TPS voltage problem
 

So here is the story. i own a 1989 toyota supra turbo. the problem i am having is the voltage at idl and e2 at the ecu. When i probe these leads i get 10 volts instead of the 4-6 that toyota calls for. when i unplug the ect for the transmission the voltage across idl and e2 drops to 5.2v. this is where it is supposed to be. Anyone know what the problem may be.????? please someone help i am ripping my hair out wondering where the problem may lay. thanks

Anyone??????

if its faulty, replace it bro

thats the thing i dont want to pay for something i dont need. im going to run it how it is. it runs ok just runs rich but that may be because i had the battery disconnected for a few days. only had it idle in the garage. the computer needs to relearn the fuel pattern.

Measure the resistances across the TPS connections as detailed in the EFI section of the TSRM. Disregard the info you have concerning the voltage, if you look in the ECT section of the TSRM you'll find it specifies approx 4v.... The ECT computer pulls the voltage down, a manual equipped 7M should have 10v to 14v. It's pretty broad as it's not there to give any signal beyond on/off.

A bad IDL switch isn't going to cause you to run rich either.

thanks cre. what would cause the car to run rich?

There are many, many possibilities... More than I feel inclined to just blindly list off.

When is it running rich and how did you test it?

Are there any diagnostics codes stored (or were there before you disconnected the battery)?

its running rich on idle. before the i replaced the manifold gaskets at idle the car would run at 14.7 on the afr gauge. now that i put it back together i find that the car idles at around 12.5 or so. no codes that i have found but the check engine light will not light up if there is a code. it does turn on when i turn the key to the on position indicating that the light works. i have to jumper the terminals in the diag box to find if there are codes. really weird. my truck is the same way. but i think i may have found the problem. it may have been a broken signal wire to the oxygen sensor just off the down pipe. its a shielded wire. i fixed it and put a new connector on and decided to replace the main front crank seal seams i have it all ripped apart and the old one was dry rotted. i will have it running by tomorrow hopefully.

The AFR will be around 13, maybe a little richer, when the ECU is operating in open loop (cold starts, bad ECU temp sensor, bad TPS signal, no OX signal, etc).

ya thats what i was wondering. it could be that broken wire to the oxygen sensor. the tps sensor is within spec that the manual gives. ecu temp sensor is brand new and test out ok. it has to be the bad oxygen sensor wire. what causes the cel to not come on when i have codes but does only shows the engine light when the diag box is jumped??? Appreciate the help cre and everyone helping

If there is no OX signal the ECU obviously can't go into closed loop operation.... Thus you're stuck in open loop operation full time. If that's wire is broken it will absolutely cause the vehicle to run rich (to some degree all the time and under all circumstances). There may be other problems but a broken OX signal wire must be addressed before you bother with anything else.

The CEL only turns on for certain high level codes and only remains on for persistent or severe diagnostic events. There are very few which trigger the CEL permanently. The supposition is that a vehicle's owner will take their vehicle to the dealership for regular maintenance where it will be checked for codes on a regular basis without alarming the owner if a minor problem is recorded. This is still the case with current vehicles although there are a lot more possible codes and more of them will present at least a temporary CEL. It's a good idea to check for codes whenever you change your oil (or more frequently if you like).

well got the car running today. when i started the car it ran really lean. 17.5 on the afr gauge. and at idle. just stays there and when i push the throttle it goes to like 15 or so. I bled the radiator again to make sure all the air pockets were out and there were some air pockets in there. when the bubbles came out the car started to run rich again at 12.3 again. could the oxygen sensor just have gotten bad. took a look at the spark plugs and they are brown like they should be. seems to be burning good. some carbon on the rim of the spark plug. it runs good just the gauge says its running rich. Replace wideband sensor?????? its just really weird how it was running fine before i took the manifold off. not the same as it ran before. replaced all the vacuum lines and made sure they were all hooked up correctly. could a bad egr valve cause the car to run rich or act like a boost leak??? i did replace it with one that was on a spare car in the junk yard being that i broke the original one when i took off the manifold!!!! so my questions are
1) could the oxygen sensor work then crap out the next day meaning can it go bad anytime?
2)could the wideband sensor be bad, sending a false reading to the computer or gauge
3) is the wideband sensor hooked up to the computer of the car acting like a secondary ox sensor?
4) would a bad egr valve cause the car to run rich or does it act like a boost leak?

your grasping at straws here.. you said it yourself, it ran fine before I replaced the manifold.. replace the gasket and make sure to use the correct torque this time... oh and yea. get a new 02 sensor. 50 bucks @ summit..

