Can the IAC cause a surge?

[mrjones]

My MM has had for some time, and continues to get worse, an rpm surge just above idle when cold. When the car is first started after setting some time and I drive off at very light throttle settings, the engine surges slightly. RPM will rise and fall slightly, but it's noticeable and getting more so.

Could the IAC be causing this? I thought that it worked only at idle and not above, but I'm not sure about that.

I have a Lidio tune, but the problem is not related to the tune. I've removed the tune and continue to have the same problem.

Has anyone else seen this problem or have any ideas about it?

[Got_1]

i'm thinking TPS...

[Blackened300a]

Is your intake tube tight? I had a similar problem when mine loosened up.

[Marauderjack]

Off idle the IAC does not operate and it could be the TPS but if it goes away after the engine heats up I doubt it!!??:shake:

Mine has done it forever and it seems to be in sync with the fuel pressure which runs up and down a few PSI......but I have a "non-OEM" fuel pump and Supercharger so I don't have any experience with the OEM fuel pump/pressure relationship!!:cool:

Does it go away after warm up?? :confused:

[bob6364]

Sounds to me like unmetered air getting in or dirty maf ,clean the maf with maf cleaner from your local flaps and reassemble.
http://t3.gstatic.com/images?q=tbn:Vcyf0JUS_FCiXM:ht tp://www.m5board.com/vbulletin/attachments/m5-e39-e60-tips-tricks/54440d1198700104-tech-clean-your-maf-dont-replace-maf-cleaner.jpg

[CBT]

My MM has had for some time, and continues to get worse, an rpm surge just above idle when cold. When the car is first started after setting some time and I drive off at very light throttle settings, the engine surges slightly. RPM will rise and fall slightly, but it's noticeable and getting more so.

Could the IAC be causing this? I thought that it worked only at idle and not above, but I'm not sure about that.

I have a Lidio tune, but the problem is not related to the tune. I've removed the tune and continue to have the same problem.

Has anyone else seen this problem or have any ideas about it?

Happened to me, brother. I changed plugs, no help. Changed coils, no help. A week later I got NEW new plugs, a bottle of Sea Foam, about 8 cans of throttle bottle and MAF cleaner, and took apart everything from the throttle body (including the throttle body) to the air filter and sprayed the bejesus out of everything, let it all dry, put it all back together, car ran great.

[musclemerc]

Definately MAF related.

[Local Boy]

Vacum leak!

Aloha

[mrjones]

Yep, it goes away completely after the car warms up, it's only for the first two minutes at the most, even after what passes for cold here in south Texas. After that, it goes away and doesn't surge anymore unless it's parked for several hours.

Thanks for the suggestions; I'll check all those things.

[burt ragio]

Clean MAF and check ALL lines for vacum leak.

[Local Boy]

Keep in mind that surges are common if you don't let the motor warm up a little.....

If you just put it in gear and go , as soon as you start it...it will surge...

Basically, the computer is trying to warm up the engine, while you're driving off, in this case...

The computer is still in a "start up mode"...

Hence, the surging...

Try and give her a little bit more time to warm up...

ALOHA

[mrjones]

But why would it not do that when brand new, begin it later almost imperceptibly, and then the surge grow stronger years later?

Is it like me, and needs more time to "warm up" as it gets older?! ;)

[Local Boy]

Modifications?...Perhaps...;)

Aloha