KA-T hesitation, please help.

[kas14slider]

***UPDATE AT POST #4***

Hi guys, I just got my 96 240sx turbo'ed and I am having some hesitation problems at high throttle. I just ordered a wideband today and right now I am just using an SAFC II with a narrowband to try to tune the car so that it is driveable. My setup:

-Bottom mount s14 t28 at stock boost (7 psi i think) -Godspeed FMIC -Megan 2.5" catback -Walbro 255 pump -stock FPR -JGS tools 0.050" oil feed restrictor-SAFC II -SR 370cc's -stock s14 MAF -timing fully retarded at distributor -NGK brk7's gapped to 0.32 -using 93 octane gas -Blitz DD bov & boost gauge t'eed into FPR vac line.

The car runs fine and will hold boost no problem as long as you stay under whatever % throttle you set for HI throttle on the SAFC II. But it seems like no matter how much correction I run ( I have tried everything from -35% to -10% accross the rpm range) the car will hesitate and stutter at or above the HI throttle point. So if I have the HI throttle set to 40%, the car will hesitate when I reach 40% throttle. Sometimes I can get away with going higher to like 60% to maybe 70% throttle without hesitation. I have also tried some HI and LO thr settings such as 10 low 30 high, 30 low 60 high, and some others. The car runs fine on low throttle which has a -27% correction at all rpms.

For the sensor type on the SAFC II I have hotwire and have tried 2 in 2 out and 5 in 5 out. Does playing with in and out values affect anything? I am pretty sure the car is running rich but is it possible that it is running so rich that correction levels around -40% and up are needed. It wouldn't make any sense because I have read a lot of SAFC settings threads and no one ever has it set that low even when running big injectors because wouldn't you lean out with such low correction values? Also ( don't know if this matters for the hesitation) the car seems to run the same with the 02 sensor plugged in or unplugged. I am getting the wideband and was thinking of just having that replace my stock sensor.

Sorry for the such a lenghty post. Anyone have any suggestions or tips on what may cause my hesitation?

Alex.

Modified by kas14slider at 12:05 AM 6/11/2007
Modified by kas14slider at 12:11 AM 6/11/2007

[partymonster 975]

I haven't read the whole thing but It might be ur tune.

[Florida240sx]

Get the wideband in and tune.... If anything you need to add fuel in high throttle. Otherwise your runnign real lean. I would go check my friends ka-t with similiar set-up by it's ashes now Get wideband, your either real rich or real lean. Those narrowband wideband are a waste of money... Don't trust them

[kas14slider]

I realized something today after messing around with the settings. I can now go into WOT throttle fine but my car starts hesitating as soon as it goes above 5psi on my boost gauge. So the car is happy under 5psi but as soon as it goes over it just hesitates and stutters. I know I have an exhaust leak somewhere around my cat but would that cause the problem? I have a manual boost controller that I need to install so I could limit it to 5psi but I thought you can't go below what your wastegate is set at, right? I think a stock t28 wg is at 7psi

[1995240sxSE]

more like a big vac/boost leak. check and see if you have boost leaks. I do and my afr's are all over the place and when driving out of boost it runs like crap.

[kas14slider]

more like a big vac/boost leak. check and see if you have boost leaks. I do and my afr's are all over the place and when driving out of boost it runs like crap.

I'll have to try and build one of those boost leak testers. I just need to get an air pump first. Know any good stores to get one so I don't have to order one online?

See, my car runs fine though when out of boost and it runs fine til 5 psi, can it still be a boost leak?

[Florida240sx]

You don't know anyoen with an air compressor? Takes 5 minutes to check for a leak. If that... Usually find it in 20seconds... Pvc cap to fit inside turbo coupler, drill a hole in it... have the blower adapter for the pump and spray inside the cap. takes 2 people..

[kas14slider]

Well, we finally figured out the problem today but then it came back. Turned out I had a bad engine ground, as soon as we fixed that the car ran perfect with no hesitation and with my ngk's gapped to .35. So I was driving on the highway and did WOT in 5th for about 6 sec to catch up to my buddy then I let off and when I got on it again (not WOT) the car started hesitating and sputtering worse then before. Since then I got new bkr7e plugs gapped to .32. Car still hesitates and I can't accelerate at all. I have no idea what the problem is now. I guess I can try regapping them to .35 I doubt that will help, the hesitation is a lot worse now. My coolant and oil is clean so it's probably not a headgasket, and I guess I could always try to check the compression again.

[red ka-t]

It sounds like the dreaded boost leak. Just make a boost leak tester so you can find your leak.

[Florida240sx]

Check the couplers they could be cut

[1995240sxSE]

what does airflow say on your afc when hitting 5 psi. maybe maxing out maf? Or did you get this problem fixed