Only after my 1990 honda Accord LX gets up to temperature the Check Engine light comes on and the car statrs idling rough. Also sometimes when this happens the Speedometer drops to zero and will not move. In addition I have seen it where the Check Engine light comes on, the Speedometer goes to zero, and the Sport light(transmission has a sport or normal driving option) also starts flashing....This is really weird and it doesn't happen all the time.....A mechanic has told me I need a new Throttle body valve and it costs $650....Anyone else has any opinion on what this really weird problem may be?

 

I'm still a little new to this, and i'm sure some one will correct or adjust what I am saying. From what i've seen, the sport light is usually on when there is a tranny code to be looked at, which could be pointing to your speed sensor. Bad speed sensor = bad speedo read. I am not positive if that would cause a rough idle, unless this is related to the bad throttle body, as it does have to work with your transmission. Anyone?

 

Wagonis is on to the likely problem.

First step is to extract transmission and engine codes due to your problem. This will confirm or not the Vehicle Speed Sensor (VSS). Codes are 17 (engine) and 4 (trans) for VSS failure. Note, it could be connector or wiring to the VSS also, but sensor is notorious for failures.

A new sensor is $125-$150. Search ebay for used VSS or local junkyard. I paid $35 for mine.

regards