Idles rough then dies?

MadMikeyL

SCCoA Member
I just bought an 89 XR7 5-speed. It's got 140K on it, and its acting weird. I bought the car 2 days ago, and when it was delivered, it needed to be jumped, but it ran fine. I started it a couple of times when I first got it, and everything seemed to be good. Well I registered the car today and I was about to drive down to the shop to do some work on the car, and it started and idled real rough and wouldn't rev up at all, then died. I replaced the battery incase that had something to do with it, and now it will start without needing a jump, but does the same thing with idling rough and dying. I tried unplugging various sensors to see if it made any difference, but none of them did. Anyone have any idea what this could be? Thanks.

Mike

PS. After my last SC I decided to stick to V8s in the future. Now I'm starting to remember why.
 
well

maybe your computer needs to relearn an idle. and after some time it should go away. otherwise, did you check your MAFs?

you said you unplugged sensors, where?

If you see no difference without a MAF then with it pluged it, clean it, and if no go, change it out.

does the tach jump around?
does it happen randmly or after a certain drive time, or idle?

i love my supercoupe, but finding random misfires, and things like this are so annoying. my problem was really dirty injectors, and regular 91 couldnt clean em out, so i used seafoam. worked like a charm. any codes? CEL light?

what about your boost gauge whats that reading on the vaccum side?
 
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It sounds like the computer is in cripple mode,it will run that way so you can get to a garage.Is the check engine light on,then get a code reader and see what the codes say.
 
Oh this isn't limp home mode. I can't even drive the car. The tach does move when cranking, and then when it fires its running between 200-400rpms. No matter where the gas pedal is, it won't rev any higher. As soon as I let off the clutch at all, it dies. As for what sensors I unplugged, I unplugged the MAF, IAC, and TPS sensors each individually, and none of them made any difference. Also there is a plug coming out of the DIS module with a little thing plugged into that. I guess this is an octane plug or something. Anyway I unplugged that and it made no difference either. I didn't see any check engine light, but now that I think about it, I don't think it lights up when I just turn the key on, so I will have to pull the codes to be sure. I'll probably do that tomorrow. What's really confusing me about this is that I had it running for about half an hour 2 days ago and there was absolutely no problem. I didn't drive it anywhere cause it wasn't registered, but it idled just fine, and as soon as I register the car, it won't idle at all.

Mike

Oh yeah, the boost gauge is reading between like 5"Hg and sometimes going up to a couple PSI of boost when its just trying to idle.
 
MadMikeyL said:
Also there is a plug coming out of the DIS module with a little thing plugged into that. I guess this is an octane plug or something. Anyway I unplugged that and it made no difference either.

That's the spout connector. IIRC, if you can pull that, and the car starts and runs with no problems - the DIS is bad. In this case, that doesn't appear to be it. Like I posted on TCCoA, I'd check the plugs and wires. Sometimes the simplest idea is the cure.

-Melon

EDIT: See if you can pull a plug, one of the few easy ones to get to and make sure it's not fouled. I saw your reply on TCCoA so if you didn't do anything with it, the firing order is probably still good.
 
only reading 5HG at idle? Even though its only 400 rpm, you should have more than that. Sounds like you have a serious vac leak. Look for hoses off or cracked, make sure your intercooler pipes are sealed up good.

Or you could try dropping the insurance, throwing on some expired tags and unplugging your tail lights, these cars like to run on the ragged edge......:)
 
check your TPS, IAC, MAF, CAM sensor, check for vaccum leaks.

unplug MAF and start engine
if stull doing the same
connect it back in when engine running

do same for IAC when engine is running
if it quits and will start again and quits but have to use peday to idle
plug it back in and idle comes up

does it run like that when cold, warm, hot, everheat?

also check you knock sensor, and ACT / IAT

42277123
 
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I think it's the DIS Module or your balancer is about to fall off and your getting a bad signal from the crank sensor.

David
 
May have found something

Ok, I was looking at the car today, and I noticed something that might have to do with this. By the cam sensor there are 3 plugs. One plugs into the cam sensor, and then there is a loom coming up from what looks like the crank sensor. That loom mostly goes to one connector, and then there is one other wire that splits off from this loom and goes to another connector of its own. That wire had a section replaced, but they replaced it with uninsulated wire and what part is insulated is cracking and breaking. Does anyone know where this wire is supposed to go so I can re-wire that and see if it improves the situation. Thanks.

Mike

PS. The check engine light does come on when the key is turned on, but it doesn't come on when the car is barely running.
 
cats

I have a 92 5.0 H.O that had the same problem. I replaced the fuel pump to no avail. Then I took the intake tube off and tried to start it. It started then quit blowing exhaust smoke out the intake tube. I found out the cats had fallen apart inside clogging the exhaust, idling around 4-500 rpms then dying at the slightest hist of hitting the gas. I fixed the cats and it fixed the problem.
 
Ok, I messed with that botched wiring some more, and where before it would start and barely run for a little while, now it won't start at all. That leads me to believe that the wiring is the problem. Can anyone tell me exactly where that wire goes to so I can re-run a new wire and see if it fixes it. I'm talking about the wire that comes up with the wiring for the crank sensor then splits off and has its own seperate connector. This is on the front of the engine right between the DIS and the cam sensor. Thanks.

Mike
 
The only wires headed that way on mine ARE the crank sensor wires. Sounds like you found your problem. I would be really leary of your balancer though...
 
Reminds me, when I replaced my crank sensor/balancer. The factory sensor has two plugs and one has only one wire and had what looked like a replaced section with loose cloth insulation. Thats the way it came from Ford....
 
Well I figured out the problem. I was too busy looking at all the sensors and trying to find something complicated that I missed the obvious things. Turns out the gas gauge just isn't very accurate and the car was out of gas even though it said it had 1/4 tank. Took the car out driving for about 2 hours last night and it runs awesome.

Mike
 
MadMikeyL said:
Well I figured out the problem. I was too busy looking at all the sensors and trying to find something complicated that I missed the obvious things. Turns out the gas gauge just isn't very accurate and the car was out of gas even though it said it had 1/4 tank. Took the car out driving for about 2 hours last night and it runs awesome.

Mike
make sure its the premium, and from chevron or 76. arco makes my car run crappy at idle, and boost.

also try no tto let the gas get under 1/4 full. it will burn up the fuel pump faster, supposedly. makes it hotter.

glad to know it was a relativley cheap fix:D
 
im having a similer problem the car decides it wants to idle sometimes then sometimes i start it and the tach jumps around
and shes dying when shifting from park to reverse or park to drive or when sitting at a red light

dis?
 
TwoToneThunder said:
im having a similer problem the car decides it wants to idle sometimes then sometimes i start it and the tach jumps around
and shes dying when shifting from park to reverse or park to drive or when sitting at a red light

dis?

Tach jumping around is usually caused by a bad cam sensor....easy fix.

David
 
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