Experienced SC oppinions please!

FastBird91

Registered User
----The problems i am having on my 91' SC aod.---- The "perfect running SC" i have has just started running like crap and getting worst as time goes on. The problems is this......Now even at cold start up it idles a little funny, when it warms up it gets worst and might even start to shake bad enough to shut off. Often at restart.....it acts like the timing is waaay off, and eventually pulls enough power from the battery to crank it over and starts. My idle sticks at around 1500rpm especially when i gas it to stop it from shaking at a stop. The car smells lean. The harmonic balancer or the pulley seem to be wobbling or both. Can this all be caused by the harmonic balancer or pulley being broke or breaking??? Oppinions please.
Thanks
 
Ive been having the same exact problem with mine. My problem was the MAFS. Try this... unplug the MAFS and start it up and see what happens. If it runs fine its your MAFS. It could be a lot of things. I really dont know if the ballencer would be causing it to idle rough or not but if its wobbling its not helping any. Its a long and time consuming process but dont give up. Let me know what happens.
 
Hard Starts and FMEM

The Failure Mode Effects Management (FMEM) system may be in effect due to a problem in the DIS. A hard starting engine, where it takes several trys of turning the engine over, (turning the key off, and back on, and trying again) is a sign of a DIS problem. Maybe this is what you are experiencing when trying to start the engine. This is referred to commonly as "Limp Home Mode."


If you lost the Positive Impulse Pulse? (PIP) signal from the Krank Shaft Position Sensor (KPS), the Distributorless Ignition System (DIS) will fix the timing to 10 deg. with no advance; and use the Cylinder Identification Data? (CID) from the Camshaft Position Sensor (CPS) for Tach and spark timing.

A worn timing chain, or a CPS that is not adjusted exactly, will cause the timing to be off, as 10 deg. to the EEC could just a well be 0 deg. in reality if the CPS is off that much.
 
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Yes Paul i live so. Cal. Ontario to be exact. Do you have scanners etc.. to help me try and figure it out?
Thanks

Discipled1, I dont think its the Dis because it causes most of the problems when the car is warm unless the D.I.S. is failing at warmer temperatures.
Thanks again
 
FastBird91 said:
Yes Paul i live so. Cal. Ontario to be exact. Do you have scanners etc.. to help me try and figure it out?
Thanks

Discipled1, I dont think its the Dis because it causes most of the problems when the car is warm unless the D.I.S. is failing at warmer temperatures.
Thanks again
Give me a call after 4:30 weekdays (leave a voicemail if I dont answer, I generally return calls within 15 minutes). Judging by your user name, your car is a 91? We can check for codes without a scanner. I also have a spare DIS we can swap out for diagnostics if need be.

Paul
 
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Thanks Paul, This weekend i am installing a new powersteering pump on my SC and i also have another D.I.S. i was going to swap with to see if it takes care of any of these problems i have. I will let you know by posting to this thread hopefully no later then this weekend. Again thank you and if i need to come see you i will ask you if i can do it early next week if thats ok.
Bill
 
Hey Chadder1313, I went down to my SC and unplugged the mafs and started it up. The SC wassputtering a bit so while it was running i plugged it back in. After awhile it started to correct itself from sputtering and ran a little smoother. I unplugged it again while it was running and it started to sputter alittle again, I gave it some gas for a split second and it sort of stuck there at the higher rpm. I plugged the mafs back in and it immediately dropped rpm's but not to 800 or 900 like it should. The car was also warm so it should of idled at a lower rpm.
Thanks
 
FastBird91 said:
i also have another D.I.S. i was going to swap with to see if it takes care of any of these problems i have.
Be sure to get some dielectric grease for the DIS swap. DO NOT use heat sink compound.
Again thank you and if i need to come see you i will ask you if i can do it early next week if thats ok.
Sure, just let me know.

Paul
 
Paul, make sure to let Bill know that the problem usually ends up being the last thing you look for. :D

Hope you get it running good again.
 
The harmonic balancer or the pulley seem to be wobbling or both. Can this all be caused by the harmonic balancer or pulley being broke or breaking??? Oppinions please.

I think this is the problem. Yes it can cause it to run crappy.

Take a look and see if the head of the bolt that holds the balancer to the crank is still there. Try moving the pulley up and down or side to side.

