New SC given me probems

midnight rider

Registered User
Hey, I just purchased my 3rd SC off my friend who had replaced the crank and the balancer after his old one broke. Well now that it is running (somewhat) it is giving me all kinds of problems. When started sometimes its smooth then the warning lights will shut off tach drops to zero lights come back on tach jumps back up and it starts missing like crazy and all this happens in a split second. Sometimes when you start it its already missing real bad and when you rev it it smooths out for a second then it starts missing again and the whole time this is going on the tach seems to work right sometimes and do what it wants the rest of the time. I have swapped out the crank, cam, ICRM and DIS module. I do know that it needs the plugs and wires changed which I am going to do this week, but timing and the firing order is correct. I also know that he used a differnt wiring harness of another SC motor for the top half of the motor because he couldn't find his at the time. The car has sat for about 1 year since the motor has been finished and it was doing the same thing when we first had it running. So, if anyone has any ideas thanks in advance.

Shawn
 
It definitely sounds like an ignition problem, like crank sensor or DIS module. I wonder if you might have a bad wire somewhere? Maybe your friend had to make some splices with the different year harness?
 
Hey, I just purchased my 3rd SC off my friend who had replaced the crank and the balancer after his old one broke. Well now that it is running (somewhat) it is giving me all kinds of problems. When started sometimes its smooth then the warning lights will shut off tach drops to zero lights come back on tach jumps back up and it starts missing like crazy and all this happens in a split second. Sometimes when you start it its already missing real bad and when you rev it it smooths out for a second then it starts missing again and the whole time this is going on the tach seems to work right sometimes and do what it wants the rest of the time. I have swapped out the crank, cam, ICRM and DIS module. I do know that it needs the plugs and wires changed which I am going to do this week, but timing and the firing order is correct. I also know that he used a differnt wiring harness of another SC motor for the top half of the motor because he couldn't find his at the time. The car has sat for about 1 year since the motor has been finished and it was doing the same thing when we first had it running. So, if anyone has any ideas thanks in advance.

Shawn

  • Tach jumping around has almost always been a crank sensor. Also check your coil wire and cam sensor connectivity.
  • If the Wire harness is in question, swap it out.
  • If it's just running rough that could be a vacuum leak through the IC tubes. Insure you have a good joint connection and the two bolts on the brackets to the IC and IC manifold pipe are torqued properly. I used 220 inch pounds and the teflon IC gaskets but if you want to cheap it out, use some good strong RTV.
 
Still no luck

Thanks for the response, I changed out the plugs, wires, coil pack and alternator yesterday and it seemed to help a little bit but it is still missing real bad and the interior lights keep going off and coming back on along with the tach dropping out and coming back up and everytime it does that it starts running worse. I am going to check my grounds and change out the pcm this evening if it quits raining.

Shawn
 
I have the same exact type problem on my 92 SC..i posted about it a few months ago when i first bought it...haven't had no time for it really but mine is doin everything yours is but the IRCM buzzes too and now it won't start...i traced some more buzzin noises to back behind the SC...my problem might be in the fuel rail wiring harness cuz i can touch the wires and feel the buzzin if that makes any sense and smell the insulation on the wires burnin..so i gotta tear into it...i'm curious to see what responses this thread gets because i also need help with mine but im goin to suggest to check ur wiring...seein how u already replaced everything pretty much...
 
I believe what you both are experiencing is a direct electrical short. The missing in the engine is the ECM losing a heck of alot of DC voltage, almost to the point of shutoff. This would also explain the electrical gremlins in the cabin lights and the Tach and the warning lights too. You said this is a 92? Put a VOM on the battery and see if you have a massive voltage drop when the symptom occurs. Also when it's happening open you door and see if the seatbelt moves forward really slow, (if you dont do the volt meter test). Also check at the pigtail connector on the passenger side firewall to where the main Engine harness comes in. I had an SC do that and it turned out to be 2 things. 1 was a short in the Main radiator fan, somehow fused the IRCM relay and was not blowing the fuse in the underhood fuse panel. And 2 was a pin connector popped out of the pigtail and started to touch ground of the car.

Good luck!

I have the same exact type problem on my 92 SC..i posted about it a few months ago when i first bought it...haven't had no time for it really but mine is doin everything yours is but the IRCM buzzes too and now it won't start...i traced some more buzzin noises to back behind the SC...my problem might be in the fuel rail wiring harness cuz i can touch the wires and feel the buzzin if that makes any sense and smell the insulation on the wires burnin..so i gotta tear into it...i'm curious to see what responses this thread gets because i also need help with mine but im goin to suggest to check ur wiring...seein how u already replaced everything pretty much...
 
Now that I think about it, deffinatly check your ignition switch!!! Sounds like a momentary power loss due to direct short in column causing your issues

I believe what you both are experiencing is a direct electrical short. The missing in the engine is the ECM losing a heck of alot of DC voltage, almost to the point of shutoff. This would also explain the electrical gremlins in the cabin lights and the Tach and the warning lights too. You said this is a 92? Put a VOM on the battery and see if you have a massive voltage drop when the symptom occurs. Also when it's happening open you door and see if the seatbelt moves forward really slow, (if you dont do the volt meter test). Also check at the pigtail connector on the passenger side firewall to where the main Engine harness comes in. I had an SC do that and it turned out to be 2 things. 1 was a short in the Main radiator fan, somehow fused the IRCM relay and was not blowing the fuse in the underhood fuse panel. And 2 was a pin connector popped out of the pigtail and started to touch ground of the car.

Good luck!
 
Well, after throwing lots of parts I checked the intercooler tubes by spraying carb cleaner on them while it was running and found the bottom intercooler tube was loose, which when tightened helped tremendously. It still has a miss which I think is due to bad gas for sitting so long. I still haven't figured out why the lights flicker, which it is everything that flickers and there is a relay under the hood which I think is the fuel pump relay clicks when this happens, like its loosing power then coming back on.I've checked the wiring under the hood it seems ok no bare wires and no cuts, I still have to check the switch on the column which I will get done today. It is a 90, and thanks for all the help.
 
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