Danielboon

Ok before you guys jump all over me I have researched this issue for the past week. Ive given about 5 hours a day playing with the car, replacing parts, and im still having problems. So in an effort to save money ive signed up here to see if anyone out there can help.

I just bought a 1999 GS 300. Its having some sort of starting/ idle problem. Normally when its cold it will start and run just fine. I was having issues with it staying running and starting when the motor was at normal operating temp. So first thing I did was check the codes. First code was for the ignitor so I replaced it. Next code was the TPS, I replaced that and set it to .64 V with the engine off and the key to the ON position. Then another code came up and was for the throttle body motor. Replaced that.

Now I have no codes, I disconnected the battery and let it sit for about 10 min. After hooking it back up I cranked the car (it started fine) and let it get back to operating temp. It seemed to idle fine right at 750 rpm. I let it run for about 10 minutes to make sure it re learned everything. I turned it off, let it sit for about 1 minute and cranked it back up. It idled fine maybe 50 rpm lower than before. I turned it off again let it sit for 1 minute cranked it again. It now idled at about 600-650, strange I know but it did hold an idle and ran until I shut it off. So I went inside grabbed a snack, ate, came back out (10 min) tried to start it and it wont start unless I give it just a little bit of gas. Then when it does start it idles really low and rough and stalls out. Ive been dealing with this rough idle and stall for a while now and im just about fed up.

Any ideas? Ive checked for vacuum leaks and cleaned the throttle body and mass air flow as well.

teeekuuu

Did you try running the car without the MAF when warm ?

Danielboon

Just crank it with the maf unplugged?

*OK so I started the car let it idle, unplugged the maf and the car died.

MrHimbert

Dude mine is very similar right now. I figured I would just move the tps to bring the idle up a little. Still sitting at .70 volts. Let me know if you find something out, I'm still researching/trouble shooting. The thing flies to 100mph yet idles oddly low sometimes and almost stalls if I slam the brakes or even hit the gas from a stop. Weird hesitation. Clean throttle body, and maf sensor, just put in new plugs and valve cover gaskets too. So I'm on the fence right now. No codes either

Danielboon

Please let me know if you find anything out I went back and double checked timing today which seems fine. It seems as if every time there is a load put on the motor it wants to die. Like when the a/c turns on or even just the cooling fans. Also my tps is set to .57 v anything higher and it won't even start

MrHimbert

Looks like that's a good clue right there. You should be between .64-.72.

Just keep researching. Take vids/pics if you need more help.

I honestly adjusted my tps to .70 while it was running. It works fine now. Second wire down from the top of the sensor to ground is the correct wire. Not the third one down like a lot of people are thinking

Danielboon

Ok so the tps is set to .67 volts. In order for the car to start I have to give it gas. Also the gas pedal does not respond until it's almost floored, it shifts hard when shifting from park to R or D. Idle seems to be fine but it hasn't reached operating temp yet.

Danielboon

Update, I let the car run until it warmed up. I turned it off let it sit for an hour and cranked it again, now the tps is reading .9 v and I haven't moved it. It's also throwing code p0121 and 01128 which is tps and throttle control motor both are new.

MrHimbert

well if it is in limp mode, than you are running off the cable throttle. So just adjust that part until there is no slack in the line. That should help bring up the idle and response time when in limp mode. After that its on to the trouble shooting.


I personally cleaned all my sensors and plugs out with rubbing alcohol or electrical cleaner. Some people say that isn't something you should do, and i agree to an extent. But i worked on Avionics systems on-board 22 million dollar helicopters. People told me the same thing on that as well, but i did it anyway, and it ALWAYS worked. So i did it on my car, adjusted my TPS, and boom. It works. So its up to you, but id do all this with your negative cable off your battery, and put it back on last.

lexusalot

I am about fed up with mine too I love my car but it’s doing the same thing and has been for a long time rough idle but on the highway cruises like a dream but start to slow down and it’s rough about to die it’s been frustrating replaced the coil packs the spark plugs wires the alternator the battery cleaned everything out all the filters checked the vacuum I have no idea I am not ready to give up on my car but I can’t figure out why it’s doing this and I don’t know if anyone has found anything out on this issue lately but something somethings up if all of them are acting like that so I hope one of us gets it