Help! 1993 STS will not start!

[bringer]

Hey guys!

I own a 1993 Cadillac STS, fully equipped with the Northstar engine, of course. Over the past few days I have run into a multitude of problems, and not having much in the way of liquid currency to spend on it at the moment, I need help getting this sorted out so I can get to work.

When I attempt to start the car, it cranks over and sputters. It will not catch, and the engine will not start. I have charged the battery, and checked all of it's connections. They are nice, tight, and clean. I pulled the #2 spark plug to check its condition, and I could tell they haven't been changed in a while. It looks to me as though it is still good, however. The plug wasn't really fouled up or over gapped. I removed the EGR valve and cleaned it, just in case it was causing a vacuum leak. The valve was responsive prior to cleaning, and is now very responsive. I've checked the throttle body, its movement is firm, but it seems to be able to move fully. I've looked for any disconnected vacuum lines and/or wires. No luck there.

Quite frankly, I am at my wits end. I had some troubles starting it last week, but it just turned out to be a loose battery terminal, which was tightened immediately. Prior to my current situation, the car was acting extremely sluggish, as though it was powered by gerbils. It would take a good 30 - 50 seconds to reach 60 km/h. As we all know, any vehicle with a Northstar engine is significantly faster than that. The engine couldn't get above 4000RPM, and even then, it was a slow climb in revolutions. I attempted pulling error codes, and there were quite a few. Most of them related to the suspension, which has been changed out. The only current code was for the RR Wheel Speed Sensor, which is a problem I am aware of. All of the PCM codes were stored in history, they were:

P026 - Shorted Throttle Signal Switch
P030 - ISC RPM out of range
P052 - PCM Memory Reset
P095 - Engine Stall Detected
P109 - Keep Alive Memory Reset

I am not sure what to do, and I need to get to work. I don't have a second vehicle.

Any help would be greatly appreciated.

John.

[NickySantoro]

You might check the wiring to the throttle position sensor for fraying or grounding. TPS itself may have failed.

[bringer]

Sorry, I am a bit of a newbie with this. Where abouts is the TPS located, I assume on the throttle body, but what does it look like?

[patmc]

I know that you get code p052 whenever you disconnect the pcm. I would check the connections at the pcm. The pcm is located underneath your glove box. Under your glove box there are two screws on either side of the plastic piece that covers your pcm and other wiring, take them off. Your pcm should be a silver box with three harnesses, red, white, and blue. Just check all of the connections, you might have to take off the pcm to really be able to see. I have had one single wire come loose on the pcm, and the car ran like absolute hell. That's where I'd look, just be easy with the pcm and wiring. Good luck.

[jorghenry]

Originally Posted by bringer

Hey guys!

I own a 1993 Cadillac STS, fully equipped with the Northstar engine, of course. Over the past few days I have run into a multitude of problems, and not having much in the way of liquid currency to spend on it at the moment, I need help getting this sorted out so I can get to work.

When I attempt to start the car, it cranks over and sputters. It will not catch, and the engine will not start. I have charged the battery, and checked all of it's connections. They are nice, tight, and clean. I pulled the #2 spark plug to check its condition, and I could tell they haven't been changed in a while. It looks to me as though it is still good, however. The plug wasn't really fouled up or over gapped. I removed the EGR valve and cleaned it, just in case it was causing a vacuum leak. The valve was responsive prior to cleaning, and is now very responsive. I've checked the throttle body, its movement is firm, but it seems to be able to move fully. I've looked for any disconnected vacuum lines and/or wires. No luck there.

Quite frankly, I am at my wits end. I had some troubles starting it last week, but it just turned out to be a loose battery terminal, which was tightened immediately. Prior to my current situation, the car was acting extremely sluggish, as though it was powered by gerbils. It would take a good 30 - 50 seconds to reach 60 km/h. As we all know, any vehicle with a Northstar engine is significantly faster than that. The engine couldn't get above 4000RPM, and even then, it was a slow climb in revolutions. I attempted pulling error codes, and there were quite a few. Most of them related to the suspension, which has been changed out. The only current code was for the RR Wheel Speed Sensor, which is a problem I am aware of. All of the PCM codes were stored in history, they were:

P026 - Shorted Throttle Signal Switch
P030 - ISC RPM out of range
P052 - PCM Memory Reset
P095 - Engine Stall Detected
P109 - Keep Alive Memory Reset

I am not sure what to do, and I need to get to work. I don't have a second vehicle.

Any help would be greatly appreciated.

John.

If possible get a FSM. Definitely check the TPS. Check the ISC motor & harness.
Memory resets may be due to battery being disconnected. I have some code interpretation in my website www.gaisha-shuri-buhin.com.
If you check the PCM, just get the right front corner of carpet lifted up. This will give you a good view at the PCM harness connectors. Very unlikely any wires come out unless you mess arnd the area. good luck.

[Ranger]

Get a fuel pressure gauge on the service port on the fuel rail. Turn the key on and see what kind of fuel pressure you have.

[bringer]

Just wanted to give you an update. The problem has been solved.

Using a coil tester, we tested each individual contact on each coil. Two of the coils were sparking just fine, the other two were not. We switched up a good coil with one of the ones that was not sparking to see if the problem was with the ISC or the coils themselves. Upon doing so, the car started and we got sparks off of all of the coils. I am not 100% sure what was wrong, but it seemed to solve the problem. I used the built in diagnostics to test the firing of the cylinders, and I seem to have misfires on cylinders five and eight. I am attributing this to either plugs or wires and am going to replace them and see where I stand, as I don't beleive these cylinders are associated with the same coil.

Thanks for the awesome help everyone, I really appreciate the speedy replies and outstanding amount of insight you've had into the possibilities of what could be wrong.

Any more insight on the misfiring and/or potential causes of my problem would be greatly appreciated. I am also still getting an active P0030 Code - ISC RPM out of range. Is this something that I should just replace?

Thanks!

John.

[mikeay]

John,
Glad it started...verify the resistance on each coil. I sounds like you have a wire shorting out and by changing the coil you moved it in the right direction.

I can get you the resistance values...micyan@gmail.com

[bringer]

Okay.... So as to my earlier post -

The car WAS starting and running just fine, then all of a sudden it stopped dead and would not start. Same problem as before..

Maybe a bad ICM? Coils? Wires?

Ack!

John.