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Unread 07-17-2011   #1 (permalink)
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Default 96 SVT Cobra engine stalls, runs rough, runs rich all of a sudden

I bought a 96 SVT Cobra today with 39K original miles. I've been looking at this over 2.5 weeks. I test drove it, had my mechanic look at it, and the owner recently put like 250 miles on it, ran perfect. We go and transfer title. I go to take it home and not being used to a car with an alarm I set off the alarm. We disarm it and I drive home, literally 3 blocks. Runs great, We sit outside house with car idling, AC on, it's purring. It is low on gas but not on E. All of a sudden it stalls out. The check engine light and the Theft light come on. We try to start it. It starts rough, misses, and black smoke comes out drivers pipe. I'm freaking out. 1st I go get 5 gallons of Sunoco 93 and put it in, no difference. So I call the guy I bought it off, I'm thinking stop payment on check. He's cool and drives right over, he's freaking out too. He realizes I drove like 1/3 mile max. He see's what it is doing. He disconnects the battery for a few moments. Starts it up and after blowing some rich gas out of pipe all is fine. He revs it a few times it's fine. I drive it 18 miles, it works great, I fill it with Shell 93 and drive back 18 miles, it's great. Any idea what the hell happened other than to scare the **** out of seller and buyer who are both adults. This car was pampered, kept in a heated garage with a trickle charger. It's a 4.6 with a Super Chip, 5 Speed, New H pipe and flowmasters, no CATS, K&N Air Filter and always run on Royal Purple oil. Something with theft alarm. Could it have run low and drawn in gunk from bottom of tank? It was blowing so much smoke I was thinking rings or head gasket. Now exhaust is clean as can be, runs strong, idles about 800 RPM and smooth. Thanks, Spiney. BTW All gauges were normal.
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Unread 07-17-2011   #2 (permalink)
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buyer beware...sounds like the ECU has a problem and if I was the seller and you stopped payment on a check I'd have you arrested for Grand Theft Auto( note to anyone selling a car, make them pay you in cash!), the minute you take possession of a used car, it's yours, good, bad or ugly
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Unread 07-17-2011   #3 (permalink)
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I wouldn't have stopped payment, I was just freaking out. I'm on disability from 4 back surgeries. I've drove beaters for 20 years. It took all I had to get this and I owned it literally 5 minutes and drove 3 blocks when this happened. Seller was equally freaked out. He's a great guy and we both had a lot of trust. So far it's worked out after reset with battery it drove rest of day 36 miles flawlessly. Hopefully it was just a car brain fart.
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Unread 07-17-2011   #4 (permalink)
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it also could be that the imrc plates are sticking, I gotta tell you that a 96 Mustang could have alot of issues at any time...my stone cold reliable car is a Jap car...go figure
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Unread 07-17-2011   #5 (permalink)
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Could have been the chip had a hiccup or something. Especially after it ran fine after the battery was disconnected.
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Unread 07-31-2011   #6 (permalink)
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Default Update on 96 Cobra stalling issue

The car stalled on me again after a week or running flawlessly. Same situation as before I was sitting with AC on, car idling. It was very hot out, all gauges were reading normal. What I noticed this time is car stalled when I touched the Radio power button. Again engine stalled, check engine light and theft light come on. Car re-starts rough with black smoke coming out drivers side pipe. I was away from home and had no tools to disconnect battery. I let it sit for awhile, cycled the locks with key FOB. Then Theft light went out and car started fine. Almost seems to be something with anti-theft system, but why does touching radio set it off. When I reviewed last time this happened my wife was in car and she also touched the radio just as it stalled. Radio, CD, Tape, all work fine. Previous owner says this never happened to him and I believe him, he has been very up front and honest with me. It may have never happened to him because he told us he NEVER used the AC. He always drove with windows down. One thing I did since I had time and no tools was to remove and re-seat every electrical connector I could find under the hood. I know connections can go bad from a car just sitting. I plan on doing this again, but shoot some contact cleaner in each connector before putting them back together. If that doesn't fix it, I'm going to take it to the original dealer who serviced this car since it was new and have him run a diagnostic on the reader port and see what error code comes up when this happens.

Where is that port on a 96 Cobra? I know that's where the Super-Chip is located. I thought of removing that but I don't know where it is. Will removing that put the car back to original tuning specs or is there more to it than that?

I also wanted to remove the radio and see if there were any loose or pinched wires there, but I don't have the faceplate or radio removal tool. I guess that should have come with the car yes? Thanks in advance for any feedback. Spiney-dave
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Unread 07-31-2011   #7 (permalink)
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FWIIW, I have seen several threads where the car goes insane and it eventually gets traced back to an external "chip" in the PCM. What happens over time is the contact corrode and don't make good connections.

One thread I remember the OP found that water had leaked onto the PCM.

If this is a modified Cobra with larger injectors, the tune is required to make it work correctly. The motor suddenly running pig rich may be a symptom of reverting back to the stock tune.

That may give you someplace to start.

If you don't have an ODB2 scaner that is able to log operational data, perhaps it's time to consider getting one. It would really help on problems like this.

Say for example you noted that the MAF air flow suddenly increased by a large amount. Then you would focus on some sort of MAF problem.
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Unread 08-29-2011   #8 (permalink)
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Talking I think I fixed it!

I think I fixed it! I finally was able to get the kick panel off and get to the ECM. After much coaxing I was able to get the ECM out. When I did I found the Superchip was not seated correctly on the ECM. Further investigation found there was corrosion on both the Chip's contacts and the edge connector on the ECM. I cleaned them up with some Radio Shack Contact Cleaner and a toothbrush. Once I was happy with that, I re-seated the chip and then held it in place firmly with Gorilla Tape. Put it back in, crossed my fingers and she started. Ever since then, about 2 weeks now, she has been running pretty good. I do plan on adding the Hi-Flow Cats and getting a proper tune next spring but for now I'm going to save my money. Thanks for all of your feedback and advice. Spiney-Dave
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