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2G GHS GSX Project- High Idle

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gijoe985

15+ Year Contributor
562
20
Dec 13, 2007
Grandview, Washington
Hey all,

So, we've got our high school shop car finally running and premsumably boost leak free. (We will check once again for boost leaks, we may have a small on at the throttle body, but they we're mostly handled a while back.) So, if you've seen our other threads, we've got a 95 gsx, 880 injectors, and DSMlink V2 (and more stuff). Right now I have to unscrew the BISS pretty far to get it started and idling, but it idles at 2k. I can start screwing it in and get it down to 1600ish, but it eventually runs rough and dies. It has good compression all around, etc. I may need to check soon for a leaky inejctor or something. Anyway, I'm open to hear your guys' thoughts, we've done most of the basics.

If I ground the diagnostics ports via dsmlink, it kills the engine almost instantly.

Wideband shows 13.5-14:1 at idle.
 
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Check for throttle closed. Ecu should cut fuel at 1500 at idle. If it doesn't it isn't really closed or possible throttle stop or tps adjustment issue. If you biss screwed out some and grounding kills the car....hmmm...did you check isc?
 
Also make sure all boost leaks are gone they have been a huge plague that has messed with me and my setup for a while. It can cause all sorts of issues that you wouldn’t even think of including idle issues and power loss. Not sure if this will help but it can’t hurt to check.
 
Check for throttle closed. Ecu should cut fuel at 1500 at idle. If it doesn't it isn't really closed or possible throttle stop or tps adjustment issue. If you biss screwed out some and grounding kills the car....hmmm...did you check isc?
So, we received this car modified and not runnign, so we set the SAS to the factory suggestion or 1-1/4 turns opened once it begins opening the throttle plate. We then adjusted the BISS (pretty far out, like 4-5 full turns) until the ISC read 30 on DSMlink. Idle was still at 1500+

Also make sure all boost leaks are gone they have been a huge plague that has messed with me and my setup for a while. It can cause all sorts of issues that you wouldn’t even think of including idle issues and power loss. Not sure if this will help but it can’t hurt to check.
We do need to do this again. A student with a DSM borrowed the leak tester, so once he brings it back we will check again. We did swap throttle bodies. So need to see if the one we're using is leaking.

Timing is off a tooth. There's no reason a car goes 1600 idle and stalls out instantly under that
I doubt it, but it honestly doesn't hurt to check.


And thank you guys. I know that there are a lot of threads dedicated to similar issues, but with the school year widning down and me having 4-5 car projets kids are working on, my brain hurts from troubleshooting. It's great to be able to share the load.
 
Anyone have any other input considering our throttle body settings? We set the SAS back to what the manual said and then the BISS still needed to be turend out about 5 FULL turns.

Trying to get the boost leak tester back today.
 
OK, so I think boost leaks are gone. We replaced the TB seals and blocked off the EGR.

NOW, still doesn't run great. Small steps forward, but not good.

I want to get new plugs, we have Autolites in there right now which was all the store had at the time. We'll pick up some NGK coppers.

That said, I've used a laser thermometer to check exhaust temps and Cylinder 1 is running hotter than the rest and cylinder 4 cooler than 2&3. 2&3 are about even. So I'm kind of wondering about the condition of my injectors at this point. They came with the car. I don't know much about them other than they are supposed to be 880cc. I'm kind of wondering if it is worth having them professional cleaned, or to just buy new injectors at this point. If so, what?
 
Anyone have any other input considering our throttle body settings? We set the SAS back to what the manual said and then the BISS still needed to be turend out about 5 FULL turns.

Trying to get the boost leak tester back today.


The verbage in the manual also dictates the amount of screws on a brand new car with brand new compression, and a used car, are not set variables. The biss is used once the car is fully warmed up and the idle air control valve is in position 30, to set idle speed. It's also relative to the temperature of the coolant, so the screw is to be calibrated once the car has gotten up to full temperature, because the stock throttle body is heated by coolant

So you can't just say it's a finite number of turns, it can be different for different cars. Engine vacuum, coolant temperature, ambient air pressure, all play a role in where the screw should be set at. I want to say I even saw a tech note in one of my manuals that cars sent to higher elevations were expected to need calibration once they arrived
 
And we're back... a year later.

Ok, so we replaced our head gasket and now run an even 155-160psi on all cylinders.

We started the car and it runs, but not very smoothly at all. So now we are diagnosing things again. Right off the bat I am a bit leery about the 880cc injectors that have been sitting for 4 years now on the engine. I wish I knew for sure that they were flowing well.

I fond that we've got a leak still at the TB. Which is frustrating because we replaced the shaft seals last year. So I have no idea why it is still leaking. We have a second TB that I may just try putting on to see if it is any better.

Stay tuned.
 
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