Ran an event last sunday and about the last our I developed a miss at idle. Limped it through the rest of the day and got it home. I got another event goin this weekend and really don't want to miss it.

S4 6-port turbo motor
ECU stock t2 w/rtek1.5 chip
walbro
FMIC
No emissions(de-pinned at the ecu)

Car ran PERFECT before this.

Symptoms:
Really rough idle
sputters and heavy hesitation on throttle
clears up when I hit boost
Compression is 90-90-90 front and 90-80-80 back
Every once-in-a-while get a back fire out the intake
Heavy smoke
Big blue flames out the exhaust(more than usual!)

Things I've tried:
Sprayed carb cleaner for vacuum leaks
No stuck injectors
Swapping CAS' tonight....
Timing hasn't moved

I'm stumped and running out of time.
Help me rx7club. You're my only hope!

 

swapped ecu with stock one still nothing.

If I turn the safc up to like +35% at 1000rpm(idle) it smooths out.

Pressure regulator?

 

check tps

 

tps checks out
boost sensor checks out

The FPR won't hold a vacuum. As soon as I unhook the line and cap the line idle smooths out. I'm getting an aftermarket FPR tomorrow and crossing my fingers!

 

I'm getting ready to burn this thing to the ground..............................

Put an aftermarket fpr on and still no go.

The only way the car will even idle is:
1)crimp the return fuel line closed with vise grips while having the safc turned +50
2)pushing the afm flap by hand

I'm not going anywhere this weekend so please take your time..........

 

fuel pump crapped out?

 

Swapped out my walbro for the stock pump and same thing.

Is it possible to have a cracked apex seal or something that would be a "vacuum" leak inside the motor? I'm wanting to know whether I just need another short block or if it's something external.

 

If you cracked a apex seal, their would be noticeable compression loss on that chamber.

Is this in the 85 in your sig or a FC? Have you tried hard-wiring the pump to rule out the wiring?

 

Yeah did a t2 swap in it early fall. I've jumped the check connector and I can hear the gas flowing. I'm getting 12v to the pump.

 

Fuel pressure is good.

If I prop the afm open with a screw driver to 1.5v at idle everything is fine. I can push the flapper as I throttle up and everything is fine.
My new question is what is the voltage at idle supposed to be for the afm? Am I actually fixing it or just compensating for something else not working?

 

Metered out the injectors to the ecu and got 13.1ohm for both primaries and 12.6ohm to both secondaries.
Tried adjusting the spring tension in the afm to get it to read the aforementioned voltage at idle. it worked for a little while but soon started to bog again.

 

Soooo I'm the only one responding to my own thread.... nice......


Anywho, swapped out the afm and still no go.

What all "tells" the ecu the motor is running?

 

only thing i can think of would be either a tps problem or afm problem. but it looks like theyve checked out good. could it be a vacuum leak?

 

the CAS is the primary sensor that lets the ecu know it's running, but it essentially only controls the timing of the plugs/injectors.

check your water temp sensor in the water pump housing.

 

The cas meters out ok and the timing is spot on.
Haven't really checked the water temp sensor. Will do in a couple minutes.

Gettin' ready to dive into the harness. Maybe something is pinched or sliced....who knows.

 

is it possible to have a blown motor and still have good compression??

 

Swapped out primary injectors all is good!

Problem solved,