The unfixable mystery problem

mamory · 07-11-2009, 02:23 PM

I had a similar problem and it was actually a misfiring at high rpm.(this is not what it felt or sounded like.) New valve cover gasket, plugs and wires solved the problem for me. Oh i changed original fuel filter (88 turbo). took me longer to do the filter than the gasket, plug and wires!

*Deadman* · 07-11-2009, 02:38 PM

if it is a vac leek get some newspaper and light it on fire keep it away from the filter and run it around the vac lines and if you get a blow or suck of air cheak around that air for a leek

GettaRobo · 07-13-2009, 06:36 PM

Just for an update, I guess the mechanic tested compression and said it was very strong. He's going to check the timing belt for missing teeth as he said that could be an issue. He also didn't think that a vacuum leak would cause this problem.

Beals · 07-14-2009, 05:52 AM

hmm, I know on my '88 supra I'm using as a donor motor for my '87 in much better shape that it had some old hoses and lines on it that were all split and it completely sucked the power right out of it.

GettaRobo · 07-14-2009, 05:49 PM

That is a good suggestion, however, that is not the case with this problem. The car will run fine with lots of power up until 4k. After that, the car simply feels like it is not getting more power. If you depress the accelerator to about 3/4, you can rev it to redline. If you put it right to the floor, it will stop revving at 4k.

Beals · 07-14-2009, 07:21 PM

Quote:

Originally Posted by GettaRobo

That is a good suggestion, however, that is not the case with this problem. The car will run fine with lots of power up until 4k. After that, the car simply feels like it is not getting more power. If you depress the accelerator to about 3/4, you can rev it to redline. If you put it right to the floor, it will stop revving at 4k.

Sounds like their is some kind of limiter on your electronics end. Have you checked into the fuelcut? I know HKS makes a fuel cut defender (FCD), you could look into this. It might solve your problem.

GettaRobo · 07-14-2009, 07:48 PM

I've definitely heard of them. I've also heard that they may not be so great to use as you can potentially bugger up your engine. I suppose that only happens if you're doing something super retarded though. I know that the mechanics have looked for a rev limiter in the ignition system and such and they haven't found anything. I guess the only way to know for certain would be to swap the other engine I have to see if it does the same thing. I'm about ready to throw in the towel and live with it for now, but we'll see what happens (I should know later today.)

carl johansson · 07-15-2009, 11:26 PM

First place I would look is the throttle position sensor - but to tell you the truth I don't even know if the supra has that. Alot of high performance shope sell a bogus "power enhancer" that is a throttle position switch that tells the computer that you are at full throttle - when you are only at 3/4. doesn't really add power - the petal still goes full - just no gain after3/4 throttle.

This problem sounds like the switch is working backward for some crazy reason! Like I said - it's a shot in the dark - but if someone burned a performance chip and it got screwed up - this could be the issue!
AFAIK - The Rev limiter on this engine is burned on the ECU chip! ( we hit it on occasion in the lemons racecar!)

Carl Johansson

Stormin · 08-27-2014, 11:22 PM

I have a 1989 turbo with recent mild modifications, a slow work in progress. The car backfired badly a few weeks ago at speed, the check engine light came on and I had similar symptoms, would not rev above 4,000 rpms. Checked everything, changed TPS, etc., no luck. Finally found a simple cost free problem. The lower intercooler hose had come off, huge vacuum or pressure leak. Re-attached it and made sure it was secure, problem solved. One possibility. Hope this helps.

07-11-2009, 02:23 PM	#1
mamory Stock Join Date: May 2009 Location: michigan Posts: 4	???? I had a similar problem and it was actually a misfiring at high rpm.(this is not what it felt or sounded like.) New valve cover gasket, plugs and wires solved the problem for me. Oh i changed original fuel filter (88 turbo). took me longer to do the filter than the gasket, plug and wires!

