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1994 Geo Tracker 4WD 3spd with a 1995 PINK Body
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Discussion Starter · #1 ·
1994 Geo Tracker 8v 4x4 3 speed TBI. 173k Miles.

Just replaced the fuel pressure regulator and injector along with spark plugs and a million other things. When I got the car last month, it had a few new looking parts on it and the previous owners mentioned it had just had a “tune up”. Who knows what that actually means. This car has already made the top of my head bald from all the head scratching. Coming from Chevy V8s- it’s been a process figuring out this little car.

Situation:

Rough idling once warm. When it’s cold it isn’t half bad. Even sitting in the sun not running in Texas is enough to kick off the wonky idle. Bounces all around the range of 200-1500 rpm. Keeping the RPMs above 1500 kept me alive at red lights, otherwise it would’ve certainly died after 20-30 seconds of idling in any gear. Stalled on me a few times at red lights after cruising 100 miles on the highway easily. Really seems like it’s missing. Smells a little rich but with the idle losing it’s mind, I can sorta understand why. It’s acting like it’s got a vacuum leak, so I sprayed starting fluid all over and couldn’t get any “response”. I don’t think this problem is from a vacuum leak.

Reading through the forums I could somewhat-confidently narrow it down to the IAC or EGR system. The EGR assembly looked pretty new, as did the IAC assembly. I went ahead and took off the IAC and it looked like it had maybe 500 miles on it. Fresh gasket, clean metal, no carbon really, etc. I went ahead and cleaned it anyways just to make sure there wasn’t a chunk of crap in it, seemed perfectly fine to me with the exception of the waxy allen head looking absolutely stripped. Once that was off, I could see the EGR assembly had a Mitsubishi looking emblem on it. Also visible was a brand name on the throttle body “Mikuni Corp.” Seems aftermarket to me?

Could these aftermarket parts give me some trouble?

The IAC, EGR, and whatever the throttle body component was looked like it was from the same manufacturer. Same font and serial number styles. All look about the same age too. I’ll post pictures. (A piece of the IAC gasket fell off upon removal)
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99 Tracker, 5 door, 2L, 4x4
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You first need to confirm the engine timing, then the ignition timing, look up the procedure for checking and adjusting the TPS, all this before chasing any idle adjustments..

What you have is known as hunting (ECU is not in control of idle...)
 
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1994 Geo Tracker 4WD 3spd with a 1995 PINK Body
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Discussion Starter · #3 ·
You first need to confirm the engine timing, then the ignition timing, look up the procedure for checking and adjusting the TPS, all this before chasing any idle adjustments..

What you have is known as hunting (ECU is not in control of idle...)
Timing is good. Just redid the timing belt, valve lash, distributor o rings. Timing seems perfect. and i’ve played with it a good amount to make sure it’s as good as it gets.
 

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1991 Hardtop 3-door Tracker 1.6L 4WD 5-Speed No A/C
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998 Posts
I can't speak to your exact vehicle, but there are plenty of parts in Trackicks from other manufacturers. Lots (most?) ECU, for example, are from Mitsubishi.

That being said, it does not mean that any particular "off-brand" part on yours is original.

Mikuni is a maker of lots of carburetors, and fuel system parts.
 

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Just for your info, the timing belt on these vehicles is done to #4 firing. There may be 2 different marks on your cam pulley, an E/60 mark and an I/80 mark. We use the E/60. Doing a compression test will verify the valve timing. On the 8v engine, a vacuum leak will make a high, constant idle, which is not your symptom.
As Aqua says, I’d first confirm your timing belt/valve timing at #4 firing, ignition timing at #1 firing, spark plugs gapped to .7 mm, and then look to calibrating the TPS idle switch, after confirming those other circuits are correct.
You don’t advise exactly what your 8v does from cold start, but it should rev to about 2000 rpm at start up, and then drop about 500 rpm as the throttle opener closes, The idle then slowly drops from 1500 to factory 800 rpm as the engine warms up…..
 

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1994 Geo Tracker 4WD 3spd with a 1995 PINK Body
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Discussion Starter · #6 ·
Just for your info, the timing belt on these vehicles is done to #4 firing. There may be 2 different marks on your cam pulley, an E/60 mark and an I/80 mark. We use the E/60. Doing a compression test will verify the valve timing. On the 8v engine, a vacuum leak will make a high, constant idle, which is not your symptom.
As Aqua says, I’d first confirm your timing belt/valve timing at #4 firing, ignition timing at #1 firing, spark plugs gapped to .7 mm, and then look to calibrating the TPS idle switch, after confirming those other circuits are correct.
You don’t advise exactly what your 8v does from cold start, but it should rev to about 2000 rpm at start up, and then drop about 500 rpm as the throttle opener closes, The idle then slowly drops from 1500 to factory 800 rpm as the engine warms up…..
Valve timing and ignition timing is spot on. Plugs are now cleaned and gapped, two were slightly off. I calibrated the TPS and have it spot on. It was wrong before. It was turned clockwise too far making the throttle position read too high. Now that the TPS is calibrated, New symptoms have emerged. No more missing- running really smooth in D and R (700-1000 RPM at a stop). Exhaust smells less rich and i’m getting about 10mpg. But parked and neutral RPMs are 1400-1700 warmed up. Cold RPMs start at 2000 then go down to 1500 as it warms up. No CEL and I verified the CEL works. Just doesn’t seem to drop the RPMs after warming up. Idle adjustment screw is in all the way, messing with it doesn’t seem to do anything really. And the brake dash light is on now. It gets brighter when I engage the parking break so it’s a legitimate warning light, not sure how to diagnose it since there isn’t a CEL and the brake system was just replaced.




Otherwise drives pretty nice. Unless the high idle is an easy fix, I’ll probably just leave it. Since it doesn’t seem to cause too much harm and charges the battery and gets the A/C working faster, I’ll leave it.
 

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How can you adjust the ignition timing, when you cannot achieve 800 RPM in N or P?
 
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I’m curious as to what ‘spot on’ actually means. Have you done a compression test to verify the valve timing? If not, please do one, and post your results, cylinder by cylinder. That’s normally the best place to start, as everything is based on proper valve timing. If that’s incorrect, then testing other circuits is immaterial.
 
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