if the maf is junk. When was the last time you replaced the maf

 

I've checked for a vacuum leak but can't find one. Might pick up a mechanics stethoscope tomorrow and see if that helps.

I unplugged the MAF before posted tonight and when I did that it wouldn't even start. MAF has never been replaced. Cleaned but not replaced

 

Could be a problem with the maf I heard they go bad after a time on our cars but what are you going to do with a stethascope that's just for noise...?

 

Better pinpoint the vacuum leak if there is one.

 

For anyone wondering and to end this thread, I had the car picked up and taken to a local mechanic. Diagnosis - Lower Intake Manifold gasket. $300 later she runs again.