07-11-2009, 02:38 PM	#2
Deadman Stock Join Date: Jul 2009 Location: Christchurch Posts: 12	if it is a vac leek get some newspaper and light it on fire keep it away from the filter and run it around the vac lines and if you get a blow or suck of air cheak around that air for a leek __________________ "88 Turbo A 150xxx ks Stock (Wreaked) "86.5 widebody shell aero top factory manual Soon to come 86.5 with 7mgteu and r154 aerotop w/ leather seats

07-15-2009, 11:26 PM	#8
carl johansson 3" Exhaust Join Date: Nov 2007 Location: Auberry, California Posts: 141	First place I would look is the throttle position sensor - but to tell you the truth I don't even know if the supra has that. Alot of high performance shope sell a bogus "power enhancer" that is a throttle position switch that tells the computer that you are at full throttle - when you are only at 3/4. doesn't really add power - the petal still goes full - just no gain after3/4 throttle. This problem sounds like the switch is working backward for some crazy reason! Like I said - it's a shot in the dark - but if someone burned a performance chip and it got screwed up - this could be the issue! AFAIK - The Rev limiter on this engine is burned on the ECU chip! ( we hit it on occasion in the lemons racecar!) Carl Johansson Last edited by carl johansson; 07-15-2009 at 11:29 PM.

08-27-2014, 11:22 PM	#9
Stormin Stock Join Date: Aug 2014 Location: Upper Marlboro, MD Posts: 1	Possible Solution I have a 1989 turbo with recent mild modifications, a slow work in progress. The car backfired badly a few weeks ago at speed, the check engine light came on and I had similar symptoms, would not rev above 4,000 rpms. Checked everything, changed TPS, etc., no luck. Finally found a simple cost free problem. The lower intercooler hose had come off, huge vacuum or pressure leak. Re-attached it and made sure it was secure, problem solved. One possibility. Hope this helps.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
ABS Problem?	rasclaat_98	MKIII Supra	6	12-13-2010 09:53 PM
speed sensor problem	nadircicek	Non-Generation Specific Questions	8	10-09-2009 05:58 PM
another heater problem	nicnet	MKIII Supra	16	12-05-2007 10:18 PM
found the problem	brs86supra	MKIII Supra	0	05-02-2006 03:42 PM
Boost Problem, I Guess	nonstop213	MKIII Supra	0	02-23-2006 07:32 PM

07-13-2009, 06:36 PM	#3
GettaRobo 3" Exhaust Join Date: Apr 2009 Location: Saskatoon, SK Posts: 65	Just for an update, I guess the mechanic tested compression and said it was very strong. He's going to check the timing belt for missing teeth as he said that could be an issue. He also didn't think that a vacuum leak would cause this problem.

07-14-2009, 05:52 AM	#4
Beals Intake Join Date: Jul 2009 Location: Canada, Alberta Posts: 32	hmm, I know on my '88 supra I'm using as a donor motor for my '87 in much better shape that it had some old hoses and lines on it that were all split and it completely sucked the power right out of it.

07-14-2009, 05:49 PM	#5
GettaRobo 3" Exhaust Join Date: Apr 2009 Location: Saskatoon, SK Posts: 65	That is a good suggestion, however, that is not the case with this problem. The car will run fine with lots of power up until 4k. After that, the car simply feels like it is not getting more power. If you depress the accelerator to about 3/4, you can rev it to redline. If you put it right to the floor, it will stop revving at 4k.

07-14-2009, 07:48 PM	#7
GettaRobo 3" Exhaust Join Date: Apr 2009 Location: Saskatoon, SK Posts: 65	I've definitely heard of them. I've also heard that they may not be so great to use as you can potentially bugger up your engine. I suppose that only happens if you're doing something super retarded though. I know that the mechanics have looked for a rev limiter in the ignition system and such and they haven't found anything. I guess the only way to know for certain would be to swap the other engine I have to see if it does the same thing. I'm about ready to throw in the towel and live with it for now, but we'll see what happens (I should know later today.)