Are there any? Have a car that idling at 3.6 ms pulsewidth, idling stably (very big cam, 408, hyd setup) it will just shut off. Was looking into the problem with Freescan, had to reinstall my Datamaster stuff to notice that it was actually randomly (seems to be anyway) and intermittently cutting pulsewidth back tosomething like .90 for a split second (which must be the hardcoded lower limit?) Sometimes it can recover from that and you hardly notice its doing it, other times, it shuts it right off. You can see it do it (pw drop) and engines stalls, and watch pulsewidth come back up again as the engine is on its way down, but its just not going to recover this gnarly of a cam at 400 rpm falling hard because fuel was cut.

Anyone seen anything like this, know what could cause it to cut fuel that suddenly and get back just as suddenly? Its idling at 75-85kPa, nothing drastically changing there, I saw it go from fuel trim cell 16 to 17 when it did it a couple times but last time it died and I captured it trim cell stayed right at 16. If kPa doesnt change, TPS is steady .63-.65 volts and rpm is steady how can there be a fueling change?

Cars in Speed Density by the way

 

This is obviously not the car (cars?) in your signature. You're running OBD-I PCM. Are you running MAF or speed-density? How did the programmer tune the PCM to handle what appears to be a huge overlap, as indicated by the high MAP at idle. It's going to be blowing a lot of air and fuel through the open exhaust valves, so he may have altered the programming significantly to deal with it, and prevent the PCM from over-fueloing it in response to the O2 sensor false-lean. Is it an open-loop tune?

Have you asked the programmer for an explanation?

Intermittent MAF signal might cause a pulse width drop. Did you look at the MAF reading vs the pulse width?

An O2 sensor that suddenly showed a rich condition would also cause the PCM to reduce the pulse with. Did you look at O2 voltage vs pusle width?

 

I tune it it's in open lo op, no maf. It's well past the basics

 

Hard to even attempt an answer when you don't provide all the info up front. You might want to try the "Computer......" forum.

 

All the pertinent info was in the first post

 

whats your idle set at in the tune?

 

This needs to be closed, because it was reposted on the "Computer......" forum as suggested.