Engine stutters and dies as soon as it warms up, especially under acceleration - Help
 

I've tried looking for an answer in the existing posts, but haven't been able to find a similar set of symptoms. It would be much appreciated if anyone has any suggestions for me to try...

1991 Mazda RX-7, non-turbo. It's always had some troubles starting when the engine is hot, but a new symptom has suddenly occured this past week. It basically renders the car useless. As soon the engine warms up (3-5 minutes of driving), the engine stutters tremendously, loses all power, and eventually dies as soon as the clutch is pressed. Slight acceleration sometimes keeps the car moving along, but moderate or greater acceleration simply kills the engine. It makes terrible knocking noises, smells bad, and kinda acts like it's starving for fuel. As soon as the engine cools down, it can be started again but repeats the whole scenario as soon as it warms up. Very thick white/gray smoke is exhausted for a minute or so when it is restarted after a hot shutdown.

I just installed new plug wires. There doesn't appear to be any blockage with the air supply. I checked fuel pressure coming out of the filter with a gauge and it seems to delivering ok (at least while it is sitting still in the driveway). I disconnected the exhaust right before the catalytic convertor and it doesn't help anything (just makes it loud). I've checked just about every sensor the Haynes manual suggests. I'm out of ideas.

Anyone have any ideas or suggestions????

Thanks in advance...

Well, it's a bit of a longshot, but does the car have aftermarket ignition coils?
Poorly mounted packs can lead to heatsoak that severely increases resistance, which decreases the amps making it to the spark plugs. The symptoms are similar to what you're getting: it runs fine until the engine bay heats up, then the motor wants to die.

And if you don't have an aftermarket setup, it still might be worth checking out the stock coils. If you can get it to idle under 1000 RPM long enough, a timing light will let you see if you're getting uniform spark. Also check the plugs after it's warm to make sure they're not soaked in gas or anything out of the ordinary.

Thanks for the idea - coils
 

Interesting thought. The car still has the original stock coils. I was performing a resistance check on the secondary coil a few weeks ago, and it showed some problems. Then I checked it a few days later, and it was fine. It could be intermittent. From what I read, the secondary coil shouldn't be a big factor in any performance issues. What do you think?

I have a timing light, but I can't seem to get it timed right. The car dies as soon as I get the marks close. I checked it when the idle is about 1000rpm, but I have to keep it a bit advanced to keep it running. Is this any relation to the problem?

Any chance this could be a simple spark plug problem? I recently replaced the wires because one was leaking (it shocked me), but I have no idea how old the plugs are. I am not familiar with this type of plug, so I can't tell if they are ok by just looking at them.

Thanks for the advice. I'll be messing around with this more today...

I'm having a similar problem, without the smoke issues. Please let us know how the diagnosis goes, 'cause I need all the help I can get on this one.

I'm just not familiar with 2nd gens yet, my experience has been confined solely to 1st gens and carbs.

Compression ?

Fixed
 

It seems that I have fixed it. I simply installed a new set of plugs and reset the timing. Everything seems to be working ok. I drove it around the neighborhood, and its behaving just fine. I'm really having troubles figuring out this rotary stuff. My knowledge of conventional engines doesn't transfer well.

Thanks to everyone for the ideas and advice!