Loss of power at 4k wot

[redX90]

Looking for help from some experienced DSMers on this one. This is on a 90 GSX. This problem happened all of a sudden. At WOT around 4krpm I lose power, similar feeling to hitting rev limit, not fuel cut. It just makes a sound like way to much fuel is dumping in with king of a warbling feeling / sound. Its fine WOT all the way to 4k at 15psi. My A/F is odd too. Normally at WOT my Phantom A/F Guage will read about 85% but when this happens, about 5 LEDs down towards 50% are all lighting up too, All roughly the same intensity. I'm having trouble thinking with that one. Anyways, I logged everything I could with my TMO and everything is exactly as it should aside from about 20 count of knock when it happens. (0 knock any other time). Timing is fine, new t-belt is fine. I also notice my vacuum seems a couple psi lower than normal. I figured a leak on the down stream side of turbo would make a squeel or something if that were the case. I'm in the process of building something to verify that its not a leak. Anyone have any ideas on this?

 

[ss94s10]

sounds like a fuel pump dieing

 

[andymoraitis]

I'd go with either of the following:

1. Fuel issues (as mentioned above) like the fuel filter, fuel pump or injectors.
2. Leaking caps or a bad board in the ECU.
3. Spark issues (coil packs, igniter, plugs, wires)
4. 02 Sensor (may be an indicator of your wierd A/F readings).
5. Boost Leaks

Another possibility is the knock sensor. At 20 counts, your ECU would pull timing like a madman and make the car feel like it was dragging an anchor. Since the car is 15 years old, it could be any of those things, but you can start with these and let us know what you find.

Hope that helps!

Andy

 

[Defiant]

How old are the plugs and wires?

 

[redX90]

Thanks for the input. I have a Hahn race pump thats a couple years old. Accell wires are about two years old. Three year old ND plugs. O2 is exactly two years old. I just changed the filter and regulator last night and will test for boost leak this AM. I'm running a 92 ECU setup with 105' caps that I installed a few years ago so I was looking in that direction. I will check pump pressure this AM too. After thinking about it I thought maybe its a pressure problem. Its just weird how it just started all of a sudden. One munute it was fine. I shut down the car for about three hours. Started it and getting on the freeway... blub blub blub. I did miss a shift earlier that day and took it a little over redline but that was about 60 miles prior and everything seemed ok at that time. Anyways I will post what I find today afer I get done checking more stuff.

 

[redX90]

Update. Problem still exists. I did ' find a couple downstream leaks and fixed all but the throttle body bushings (little leak). Pump pressure is fine. I did find that my fairly new wires has one shorting to the valve cover. I will replace those and see what happens. It doesn't really feel like a spark problem though, as I've never seen a problem with spark under the conditions I'm experiencing. I would think it would be shorting all the time and very noticeable.

 

[CanadianTSi]

Chnage your plugs and wires and do a boost leak test, then get back to us

 

[redX90]

Well the wire a that seemed to be shorting must have been the culprit. After new wires its a happy camper again. Boy do I feel stupid for not noticing such a simple thing. Apparently it only shorted when I would get to 4k WOT or above and drop out that cylinder. I could take it to and past 4k at 50% throttle and it would never manifest itself. Wierd. Anyways the "warbling" thing I mentioned makes sense now. Thanks for all the input.