SR20DET falls on its face @ 5.5K rpms
 

I've been working on my friends SR20 and I can't figure out why it's doing this. It's almost like it hits fuel cut, or a rev limiter, and just completely stops building boost, accelerating, etc.

There are no boost leaks, AFR's are good, etc.

His set up is:

S15 T28 Turbo at stock boost
Apex'i AVCR
Sard 550cc injectors
Z32 MAF

I have checked timing,ignition timing, i've tried turning the AVCR to "off," I've checked plug gaps, etc. I've tried all I can think of.

Also tried to completely remove the AVCR from the picture, by unplugging it, and routing the wastegate straight to the hotpipe, instead of the boost controller. Same issue.

Any thoughts?

.............

What are the plugs gapped to?

CHECK UR TPS SENSOR next to throttle body might have a dead spot in it holddd it all the way down with a screw driver and have some one rev and see if its thatt

0.28 and tps was fine we checked

fuel pump checked yet?

edit: what is the fuel pump?

walbro 255

do you have the stock rubber intake piping?
check that. sometimes the spring inside of it screws up.

boost leak

Yes, it has stock rubber intake piping.

How can the spring cause it to do this?

We've checked all couplers, even made a boost leak tester...there is no boost leak. However, the Greddy RS bov has a little hole on the back of it (factory), and it leaks during the boost leak test, why is this?

hi just checked my buddy car and lil update when the car was cold it goes the boost no problems and no fuel cut ...so what could be it ?..bad fuel pump or coil?

That part is ok, it's just a little vent to aide in the operation of the blow off valve -- it leaking doesn't effect how the car runs.


WHen this condition occurs, can you go WOT and the car continues to run, albiet off the 'limiter' sort to speak.

what do you mean it stops building boost?
does it maintain boost or it falls back to 0?

can you be more specific?

Oh, alright.

When it happens, yes the car continues to run, it doesnt turn off or sputter or anything. It just hits a wall. When the car is cold, it does not do this. I'm thinking maybe fuel pump....or coil harness?

The car hits a wall and does nothing...that's as specific as it can be explained haha.

To check the coil pack harness you could check resistance and readings via Multimeter and FSM, I'd do that as if it checks out you can rule that out.

Member Jspaeth on here had an issue like this and his ultimately was solved by back probing the ECU pins and making sure they were making contact. I had a similar issue to this and it was a loose coupler, that had escaped my initial inspection of all couplers.

Aside from that, use the FSM to troubleshoot your main sensors....TPS, CAS, CTS, MAF and O2. It doesn't take long to check signal wire integrity.

u should rewire ur fuel pump
with heavy duty wire and relay
definatly check ohms on coils
also check the two plugs that power engine harness
to see if all wires r getting full 12v...
also is the engine like gurgling at 5.5 k ?
or cutting off?
also do u have a tuned ecu ?
if so try a stock one and see wat happens

i say pump.... throw in a gauge and see hwat it reads at WOT when it happens

Coil harness checked theyre reading 12.5 in all 4...

hi i was at my buddy car earlier and checked the ohm in coil harness,tps,injectors,...tps was fine ,injectors at .14, coil harness all of them are 12.5 and when u go half throttle it goes fine and pass without fuel cut except when its full throttle than it gets fuel cut exactly at 5000 sometime 5200..could it be fuel pump getting bad?

I knwo plug gaps were checked, but what are they set at?

They were gap at .28

also i meant the ohms on the coil packs not just the 12v source they have to be 1k ohms
put a stock ecu on it and see if it happens again

Try gapping them down to .022 and see if that fixes it up. It may be spark blow out. With the age of these components getting older and olrder, it's hard to say how capable a 20 year coil pack is anymore.

I'd bet 5 dollhair its the knock sensor

Knock sensor shouldn't even be working at that point, it's sub 4000 IIRC

Alright guys.

- I checked ECU codes, there is no knock sensor code. I built the motor and the knock sensor is good, and the wiring to the knock sensor is good.

- Today I gapped the plugs from .028 to .025, and it's the same deal.

- I tried retarding and advancing the timing, like 20 different times. Was never any better or worse, it made no difference.

- I swapped my walbro fp into it, which I know is good because it powered my KA-T just fine, problem still persists.


At this point, I'm thinking it may possibly be the coil packs themselves being bad?

Kinda lost.

Is there anyway you can get a video of it when it happens?

Yeah I can try next time I see the car.

My car is having the same exact problem! it cuts out/ hits a wall at 5000ish but when the car is cold it runs great. Please let me know if you find what the problem is i have been stumped for months.

Do you have an AVCR, Shawn?

I hope you say no, so I can rule that out as a problem lol.