david1235102

My car is a 91 Vert, 5spd with 154,789 miles and it has a couple problems.
My idle usually bounces from 1300-1500rpm when idling and car is up to temp.
Occasionally it will bounce from 1500-1800 (usually when still warming up).
After high revs (and sometimes randomly) it will idle at a steady 1500rpm or 1000rpm.
If it is idling steady and I turn on the headlights, the idle will start bouncing again. If the idle is already bouncing, it will get worse when I put a load on the engine. This made me think of the BACV...
I've done hours upon hours of research to try to figure out the problem and I'm in denial that it might need a rebuild.
I have removed and checked the BACV. It measured 13.1 ohms which is ~1 ohm above Mazda's accepted value. I blew into it with it closed and no air went through. I also connected it to a 12V source and made sure it was clicking open and close quickly and smoothly.
I adjusted the TPS with the light method, then proceeded to measure its resistance. It was within Mazda's accepted values at idle and at WOT. I also checked to make sure it was not breaking the circuit under acceleration and it works smoothly. I even checked the full range side as well and it was also good. Either way, I replaced it with another and checked/adjusted it the same way and the car doesn't run any differently.
I did my best to check for any vacuum leaks and replaced some hoses that looked old and cracked.
I checked the MAP sensor as well.
I cleaned the ecu ground and a couple other grounds as well.
Other random things I've done include a new fuel filter, an oil change (Castrol GTX 10W-30 conventional), and cleaning the spark plugs (which weren't bad to begin with).
The car is completely stock except a straight pipe has been installed to remove the cat. The double throttle diaphragm won't hold a vacuum so the butterfly valves are always open and I blocked off the vacuum hose going to it. The check engine light is not on. It is also not burning any excess oil; about 1qt for every 3000 miles which is normal.
I do need to do a compression check but I really hope that isn't the problem; I think that's about all that's left. It runs great when accelerating or engine braking.


I also think I may have a problem with the AWS. It only revs the engine to 3k some of the time; it seems to do it more when it's around 40-60 degrees. Half the time it does work, it will even rev up to 4k instead of 3k. Now, with temperatures in the 20s and below, it runs rough when I first start it and only goes up to about 2k rpm for about 10 seconds. I have no idea what this is about but 4k rpm can't be good on a cold engine and I just want this to work reliably and never go above 3k rpm when I start it.

What are your thoughts on these? Any help would be greatly appreciated. I apologize if this thread is a little hard to follow and scattered; I just finished my exams for the term and I'm tired/braindead.

satch

iTrader: (1)

3k startup is dependent on the coolant temp. Too cold and it won't initiate the high rev condition, warm enough and it does. It's also dependent on the ECU thinking the engine is in neutral gear. If it thinks otherwise it won't initiate the high rev process.