Throttle hang (again)
 

I've read through a lot of the other throttle hang threads, but it seems like in each one of them there are multiple different problems and I haven't found a resolution for mine.

My RPM's drop slow. That's fine, I can deal with that. However, when I bring the car to redline (say in 4th gear) and let off, the RPMs drop to 4k then stay there for about 10 to 15 seconds. Pushing the clutch doesn't seem to help much, tapping the gas doesn't help much either. I had noticed this problem before, but it wasn't as bad as what I just described...that started this evening. It actually started on the dyno getting tuned, so I know it doesn't have anything to do with the tune.

FYI it's an '05 with 30k miles. It idles great once it gets there or when you start the car up. If you're just driving around normal you wouldn't have the problem either...obviously you're not getting above 4.5k RPM. The tuner suggested I check the idle speed motor. I have to assume it's something like that. If it was simply a leak somewhere I would notice it other RPM's. Because it always gets hung up at the same spot, I have to assume it's something actually controlling the idle at that point. Any other suggestions?

Mine was hanging but it idle. What I did to fix it was spray carb cleaner on a shop towell and wipe out the throttle body in the area of the throttle butterfly.

I've tried all that. You would think if it was something mechanical or even a vac leak it would happen starting at lower RPM's and work it's way up. This hangs at ~4K and just holds there. Anywhere from 15 seconds to I have to let the clutch out slow in any gear while stopping or stopped.

I suspect the idle speed motor does more than just control the idle. On my '92 DSM it would open up when decelerating. This was called the dashpot function. Stuck open it would cause a 2500 rpm idle on a DSM (had that happen). When the stepper motor would hang spraying some silicon inside the pintle would get it working again for awhile. I eventually had to replace the unit.

15 seconds of hang? thats ridiculous. Something is mechanical wrong with your car.
normal throotle hand is like 200-400 RPM lasing a split secons.

You said that under normal driving conditions it does fine but under harder driving it hangs up. Perhaps when you reach those higher rpms something binds or something may come loose at that point and hang something up. Does it only do it when your driving or have you tried doing sitting in the driveway perhaps?

It doesn't sound electrical it sounds more to me like something mechanical. Perhaps your throttle cable is binding or flooring it may have pulled the cable out of adjustment or something. Maybe even check around the accel pedal area. Sorry for nothing concrete just throwing some ideas out there if you hadn't thought of them already.

Only taking it above 4500RPM or so will do it. It has nothing to do with boost or speed, because I can do it with the clutch in or in neutral. 15 seconds is the minimum. I'm actually standing over my car now. The cable to the throttle body is dirty, but everything seems to move freely. I'm going to wait for my brother to get home and have him rev it to 4500RPM and see if everything still moves as it should.

Thanks for the input. Any other ideas while we're at it? I'm going to clean the cable up. Is there a way to adjust it though? Someone mentioned it slipping out of adjustment..

My car does the same thing. Throttle hangs at exactly 4k RPM til you give the car some gas. Happens under the same conditions the OP posted but not as often. '05 with 40k miles. Notable mods- cams, fuel pump, turbo back, intake, tune. Hoping for a solution as well.

Our mods are similar then. When did yours start? I mean did it start right after doing one of the mods or was it just random?

More notes...when it's stuck at 4K, the vac is reading higher than idle (my idle is about 11, it reads about 17) I checked for vac leaks anyhow and found nothing.

I checked the TB just to make sure it wasn't dirty or anything and it was actually extremely clean. Pulled the IAC and same thing. I'm calling the dealership on Monday to get a new IAC. I figure it's a starting point anyhow.

With the above info known, could it still be the DV? I would assume if it was the DV sticking that I would notice something out of the ordinary on the boost gauge. Not only does the boost fall off like normal, but the vac goes all the way to around 17.

Happened way after the mods. Old owner did all the mods. I asked him and he said he never experienced the hang. The hang has happened to me once and 2 friends once each. Haven't experienced it in a while. I wasn't paying attention to boost or vacuum so I can't comment on that. I have a Greddy Type S bov that is recirced so we have pretty much the exact same mods.

Frustrating. I'm trying to find someone local to switch their IACV to my car to see if that's it. I plan on pulling the TB off today too to make sure there isn't anything I can't see. Shouldn't be though...no vac leaks there so it shouldn't be something like that, and it's the OE TB so the plate should be centered.

After answering your PM, that was my next thought.

I'm thinking more and more that will be it. I have a post on a local board trying to find someone. We'll see what happens. I assume it's a dealer only part and it's about $200 which sucks.