1993 SHO potential problem

[Obi]

Hey everyone
I have been eyeing this 1993 sho at an auction
I requested an inspection since I can't physically inspect the car myself and got the follow response from the inspector:

When the vehicle was started the first time it idled good; however, it was started a second time and once warm it had a rough idle and misfire until turned off.

What could this be?

Thank you in advance

 

[luigisho]

Oh jesus it could be anything. If it is good until warm then usually the loop programming changes to more sensor input. Something isn't right and was there a difference in how long it ran? Crapshoot. Idle air, MAF, crank sensor...

 

[Obi]

Oh jesus it could be anything. If it is good until warm then usually the loop programming changes to more sensor input. Something isn't right and was there a difference in how long it ran? Crapshoot. Idle air, MAF, crank sensor...

i wish i know exactly what happens after that ... but they said it doesnt over heat but runs rough when its warm... also said that belts need to be changed

 

[NoSlo]

90% crank sensor. 8% DIS module etc. 2% IAC problem. Probably why it was sent to auction. $200+ sensor remanufactured (or used) & significant labor.

 

[BaySHO Performance]

If it was the crank sensor, the car wouldn't start at all, so it can't be that. Tough to pinpoint without pulling the codes. It could be the camshaft sensor acting up (especially if the tach misbehaves). Or the DIS breaking down with heat because of a lack of heat sink grease on the back. If that was the case, and especially as it was misfiring, the car may have not been running on all cylinders, in which case raw fuel could have got into the cats. That will have at least compromised them, and could easily have damaged them. May even be a bad plug or plug wire, or a vacuum leak.

 

[Obi]

Sorry what are the "cats"

If it was the crank sensor, the car wouldn't start at all, so it can't be that. Tough to pinpoint without pulling the codes. It could be the camshaft sensor acting up (especially if the tach misbehaves). Or the DIS breaking down with heat because of a lack of heat sink grease on the back. If that was the case, and especially as it was misfiring, the car may have not been running on all cylinders, in which case raw fuel could have got into the cats. That will have at least compromised them, and could easily have damaged them. May even be a bad plug or plug wire, or a vacuum leak.

 

[NoSlo]

If it was the crank sensor, the car wouldn't start at all, so it can't be that. Tough to pinpoint without pulling the codes. It could be the camshaft sensor acting up (especially if the tach misbehaves). Or the DIS breaking down with heat because of a lack of heat sink grease on the back. If that was the case, and especially as it was misfiring, the car may have not been running on all cylinders, in which case raw fuel could have got into the cats. That will have at least compromised them, and could easily have damaged them. May even be a bad plug or plug wire, or a vacuum leak.

The crank sensors seem to go out gradually in a large number of cases - running until they get heated up, then intermittently cutting out until non-functional. A cool-off, and it works again for a while, getting worse until it ultimately fails.

This thread reflects my experience: https://shoforum.com/index.php?threads/rnginr-shut-off-while-driving.128333/

 

[BaySHO Performance]

I've never had a case with the some 250 SHOs I've worked on in the last 21 years where the car has misfired because of a bad crank sensor (CPS). They either run fine or the car dies. Car will start again after the CPS cools down or after the coolant from a leaking water pump that shorted it out evaporates.

"cats" are catalytic converters.

 

[Obi]

I've never had a case with the some 250 SHOs I've worked on in the last 21 years where the car has misfired because of a bad crank sensor (CPS). They either run fine or the car dies. Car will start again after the CPS cools down or after the coolant from a leaking water pump that shorted it out evaporates.

"cats" are catalytic converters.

Interesting

 

[NoSlo]

I've never had a case with the some 250 SHOs I've worked on in the last 21 years where the car has misfired because of a bad crank sensor (CPS). They either run fine or the car dies. Car will start again after the CPS cools down or after the coolant from a leaking water pump that shorted it out evaporates.

"cats" are catalytic converters.

You write yourself in another post: "Well, one would think that, because the CPS allows the car to start once it has dried out, it survives the ordeal. However, I tried a compromised CPS in a different car, and it kept on breaking down once the engine got hot."

 

[BaySHO Performance]

You write yourself in another post: "Well, one would think that, because the CPS allows the car to start once it has dried out, it survives the ordeal. However, I tried a compromised CPS in a different car, and it kept on breaking down once the engine got hot."

Yes, I said that. And it does happen. But the key here is that when the CPS malfunctions, it ALWAYS kills the car. It NEVER causes it to run rough or misfire, as is happening in this case.

 

[NoSlo]

Yes, I said that. And it does happen. But the key here is that when the CPS malfunctions, it ALWAYS kills the car. It NEVER causes it to run rough or misfire, as is happening in this case.

I guess the key is if I misread the first post as "until IT turns off".

If the car keeps running but just poorly, the first thing to do is don't let the owner see the inspector pull out the spark plug wires to spot the 1" deep oil in the spark plug wells. Pay cash, get the title, then blow them out and drive away..

 

[rubydist]

First, your inspector did you a dis-service by not providing you with the codes since it was apparent to him/her that the car did not run right. I would request my money back.

Second, Nick is right that it is highly unlikely to be a crank sensor issue, because the failing crank sensor causes the engine to die, not to run poorly.

There are a bunch of possibilities ranging from easy to hard that could be the issue here, but since you have no codes to guide you, you are still in the dark.

 

[Obi]

First, your inspector did you a dis-service by not providing you with the codes since it was apparent to him/her that the car did not run right. I would request my money back.

Second, Nick is right that it is highly unlikely to be a crank sensor issue, because the failing crank sensor causes the engine to die, not to run poorly.

There are a bunch of possibilities ranging from easy to hard that could be the issue here, but since you have no codes to guide you, you are still in the dark.

Well the car is at an auction and so far the bid reached 1800 and I dunno how far I show take it lol.
It's 1993 with manual transmission , and low miles

 

[BaySHO Performance]

To my mind, none of the possible problems will cost much to fix with one exception. No biggie if it's a camshaft sensor ($38), DIS Module ($201) or bad plug or wire. Don't think it's a vacuum leak causing a rough idle.

The one thing to watch out for is that the misfire may have compromised the catalytic converters. Whole MTX Y Pipes are available from SHO Source for $600, I think a ball park for a pair 49 State cats is around $400. If so, cheaper to get a SHO Source Y Pipe when adding the labor cost, unless you can do your own welding.