View Full Version : JDM idle trouble shooting

10-05-2010, 06:54 AM
This has gotten worse since I started really driving it past couple days. It idles great most the time at the stop light about 1000 rpm. But sometimes it would idle low around 300. Today on the way home it started dieing every time I stopped and put the clutch in. Unless I kept a foot on the gas to keep the rpms up. It runs very smooth, just wouldnt idle. Im sure I got all the vac leaks plugged now. The extra PS vac line wasnt plugged, and found a rip in the line on top of the intake, but those are plugged now. And it is intermittent problem.

So what are some things I can start to check? My xp with other cars would suggest checking TPS or IAC but on my JDM 3SGTE I could use a general list of things to check.


10-05-2010, 11:32 AM
Those two would be the place to start, if you have assured yourself there are no vacuum issues.

10-05-2010, 06:35 PM
Just FYI, the JDM 3SGTE is 99% the same as the US version of the same year, VERY few differences.

10-05-2010, 07:05 PM
I dont remember seeing anything like an IAC or TPS on the throttle body. Is that where they are or somewhere else?


10-06-2010, 01:01 AM
IAC is located at the bottom of the throttle body facing the front of the engine. It's white if I remember correctly.

The TPS is on the side of the throttle body facing the transmission.

10-06-2010, 06:57 PM
So is the method the same as a mustang? Use a tester and adjust the TPS until it reads as close to 1 as possible? And take the IAC apart and see if the valve is sticking?



I found instructions for 88 celica 22re but that probably wont help, and nothing in the BGB either that I could find.

10-07-2010, 01:51 AM
It's not voltage based, it's resistance based..

Here's the BGB that you need to look through. It's under EFI: It gives both trouble shooting for the throttle body and ISC (Idle Speed Control). You and I both know it as IAC (Idle Air Control)


There is also a mechanical way to adjust the idle (no, not adjusting the cable). But you need to check for total functionality before you start playing with the bleed screw. Also, are you sure that this is an air problem you are dealing with?

is there a chance that you have something else causing a low/rough idle? (rich condition, clogged muffler/cat, poor ignition)

10-07-2010, 02:42 AM
Well its a low miles JDM swap. All factory settings. Since I didnt know how to test IAC or TPS I took them off my old intake and tested the resistance on the sensor pins, then I tested the pins on the sensors on the car and they are the same. So I did the only thing I could and adjusted the cable. Went for a drive and didnt have the prob so ill drive some more and see if it comes back, when hot it idles at 1200. I noticed that now my turbo doesnt seem to build pressure or at least help accelleration like it did before so Im guessing thats related to adjusting the cable? I dont have a working boost gauge so not sure. Ill have to go through it this weekend.

10-07-2010, 03:49 AM
what is your timing set at? This sounds more like an ignition related problem. (be sure to check timing jumping the terminals on the ALDL)

10-07-2010, 03:58 PM
Do you mean to use a timing light while jumping the ALDL? Diagnostic panel? To B1?

anyway the timing should be factory, everything should be factory set, I didnt mess with any of that. But I can check it.

10-07-2010, 06:41 PM
Trusting the timing is still "factory" after a swap is like buying a used computer and not doing a complete reload. You have to know what you are starting with and timing is something I wouldnt trust to someone else. Also I suggest you do a compression test just to know where that stands as well.

As for your idle issues, I would also suggest burping the coolant system. Air bubbles passing by the coolant temp sensor can cause erratic idle.

10-07-2010, 10:19 PM
Id think its pretty safe to assume that between being ripped out in japan, shipped, sold, shipped. Than anyone would bother to mess with the timing. But I will still check it. Your right. And they sent me the results of the compression test before they shipped it to me. If that can be trusted.

I did just add a bunch of coolant pretty much the day before I started driving it. Hope I can find how to "burp" it. Thats all on the list for the weekend. Thanks

10-07-2010, 11:50 PM
Yeah.... I wouldn't trust the maintanance on a used engine...

How likely are you to spend the money and time to do the normal maintanance on an engine that you know you will be getting rid of in a year?

I just got my JDM RC engine, I am replacing all wearable parts, re-sealing the engine, and rebuilding all the pumps/starter/alternator before I drop it in.

At the very least, you should be changing your cap/rotor/plugs and setting the timing.

If you have idle problems and power problems under boost, that's making me think ignition.

10-08-2010, 02:47 AM
It's very possible during all that movement and shipping out of the car that the timing could have slipped. The distributor could have moved a little through all that. Definitely check the timing.

If you're idling now at 1200 warm, that's too high. I know the BGB says something like 800 or so, but you really shouldn't be above 900-1000 RPM's. Adjusting the cable or idle screw is masking the real problem I've got a feeling.

10-09-2010, 12:53 AM
. Adjusting the cable or idle screw is masking the real problem I've got a feeling.

