Car idle and acceleration hesitating

[m3f_MOTRSPRT]

About a month ago my 1998 started running terrible. The idle has a misfire and acceleration is hesitating until after 3K rpm's. One caveat to all this is if I stomp on the gas it really stumbles. Probably due to the richer ecu not currently feeding my supercharger (I removed it for refreshing). During Gradual acceleration this symptom does not appear.

Anyway, I've changed the MAF, plugs, valve cover gasket, checked all possible vacuum lines, unplugged MAF and running like this now, unplugged O2 sensors to no change, and tested the coils (.4-.6 ohms). What I haven't done a secondary coil test, which I don't know how to do.

But is it typical to be able to unplug the MAF, and O2 sensors without the car even hiccuping? This doesn't seem right.

Any help is appreciated.


2007 M6

2003 M3

1998 M3

2011 Ducati 1198

[m3f_Pierre i am]

Clean the ICV

[m3f_MOTRSPRT]

Clean the ICV

That was gonna be my next step, and something I gotta do when the supercharger is off the car...LOL! It makes access to that part of the motor so much easier.

I'll post updates as this goes along. Good or bad.


2007 M6

2003 M3

1998 M3

2011 Ducati 1198

[m3f_matty.]

sounds like a vacuum leak, bad maf, or...

[m3f_MOTRSPRT]

sounds like a vacuum leak, bad maf, or...

Right? But I cannot find any vacuum leaks. And I've replaced the MAF already to no change.


2007 M6

2003 M3

1998 M3

2011 Ducati 1198

[m3f_MOTRSPRT]

I just thought of this today. But my e46 m3 sits right next to my e36 m3 in my garage. It has 6 perfectly good ignition coils I can replace on my e36. Not sure why I didn't think of this before. However, both were out tonight preventing me from swapping the coils to troubleshoot...


2007 M6

2003 M3

1998 M3

2011 Ducati 1198

[m3f_Pierre i am]

Start with the easiest fix and move on up. It sounds to me like it's probably coils or ICV. Keep us posted though, also do you have better photos? Your ride is

[m3f_Purple99M3]

Do you have any CELs? Do you see any come and go away?


I had a similar issue with mine.. Turned out my knock sensors were shattered (literally)... The CEL would come and go.. Hesitation was there and it was slower to accel but then boom I had power. Something to check.

[m3f_Eclipsetrbo420A]

Smoke test the intake / vacuum tract

[m3f_MOTRSPRT]

Smoke test the intake / vacuum tract

I don't know how to do this?


2007 M6

2003 M3

1998 M3

2011 Ducati 1198

[m3f_andreialta]

cam sensor also might play

[m3f_MOTRSPRT]

Start with the easiest fix and move on up. It sounds to me like it's probably coils or ICV. Keep us posted though, also do you have better photos? Your ride is

Just cleaned the ICV. At first I couldn't hear the valve moving around and figured it was pretty dirty. Got it cleaned up and that valve was moving very freely. Crossed my fingers and started the car. There is absolutely no change.

I want to explain a little better about the idle and blipping the throttle. When the MAF is plugged in it doesn't idle very well. It has a miss to it. When I press on the gas and it goes to 1800 rpm it's very jerky. If I start blipping the throttle aggressively it dies. If I keep pressing on the gas past 2K rpm then the rpm's will climb. But it's not a pure clean sound.

Now when I unplug the MAF the idle is more stable. I can press on the gas to 2K rpm without any stumbling or jerkyness to it. When I blip the throttle aggressively it doesn't stumble or die. Driving is the same between the 2 scenarios where it's worse to drive with the MAF plugged in than without.




2007 M6

2003 M3

1998 M3

2011 Ducati 1198

[m3f_Pierre i am]

I would just get a new MAF at this point. It seems like it's your culprit.


I'm always been a huge fan of Dakar and your sedan is beautiful.

[m3f_MOTRSPRT]

I've already replaced it though.


But thanks for the props on my car. Second owner from 2004 and 38000 miles. Now it has 180000 miles. Never had a car payment on it, so never had a reason to sell it .


2007 M6

2003 M3

1998 M3

2011 Ducati 1198

[m3f_MOTRSPRT]

This ICV wasn't really dirty but it's really clean now...


2007 M6

2003 M3

1998 M3

2011 Ducati 1198