Miata stumbles, wont fire

M

Mike Mackaman

New member
Sorry to post street car questions on here, but I have a '94 1.8 Miata that is my DD. Recently had a washer go through the timing belt and cause the timing to be off. Reset everything and life is good. Now the car will occasionally just fall on its face, usually from a stop, then pick up. Last Saturday at my cousin's house, and this morning in the driveway, I start it, it runs really rough for 10-15 seconds, dies and will not refire. Stuck a plug in the #1 wire, and laid it on the valve cover and I didn't see spark, but it was very sunny, I was trying to get to work, etc. Saturday on the highway I noticed the tach drop from like 3800 to 3200rpm a couple of times. The car doesn't feel like it has quite the power it had before the timing belt washer incident, and the mileage is down too, a few mpg.

Any advice would be greatly appreciated, love the little car, but I need to get there and back every time!
Mike
 
Coils? My son's Miata did this and replacing the coils solved it. Might swap the coils and see if no spark follows the coil change. And FWIW, make sure you have the timing right. It took me three tries to get it right and get the belt tension adjusted correctly. Be sure to follow the procedure and rotate the crank 1 and 5/8 turns for the tensionser. Good luck

Paul
 
Thanks! That was what I was thinking, but as I have no spares on hand, it is kind of hard to swap things around! I will reverify the no spark, I put new plugs and wires on it at lunch. Still no ZoomZoom! Now that it is dark, it is easier to verify spark, etc.
Mike
 
Don't know what happened, but it started when I tried this evening, rough at first, but then smoothed out. That is twice it has done that. Any ideas?
Mike
 
Update - Since I had issues with cam timing changes, I rolled it around to verify everything was where it should be. Intake cam was off a tooth. Put it back where it was supposed to be and it runs better. Still having some issues with extremely low, low end power. Better than before, but not great.

Mike
 
OK, it finally died and would not fire no matter what, and when it did run was so weak it would barely run and required nearly full throttle to get the revs up enough to get moving. I replaced the coil pack with another, no change. Swapped the CAS and it started right up and seems to run fine. Have to button everything up tonight so I can drive it, but it reved like the all is wonderful again! Zoom Zoom!
Mike
 
I am a Nissan guy, so I really don't know. Bottom end is still not as strong as it has been. Once the VIR race is done this weekend, I will dig further on this, just happy to have it running again.
Mike
 
OK, it runs and drives, but the more I drive it, the more I realize that there are/were two problems. The low RPM power is still not there. I mean it is even hard to get the car rolling, but at WOT and greater than 4000 RPM, it is like a rocket ship.

Tell me if I am crazy here. When the cam timing was all messed up, and I was moving things around and taking the valve cover on and off so much, I put the PCV valve hose on the manifold and left it out of the valve cover. The car backfired so hard it shot the hose and PCV valve about 20-30 feet across the yard! I wonder if I ruptured the diaphram in the fuel pressure regulator. That would cause it to idle rich, and have no power off the line and then get better with throttle and RPM. I had been thinking TPS, since it doesn't seem to have good power on part throttle tip in. Like the accelerator pump wasn't working right. But then I realized that it wasn't popping lean it was just flat, rich! Then I realized that the vacumm drop changes the fuel pressure to richen it up like an accelerator pump, so if we are already at max fuel pressure, it would act just like it is.

Guess I will be putting a tee in and hooking up my fuel pressure tester tonight!

Mike
 
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