Engine Cutout at full boost?
 

My engine cut out only at full boost as if it is not getting enough fuel. The engine has less than 30k and the wiring harness was replaced by a donor harness less than 15k ago. Problem is new and I'm sure what the problem is, fuel pump, computer, relay??? No mods and rebuilt turbo 20k ago.

Sounds like you're hitting fuel cut. Are you showing any codes?

Engine light is on but no codes flashing, the previous owner said the engine light has always been on and after MANY times in the shop to find the issue with the engine light always being on it has never been able to be turned off. If there is another way to pull codes without looking at the check engine light please let me know. :dunno:

Don't suppose your car has the Super Monitor does it? Super easy if it does, but most Supra's don't have it (even 87's and 88's, pretty much the only years it was offered). If not, here's a link to walk you through the process...

http://www.cygnusx1.net/Supra/TechTi...ror_codes.aspx

Mine is a 1990 and it has that port shown in the link, I went to look at the port and it looks like it had been hit with battery acid from a car battery that went bad, I need to find a new or used port if possible, I know I can always jump the wires from the bottom of the port but now I am concerned about the condition of the port.... Thank you very much for the link, I will check it out this weekend and see if I can get the info from the link to work.

I think Toyota put a big smear of dielectric grease across the terminals at the factory. Every harness I've had or seen at a junkyard has a white or brownish paste in the terminals. You should not have to clean it all out to jump the terminals and pull codes.

Okay, done... It was just dried up and I was able to get codes, I got these codes, car runs a little rough when started for about 60 seconds then it is fine, then I have the problem with fuel cutout at full boost, these are the codes I pulled

21 Oxygen Sensor Signal Diagnosis

• Detection of oxygen sensor deterioration.

Trouble Area

• Oxygen sensor circuit
• Oxygen sensor
• ECU

22 Water Temp Sensor Signal Diagnosis

• Open or short circuit in water temp sensor signal (THW).

Trouble Area

• Water temp sensor circuit
• Water temp sensor
• ECU

52 Knock Sensor Signal Diagnosis

• Open or short circuit in knock sensor signal.

Trouble Area

• Knock sensor circuit
• Knock sensor
• ECU

Does it look like I have several bad sensors that have been replaced over the past five years or do I have a problem with the ECU that seems to be common with all three codes?

All those sensors are in the same general area on the exhaust side of the engine. Check to see if the wiring could be fried. Check continuity from the sensor plug back to the ECU. Bad ECU's are rare but do happen. I suggest checking wiring first then check if the sensors are good. Have you cleared the codes recently to ensure these are not old codes? They'll stay in the ECU memory until reset, even if all is well now.

I pulled the EFI fuse for five minutes from what I read on this forum and that was suppose to reset the computer, is that also the way to clear the codes?

You only need to leave it out for 30-60 seconds to clear the codes and reset the ECU. You can take it for a drive and check for codes again. Fix these codes first and also check for boost leaks. The hose coming from the bottom of the turbo and the coupler right at the throttle body and 3000 pipe are two common leak locations that can be hard to spot. You say full boost, but what PSI are you hitting? Stock boost gauge?

The code 52 (knock sensor) is usually triggered by deteriorating wiring from the 2 knock sensors to the ECU. When this code is stored in the computer, it over enriches the air/fuel mixture (makes it very rich in fuel) and drastically pulls ignition timing, especially as boost increases. In my experiences in a Supra with a code 52, it will idle and drive fine at light throttle, but the car will fall on its face around 3000 RPM and have absolutely no power while under boost.

There are several good write-ups on the various supra websites on how to rewire the knock sensors using the existing plugs (there are 2 sensors under the intake manifold, you need to rewire both). Be sure to use shielded wire, as the electrical signal the ecu reads from these sensors is extremely fine, and any electrical interference from other wiring can cause problems and signal degradation.

Rewired the knock sensors, took a little while because of busy schedule and work.

The knock sensor code is gone but I now have code 34 (that I think is caused because of boost leak). The fuel cutoff seems to happen at a higher RPM and what I have read it may be from leaky turbo pipes. Any thoughts?

Time to check all your piping and clamps if you haven't already done so, both sides of the intercooler and turbo. Hopefully you'll just find a loose section or clamp.