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-   -   Mystery abnormal throttle response (http://forum.e46fanatics.com/showthread.php?t=803531)

Fr3nch 11-08-2010 08:43 PM

Mystery abnormal throttle response
 
I bought this car with 130K on it from the original owner. 2002 325 XI with the electronic throttle (no cable). There is one annoying problem that I can not get resolved.

The problem:
When I give it 100% throttle then suddenly let off the car continues to go full power for about a half second, then goes to less power for half a second, then cuts all power. So from full throttle to no throttle there is at least a one second delay in response. This only occurs when the engine is under load, it does not happen when the car is out of gear or the clutch is in (free revving).

Some other possibly related things (that I am not even sure are problems): when the engine is revved briefly, it dips below idle, then goes above idle, then settles at idle. If the engine is revved high is does not do this.

Things I have tried:
I cleaned the TB (throttle body), ICV (idle control valve), disa (?), replaced the intake boots, and reset the throttle memory. I had the car smoked tested for vacuum leaks which came up negative. The car has a new MAF (mass air flow) which is from a hyundai sonata, but this issue was the same before changing the MAF. The TB seemed to function properly, it wasn't sticky or anything. The previous owner replaced an o-ring in the clutch assembly which means bleeding the clutch hydraulics. There is no guarantee this was done right. (may be why this only happens when the car is in gear.)

My indie confirmed this issue but has no idea what to do next. He suggests I take it to the dealership to use their big expensive computer, which I assume means a big expensive diagnostic fee. ANY input would be good, I am getting desperate and completely grasping at straws here.

Importjunkie 11-08-2010 09:44 PM

I have this exact problem.. however I just cleaned the ICV last night and it made this happen less frequently, but it still happens sometimes. Did you notice any difference at all when you cleaned ICV? I'm thinking I just didn't clean it enough. there was still a little bit of gunk in there when I put it back, since the cleaner I used couldn't seem to get it out.

Fr3nch 11-08-2010 10:34 PM

Quote:

Originally Posted by Bryce v2 (Post 12442950)
I have this exact problem.. however I just cleaned the ICV last night and it made this happen less frequently, but it still happens sometimes. Did you notice any difference at all when you cleaned ICV? I'm thinking I just didn't clean it enough. there was still a little bit of gunk in there when I put it back, since the cleaner I used couldn't seem to get it out.

I cleaned the ICV as throughly as an ICV can be cleaned. I used 2/3 of a can of TB cleaner on it in addition to rags and stuff. If you twist the ICV back and forth about its long axis you should hear the valve inside click. It should be a metal to metal click. If its more of a dull thumb or thud, then it needs more cleaning. Make sure that it is perfectly dry before you reinstall it.

I thought I noticed a difference the first time I put the ICV back in, but it was only for a mile or so and I am not sure if it was in my head or not. Besides that there was no difference at all.

I am sorry you have the same problem, but am happy to hear that I don't have some freak E46 and am never going to find a solution. Lets keep in touch, you are the first person I have talked to with this same issue, and I have been trying to solve it for 3 months now.

Fr3nch 11-08-2010 11:09 PM

One more thing, your profile says you have a 2001, do you have the all electronic TB? Or do you have the one with the cable? Knowing this would help eliminate an entire system as a potential problem.

jgold47 11-08-2010 11:43 PM

I had this problem on a Honda I used to own. I had to really get into the throttle body to clean it, the butterfly had gunk on the 'rim', so even thought I cleaned the insides it was still sticking.

Fr3nch 11-09-2010 12:06 AM

Well I am pretty sure I sufficiently cleaned the TB. The butterfly was perfectly clean. But there was still some discoloration on the tube part of the TB, not enough to cause a physical change to the surface of the TB. Holding the TB im my hand and manually opening/closing the butterfly, there was not any abnormal resistance in the butterfly valve action. There was a slight delay because the spring in the TB was moving the electrical actuator but that delay was not even enough to measure. (maybe a 1/10th of a second). Even then, if TB buildup were the culprit, cleaning it would have improved the problem. I am not going to say that the TB is not the issue, but if it is I think it would be the TB motor itself that has gone bad. I really don't think this is caused by any kind of buildup or anything. On the other hand this is the first "modern" car I have tried to trouble shoot, so feel free to argue with me. I am by no means an expert.

Importjunkie 11-09-2010 10:40 AM

Quote:

Originally Posted by Fr3nch (Post 12443366)
One more thing, your profile says you have a 2001, do you have the all electronic TB? Or do you have the one with the cable? Knowing this would help eliminate an entire system as a potential problem.

Yes, it's electronic; I don't have a throttle cable. I'll help keep this thread bumped until we can find a solution. I'm sure it's probably bugging me just as much, since I've been dealing with it for years now. Have you done your vanos seals yet? I did them last year and it made the ride a little smoother.

Fr3nch 11-09-2010 12:36 PM

I have not done the vanos seals, and don't plan to for a while. Probably next summer or something. My mechanic said I don't have a rattle or anything so I am not too worried about it.

SweetBMW 11-09-2010 01:37 PM

Might be your accelerator pedal module-... BMW SI bulletin says that customers have complained about this exactly problem with a delay in throttle response. This was resolved with a new module at the cost of 150USD

Importjunkie 11-09-2010 06:42 PM

Quote:

Originally Posted by SweetBMW (Post 12445257)
Might be your accelerator pedal module-... BMW SI bulletin says that customers have complained about this exactly problem with a delay in throttle response. This was resolved with a new module at the cost of 150USD

this is interesting.. i've never heard this before.

can anyone give more info on this issue?

Importjunkie 11-10-2010 10:09 AM

bump

rowdy lee 11-10-2010 11:49 AM

delay...
 
A delay in throttle closing too quickly/abruptly is normal, and is for pollution control.

rpm drops, hesitation etc. don't sound normal, and may be a module...

Fr3nch 11-10-2010 01:08 PM

A slight delay inthe throttle closing may be normal but this definately is not. Like I said, there is aleast a second of hesitation between letting off the accelerator and the engine cutting power. Its enough time to move your foot all the way from the gas to the break and apply the breaks. This is confirmed by my mechanic. But it may be something in emission control malfunctioning. Any idea what that could be?

jonesro 11-10-2010 01:20 PM

A lot of manual trans cars are programmed to drop the rpms slowly when moving to aid in shifting, BMW may be the same and you have an issue that aggravates this. may have to have it put on a scan tool to see tps, fly by wire, etc settings. Is there some maintance of the throttle body that is recomended? something that could benefit from lube?

iansanderson 11-10-2010 01:27 PM

this sounds like the idle control valve is mechanically sticking. Although, it could be an issue with the actual electronic throttle body. Unfortunately, you really should have the BMW codes pulled from the DME. You may find a fault already exists with one or the other which could help you in finding the problem.

jonesro 11-10-2010 01:44 PM

Quote:

Originally Posted by iansanderson (Post 12449274)
this sounds like the idle control valve is mechanically sticking. Although, it could be an issue with the actual electronic throttle body. Unfortunately, you really should have the BMW codes pulled from the DME. You may find a fault already exists with one or the other which could help you in finding the problem.

this could very well be, cleaning does not always work. I would replace it because if you do take it to dealer they probably will at 3 times the cost of you doing it yourself

Importjunkie 11-10-2010 02:33 PM

ugh i really hope its not the icv because it was a real pain in the ass getting that thing out lol

Importjunkie 11-10-2010 11:29 PM

bump

Importjunkie 11-11-2010 10:38 AM

bump

Fr3nch 11-17-2010 01:14 PM

Last bump before I take it to the dealer. If you have any input please help.


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