Hello everyone,

I have a mystery as to what may be causing my RPM to fluctuate. It does it at random times. At first I thought it was only in the day but then I noticed that it happens at night as well. There are no problems with engine surges, acceleration or hesitation of any kind when this happens. Sometimes I start the car and the RPM is at dead zero after I flick it it wakes up but then can as easily come down again. Have read about IC in other post but seems like those problems are not exactly as mines. Any help or input would be greatly appreciated.

 

Most likely the tachometer drive circuit on the gauge panel is faulty. New, used, or repair to gauge panel should be fix.

You can check that ECM/PCM is sending a tach signal by connecting an oscilloscope to connector 33 under hood near battery. It should have a single blue wire. A multimeter set to AC voltage may detect the signal voltage but won't show any frequency info. Voltage level likely < 5V.

good luck

 

TexasHONDA,

Thanks for your input. Since the problem is intermittent and when it works it functions fine I would probably lean more towards your first answer. The reason I say this is because I am pretty sure there is a short on the cluster since the CEL and CE lights are always sorta dim like they are receiving some voltage. Do you know what I should look for on the cluster itself to possible resolve both problems?

Thanks so much for your time.

 

There are posts relating repairs to solder jts. It is common for solder jts to fail due to metal cracking (fatigue). Look for a jt w/ a circle around the pin. You can use the pin (B1, blu wire) diagram (shop manual) to trace the ECM/PCM input signal to tachometer drive circuit.

good luck