johnnyo808

My 2001 GS430 has had the VSC lights and a check engine light on for a little while. However, I had not noticed any change in performance of the car. As my inspection date is coming up, I wanted to get it cleared up. I took it to my mechanic, who then took it to Lexus, who got me for a set of spark plugs!! This did not solve anything, as most of you could have guessed. By the way, do no dealerships have "mechanics" anymore? They all seem to be "certified part changers"!!

Now we are getting random misfires P0302, P0303, P0305 and most notably P0307. This only happens under light load, though! At idle, no codes, and under heavy load, no codes!

The plugs have been replaced, injectors were cleaned and resealed, injectors and coils have been switched to good cylinders, and we still get the same codes.

Any suggestions would be appreciated before I have to go back to the "Part Changers"!!

Thanks.

99 GS3

iTrader: (14)

I've dealt with random misfires on a couple previous cars, One was on my bagged ranger, it drove me crazy trouble shooting for weeks, and it turned out there was some water in the gas tank from when it had rained while the bed was off for a couple weeks and it seeped in. Water is heavier than gas and settled at the bottom were the pump picks up I had to drain the tank. (that's an extreme situation obviously)

Second was my wifes civic, and it turned out to be bad gas. We had moved to a different part of town and she started filling up at Wawa every few days and here milage went way down and started misfiring alot. I had her start going to a Shell right near and on

GS_OREO

good advice, run the gas tank empty!

99 GS3

iTrader: (14)

Uh, not sure if your being literal or sarcastic.. No emoticons makes it tough

But don't literally drive the gas tank empty and burn up the fuel pump.. But do replace the current tank of gas with a good brand of fresh gas.

Crappy gas can most definitely cause misfires, sputtering, or hesitation. Random misfires are more likely because the gas is going to all cylinders. It's doubtful that like 4 plugs, coils, or injectors, would go bad at once. Rule it out first, cheap and easy to try..

jcat_350

not once have we confirmed octane...


OP..what are you using for gas (octane wise, 87, 89, 91+ etc?)

GS_OREO

No I wasn't being sarcastic. Bad gas can cause your vehicle to run erratic. Espically with intermitten random misfires, or running lean mixtures.

johnnyo808

We have run it through 3 tanks, and are using the high octane (92?) from Mobil and Sunoco. Again, the odd thing, is that I don't notice or even feel the misfires. Without the cel, I would have absolutely no idea anything was wrong.

99 GS3

iTrader: (14)

The crank position sensor detects misfires. Maybe it is going bad?

Might be possible to why it throws codes but runs fine..

You can test the sensor for the proper resistance with a multimeter. But you need the specs from the service manual to know what the readings should be. I'm not sure on that tho. Link to the PDF from a sticky:
http://bahamutcars.free.fr/workshop/...nts/index.html

Lots of things can cause misfires, but you should feel it under load. I would think multiple cylinders were really misfiring you would notice for sure.

johnnyo808

My mechanic had suggested the crank sensor. I've been trying the link you provided, but I am having trouble getting to the PDF files. I'll keep trying and let you know how things work out.

Thanks.

99 GS3

iTrader: (14)

I couldn't get it to open in firefox, but it worked in internet explorer. Just incase you were trying with firefox, but it may work with the ie tab addon for ff, but I didn't try that..