I've got a '90 TurboII (listed in sig). Earlier this season I put in a Racing Beat FCD that I got from a friend, it's made for a S5 (although it has '89 written on it). I don't know if I've ever gone beyond where fuel cut would occur, but I have it on there just in case. It's installed properly (not very easy) and mounted solid to the body of the car so it doesn't bounce around.

Now, the strange thing is this.. every once in a while, immediately after I upshift (sometimes when I'm hammering it, and sometimes when I'm just accelerating and upshifting a little faster than "average") I'll shift and put the gas down and It'll *duhduhduhduhduhduhduhduh* until I get off the gas and then put the gas back on, and it's fine again. When it's doing that, there's nowhere near as much power as there should be, which leads me to believe that it's cutting either spark or fuel to the rear rotor. BUT the thing is, the exhaust doesn't pop (so I'm guessing it's cutting fuel if it's doing anything).

Anyone have any ideas on this? It's pissing me off, although it only happens once every other week or so, but I don't want to screw with it.

 

My escort does the same thing... I am thinking it is a vacume tube problem although it could be something on the distributer cap... I still havent figured it out. Does it happen when the car is cold and warm or one or the other?

 

I never mash on it when it's cold, it's always when it's warm.

You're saying your escort from time to time will just stop firing on a cylinder?

I guess it could be the plug wires, I dunno..

 

Sure it's fuel cut? My '89TII would "kick back" upon hvy. acceleration in 3rd/4th. If I took it easy, I could get to well over 100, but as I said before, if floored, it would kick back. Numerous compression tests were perfect. Long story short, afetr many months of testing and evaluation, it turned out to be a stuck or cracked seal. Replaced engine.
I hope yours is fuel cut.

 

It could also be detonation or a bad TPS causing stuttering. Does it make any nasty noises while this is happening? Any black smoke coming out of the exhaust?

 

I was having that problem with my FB. What I did was hard-wire it with a switch. Turning it "on" when I wanted the fuel pump on. It solved my problem.

 

Have you read up on what the FCD does?
Do you have an aftermarket boost gage?
Your sig is not turned on, so I am guessing your setup.

 

Odd, a friend has the same problem. Its a completely stock S4 T2 but is boosting 7psi with a fuel pump and FCD. On full throttle, it seems to stutter/break up momentarily, almost like a fuel cut.

 

i think mine did that too...

i chalked it up the 3800 rpm hesitation , as that was around the range of RPM i was always around when it would stutter...

i hit fuel cut once....it sucks....made me think i fucked the car up real bad....but i got the racing beat FCD and that stopped, but i still got the hesitation if i slammed the gas....if i did i gingerly it would'nt stutter at all....only when i hammered it

 

Sorry about that..

And yeah I have an aftermarket mechanical boost gauge. Shows 5 lbs.


yeah but it'll keep doing it until I get off the gas, then it's fine. It's weird.

It won't do it unless it's RIGHT after a shift, at least I think. I don't think it's a boost spike either.. it was boosting normally just fine.

 

Here's a thought: The primary ground is probably good, but not perfect.
The firewall ground is OK, but with just a little tarnish on the cheesy clip.
As these connections age, the alternator & spark load starts to be seen by the ECU's grounds.
They get biased just a little - maybe 0.5 volts.
Now the ECU tries to compensate and it starts to go nuts.
Then you go nuts.

The lesson - beef up your grounds & see what happens..

 

Already done that. 2 pieces of battery wire.. one from neg terminal to shock tower, and from the shock tower to the alternator mounting bracket.

 

i don't know... when i did my clutch job and forgot to reconnect the ground cable near the wiper motor to the bell housing the car would drive fine until ti got warmed up.

Then teh car started to hesitate and buck and stall out on the slightest bit of load. Including going from stand still to speed.

I would check grounds.

 

You have probably been through most of these.

Missing orifice pill in the boost sensor line?
Ohm out the plug wires?
Re-check the plugs (tan Or black?) (all the same?)
Loose secondary injector plug?

I'm still thinking...

 

There's a FCD, so even if it spikes it shouldn't fuel cut, right? And I'm NOT going to dig for that stupid pill, it's friggin' crowded as crap with the ABS in there.

I might just get new wires though, and doublecheck the plugs.

 

Does it do it on a full tank of gas? I'd say check your filter in the tank and see if it's holding gas or just pissing it out, perhaps when you shift real quick the quick change is splashing the gas forward causing a hickup because your sump (or whatever) isn't holding. I've seen that happen quite a few times.

 

that's an idea.. I don't know if it only does it on a low tank of gas.. hmm.. that's a possibility I guess.. but then it's weird because it stays doing that until I let off the gas.. and ther's like NO power so it's not like the gas stays sloshed back..

And I never let it get below 1/4 of a tank, and if it ever did, I wouldn't hammer it.

 

*brainstorm*

 

Simple test on the boost sensor line – this works on NA’s also:
Engine idling – pull off the hose at the sensor.
Cover the end with your finger.
It should take a second for vacuum to build.
If you feel vacuum instantly – no orifice pill.

 

good idea..