I have a 2001 vvt miata BP4W
Custom t28 kit
550 cc injectors
2.5" downpipe
BOV recirculated
AEM FIC
Boomslang Harness
AEM UEGO

It was running great on freeway one day then I get on my road and it starts bucking and hesitating. Next day checked spack plugs- Fine
Wires- Fine
Jumped f/p and ground terminals and fuel pump runs
Cleaned MAF sensor
Regapped plugs

Tightened all hose couplers and checked for bad 02 wires found nothing
My MAF voltage isn't fluctuating abnormally my wideband is reading 14.7:1 when it cranks.

Checked and tightened all bolts and lines. Found that I didn't plug my egr connector in. Plugged it in changed nothing.

Cleaned MAF again. Starts and runs OK little rough but OK.
I pull into drive way. Shut it down and it starts up and it runs fine till I hold it at 3k rpm and it starts missing.
Today won't start

I'm pulling my hair out on this one
Any suggestion s would help

 

If you think you're getting fuel, check for spark and things that help deliver spark signal.

Maybe it jumped timing manually? Is it just turning over, or coughing back through the intake?

 

If your WBO2 is reading 14.7:1 when the car is cranking but not running, then your WBO2 is broken.

-or-

It hasn't heated up yet

-or-

It's not getting correct voltage


-----bottom line------

A WBO2 reading when your car is cranking is of no value.


Can you get the car to start at partial throttle?

Definitely have a friend help you check for spark.

I suspect joe may be on to something in regards to being possibly mistimed.

Another possible culprit may be a CAS giving out when it gets warmed up.

 

Check the gap on the crank sensor

 

Check your cam sensor. If it has the mitsubishi symbol on it, its ones of the shitty ones and might be the problem.

 

It coughs and stumbles while cranking. I I can't hear it cough through intake but it makes engine shake like crazy. It has a brand new timing belt in it only 3000 miles on it.

I did have a problem with CAS before I'm gonna regap it and start from there

 

And WB02 reads 14.7 at idle not cranking sorry missed typo

 

So figured out when my car wants to die it drops voltage from 14 volts to 11 volts then goes back to 14 volts then engine recovers. Alternator or battery?

 

That's at the battery

 

Car idles great till both fans kick on. fans unplugged it drops voltage under load

 

This sounds very familiar. When I first had my car running tryng to warm it up in grid I would known when the car was up to temp when it stalled when the fans tried to come on. That was back when the wires for the cam sensors were loose and the pins for the ignition coils were stretched out. And it didnt have the ground from the intake manifold to the frame.

 

Found the problem.....cat is shot
Found element chunk blocking exhaust port. Unbolted cat runs great now