Rpms not dropping

[gikser]

Hello there i have a 2000 boxster s and when driving and letting off the throttle especially between shifts the rpms stay hung up at whatever rpm i was cruising at. Its alot more noticeable with the ac on. I tried pulling codes but have none relevant to this problem. I took the throttlebody out and cleaned it as well as the maf but to no avail. Ive tried searching on here many times but cant find an answer. Im stumped. I also thought maybe the iac is going bad but there isnt one on the throttlebody with e-gas. Has anyone run into this before?

[j.fro]

I've got the same thing happening with my car, and I've also cleaned thoroughly with little result. Hope a solution comes along!

[gikser]

Hopefully someone has an answer

[gikser]

someone please!!! today it rev'ed up to redline when i stepped on the clutch had to turn the ignition off and restart the car.

[RandallNeighbour]

Not to insult your intelligence, but have you checked the pedal to see if it's sticking? Is your floor mat jammed up next to it?

Sometimes, the most obvious things are overlooked. Since you didn't mention you checked these things, I thought I'd mention them.

[gikser]

No offense taken. But i have no floor mats and i pulled on the pedal to see if it made a difference and no difference.

[sparker]

I had a similar problem after taking my throttle body off. Turned out just to be the throttle cable being too tight holding the butterfly open a tad. Just had to adjust it back so that the throttle could actually close again and all was fine.

This was obviously on a car with no e-gas though....

Sam

[brp987]

Bentley Boxster Service Manual, page 24-6:

DME adaptation for throttle unit can be done if these conditions exist:

vehicle stationary, battery > 10 V and < 16V, engine temp >5C and <100C, and
intake air temp >10C and < 100C

if the above are true then:
1. switch on ignition for 1 minute w/o starting engine

2. switch off ignition for > 10 sec


now see if it's fixed (pray...)

[gikser]

cool i will try this in the morning and hope it does the trick

[gikser]

Well adaptation didnt do the trick. Curiously enough the car idles perfectly fine at a standstill so it only happens when driving mostly on the highway. Im stumped.

[gikser]

Bump. Anyone has any clue?

[Jager]

I would start with using Durametric analyzer and look at the pedal position % as you depress and release it and see what it shows. Also what the potentiometers read.
Pedal Value - 0.00%
Pedal Encoder Potentiometer 1 -Voltage
Pedal Encoder Potentiometer 2 -Voltage

If you don't have the Durametric system, find someone that does.

[gikser]

Where can i buy one?

[mikefocke]

Originally Posted by gikser

Where can i buy one?

http://www.durametric.com/default.aspx

[gikser]

Being as im suspecting the throttlebody i guess its a good excuse to upgrade to the ipd plenum and bigger throttlebody as well as the softronic tune which comes with durametric

[san rensho]

Vacuum leak?

[gikser]

Im gonna smoke it out and see. I steered away from a leak as when i shut the ac off the rpms drop

[uladzislau]

I know it's 2011 post but I've got the same problem recently and can not find the issue as well. Throttle body was cleaned as well as the idle control valve. AOS is file as I did not find any oil in the throttle body. I was thinking that this might be a vacuum leak kind of doubt it as RPM drops back to normal in 3-5 seconds after the clutch pedal is pressed. Throttle cable is fine too - I've logged via OBD2 throttle position as I drive and I see that when the RPM get stuck throttle is closed but MAF continues to report some air flow. This points to a bad MAF or possible bad idle control valve.

So did anybody figure out this issue at the end? I'm gonna start with MAF and if it does not help will try idle control valve.

[BYprodriver]

Originally Posted by uladzislau

I know it's 2011 post but I've got the same problem recently and can not find the issue as well. Throttle body was cleaned as well as the idle control valve. AOS is file as I did not find any oil in the throttle body. I was thinking that this might be a vacuum leak kind of doubt it as RPM drops back to normal in 3-5 seconds after the clutch pedal is pressed. Throttle cable is fine too - I've logged via OBD2 throttle position as I drive and I see that when the RPM get stuck throttle is closed but MAF continues to report some air flow. This points to a bad MAF or possible bad idle control valve.

So did anybody figure out this issue at the end? I'm gonna start with MAF and if it does not help will try idle control valve.

Thanks for searching 1st, always good to post your year model & mileage also.
I agree with your plan & also recommend you have someone work the gas pedal while you watch the T/B fully open & close just to be sure it's adjusted properly.

[uladzislau]

Originally Posted by BYprodriver

Thanks for searching 1st, always good to post your year model & mileage also.
I agree with your plan & also recommend you have someone work the gas pedal while you watch the T/B fully open & close just to be sure it's adjusted properly.

Thank you for the reply!

It's an early Boxster '97 2.5L engine, no e-gas, around 70K milage. I'm pretty sure the T/B is fine, when I was cleaning it the cable was long enough to allow TB to be closed completely. Plus I did not have the issue before ever and I don't think the cable would "shorten" suddenly. Another observation, when I'm driving downhill and letting the engine to decelerate the car by letting off the gas pedal, this problem can occur randomly. I.e. I would feel that the can decelerates and accelerates while I'm not touching the pedal e.g. not touching T/B.

The problem only occurs when the car is in motion, idle RPMs are stable and no problems whatsoever. Seems like the higher speed - the higher probability of RPM to get stuck.