I agree 100%

10-09-2010, 09:26 PM
Ok so, BGB says first, in the adjusting timing section, 10. Then next section, further adjusting, 12-21. So which should it be? Right now with the diag panel jumped it times below 10 so for now Im gonna try to get it to 10. Let me know which is correct. Thanks

10-09-2010, 09:31 PM
engine at N.O.T.
jumper diag
time with light to 10

10-10-2010, 01:53 AM
Shes timed now. I also "burped" the coolant. For some reason I thought I just wasnt finding the port for the overflow can. I confirmed today another gift from the jack holes that previously owned the car. They welded it shut. Why on earth would anyone do that? Is there a logical reason? Also i think theres a leak cause theres always coolant around the edge of the top tank.

Also, theres a little bit of oil in the intercooler in front of the throttle body. Is that normal? My old setup had oil caked in the intercooler, airflow sensor tube. so on both sided of the turbo. This time, after just a handfull of drives theres a little fresh oil in front of the throttle body but none elsewhere. Also, heres a pic of inside my air flow sensor. Notice the gap in between the big square valve plate thing. Is that normal? Its my old one, never replaced it.

10-10-2010, 04:51 AM
Time to get a new radiator.

Yes, the AFM is normal. that's the counterbalance door, the metering door is on the far side in that picture. However you need to clean that shi* up! I wouldn't want that sludge being sucked through my turbo/engine

Define "a little bit" It should have a fine mist going through the system from PCV vapors. if it's coating the inside, you should do a compression test to see how bad the rings are worn (don't trust the seller's numbers)

I lucked out, my RC engine came with all 4 cylinders within 2psi from highest to lowest, and iridium plugs came out. the turbo has no shaft play (beyond normal), and it looks like the previous owner took really good care of it.

10-11-2010, 12:58 AM
Its not coating the intercooler with oil there was just a little fine line of oil in the bottom of the intercooler tube.

I might actually be able to get the radiator rebanded for free. But Im gonna check on aftermarket options for better cooling since Ill have it out. Thoughts? Worth it? I cant believe how hot the engine bay gets. They werent kidding. Cant believe stuff doesnt melt.

10-25-2010, 02:23 AM
After I got the radiator fixed, painted up nice and reinstalled. On the first start it was still idling weird, I fiddled around and was touching the batt ground point and it would start to die. The napa ground strap that installed to fix the problem with the old engine is on that same point on the tranny. Since that strap was for the old engine i tried removing it. and it started and ran fine for awhile. The check engine light goes on for awhile, then off for awhile. Then today when idling it started to increase RPM up and down between 1000 and 2000 RPM. With check light going on and off every 10 min or so. So when I got home I reconnected the ground strap and it idled fine. But its so intermittent that doesnt mean anything. But it seems ground related with the wierd idling problem. But it intermittent with or without ground strap. Friggin wierd. Last week I adjusted the timing. SO, just friggin wierd.

11-02-2010, 04:08 AM
14 months ago I had a major problem with my all-trac, so I might be fuzzy on the details. But I was getting on the freeway when I heard an odd sound come from the engine, but I was running fine so I decided to keep going to my destination and check when I got there, then I had to slow down and all hell broke loose my car sputtered and died, I lost brakes and power steering. I quickly started it again and kept on the gas then got off and limped into a Lowe's parking lot. I had had idle problems before so I immediately popped the hood and started looking for obvious vacuum leaks but didn't see any. Called my Dad, in a panic, he had me start checking some stuff but all was fine but when I started it it would try try sputter and die, it was heartbreaking. 2 hours later, after some drama with locking my keys in my car with them in the ignition trying to charge my phone which had just died unrelated though, he had me check with my hands the back of the intake, the space between the intake and firewall, he said there would be two "tubes" going down the one on the left, I think standing on the right side of the car, would continue on as a "pipe" of some sort but the other, at least on my all trac, should have been capped but the cap was missing, I was overjoyed to find it, so I used some heavy duty electrical tape, I had bought at Lowe's while I was there before I had tried limping it home unsuccessfully, to cover it And then started my car and it was like night and day my car ran totally fine. Then drove it to Shucks and got a variety of sized vacuum caps and zip ties and made a better cap then electrical tape. Anyway, sorry if I rambled a lot but maybe if you are supposed to have this cap it is loose, which would explain intermittent problems, so I guess it is worth checking. Also have you done a fog test for vacuum leaks, I know you said you plugged all the vacuum leaks but it will show even the smallest leak. Good Luck.

11-02-2010, 02:54 PM
I am aware of those 2 holes you speak of, last time I checked the cap was on the one and the other had a hose going somewhere. The next thing to check is if there is a "vacuum switch" somewhere that might be leaking or not working. If it did it all the time it would be one thing, but when it only acts up after cruising around town for couple hours, or at one stop it idles fine, next stop it idles high, and on and off. Its kinda hard to figure out. Almost always when I start it and let it warm up it will never have the problem.

At least after adjusting the timing, it doesnt die anymore, it just idles weird. Sometimes.