2G Ridiculously high idle

[Aardal]

I have a problem i cant seem to solve. I have 1995 eclipse GS-T that constantly idles at 4,000 rpm. I've had it for the last 15 years but unfortunately i just abandoned it behind the shop out of frustration. I just got motivated to rebuild it and figuring out that issue is the firt step. I replaced the map sensor, replaced the maf sensor, checked the throttle cable and throttle body, it doest appear to have a vacuum leak. Hopefully someone here can point me in the right direction. With only 130,000 on a completely stock GS-T i feel it deserves a rebuild

 

[evil_eagletalon]

Do a boost leak test. You can make your own blt for cheap from homedepot items. Vacuum/boost leaks is def #1 on the list. Also make sure the engine has the correct pcv valve.

 

[Pjj]

ya those rubber lines will def need to be replaced, was it sitting for 15 years or you just have had it for those 15 years?

 

[chrysler kid]

could be the throttle cable is over tightened. make sure the throttle body is fully closing

 

[dwb]

You have too much air bypassing the throttle plate. Could be multiple issues. Your throttle plate is open (cable too tight, binding up, stop set too high) and/or you have a massive vacuum/boost leak somewhere between the throttlebody and the head (check your BISS, PCV line, BOV line, brake booster). Another option could be a failed FIAV.

 

[Aardal]

I'll have to dig deeper, I appreciate the info. Just started on this forum and about to start a full build, got the shop, the motivation and finally the funds. Looking forward to it.

ya those rubber lines will def need to be replaced, was it sitting for 15 years or you just have had it for those 15 years?

I've had it for 15 years but its been sitting for 5. I plan on replacing everything rubber and as many sensors as I can on top of a whole lot of other things. First step is ordering door handles in bulk. I've restored and built a 71 Chevelle, 58 Chevy Apache and a 70 El Camino. But anything electronic is not something I'm familiar with. Looking for a challenge but not a headache.

could be the throttle cable is over tightened. make sure the throttle body is fully closing

Throttle body and cable are good as well as the BISS

 

[Aardal]

You have too much air bypassing the throttle plate. Could be multiple issues. Your throttle plate is open (cable too tight, binding up, stop set too high) and/or you have a massive vacuum/boost leak somewhere between the throttlebody and the head (check your BISS, PCV line, BOV line, brake booster). Another option could be a failed FIAV.

I heard somewhere that if you disconnect you maf sensor while the car is running it will disregard most or all your sensors. Legend says its a good way to figure if an issue is a mechanical issue or something isn't correctly reading what its supposed to. Do you know if this true or a bunch of bull? When i disconnect my maf sensor it idles correctly or at least significantly closer to correctly.
Ive been away dealing with other things so haven't gotten to it in a while but I think you're dead on with either the vacuum leak or FIAV.
(Hopefully that made sense, I'm not super proficient with English)

 

[dwb]

Unplugging the MAF puts the ECU into limp mode and is no longer capable of measuring airflow. Yes, it can make it seem to idle better but it will drastically reduce the performance and drive ability. Not sure about it dianosing mechanical vs electronic issue though.

At 4000 rpm idle, you have something more going on than just a bad FIAV (could still be part of the problem, though). It would normally start idle surging around 1500-2000 rpm if it were only the FIAV. Almost like it doesn’t know it is in idle loop along with a pretty big vacuum leak. Would be worth checking your TPS.

BTW, your english is great!

 

[Aardal]

Unplugging the MAF puts the ECU into limp mode and is no longer capable of measuring airflow. Yes, it can make it seem to idle better but it will drastically reduce the performance and drive ability. Not sure about it dianosing mechanical vs electronic issue though.

At 4000 rpm idle, you have something more going on than just a bad FIAV (could still be part of the problem, though). It would normally start idle surging around 1500-2000 rpm if it were only the FIAV. Almost like it doesn’t know it is in idle loop along with a pretty big vacuum leak. Would be worth checking your TPS.

BTW, your english is great!

Very good info, i appreciate it. I did not try to drive it with the maf unplugged. Interesting because it would idle surge to around 2,000-2,5000 before it got stuck that high. I'm convinced theres a large vacuum leak somewhere, hopefully not more. I'll probably wait to until i get ecmlink before doing too much fiddling.