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Idle Surge/Ignition Timing Nightmare

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90_GSX_DSM

10+ Year Contributor
112
3
Nov 17, 2008
Fleetwood, Pennsylvania
Alright guys the car is a 90 GSX. I had a pretty tough time getting the base timing to 5*BTDC. The CAS is maxxed out in the advanced position. I have Link so I'm positive I was doing this with the pin grounded. It was idleing a bit higher than 750, maybe around 850-900. Also double and triple checked to make sure the CAS wasn't 180* out. Also double and triple checked to make sure mechanical timing was on.

I recently had my head off because it threw a rocker. I had this issue before the head was off though. Also found out that my old crank pulley had spun about 2 inches on itself. Which made it impossible to set ignition timing. I got the new pulley and like I said I can get it to 5* btdc but the CAS is all the way advanced.

Last year was the last time I didn't have issues with the ignition timing or idle surge. I did change a lot of things over the winter that could affect the idle. I converted to a n/t style TB with the FIAV blocked off from throttlebodies.com. He says he tests all the sensors in the tb so I'm guessing the TPS and ISC are good. I tested the ohms on the ISC myself and it was good. Also got a new JMF intake.

I've been fighting this all year and it's kicking my ass. Car runs and pulls good minus the surge. I've looked time and time again for boost leaks but can't find any. When it starts to surge I can hear what sounds like a large vaccum leak coming from the tb but I can't pinpoint it. Idk if that's the isc opening up to compensate or what. If anyone has any input that would be awesome . Thanks!
 
you sure your throttlebody shafts are okay? thats a common leak and a big one and well mess with your base timing settings...and having the cas all the way advanced isnt a good thing, id get this issue fixed first before you go driving it.
 
I'm pretty sure I figured out the idle surge. You can't just swap a 91+ isc motor into a 90 without either switching 2 wires or using the 90 isc or the isc will run backwards. As for the cas being adjusted all the way I know it's not a "good" thing but I've been running it like that all year and my motor is 100% fine. Got the car tuned like that, and made some passes at the track. Leakdown tested it a couple weeks back and my worst cylinder is #2 @ 5%leakage through the rings. I'm running link so I can keep track of knock and the most I currently see is 0.4* of knock retard.

With all that said I still know it shouldn't be quite like that. Although I did just come from the Shootout where I saw at least 30 cars with the CAS completely maxxed out in the advanced position.
 
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well then theres something wrong there, it doesnt have to be in the middle a little bit advanced is ok but all the way its not, i want to say its a bad cas.
 
I thought the same thing. I had a 90 cas in there. I converted the the 91 style and same exact thing. I guess this cas could be bad too. I was always under the impression that when cas's go bad you know it.

Swapped in my 90 ISC to match my 90 harness and waaa laa! Idles like a champ now. Still not exactly happy with the whole timing issue but I re checked the mark on the crank pulley with the motor TDC and the mark was right in line with the TDC line. Reset the idle to right around 750, ground the timing plug and the timing light showed 5* BTDC maybe even a little bit before it around 3-4* BTDC. And around 6*-10* with the connector un-ground.

So I mean everything is mechanically where it should be it's just the cas is fully advanced.

Alright I have a bit of an update. I really wanted to eliminate anything mechanical. The adjustable cam gears I bought were a little weird in that they didn't have the normal horizontal marks because they were for an Evo. So a guy at JNZTuning tried to match them up with a stock set and marked them for me. This made me think that it was very possible for him to have accidentally marked one gear off a tooth.

So to avoid that possibility today I swapped out the adjustable gears for stock gears. I checked the timing marks before I pulled the belt and they looked fine yet. Didn't get any pictures of the before but I did snap pics of the marks when I put the belt back on.

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Then I put everything back together, started the car up, and re-checked the ignition timing. I should note I also used a different timing light than the first time because I couldn't locate the original timing light. The new timing light was way different. You could adjust timing with it (I didn't know how), read the rpms, and see different cylinder pulses. So to be honest I don't know if I was using it right. With all that aside the timing was way advanced now. Probably at about 25-30* advanced. And it was just ALL over the place. Not staying in one spot like it should with the timing connector grounded. To get the mark remotely close I had to have the CAS all the way retarded this time. Needless to say the car didn't like that too much. So I don't really know what this now means. I guess the CAS could be bad. I guess I could have been using the timing light wrong since it was a way more advanced light than I ever used. I really need some input here because I'm at a loss.

Before I left I thought it would be a good idea to make sure the mark on the crank pulley lined up with the TDC mark on the timing cover while at TDC and it couldn't have been much more on the money. Here is a pic of that.
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Like I said any help is grately appreciated. I guess my new plan of action will be to try another CAS. That will be the third. And to try it with the timing light that I originally used.
 
It isn't my intention to resurrect an old thread, but there isn't much sense in starting a new thread if the issue is basically the same.

Did you find a solution to your issue? With the ECU grounded my timing is around 15* with the CAS fully retarded. All timing components line up at TDC including the harmonic balancer.
 
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