GGSX Idle issue.

[92_talon_awd]

About a week ago out of nowhere my GSX stopped idling when it's warm. Has been running great but now when the engine is warmed up, it dies when I get off the gas. I had 2 codes stored, TPS and temp sensor. Replaced both and no more CEL but still no idle.

When I turn on any accessories while the car is still warming up and idling fine, the idle drops but never comes back up. I checked the ISC motor, multimeter says it's fine. I replaced the ISC and the FIAV from some spares I had sitting around but no change whatsoever. Any ideas?

 

[fuel]

did you check the basics like throttle plate close adjustment - does the throttle plate close completely partially jamming up or is there complete smooth movement from closed to open? Check there isn't a build up of muck around the outside of the throttle plate further sealing off the flow.

My guess is the throttle plate is hard closed, the base idle screw is not allowing much bypass air through, and the ISC is at max adjustment when warm but the FIAV is providing enough bypass when cold to keep it from stalling.

What I would do:
1) remove throttle body to make work easier
2) clean throttle body and throttle plate
3) adjust throttle stop so throttle plate just closes but doesn't jam close, and then set TPS
4) refit throttle body and start engine and get up to temp (fully warmed up) then
5) perform base idle screw adjustment by grounding the base timing connector on the firewall and the diagnostic connector pin by the fuse box (check www.vfaq.com for this) and adjust base idle screw to desired rpms (750-800)
6) hopefully enjoy a stable idle hot and cold

 

[92_talon_awd]

The throttle plate moves smoothly, no jamming up. When I pulled the throttle body to replace the TPS I cleaned it really well. I've been using the car as a DD for over a year now and this just happened a week ago so I was leaning more towards something had failed. One day it idled fine, the next it didn't.

When it's cold and I first start it it idles at about 1500, drops to about 1000 when the temp needle starts moving and then down to about 750-800 when it's almost all the way warm. But when it's fully warmed up, the rpm's drop too low for it to stay idling. Unfortunately I can't do the biss screw adjustment because it won't idle when it's fully warm. /ubbthreads/images/graemlins/confused.gif

 

[fuel]

can you adjust the BISS when it's cold so it idles higher and then hopefully it idles at an ok level when warm so you can then adjust properly?

 

[fuel]

how is it on performance? maybe the CAS has moved and the timing has been retarded a bit?

 

[92_talon_awd]

No noticeable change in engine power when I drive it. I'll check the base timing tomorrow and make sure it's still correct. The throttle body bracket was tight when I pulled it off so it seems unlikely, not impossible though. I'll try and up the idle too and adjust from there. Thanks.

 

[idreamidrive]

Does unplugging the maf let it idle when it is warm? I was chasing my tail a little while ago and it ended up being my maf. I unplugged the maf and it idled, plugged it back in and it would die, but my car didn't have any of your symptoms as mine had a cold start issue.

 

[92_talon_awd]

I haven't thought of that, thanks for the suggestion. I'll give that a go too.

 

[KiNgMaRtY]

Its sounds like the FIAV is functioning properly. It sounds like it might be a ISC issue. Check the resistance on it.
click

 

[92_talon_awd]

The original ISC motor had the proper resistance, when I replaced the FIAV I put another ISC in with it and that one also checked fine on the multimeter. Seems like an ISC problem, the first thing I did was check the ISC and it was fine. I have heard of ISC's not working properly, even when they test fine. That's something I may have to investigate if all else fails. Just got back from my morning run so it's time to head out to the garage and test some stuff.

 

[transparentdsm]

Did you look at the ISC driver inside the ecu? maybe the board is fried.

 

[92_talon_awd]

So I checked a bunch of stuff today. I first checked the timing, somehow it was 12 degrees BTDC. I put it back to 5 but it was very obvious the CAS hadn't moved, it had deep indentations from the nut that was on it. I then checked the timing belt to make sure nothing goofy was going on there. It's set where it needs to be. I unplugged the MAF, car dies right away. Adjusted the BISS and got it to idle when it's warm but I can tell something is still wrong.

