94 SC stuttering badly

Mercutio

SCCoA Member
Okay, so my new 94 SC has been running fine since I picked it up, barring the bad oil sender problem. But now a new issue: after letting the car sit for 3-4 days and driving my other Bird, the car is stuttering and hesitating very badly. It only seems to happen when I give the car enough throttle to hit 6-7 psi or so, and the car can barely run at that point. Trying to drive this big car with such limited boost is, well, no fun. Any ideas? I'd guess maybe fuel pump or spark plugs, but I'll take any of your guesses. I can fix stuff, but I'm lousy at diagnosing it, so any help would be appreciated.
 
yeah man

could be the plugs, im having a similar problem and ill let you know.
i would also suggest cleaning the injectors and mafs. make sure your air filter isnt dirty, and make sure your getting good gas

you would probably get a better gas at 76 or chevron. make sure there are three hoses, one for each grade, too many times my cars excellerates badly from what i think is bad gas.
 
More info

Okay, after some more testing it appears that the timing is jumping all over the place. At idle the timing is about 28*. Give the car a little gas and the timing advances to 35-42*, but really get on the gas and the timing falls all the way to 7*. Next question: what is causing the timing to drop so drastically? I've already replaced the DIS module and the crank sensor. We've removed and inspected the harmonic balancer, and it looks okay, but then again this is the first SC I've ever worked on. What's up here?
 
The timing is most likely jumping around because of the missing under a load. 99% of the time bucking under boost is caused by bad plugs or wires. Suggest replacing both before doing anything else.

David
 
I tried replacing the plugs and wires early on. That solved the problem for 2 days or so before the problem came back. I replaced the plugs again, which didn't help. I did not replace the wires a second time. Could something be causing the wires to go bad so quickly, and if so, what?
 
Shouldn't have pulled that balancer off. It's a one time use deal. It will fail on you shortly. Get a BHJ now. I'm not joking. I had mine off, put it on with a new bolt, and less than a year it broke off and left a chunk pressed onto the snout of the crank I had to drill it off.

As for the missing, time for a tuneup. Get some Autolite plugs have them cross reference AWSF32PP and get you the autolite equivilent. Summit has wiresets for our cars that work nice. I actually got a set of wires at autozone w/ lifetime warranty for around $30.00 and they work fine.
 
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I have actually put in a ton of work trying to diagnose this problem. I tried the Autolite plugs; they didn't help, so I tried Motorcrafts next. As for the tuneup, I've already replaced the DIS module, cam sensor, crank sensor, coil pack and had Lonnie burn a new chip for me to see if it was a software problem. We're way beyond "time for a tuneup."
 
Have you checked your fuel filter and fuel presure. I have also seen clogged converters make cars run real bad.
 
I'm going to guess it's plug wires, since you did get rid of the problem once, if only for 2 days when you replaced the plugs and wires. Since then you've replaced plugs again which didn't help. Maybe the wires were defective? Also, everyone seems to advise using a little dielectric grease inside the boots on both ends when installing - seems to help too.

I had the exact same problem. Changed the plugs and that didn't help. Changed the wires with a regular dealer set and the problem went away completely. What brand of wires did you use?
 
I used Motorcraft wires. I guess I'll try that again, but I should also mention that the fuel pressure is fine, and that we pulled the knock sensor to see if it was pulling out timing for some reason, but that made no difference either.
 
throwing this out

but couldnt it be a bad cat?

figure you had a bad set of plugs letting excess unburnt fuel through into the cat, now its bad, causing problems under boost.

when a similar problem happened with my fiero gt i was on the freeway, and i saw sparks shooting out of the exaust, i dont use the bottle so i knew it was time for new cats.
 
I can promise it's not cats, since I don't have any. The problem is the timing--what's causing it, the computer, crank sensor, knock sensor, what?
 
If it's sensor-related (crank, cam, etc.) you'd probably have error codes, and possibly the check engine light on. Have you tried to pull your codes?

With my bad plug wires, I wasn't throwing any codes at all, but whenever I'd get into any boost, it would just stutter and go nowhere :(
 
the check engine light is on because the EGR system has been removed, but the computer doesn't throw any codes.
 
Did you replace the DIS with one from ford??? I have heard some bad things about chain auto parts stores DIS's.
 
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