Guest Andyewen Posted June 15, 2010 Share Posted June 15, 2010 I hope someone can shed some light on a particularly nasty problem my MKIV Supra has developed. First serious issue in over 7 years ownership. Car details: 1996 Twin Turbo Import Auto 129K Miles in exceptional condition. SuperDragger Exhaust & K&N - rest of engine totally stock Recent full main dealer service including Cam Belt - no issues found. Fault: After 15-20 miles of fast driving, when you stop, (at a junction, roundabout etc), the revs drop to about 100RPM and then quickly flick back up to idle, (around 650RPM) - it never completely stalls. After that, it then changes gear at the wrong time and sort of 'clunks' when changing down; all to do with messed up revs I presume. If you leave the car for a few minutes, the fault goes away and will not repeat until it gets driven hard again. There is no loss of actual power at any stage; it still goes like a missile. I've had it in 3 seperate garages and they've all experianced the problem but have no idea what is causing it. We've tried the obvious stuff; cleaned out the throttle body, made sure the air idle control valve is working properly and had the car on various diagnostic machines. No error codes have been reported. Two seperate garages thought it might be the Torque Converter, including Toyota Chelmsford, (really excellent people). However, they delivered it to A&M Transmissions in Chelmsford who specialise in re-building Auto boxes and they don't think it is the Torque Converter so they sent it back to Toyota which is where it is again now. This has been going on for 4 months and I'm almost at the stage where I take it into a quiet field with a shot gun and put it out of its misery, (and mine). Any help in diagnosing this problem would secure you a place in heaven, (or the afterlife of your choice), Thank you, Andy. [email protected] Quote Link to comment Share on other sites More sharing options...
Scooter Posted June 15, 2010 Share Posted June 15, 2010 It could possibly be the speedo convertor......... Quote Link to comment Share on other sites More sharing options...
Scooter Posted June 15, 2010 Share Posted June 15, 2010 http://www.mkivsupra.net/vbb/showthread.php?t=198736&highlight=idle+converter similar symptoms Quote Link to comment Share on other sites More sharing options...
stevie_b Posted June 15, 2010 Share Posted June 15, 2010 At the edge of my knowledge here, but I wonder if it's something to do with a nick/tear in one of the vacuum hoses? I may be talking rubbish. It sounds like only the choke is saving the engine from dropping its revs when it hasn't warmed up yet. Quote Link to comment Share on other sites More sharing options...
Guest Andyewen Posted June 15, 2010 Share Posted June 15, 2010 Thanks, that's an area we haven't looked at. My Supra was fully converted by JIC before I bought it, ODO & Speedo are in MPH and it is definately delimited, (had it up to 170MPH on a trip through Germany - bit scary). My symptoms are a bit different though and do seem to be heat-related; something is getting too hot and breaking down to cause this. Hopefully, someone reading this thread will have had exactly the same fault and tell me it's an easy cheap fix Changing the Torque Converter will be over £1000 but I'm prepared to do that if it cures the fault. Quote Link to comment Share on other sites More sharing options...
Guest Andyewen Posted June 15, 2010 Share Posted June 15, 2010 Yes, I discussed a possible break in a vacuum hose with another engineer. Guess I'll have to go over all the hoses and check. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted June 15, 2010 Share Posted June 15, 2010 JIC went through a phase of using speedo converters mounted in the transmission tunnel, under the car, where water ingress made them do "strange things". I would suggest this fault of your car's is typical of a speedo converter that's gone up the pole. Quote Link to comment Share on other sites More sharing options...
Guest Andyewen Posted June 15, 2010 Share Posted June 15, 2010 Wow, best bit of info yet, thanks Chris. Quote Link to comment Share on other sites More sharing options...
Guest Andyewen Posted July 7, 2010 Share Posted July 7, 2010 Well, managed to locate the speedo converter chip, 'twas behind the dash board. This has been replaced with a new one by Totota Chelmsford but unfortunately, the problem of the dropping revs still exists. Anyone got any other ideas? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.