98 gst, 4k rpm idle... wiseman help appreciated!!!

[black99gst7]

Ok, i have a 98 gst that is my 2nd car while my 99 rarely gets drove. The car has ran good and is bone stock. last july my girlfriend who drives the car washed it and took off the stock intercooler pipe off and sprayed intake cleaner into the throttle body elbow with the car off. i came home and we started it and the rpm's shot straight up to like 6k rpm and i cut it off ( the car ran perfectly fine that same day bedore the spray ) I need very badly to get the car running now since it needs to be daily driven now so tried starting it for first time since august. Still way to high of idle to drive. i got a good new OEM iacv and put it on today and took a lint free cloth and wiped inside the throttle body good. put everthing back together and car still starts and idles way high.... but did go down a little to 3500k after new iac. also took it for short drive around my subdivision and while driving in like 2nd gear at 20 mph and giving it no gas the boost gauge is reading only about -5 vac. on my 99gst i know my vac is usually like -20 vac when off throttle. Any help is appreciated guys. we just had my first baby boy a month ago and gotta get this running as my other daily driver messed up on us. And sorry for the long read but i know the more detailed info the easier it is to help.

 

[Chaosweaver]

Possibly the TPS, make sure that everything is hooked up. Does it stay at one point at all times or does the idle bounce up and down?

 

[sniver]

The fiav is down there with the iacv. Maybe cleaner damaged that.

Options as I see it.

Throttles getting held open. check the tension of the throttle cable, make sure theres a hair of play.
fiav is stuck open. No test.
iacv is stuck open or unadjusted. need drb-II to adjust, or dsmlink.
Vacuum leak. Spray ether all around the intake to ensure theres no vacuum leak.

 

[banishedmunk]

perform your usual boost leak test prior to changing and buying new sensors.

 

[DSMReviver]

I would definitely check the IAC(idle air control, right below tb elbow). i had similar issues with my car. my car would rev to the moon at first start and once it was warmed up it come down slightly. i changed it out and it idle fine. your gf might of damage it using the spray. i would check about replacing it. go to junk yard and grab you one, they are cheap.

i hope this help, good luck. and congrats on the new born.

 

[black99gst7]

The fiav is down there with the iacv. Maybe cleaner damaged that.

Throttles getting held open. check the tension of the throttle cable, make sure theres a hair of play.
fiav is stuck open. No test.
iacv is stuck open or unadjusted. need drb-II to adjust, or dsmlink.
Vacuum leak. Spray ether all around the intake to ensure theres no vacuum leak.

It stays that idle... not bouncing up and down. I did clean the TB with the elbow off and from what i can see the butterfly is opening and closing fine and not stuck. as far as the cable... that is something i thought of but didnt think it could make it idle that high. The fiav is something i dont know about unfortunatly.... i thought the only 2 sensors on the TB were the iacv and the tps. where is the fiav and could any of these sensors cause it to idle that high? And the i did put a good iacv on it yesterday so that should be good. Thanks for the replies guys! Maybe i will get this figured out after all.

I would definitely check the IAC(idle air control, right below tb elbow). i had similar issues with my car. my car would rev to the moon at first start and once it was warmed up it come down slightly. i changed it out and it idle fine. your gf might of damage it using the spray. i would check about replacing it. go to junk yard and grab you one, they are cheap.

i hope this help, good luck. and congrats on the new born.

Thanks man, being a dad is a great thing! I actually rreplaced the iacv yesterday with a good oem one and it still has the problem My idle also does not go down even after the car warms up. Could the intake cleaner have really caused a boost leak on a almost stock car since the car ran just fine right until the intake cleaner got sprayed... even that same day

 

[Tanro]

You've got a massive ####ing vacuum leak. Nuff said.

Do a boost leak test, this should give an indication of where it is if it is pre throttle body.

Also, it really sounds like your brake booster is unplugged. I seafoamed my Saturn and forgot to plug the brake booster back up and it idled at redline. I shut the car off and thought it was ####ed. Found the massive vacuum line from the manifold was unplugged. Fixt.

