2 replies to this topic

[Bench Racer]

Trying to find an issue with my 1990 Miata engine using the OBD via the "Check Engine light" light flasshing code and using the "diagnostic box" under hood drivers side with a jumper wire and a second jumper made out of a LED light wih a resistor per instructions on Miatanet to flash a code. I cleared any potential codes thru the disconnect negative battery post, step on brake pedal process. Started the engine, stopped the engine several times with the fault occuring during each engine run time frame. Neither the check engine light or diagnostic box will provide any fault code.

 

Thoughts if you have tried this process, successful or not successful????

 

Thanl you

[Brian129]

On a 90 the obd is pretty basic
It only can read a few sensors, and what they are supposed to read. If it's not way out of spec on one of them, it really won't know what is wrong with it.

So as I read it you have some type of issue with how the car runs, but you are not getting a check engine light now after clearing it?

What is the issue you are having with the engine?
Did you look at the code before clearing it?
What did you work on on it last? Usually something you just touched is the issue.

[Bench Racer]

I didn't see any code blinking during any engine running at the track or in the garage before clearing.

At the last race entering one specific corner when slowing down drastically braking and shifting down to third the engine backfired continuiously. Did another lap, all was good untill the same corner where a repeat occured, pulled into the pits. When on track, AutoMeter mechanical oil , water gauges along with fuel pressure outside windshield were all good. In paddock without turning the engine off, I slowly raised the engine RPM and at 2,200 rpm with accelerator pedal held steady then rpm droped to 1,700 rpm and the engine speed will pulse between those two rpm's. This issue occured on Sun. and I had qualified both days and raced on Sat without an issue.

After the above on track issue and the padock engine hot pulsing issue the pulsing issue in the garage with will not occure with a cold engine start. After engine running for a few minutes and with the temp gauge not off the 140* gauge pin, with cam cover warm, radiator cold the pulsing issue occurs. Thinking the two issues (backfire and pulsing) may be caused by the same whatever.

Thanks
David