The car is a 93 RX7 with a 98 LS1. I drove it home with a borrowed 98 PCM, then had my PCM flashed to remove VATS and the emissions stuff.

Ever since I brought the car home, with both the old PCM and the new PCM I've been having a problem.

The car runs perfect, no problems at all except on a hot start. Lets say we park, wait 15-30 minutes and drive it again, the car will die and stumble hard, like zero power and the RPM's fall in 1st and 2nd gear at around 2000rpm.

Doesn't happen all the time, but some of the times.

Today it did it at 3400rpm. It almost always does it twice. Let off, get back on the gas and it will either be fine or do it again.

Only does it on hot start, never on cold start, and never after being driven more than a mile, and never more than twice within the first minute or so of driving.

It usually happens comign out of the driveway, pull out, hit the gas, it dies, comes back and your fine. Today the same thing but all way in 3rd gear at 3800rpm. Really freaked me out then, slowed down, put it in 2nd at about 3000rpm and pulled to redline just fine, after that it was fine.

The new PCM has all the emissions stuff removed but I am getting a code "Map Sensor - Low Voltage'

As far as I know MAP is a backup for the MAF if there is a problem, or its a 'doublecheck' against the MAF info.

Anyone know what pin the map sensor is on the harness into the 98 PCM? I'm not sure if I had that code before the new PCM and might have knocked a wire or something swapping PCM's, its very tight down there.

What voltage range should I expect from the map sensor if I put a meter on it?

Also can that code cause a high idle? The TB was sticking, so I adjusted the throttle blade to be open a bit more. With the old PCM it idled fine, with the new one it idles at about 1100, but once in a while drops down to 850 where it should be. There might be a lose wire, on the RX7 you put the PCM is the passenger footwell and its very tight, plus everything was spliced by hand, so its possible when I swapped PCM's that a connection might have come loose.

Thanks

 

Sounds like you need a better tune? Or your idle air isnt up enough? What TB are you using?

 

Its a stock motor and stock tune, not to mention a stock TB.

The TB was slightly ported but I have a new one on the way, but there is still the stumble problem, I'm just not sure if the MAP code and the idle could be related, it did not start idling odd until I swapped the PCM's.

Both PCM's had identical tunes on them. The borrowed PCM's maps were copied from the PCM that came with the car, all it did was have VATS turned off. The PCM that came with the car I shipped off to have VATS/Emissions turned off and nothing in the tuning was touched at all except raising the rev limit to 6600rpm. The PCM is dead stock otherwise.

 

Sounds to me like you've a got a loose connection somewhere. When the car is cold, all of your connections are making contact because they haven't expanded from the heat. With a motor swap like you've done, I would make sure no wires have been chaffed or pinched. If you're having a code with the MAF, maybe thats a good place to start. OHM the wires and look at the pins themselves to make sure they're making contact and double check your hardwire job. Just a thought anyways.

Heres the link that i have to the ECM pinout.98 ECM Pin

As far as the throttle blade is concerned, it will set a code if you turn the blade too much. I'm not sure of the voltage but I believe its somewhere around .62-.65 volts. So you need to make sure you stay under this voltage when opening the throttle blade.

Alex

 

Thanks for the pinout.

Just to clarify, its a MAP code, not MAF. If it was MAF it would make sense, but MAP wouldn't effect things as much.