95 Ls 400 Replaced Tps Now Idles Rough And Stalls

[irishtxun]

Please help me help my mechanic. I have a 1995 LS400. Codes recently came up for the transmission solenoid and throttle position sensor. The car had been shifting hard and strange so I thought it made sense. Since replacing both of them the car has immediately taken on a new set of problems, with no new codes appearing. It idles very rough at start up and usually will stall out. If I do get it going it stalls out while driving down the road. My import mechanic says he cant figure it out. Any help on what could have happened by replacing the two parts mentioned? Thanks

[curiousB]

There is a known problem with these cars of a broken ground wire in the rear trunk hinge cable harness. It is often suspected for strange electrical problems which otherwise don't make any sense. Search the forum on that and see if that could be your problem. Since you popped two unrelated codes I wonder if that has something to do with it.

If he's changes the TPS I believe there is a procedure for alignment. See that he followed that.

Poor idling is often related to a dirty throttle body and/or a sticky IACV. Cleaning these up is just good maintenance anyway as they get carboned up over time. Maybe as a gesture of goodwill, for a suspect job, the mechanic offers to clean these up on his nickle.

[irishtxun]

Thanks for the response. He says he did clean clean the throttle body and even installed a second new TPS and then reinstalled the original, all to try and correct what is now happening. He thought he may have received a bad part. He has a similar Lexus at the shop and has been comparing the settings but nothing he has tried has reversed what replacing the original parts apparently created. It had never stalled or idled rough until he replaced the solenoid and TPS .

[landar]

You didn't leave a vacuum line off of the intake, by chance?

[irishtxun]

Thats what I am thinking. That is why I came here, to find out some of the things he might not have replaced when doing the original repair. I will ask him. I don't mind if he is offended by suggestions because he is lost right now.I am already into this repair for $700.00 and need to get my car back. Going on 2 full weeks. Thanks for any help.

[landar]

...and it is very easy to crack the old, dry hoses when gaining access to the throttle body. You might want to carefully examine for old, rotted looking rubber and perhaps even the accordian shaped intake hose has a crack or two. Its easy to miss. Replace any that do look old and cracked. Also check for loose or unconnected electrical plugs. That is also easy to miss the first time around.

And finally, did the mechanic put new gaskets on where needed when pulling things apart? Bolts/nuts all snugged down correctly? (you really should not need to tell a good mechanic to do those things but since he seems 'lost', I cannot assume).

[irishtxun]

I appreciate all the responses. Unfortunately I will have to wait until Monday to tell him to try these ideas. It is locked up in the garage and they don't work weekends. If anyone else has a suggestion, I will try anything. I will let ya'll know if any of these tips worked once they get back to work on it. Thanks again.

[landar]

Yeah, final suggestion...hint, hint... (whisper in your ear)....find a new mechanic!

[curiousB]

if you get a piece of 3/8" dia. or so tubing a couple feet long you can use this to "listen" for a vacuum leak. Just hold it near your ear (don't stick it in your ear) and move the other end around areas you suspect might be leaking. It works like a poor mans stethoscope. I used this method to find small leaks in an exhaust gasket. Worked surprisingly well. You can really pinpoint something once you get a confirmation.

[irishtxun]

He has rechecked all vacuum lines, hoses, trunk wire, etc and still no solution. He says there are 2 TPS on this car and is ordering the other to eliminate the possibility the new one (that threw the code) is not working with the one he did not replace. He put the old one back on and it brought the error code back. With the new one on it eliminates the code.. He will have the other TPS tomorrow. Thanks

[irishtxun]

Still without my car. Can anyone tell me if by not disconnecting the negative battery cable after installing a new TPS and transmission solenoid that it could create the problems I'm having? A friend told me this needed to be done to reset the computer. Is it now too late to reset. Could anything have been damaged by driving it without having "reset" the computer? Thanks

[curiousB]

2+ weeks for a TPS idle problem tells me its time to find a new mechanic. Maybe a trip to the dealer is in the cards so you can get back on the road. Its seems your mechanic is stumped.