 

[black99gst7]

So vacume leak is what i am thinking as a good possibilty with the car reading no vacume while driving it around my subdivision last night. why would the brake booster be unhooked if the car ran fine up until the cleaner was sprayed though? Also exactly where is this vacume line that would cause my high idle? thanks for the replies guys... i figuered somebody has had this issue before since i camt figure it out.

 

[XiKeiyaZI]

1 : You need to look up a vacuum diagram using the search function that this site is equipped with.

2 : You NEED to perform a boost leak test. While to my experience, a boost leak usually results in lopey, stumbling idle, you never know.

3 : The cleaner could have damaged the seals on the throttle body. Remove the entire throttle body assembly and inspect it closely.

4 : Check the BISS screw. Screw it all the way in and start the car, see if the idle is significantly lower.

5 : Check the throttle plate adjustment screw and make sure that it wasn't screwed in somehow during this cleaning experience causing the throttle plate to be slightly open.

6 : Loosen the tension on the cable a hair. It could be just tight enough to allow the engine to be revving. I had this same issue on my first DSM and it scared the hell out of me.

 

[black99gst7]

I will do the search but i can just look at the diagram under my hood. i was just wondering which specific one he ment. Also i forgot to mention that as we were driving the car last night in just 1st and 2nd gear... the car also was chugging and running pretty rough.... but when at idle it is pretty smooth just way way to high.

 

[Sundance 6g72]

did your girlfriend hoop up the intercooler piping correctly? you said she took it off... my money is on that causing a leak.

someone mentioned that the TB might be leaking. My buddies gsx has a leaky TB but still drives fine around town until he hits high boost then the car just freaks out. That should be fixed soon.

 

[gofer]

I've never seen a bad enough vacuum/boost leak cause the car to rev up to 6k and sit there, if its that bad of a leak the car won't start. I see 3 or 4 members here suggesting that you check your throttle cable to make sure it isn't holding the throttle plate open and you haven't said anything about checking it, so did you check it?

READ through both of the threads if you aren't sure how to adjust the cable properly.

- Gas Pedal Stuck Down
- Throttle Cable Stretched​

What were the results of your BLT, or have you done it yet?

 

[black99gst7]

I've never seen a bad enough vacuum/boost leak cause the car to rev up to 6k and sit there, if its that bad of a leak the car won't start. I see 3 or 4 members here suggesting that you check your throttle cable to make sure it isn't holding the throttle plate open and you haven't said anything about checking it, so did you check it?

READ through both of the threads if you aren't sure how to adjust the cable properly.

- Gas Pedal Stuck Down
- Throttle Cable Stretched​

What were the results of your BLT, or have you done it yet?

Gofer.... i actually just came back in fron driving the car i as well did not think a vacume leak would cause it to rev that high and stay. even though its only been going to 4k... just went to 6k that one time. today i pulled the tps and iacv back off the tb and pulled the elbow off and took a toothbrush to the tb and butterfly inside it. cleaned it all out and put it all back together. put some new ngk's in it cause the ones that were there were black from the gas and it running rich. started it and the idle was alot better but still not right... it was like 2-21/2K rpm. So i then adjusted the 2 10mm bolts on the throttle cable and adjusted the bracket a little and the idle is now down to about 1800K and the car runs pretty smooth. I did however break one of the bolts holding the bracket tight by over tightening i guess so that will have to be tapped out and new bolt found. the biss screw is all the way down so i still have a litlle left to get the idle back down to 800-1000 but the car at least runs and we can drive it now. Thanks to all that tried to help.... i appreciate it! gofer, you and fmedgsx are on dsmp... im more know over there and was rotm last yr... congrats on your current win as well as ive not been as active there lately either.... just had my first baby boy

 

[thector1]

I had the same problem.. Tried everything and finally blocked the fiav. That was is! Hope that helps

 

[Marceldsm]

boost leak/vaccum leak

make sure that the intake manifold gasket is good

make sure the tb is good and all sensor ar of isc fiav etc


one of my friend had a 5k rpm idlle on his elantra it whas the intake manifold gasket

 

[sniver]

Ether sprayed around is a awesome indicator to where a leak hides.