mrgraphic

Hey Guys,
I've been having some various idle problems over the past month or so. Have been reading this site about possible causes including vacuum leaks, dirty injectors, bad cats, MAF sensors, plugs, coils, wires, EGR valve, air cleaner seating, CPS, bad gas, and probably a few more that I can't remember right now. My car is a late 2005 with 125k miles. In my case, the car always starts fine and has not stalled yet during any rough idle incidents. Cold starts are fine, idle smooth. When the engine warms up, if I stop for a light the engine seems to idle too low, so I will usually put it in neutral to get the idle up where it smooths out somewhat. The engine seems to run fine while the car is moving at speed. If I stop and shut the car off for a while and restart while the engine is still fairly warm, sometimes the idle seems to hunt and jumps around, other times it feels and sounds like the engine is running on about 6 of the cylinders. Today after driving the car for a while, I popped the air cleaner off and tried the MAF connector disconnect test. When I disconnected the plug, the idle stuttered for a second, then seemed to increase in rpm a bit and seemed fairly steady. I re-connected the plug and the idle dropped again to where it was, and the idle was ok but not super smooth. I have done a few of the easier things myself over the past couple of weeks: new MAF sensor assembly and CPS (both aftermarket) new air filters, checked for vacuum leaks, ran a tankful with Techron, replaced all rubber gaskets for MAF assembly, lower elbow and air cleaner to MAF seal, replaced all spark plugs, checked for loose intake manifold bolts. I brought the car to a MB repair shop, he found a vacuum hose that had come off at the air injector, cleared all codes, checked battery. The car seemed to run a little better until the next day when the idle acted up again. I have not returned to the shop yet. I have heard after the fact that aftermarket MAF's can be junk, I'm not sure what to make of the above mentioned MAF disconnect test. I love the car but driving every day to work with a knot in my stomach, worried about getting stuck somewhere is no way to live. I have owned all of the German car makes and there's nothing like them, but I can't keep up with the B.S. and never ending maintenance, not to mention the gas mileage...might have to look into leasing a KIA, I'm getting too old for this. OK, there, I have vented. Any input into resolving this idle problem is greatly appreciated.

mis3

Your symptoms are similar to mine a few years ago and the dealership replaced the MAF sensor under warranty.

I read from this forum that for MAF, it is better to buy MB. Outcomes of some after-market MAF can be unpredictable.

Rudeney

What brand is the MAF? If it's not genuine MBZ, Bosch or Siemens, then that would be my first suspicion, especially since unplugging the old MAF helped things. Autohausaz sells the Bosch for about $152.

mrgraphic

Today I drove the car, parked it at the store for 25 mins and when I started it up the idle shot up to about 1500rpm then down to almost stalling, then back up and so forth. I shut it down, waited a few seconds then restarted...idle started to normalize. Later, came home, let it sit for a few mins, started it up and it had a semi-rough idle. so I popped the air cleaner and pulled the MAF connector off, and the engine stalled. Tried the same 2 more times, got 2 more stalls. Started the engine again, revved it a few times, pulled the connector, idle got pretty smooth. Another thing I noticed lately, perhaps directly related or not, the trans doesn't shift/downshift at the right times based on throttle position...seems to upshift too soon when starting off from a stop. I may be heading to the dealer for a new MAF assy tomorrow.

turbocobra10

Did you get your rough idle situation sorted out? I'm having the same issue down to a T except my car will die if i come to an abrupt stop. No CEL, rough idle, vehicle does not shift correctly. I believe that's why it will stall when coming to an abrupt stop. Its almost like the car should down shift 10 MPH sooner bc the car gets so low in it that RPM stalls.

I have cleaned maf, fuel cleaner, etc... I have a new maf on its way too. Please let me know if you were able to sort out your issue and what you did to do so.

Thanks in advance!