I adjusted the BISS to 750 RPM's and then after removing the grounds from the two pins and revving it a few times the idle changed to 1000 RPM. So I reground the two pins and set it back to 750. This time after revving it a bit, it settled around 700 RPM so it looks like it is able to be driven at this point. Turning on accessories still drops the RPM's and they don't recover. With the blower on high and the headlights on the RPM's drop down to about 550. Just for fun I had the OEM alternator tested but it tested fine.

I sure hope it's not the ECU because I spent about $165 when I first got it to have ECU Tuning repair it... Guess I'll pull it tomorrow and check it. Is there a way to check for damage besides visual inspection?

Possibly unrelated question, what is the electrical connector on the power steering pump for? Is it turbo specific because my GSX doesn't have it but the VR4 does. I remember my 1g had it and it wouldn't run without it connected.

 

[fuel]

the connector on the PS pump tells the ECU to increase the idle when the steering is on full lock - I'm surprised the GGSX doesn't have it as even my base model Galant had it. Turning A/C on should bump idle speed up too.

 

[92_talon_awd]

I gotcha. The pump has the nipple, I just don't see a wire for it anywhere. I thought turning on any of the accessories would bump the idle up but none of them do. I'm gonna pull the ECU after work and take a peek.

 

[92_talon_awd]

ECU still looks good, no obvious burns, leaks, corrosion, or swollen components. Would a non turbo DSM ECU work in the GGSX or are they different? I'm probably just going to put it back together and drive it like it is. Not sure where else to look.

 

[fuel]

I think a NT 90 DSM would work but not a 91+ unless you swap ECU pins.

 

[92_talon_awd]

I know my local pullapart has a NT DOHC 92, maybe I'll trip out there and see if the ECU is still around.

 

[holeshotmoe]

GGSX did come with the pump switch wiring. It is part of the same harness that goes to the alternator. It breaks away from the harness just before the alternator wires.

 

[Breakerrr]

Quoting fuel:
did you check the basics like throttle plate close adjustment - does the throttle plate close completely partially jamming up or is there complete smooth movement from closed to open? Check there isn't a build up of muck around the outside of the throttle plate further sealing off the flow.

My guess is the throttle plate is hard closed, the base idle screw is not allowing much bypass air through, and the ISC is at max adjustment when warm but the FIAV is providing enough bypass when cold to keep it from stalling.

What I would do:
1) remove throttle body to make work easier
2) clean throttle body and throttle plate
3) adjust throttle stop so throttle plate just closes but doesn't jam close, and then set TPS
4) refit throttle body and start engine and get up to temp (fully warmed up) then
5) perform base idle screw adjustment by grounding the base timing connector on the firewall and the diagnostic connector pin by the fuse box (check www.vfaq.com for this) and adjust base idle screw to desired rpms (750-800)
6) hopefully enjoy a stable idle hot and cold



I think the solution is going to be here. I had a similar issue when I swapped my throttle body. Good warm up idle and good once warm unless I was using accessories with significant amperage requirements, which dropped the idle to about 600rpm. When driving, the engine would stall if I let off the throttle very suddenly when running high rpm and/or if I was stopping while actively braking and using the lights, heater, stereo, etc. I would literally have to plan before every stop, slowly decelerate turn off heat, stereo, check temp and turn off cooling fan if possible, brake prematurely while relying on downshifting to do most of the work in an effort to keep the engine running. It was terrible, I hated driving.

The biss screw was almost all the way closed on the swapped TB. While cold the isc had plenty of room for movement to deliver good idle stability but when warm it was fully open. Trying to compensate I adjusted fuel settings which made the car run through the stops but adversely affected the cold idle. Which led me to the beginning of idle tuning and eventually the biss.

The odds overwhelmingly point to a problem with air delivery/metering over electronic failure. Many of us, including me, skip the tedious steps of checking for boost leaks and proper operation of the throttle body and it's related adjacent components like tps because they SUCK! Every time I or one of my local friends with 4g63's had idle issues it turned out to be either a leak somewhere after the air metering device or improper or malfunction of the TV or something connected to it. Being critical of your own work ethic when mulling through the basic idle tuning crap pays off.

OH, I have a 90 GGSX turbo non-Eprom ECU I'd be willing to send you on loan if all of the basics are checking ok.