Misfire like fuel cut under throttle - Stumped!

[TwIzTeD_3kGt]

I'll tug on some wires and see what happens. So is it like a limp mode the ecu goes into when it only allows 5 degrees timing? There were a few blips of 10 degrees, and -3 degrees as well. Just looks like its going nuts to me. AFR goes super rich, then super lean. All under the same conditions.

[TwIzTeD_3kGt]

I was able to drive it to an open parking lot a few days ago to really see what it's doing. Basically, it's going into limp mode and the only constant problem on the logs is the knock sensor. Once I hit a certain load it seems, the knock sensor reading shows 9 counts and stays there for the most part. I'm able to kick it out of limp mode by revving the engine up over and over, then it drives normal. I was able to get through 1st gear 4 times in a row, but 2nd gear triggered limp mode. The O2's look like they're just slow to warm up and they're not reading well. So I'm in the process of replacing them and the knock sensor and we'll see what happens.

[DK77]

What if you start in second? I had the same thing going on before I pulled my Jester ECU out and I could make it through any gear, but as soon as I shifted and nailed it in the next gear it would cut out completely. but I've had something similar happening with my spare SL ECU as well, which is why I was thinking it was because of my boost-a-spark. Then my crank sensor failed and I'm just as stumped as you are lol

[TwIzTeD_3kGt]

I tried 2nd gear and 3rd gear pulls, and as soon as boost starts to reach 12-15psi it cuts out, check engine comes on, and it's in "limp mode". Won't let me rev over 3000rpm. To get it out of "limp mode", I have to free-rev in neutral and feather it past 3000rpm. The A/F spikes lean for a split second when it cuts out.

As of now I've verified no boost leaks, looked at the spark plugs, replaced 4 O2 sensors, the knock sensor, and tonight I swapped out the coil pack. I didn't try another PTU since the problem seems to be based on load. Idles and drives perfectly fine below ~150 load. Nothing has changed the problem at all, it's exactly the same.

Next I'm going to pull out the fuel sending unit and have a look at the hose and bottom filter. On that note, I'm still on the same fuel filter that was in the car 50k miles and 9 years ago. However, fuel pressure was right where it should be at idle. Pressure went up with RPM and pulling the regulator vacuum line, just how it should. Still possible it's dropping or not rising enough under acceleration, but I would think the A/F would go lean gradually, instead of "A/F right where it should be, then BAM lean wall".

What happened with your Jester ECU DK77? I'm starting to suspect mine.

[DK77]

Originally I had a stripped down Jester ECU (not a full clone). I was having issues like you, car would cut out at higher load and then give me the 7-8-9 knock sensor circuit dance (not consistently, sometimes it would work, other times it wouldn't). So when I sent the car to Pampena Motorsports I sent that ECU back to Adam to check out and make into a full-clone. He swapped that ECU with the one he had in his car and said it worked fine and then just gave me the full-clone out of his car. Once Ray tuned it I had no problems for a while. Then it started doing the work fine for one gear, then cut for the next randomly. When I logged it, I think the only abnormal thing was that the Barometric pressure reading was fixed. I swapped in the SL ECU I had it worked fine again for a while. But then I started having the same issues with it, which led me to believe the issue was my Kenne-Bell Boost-A-Spark as the problem only occured under heavy throttle/boost (when I had problems before if I gave it full throttle in neutral it would rev to about 3500rpm then cut). I disabled the BAS (unplugged the pressure switch) and turned the boost down (to ~18psi) and didn't have a problem during the few weeks I drove it like that. I re-enabled the BAS to try and troubleshoot it then my crank sensor failed about 5 minutes after beating on it pretty hard (27 psi 1-4 gear). I haven't had time to replace the sensor and do more testing though. I think it's possible that my failing crank sensor was causing issues, or that there is a problem with the BAS, or that there is something else in the wiring/relays that is shorting/failing. I do not think it's solely the ECU as I have had this problem now with 3 different ECUs in the car. I am hesitant to send this ECU back to Adam (again) until I can verify it works flawlessly with the SL ECU in the car and has problems with the Jester ECU.

In summary, things I have replaced while chasing this randomly occuring problem:
-Replaced coilpack (new OEM)
-Used 3 different ECUs (2 Jesters, one OEM 98 SL ECU)
-Replaced the PTU (new OEM)
-Replaced the knock sensor (new OEM)
-Replaced all spark plugs (NGK R5671A-8)
-Replaced all plug wires (new OEM)
-In the process of replacing the crank and cam sensors (new OEM)

If it continues to be a problem after replacing the cam/crank sensors, my next most likely culprit has to be the BAS, if I replace that and it continues then it has to be a short somewhere or a faulty relay, IDK. I'm running out of ideas lol. And the thing that is most frustrating is mine comes and goes so I can't just keep fixing things until it works because half the time it will start working and I still haven't fixed anything.

[DK77]

I'm going to try and get the sensor replaced this week so I can do some more testing to try and help. What you describe with the limp mode is exactly what my car was doing with the original Jester ECU I had. I'm not sure if it's been going into limp mode with the newer ECU/SL ECU because I seem to remember even when it would cut it would drive fine afterward. I guess it's possible that I've been having multiple issues that have been manifesting similarly.

[TwIzTeD_3kGt]

Sounds like we have a very similar problem and similar setup, so I'd be surprised if we both had a short or wiring issue. My crank sensor was pretty questionable last time I was in there.

Removed the sending unit tonight. Low and behold, the fuel pump retainer and bolt were sitting on the bottom of the gas tank. The pump was partially out of the output tube, which could very well explain my issues. Resecured the retainer and pump, reinforced it with a hose clamp, and put it back together. No dice, no effect on the problem at all.

Going to try the PTU tomorrow out of desperation.

So now I don't know. Seems to be between 3000-4000rpm it cuts out, load doesn't seem to matter as much as I thought. Does it in each gear if I accelerate slowly. But 1st gear at WOT seems to work fine almost everytime. Maybe because it runs through the RPM range so quickly, the ECU doesn't catch whatever problem is happening. If I stay below 3000rpm in any gear, I have no problems.

[DK77]

Can we log the crank sensor signal through evoscan? When mine failed my tach still worked. I think the tach signal is from one of the injectors rather than the crank sensor. My fuel pump was replaced by Pampena Motorsports so I would assume everything is fine in the tank (plus I've had issues before and after the pump was replaced).

[futurevr4man]

I thought tach signal came from the PTU?

[KeithMac]

I thought tach signal came from the PTU?

Yes it is, there is a tacho output pin on the ptu think it works on 1/3rd engine speed referenced on 1 coil..

When I had 2 cylinders down due to ptu failure the tacho still read properly.