RX7_Fool

Car is driving me nutz. I just put in a SAFC and now the car wont go with more than 3/4th or so throttle. It totally shuts off like it hits fuel cut or something. It drives like an angel if you stay below 3/4 throttle. RPM does not seem to be a factor though as it does it in fifth gear at like 40 MPH and like whatever RPM that is. It will accelerate good then if I jump on it, it totally stops accelerating until I let off the throttle. Then it will drive ok until I press the accelerator hard again and it will do the same. It will also shut off on me if I go way up in revs, like 5-6k. Hard to explain exactly, but just think of "fuel cut" and thats what the car does if I depress the throttle hard.

Now, it is an '87 TII with full RB exhaust and 3" TID and cone filter. Stock 89-91 Turbo and manifold. I have put in the SAFC and all settings are correct. I have tried everything from -20% at low and high throttle all RPM range to +20% at low and high throttle all RPM range. Honestly the -20% lets the car run a little longer at higher throttle....with the +20% the car almost wont run at aall due to the same hesitation, but much earlier, like 1/4 throttle. And I have the RB FCD on the car.

Help!
Mike

HeffBoost

What kind of boost are you seeing when this happens and is the hesitation directly related?

It sure sounds like you're hitting fuel cut to me. Not good in my opinion to run into it much.

Be careful with the -20% stuff. You need to find someone with a wideband oxy sensor you can borrow or get it on a dyno.

I would check out that FCD first off. I don't like the basis of the design on the RB one and I've read at least one story of failure.

Your setup is about like mine with the exception of the exhaust, which is on my short list.

Cheers

RX7_Fool

Thanks for thr reply. Basically it does not do it at a set boost level. Sometimes it will do it at pretty much no boost if I am cruising and then just floor it, it will immediately shut off the fuel. If I do this a few times, sometimes the car will barely run. Basically it will do it with no boost and barely touching the throttle. I barely got home the other day due to this happening. I would be in second gear and like going 20 mph and barely try to accelerate and it would cut off before reaching 25 mph, then let off the gas and it comes back and I try again and it goes for like a few seconds then cuts off. And I am BARELY pushing the throttle. Most of the time this problem will go away if I stop and turn off the car and restart it. Then I could get home as long as I didn't step on it hard. I think I only hit .5 on the boost gauge. However, I had a friend (Dale Clark) drive it for me earlier that day because I was boosting hard and really high and I was hitting 1.0 or so with him driving it. This is when we first started experiencing the problem. We came back to the house and found that the cap had blown off the wastegate line and the wastegate was not opening. We capped it and it helped keep the boost down, but the fuel problem has just gotten worse now. Do you know if there is any way that I can test the FCD to see if it is operating correctly? I am trying to be careful tuning, I have not heard ANY pings yet...not that I want to...but I am trying to watch the A/F gauge its a Greddy EL gauge that came with its own O2 sensor. If I run 0% straight across the board the A/F gauge is reading 8.0 and I know thats way to high. I was working on getting it as close to 12.0-12.5 as I could and unless I LOWERED it under low throttle setting, it ran way rich. But yes, I really don't know what I am doing, just trying to the best of my ability and we don't have a dyno anywhere close. The car wont make it the 5 hours to the closest one I don't think at this time.

PS if it does as explained and shuts down the the gas floored and I keep it floored after like 2-3 seconds it will kick back on and start to go, then shut off again. I only did this once, but noticed that it wont do anything if I stay on the gas.

Thanks for the reply and your assistance.

Mike

HKSTurboII

I had the exact same problem in my car! It ended up being a ceramic resistor on the front passenger side of the car directly behind the headlight. This resistor controls your secondary injectors, which happen to kick in around 3200 rpm's which is exactly why you feel your hitting fuel cut with no boost! It's just a plug in part. Try getting this part used, cause it's not cheap! Hope this helps you out!

HeffBoost

OK. I wouldn't worry about the FCD. If you guys were getting 1.0 bar(yikes) out of it before and it doesn't seem related to boost.

Have you ran the codes yet? Bad thermo switch?

Have you done a compression check? How does it idle?

Were you and Dale driving it before or after the S-AFC install. I'm trying to eliminate it as a source of trouble.

Hmm, you've got a stumper so far. Why would it be running so rich off the primaries if the secondaries were the problem?

RX7_Fool

We were hitting 1.0 like maybe 2 times. Then the third time, we started getting the hesitation problem. This was all done after the afc install. However, like I originally stated, the car did perfect a few times. then it started hesitating. I have not checked the thermo switch, would that really make a difference in this case? No compression test, but the car runs great under light boost and no boost conditions, and it is a fresh newbuild (which I know can still go bad). But it is running great other than it feels like its hitting fuel cut. I also have not run any codes yet, its an '87 and not too sure how to do it although I have ready about it a ton of times on sites.

I hate doing more stuff to the car before fixing one problem, but I was thinking of going ahead and puting in my 720cc in sec and the walboro fuel pump as well as new fuel filter to see if it helps the problem. Do you think I should wait a bit and try to find the problem first? Thanks for the help.

HAILERS

Test the fuel cut defender? Easy. Digital meter tapped into the boost sensor input to the ECU. Add a source of pressure like a Mitty VAc.

Install the Mitty VAc on the input to the boost sensor. Turn the meter on. Tun the key on. Pump the Mitty Vac. Read the meter and see where it pegged out.\

The meter should not read more than approx 3.65 to 3.70 as you boost above 10psi. Actually should stop rising b/t 8 and 10 psi.

You should also tap the boost sensors hose into the Mitty Vac/boost sensor line. That way you can read how much pressure you are applying to the boost sensor by looking at your boost gauge.

Also

StarionX

How to make S4 Tester, and engine codes.

http://home.rmci.net/panther/86_88ecu.htm

HAILERS

I'd be doing just the opposite of what you proposed with the Waldo/injectors. I'd immediately take everything back to where you were prior to having difficulties. May be your afc/whatever is the cause of your problem.

RX7_Fool

Thanks for the tester, i had read about it, just never bothered doing it. OK, I can take everything out, but really would prefer not to if I can avoid it. That means a lot of messy wire cutting and resplicing and then doing it again to reinstall later. I just wonder if it really is the AFC though, as I was boosting way up to 1.0 with no problems for a few times. Then after those few times, it started this problem. So if I can try other things besides taking it out, I'd really like to. Just tell me what you think I can check and I will and if it comes to it, I will take it all out. Thanks yall, I really appreciate it.

RX7_Fool

ok, just to eliminate what I could. I made the tester and put it in. I get the code for O2 sensor after running the car. If I turn it off and restart it at idle, no codes, but run the rpm's up to about 3k and then I get the code. I have the 4 wire O2 sensor that came with the Greddy A/F gauge in the factory location, with the specified green wire going into the O2 plug on the harness.

Also took off my FCD and have sma problem...it gets worse the more i drive it, but not too bad when i first get in a drive it...basically it is progressive, I can boost less and less the longer i drive up to the point of no boost.

Ok one more thing, is it is also RPM based and progressive as well. Originally I could slowely rev up to 5700 rpms with no boost before it cut off, but after doing this a few times I could not even get up to 3k rpms. Turning off the car and restarting seems to reset the process.

What a pain in the ***!!!!!