1) They're very delicate and part of the actual sensor is ceramic. If dropped or subjected to similar shock they can be easily ruined. Yes, it is possible, but it's not all that common for a relatively new sensor to just die on its own over night.

2) and 3) It depends entirely how the wideband is setup and what it's capable of. Most wideband controllers have at least one analog output which can be used to emulate the stock narrowband sensor allowing you to remove the stock sensor. I couldn't tell you how yours was installed... You'll need to figure that out on your own. If the wideband is supplying an emulated narrowband signal to the ECU you MUST NOT connect a narrowband sensor. Typically in these installations you would delete the engine bay wiring for the narrowband sensor altogether and plug the sensor's bung.

4) No and neither.

Agreed. Go back over everything you handled. You didn't drop or spray cleaner into the AFM, I hope....?

I thank all of you for the help and knowledge you are giving me. you dont know how much this helps me narrow things down. i did not clean the afm at all. i know how delicate that sensor is to certain sprays if not all of them. There is a brand new gasket on the manifold. both of them. torqued to the factory 13ft pds. should i have put rtv gasket sealer on the gaskets before installing them. the manual says you dont need to. but for the wideband sensor i have no idea how it is hooked up. i bought the car that way. i will have to get under it and track the wiring. its not a bad idea to have 2 oxygen sensors anyways is it? i mean the 7mge has 2. i will have to replace the oxygen sensor and try a new ecu temp sensor. take the new one back and get a replacement. A narrowband sensor is the stock oxygen sensor just after the turbo correct?

That's a relief.

A dressing such as hylomar won't hurt anything and is cheap insurance. Just make sure it's compatible with any materials used on the gasket (such as viton).

Rule number one when trying to diagnose a problem on a vehicle: Inspect aftermarket wiring and learn how to operate any and all aftermarket components. If they're interfaced with the stock hardware then disable them and get the vehicle running properly stock first.

Actually, it is a bad idea if the computer doesn't have an input and programming for two. Only the California model has two narrowband sensors. Trying to feed two sensors into the one input on any of the other MKIII ECUs will just muddy the signal and the ECU will most likely error out and disregard the OX input altogether...

A narrowband is a type of sensor. Narrowband and wideband simply describe the scope which the sensor is capable of reading. A narrowband has such a short scope that it can really only tell if your mixture is stoichiometric or rich or lean. It can't tell you how far off you are. There's a lot to oxygen sensors and I'm not going to go into it. If you have a specific question about them and can't find the info then post up and I'll answer what I can if it's not too involved.

Depending on the make and model, your wideband controller might be able to calibrate to the sensor you've already got installed. Find out the make and model and download the owner's manual before you go and buy a new sensor. You'll need to know how to calibrate a sensor if you install a new one anyway.

well the car is running. not rich as it was before. now when i pulled into the driveway yesterday the afr gauge read 17+ until the 3 lines indicated it was over 18. Unplugged the oxygen sensor and no change. while cruising the afr will move in and out of 15 and 17. it does go to 11 when i am in boost. timing is dead on base timing set to 10 degrees jumpered. 12 degrees unjumpered. what could cause the car to run lean while cruising or at idle. Now today i went out in the garage and started the car and what do you know the car is back to the running rich idle. 12.4 on the afr gauge. I just dont know about this car. it could be that the intake manifold gaskets are causing a vac leak but i highly doubt that. what could it be

here is a video of my diag. http://www.youtube.com/watch?v=3pYrf...ature=youtu.be