TPS or Knock Sensor??
 

My supra has been acting up lately. It is idling pretty weird. If I drive it for about 10 minutes or more and then turn it off, and start it up again about 20-30 mins later, the RPM goes up and down like the car is breathing really heavy. The RPM needle just goes up and down really heavily and the car sounds like it is going to stall. Once in a while it will fluctuate so close to 0 RPM that it will just stall. My engine light is on, and it says my knock sensor and TPS have errors. I took it to my mechanic, and he checked it out, and he said it was the knock sensor. But I want to make sure thats the case.

Any help/suggestions??

knock sensors generally don't cause erratic idle... they just throw a check engine light and retard the timing until the knock sensor is repaired

i would check your tps
www.supratsrm.com

under efi> throttlebody

Ok, well I guess that I read the codes wrong when I diagnosed it myself. I thought I was getting the TPS and Knock Sensor code. It was only the knock sensor. My mechanic fixed the knock sensor. Apparantly it was in two pieces and looked like it had been hit or something. The car runs better with the sensor in place, BUT i still have that problem!

I am stumped on what it could be. I have no engine light on, but it still breathes like it has severe asthma or something. I thought it might be a battery recharge problem, and i checked everything. The alternator is only a few months old and it was doing this before I got the new alternator. So that rules it out. The battery is fairly new as well. And the throttle body was cleaned out as well and the TPS is working fine. So its not a problem with wiring, at least i dont think it is. And I checked over and over for cracks and holes in vaccuum tubes and the intake tube. I am STUMPED!!!!

EDIT
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Could this just be a really bad case of heatsoak?? I sure dont have problems with overheating or anything. Im running the stock fan in my 7MGE and it seems fine. But when i turn it off for a while and turn it back on about 20-30mins later, its like the battery isnt charging, or its just overheated or something is causing it to breathe and die like it does. I dont know. :(
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Guidance please?

recheck diagnostic codes and post up the numbers ;)

You could have something blocking the intake somewhere, OR you may have a blocked cat. converter or muffler. Timing could be way too retarded. Thes cars do slip their timing belts after they get old and some of the time the car will move but barley, or not at all.


All I can think of for now. S_girl has a good plan too.

Russ

This same problem happened to me right after I put my new engine in. I thought it had something to do with the MAFS but it turned out that the dashpot was out of adjustment. So if you just mess around with the adjusting screws on the throttle body you should be able to fix the problem.

hmmm well i will try what you said about adjusting the screws. hopefully it will work out.

the idle screw & afm screws are set
unless someone has fiddled with them previously

do a diagnostic and tell us the codes and then we can help you more specifically

well i dont have any error codes at all. it was all fixed. but this problem persists. there is definetly something wrong though. it was never like this before.

it seems as tho you are talking 3rd person.... did someone else do your diagnostics & repair? or just repair?

if you are unsure on how to do diagnostics yourself there are plenty of ppl here including myself that can help you out :)



so... we'll start from square 1 and ignore tps & knock sensor

have you tried looking for leaks? intake manifold, vacuum lines etc?

OK I will try and clear this up a little more lol.

This problem of mine started not too long ago. I checked the diagnostics myself, and I thought I came up with TPS and knock sensor error codes. But then I took it to my mechanic, and they came up with only the knock sensor. So I misread the codes when I diagnosed it myself. And they replaced the sensor for me. Now my engine light is off. So it wasnt the TPS at all.

But I still have the same problem. The throttle body was cleaned out. I have checked for leaks in the intake manifold and vaccuum lines, but I cant seem to find anything that would cause it to act like this.

does anyone have a clue to what might my problem be?? because I hate driving the car for like 20 mins. then turning it off, and starting it 15mins later and have it act all retarded and just die like it does.

have you tried the idle speed control valve?

http://www.cygnusx1.net/supra/librar...fi/FI_106.html

Mine had done that some, but not as bad as yours it sounds like. I made sure that the butterfly was closed all the way. It needs a small, small gap to keep it from sticking and then screw the idle adjuster all the way in then back out about 2 turns or so. I know the engine is hunting and it is very annoying. Make sure your timing is set to at least 10 degrees btdc. Try pinching off the vacuum retard on the distributor when it is running and see if that does anything.


The ISC can be the culprit too, so make sure the electrical plug is all the way in along with the plug in for the throttle position sensor. Try pinching off vacuum lines too. Make sure your bellows is tight and has no cracks.

I am just throwing out a lot of things but I got mine to start up and run smooth eventually by checking all those things.

Keep us informed.

Russ

alright, i will check all of those things in the next few days when i have time. and i will keep you posted on whats going on. i appreciate the help on this problem.

Sorry to bring up an old post but I have the exact same problem and I have checked all that stuff. Please help!

Does anyone have a diagram on how to check the TPS ??????

Okay first and formost this problem is somethin I had as well. I know his might seem stupid, but check the preheater hose (this is the piece between the AFM and the throttle body, the part with the big round thing on it, the silencer) and check for leaks in the house. If there is is can cuase this big time. It is exactly what happnened to me. It also could be a problem with your AFM itself.

I am going to redirect this to my other post....

http://www.toyota-supra.info/forums/...9547#post29547