Bucking problem

[Chrisssssssss]

Crap.

After spending $500 on some new Flowmaster 40 series 2 chamber mufflers (when I ripped the other ones off by going through a snowbank on the WAY to go skiing) I now have a problem with the car bucking and surging. I am thinking that it would be the CPS from reading other posts with the problem being the CPS. It seems to be the same symptoms, but the car has not stalled yet.

Here's what happened... I was driving my car out of the garage for the 2nd time that day, with about a half of an hour in between. The car was not cold. I went to the end of the street and was proceeding to make a right turn at an intersection, going slowly, but still in second gear. I started going again in second gear (almost from stop) and as soon as I started rolling again, the car started to buck and surge. This lasted for about 10 seconds. Then throughout my trip (about 20 mins) I got the odd buck. Once I noticed that when the car bucked (the first time) that I was at about 2000 rpm's and then the tach pegged to about 10,000 rpms then went back to 2000 which was the right reading. The engine was not spinning that fast, but the tach went screwy.

The check engine light came on throughout the trip, and stayed on. I got a code of 511.

So I parked the car and when I went to work about 2 hours later, the car seemed to be doing the same thing.

Any Ideas? Sorry for the long post, but I know that the more detailed the post, the better the ideas. Help me out O'SHO Gods!

Please let me know if there is any other details that is needed. I know this will really suck if my car is incapacitated over the holidays, especially if I can't get a new part until the new year.

Thanks in advance.
-Chris
'92 MTX Emerald green 166K miles Superchip, K&N, and new Flowmasters.

 

[sdpatt]

Your symptoms do not sound like those of a failing crankshaft position sensor. The 511 code is "EEC processor ROM test failure." It sounds like you have a computer problem. Sorry, I wish I could solve it with a simple diagnosis.

Scott

 

[Chrisssssssss]

Do you think that with a superchip that this could be a culprit. I have never had this problem before. The only thing that comes to mind is that the car stalls once in a while when I come to a complete stop from a long drive (2 or so hours on the highway) without stopping. Like coming to a toll booth and coming to a complete stop while doing a lot of steady pace driving. It has done this to me on a number of occasions, but I did not really pay any attention to it. It never caused any problems, just restart it and keep going. (or maybe I just forgot to take the car out of 5th gear when I stopped??

Is there any connections that I should check that may be the problem?

-Chris

 

[sdpatt]

Do a test. Remove the chip and reset the idle programming. Determine if the stalling problem is still present. If so, it wasn't the chip. If no more stalling, either the chip has failed or the connections to the service port on the EEC were not making good contact. Most of the problems with aftermarket EPROM chips have to do with poor connections. The contact strip must be thoroughly cleaned with solvent before the chip is installed. The chip must also be securely attached so that it is not allowed to move. That can compromise the connections also. I have attached my Superchip with Velcro and packing tape. Any small motion of the chip (such as when bouncing over road potholes) can cause an engine control problem (stumble, lack of power).



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Scott

1991, 253K miles, glass hood, police grill, SVO shifter, Catz fogs,
K&N, 73mm MAF, Superchip, PP Y-pipe, Borla cat-back, 190 lph pump
Eibach/Tokico/polyurethane, SHO Shop front & rear strut braces,
16x7.5" Moda R1, 225/55ZR16 Bridgestone RE730, -1 deg camber x 4,
Class II hitch, Silver award at the SHOklahoma Car Show

 

[Chrisssssssss]

What is the easiest way to look at the superchip? I know that you can get access to it from the glovebox, but I have never touched it. Is there anything that I should look for?

-Chris

 

[Chrisssssssss]

What are the chances of this being related to spark? How hard are the back plugs to get to? I just drove it to the store and it is getting considerably worse, almost to the point of being un-driveable. Anyone got a quarter stick of dynamite?

-chris

 

[Chrisssssssss]

OK, I removed the superchip, and took the car around the block. As soon as I started to drive, the car is doing the same thing. Scratch Superchip off the list of problems. Anything else? HELP!!


-Chris

 

[Chrisssssssss]

OK, I thinks me found my problem! The clip is broken off of the back of the DIS module on the side of the motor, and the connection was loose. I have just put a zap strap around the whole deal, and it hasn't done it since! Thanks for all the help. Wow, my cheapest SHO repair! $.10!!! Mark this down in history!

-Chris

 

[sdpatt]

Chris,

You must also seal that connection from moisture or you will eventually have problems again. Use silicone RTV (room temperature vulcanized) to protect the electrical connectors from the elements.

The connector was damaged was when you hit the curb. The engine must have twisted up at the rear mount enough to cause the DIS connector to strike the roll damper bracket. I found this interference when I lowered the rear portion of the subframe to install new subframe bushings.

Scott

[This message has been edited by sdpatt (edited 12-25-2001).]

 

[Chrisssssssss]

thanks. I will do that. Hopefully (fingers crossed) that this won't happen again.

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Chris Nicholls
'92 MTX 155,000 miles
Superchip, K&N, Exhaust

 

[DeaconBlue]

If that doesn't solve your problem, it maybe the cam position sensor. Mine bucked a few times, but not repeatedly, before it failed.

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95 MTX
with a few mods