David
 
Hi David, thanks for your oppinion. I went and popped the hood on my SC and was trying to pull the crank pulley in every direction to see if there is any play on it and was actually dissapointed because it was solid. I felt the large bolt in the center of the balancer and also the 4 bolts going from the pulley to the balancer. I am a strong guy and know if it was loose i would of been able to shake it back and forth. I started the SC and was eye balling the pulley and crank and noticed that it seems that only the pulley was wobbling a bit. The balancer didnt seem to be wobbling at all. I dont know if maybe the pulley is bent or what.
Anyways as the SC was running i disconnected the iac harness and the car started missing just like it does when i have those problems. It also seemed to be knocking while the iac harness was disconnected but i didnt pay to much attention to that because i can redline this motor and it never knocks at all. So as it is disconnected i rev the rpms to about 2500-3000 and when i let go of the throttle the rpms drop fast just like it shoul. I did this a few times and again revved up and revved down nice and smooth. When i plugged the iac harness back in the rpms when up to probably 1200 or so and took a long time to go down to about 1000 which is were it idles every since i started with these problems. I was at a wrecking yard a couple weeks ago and took the iac valve off of another SC and swapped it with mine hoping this would take care of my problem but it didnt change. I should of waited for a SC with less then 185,000 for the iac valve. But i figured it was good now im thinking it isnt good and it might be my iac valve. What do you think?
Thanks again
 
Paul, this statement is confusing to me:

Be sure to get some dielectric grease for the DIS swap. DO NOT use heat sink compound.

I can see using dielectric grease on the connectors at either end of the early style DIS module, but I would want heak sink compound between the DIS and the heatsink (aka AC/Jackshaft bracket).
 
FastBird91 said:
Hi David, thanks for your oppinion. I went and popped the hood on my SC and was trying to pull the crank pulley in every direction to see if there is any play on it and was actually dissapointed because it was solid. I felt the large bolt in the center of the balancer and also the 4 bolts going from the pulley to the balancer. I am a strong guy and know if it was loose i would of been able to shake it back and forth. I started the SC and was eye balling the pulley and crank and noticed that it seems that only the pulley was wobbling a bit. The balancer didnt seem to be wobbling at all. I dont know if maybe the pulley is bent or what.
Anyways as the SC was running i disconnected the iac harness and the car started missing just like it does when i have those problems. It also seemed to be knocking while the iac harness was disconnected but i didnt pay to much attention to that because i can redline this motor and it never knocks at all. So as it is disconnected i rev the rpms to about 2500-3000 and when i let go of the throttle the rpms drop fast just like it shoul. I did this a few times and again revved up and revved down nice and smooth. When i plugged the iac harness back in the rpms when up to probably 1200 or so and took a long time to go down to about 1000 which is were it idles every since i started with these problems. I was at a wrecking yard a couple weeks ago and took the iac valve off of another SC and swapped it with mine hoping this would take care of my problem but it didnt change. I should of waited for a SC with less then 185,000 for the iac valve. But i figured it was good now im thinking it isnt good and it might be my iac valve. What do you think?
Thanks again

I don't think the IAC is the problem....sounds more like a small vacuum leak. Spray all the IC tube connections and vac hoses with carb or brake cleaner to see if you can find a leak.

David
 
This weekend i am installing a new powersteering pump. While i have the intercooler tubes off i will look at all the vacuum lines closely.
Thanks
 
gldiii said:
Paul, this statement is confusing to me:
Be sure to get some dielectric grease for the DIS swap. DO NOT use heat sink compound.
I can see using dielectric grease on the connectors at either end of the early style DIS module, but I would want heak sink compound between the DIS and the heatsink (aka AC/Jackshaft bracket).
George, beyond the fact that the factory service manual states in bold:
Apply an even coat of approximately 0.80mm (1/32 inch), Silicone Dielectric Compound WA-IO, D7AZ-19A331-A (ESE-M1C171-A) or equivalent to the mounting surface of the ICM
experience from my SCPerformance days further supported not using heat sink compound. During the famous DIS shortage, we had a rash of modules returned to us that had apparently failed after as little as 2 weeks. The conclusion was that the each unit which failed had heat sink compound used with it. As a result, we began advising all who purchased a module to explicitly use dielectric grease only. Never had a failure after that.

Paul
 
FastBird91 said:
This weekend i am installing a new powersteering pump. While i have the intercooler tubes off i will look at all the vacuum lines closely.
Thanks

What are you using to seal the IC tubes ? Either get a set of Wynns teflon gaskets or use Permatex Copper RTV (orange). The stock teflon tape doesn't work too good at awkward angles (like when adding a raised top).

Put zip ties on all the vacuum hoses.

David
 
FastBird91 said:
I have Wynns teflon gaskets. What do you mean by put zip ties on all the vacuum hoses?
Thanks again

Where ever a vacuum hose attaches to a nipple, add a zip tie to the hose and pull it as tight as you can get it, then trim the excess with wire cutters. It serves the same function as adding a small hose clamp. Most of these connections are behind the supercharger and are a real pain to reach.

David
 
Hi david, thanks for ellabirating. I will definately do that tomorrow while i am putting on my new p.s. pump. My top is leaking so i will take that off and reseal it with copper rtv (im sure that will work) and while i have the top off i will check all the hoses and zip tie them tight. Quick question how tight should we torque the tops nuts (or bolts cant remember) and the intercooler tubes? Also if any hoses are cracked any reccomended type to replace them?
By the way i just got new tires today, 245/50/16 they fit awesome no rubbing anywere!
Thanks again
 
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