I have a 94 LS 400 with 155,550 miles an just recently it started messing up. It has a high idle at around 2000 RPM's. While in park if engine reved it starts to missfire at around 2500 RPM's. The car has a lack power when in drive, it doesn't want to go anywhere. Only way to drive is if I put it in low then shift to second then to drive. The car has a hard time turning on and when it's on it sometimes turns off by itself. It might be the mass air flow sensor or the ECM, I don't know. Any advice please?

 

First, does your check engine light show? If yes read your codes and post them here. See http://www.lexls.com/tutorials/intro/codereading.html on how to read the codes.
If you don't have any CEL's it's probably a problem with your ECM. But to make sure it's not the AFM you can unplugged it. If the car start to work fine there's your problem. It could also be a problem with one of the ignition coils (you have 2). To check if that's your problem you can unplug them one by one to see if that make any difference on how the cars behave (I would not doing this when the car is running). If the car behaves the same, that coil is dead. You could also test them by follow the attached description which is the recommended procedure.

 

Thanks for the advice. I took the car to a mechanic and he diagnosed it and told me i needed a new fuel pump. He didn't tell me what codes came up though. Me an my uncle were workin on the car this week trying to find the problem. When I told him about what the mechanic said he didn't agree with him. Does this problem sound like a fuel pump issue?

 

why not go to autozone have them find out code 4 you.

 

I didn't know autozone could do that, I'll give it a try....thanks

 

yeah it's free and it's their job to help customers or else they wouldn't be here today. hahah I always got my code from it's all good now. they only cel with obd2 so..hopefully u get the codes from your car.

 

2 problems with that:
A-in california because of some law protecting shop owners, autozone and kragen no longer read codes or lend codereaders any more.
B-his car is an OBDI LS400 (OBDII didnt come in until '95, with the 2nd gen). so he doesnt NEED a code reader anyways.

just follow the procedure listed above and spend 5minutes getting the code.

 

Ah sorry I didn't know that, what a bummer.

 

fuel pump?..........seriously? i cant believe some of the so-called mechanics out there! what code would a fuel pump trigger? 00 as in uh oh u dont know what the bleep ur doing?

 

He didn't say the code was for the pump, he said they diagnosed it as the pump and didn't tell him what the codes were.
I don't think If the problem was the fuel pump it would idle that high, between 2000-2500. Like JAndersson said; pull the plug off the AFM to see if it runs good. Sounds to me like that's your problem.

 

so then no codes came up? sort of a vague post...misread on my part though. it could be a pump if the volumne is low. i was under the impression it threw a code.