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Speed limit

Joined
2 December 2012
Messages
3
Location
Austin, TX
I picked up my '93 auto from the service department at the local Acura dealer today. I had an electrical drain and a bad alternator, which were both resolved. When I left it ran fine until just under 40, when it acted like there was some kind of speed limiter, coughing until the speed decreased (and the TCS light was flashing), when it would run until it hit the speed again. This happened constantly, and was the same in 2nd, 3rd and Drive. The car ran perfectly when I dropped it off, and it's never done anything like this before. I'm bringing the car back in on Thursday, but I'm hoping someone may have an idea what is going on. It seems likely that they somehow caused the problem.
 
Is it cutting out at the same RPM? It may be something as simple like they washed the car and water got under the coilpack covers. That would cause the same symptoms as you are having. Anything else electrical and I can't offer more advice.
 
Is your TCS light flashing when the speed limiting occurs or is it now flashing all the time? Since it seems like you are having TCS issues, have you tried disabling the TCS to see if the speed limiting is being caused by TCS action? If disabling the TCS resolves the problem I would check to see if the TCS has any diagnostic trouble codes ( I am working from my 2000 service manual; but, I am assuming that your '93 TCS has self diagnostic capability). My initial guess might be the engine speed signal that comes from the ECU or the wheel speed sensors (a problem with a wheel speed sensor would normally also generate a DTC on the ABS system).
 
Is your TCS light flashing when the speed limiting occurs or is it now flashing all the time? Since it seems like you are having TCS issues, have you tried disabling the TCS to see if the speed limiting is being caused by TCS action? If disabling the TCS resolves the problem I would check to see if the TCS has any diagnostic trouble codes ( I am working from my 2000 service manual; but, I am assuming that your '93 TCS has self diagnostic capability). My initial guess might be the engine speed signal that comes from the ECU or the wheel speed sensors (a problem with a wheel speed sensor would normally also generate a DTC on the ABS system).

When I bought my car a couple of years ago I started getting the yellow TCS warning light after having it inspected at my local Acura dealer. The symptom was similar to yours, but not exact. After driving it for a few minutes after startup, it would stumble as if a rev limiter had kicked in, the TCS warning light would go on, and then it would recover and continue more or less normally. Shutting the ignition completely off and restarting would turn off the TCS light, but it would come back on every few times I drove it.

Eventually I pulled the codes using the shorted service connector/instrument cluster method and they were 37 and 51, both pointing to the throttle angle (position) sensor. I took it to Ben and he found that the wire to the throttle position sensor had been pulled loose. The Acura service manager and I concluded that it happened when the car was hooked up to a dyno (at another dealership) for emissions testing. The tech there probably yanked it accidentally while he was hooking up the wires to the dyno.

I'd say start with pulling the codes to find out what's really going on. Seems strange that they would put a basic engine control function like the throttle position sensor on the traction control computer, so there may be other engine-related issues reported by the TCS computer.

The previous posts appear to be talking about the green flashing light, the yellow warning light doesn't flash, at least not for me, so maybe my situation doesn't apply.
 
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Do you have aftermarket wheels? This happened to me one winter, the tire pressure decrease caused a slight change in the overall diameter, pushing the rotational difference between the front and rear to go out of tolerance.
 
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