'99 LS with codes and intermittent rough idle...
 

Hello all,
This just started today as I was sitting at a stop light. The car began to idle around 3k rpms and it started to miss. When I cruised through the light, I accelerated and the miss went away after 1k rpm's. I, then, noticed that the VSC and the CE lights were on. My drive home is approx 40 miles and it takes me about an hr to complete. The car idled rough at a few stops, but never stalled. I drove the car home, even on the interstate, and it was fine. It has all its regular power and pep. I took it to autozone and through a P0301, P0303, P0305, and a P0307, all the cylinders on the left side? Now, even though both the VSC and Check engine lights are on, the car runs fine. I have searched and each case is slightly different than the other, and some have no resolution to the issue. I'm hoping some of you can help me out.Any help is greatly appreciated! Thanks in advance!

Cliff notes:
-'99 LS400 with 245,xxx on the clock
-Car was running perfect, no warning lights
-sitting at light, car begins to miss and idled down to 3k rpms
-intermittent rough idle
-drove 40 miles at 80mph with VSC and CE light on and no problems
-autozone scans for P0301, P0303, P0305, P0307
-turn car off/on the VSC and CE light appear and car runs fine

-Brandon

When you scanned it did you get the freeze frame? If it was me I'd do the battery disconnect deal and see if the problem comes back. Could be some water in fuel, or just a transient thing. Unless it craps out all the time, its not going to be easy to find. Something not many think about is electronic controls can be vulnerable to strong electromagnetic fields, that could cause a rare intermittent fault.

I worry about the skipped timing of a tooth of the cam shaft. When did you change the timing belt last time?

Update:

I drove the card to work today, 40 miles in 30* weather, and not a single miss. Car ran great. I did not disconnect the battery like Dicer said to do b/c i wanted to see if the problem would reoccur or get worse. I will do it when i get home and see what happens. Yamae, the timing belt was replaced at 170,xxx and judging by when it happened and how it happened, I don't think the TB skipped. Thanks for your input, thus far.

I had this issue last year plus I was having issues with my fuel trims. I cleaned my maf and the issues went away. Now it's back and throwing a code for the drivers side VVT-I which relates to the OCV from all the things I have read. So I'm waiting for it to come in the mail. The code was P1349 so you might want to check into it. I'm not saying that's your problem it's just similar to mine minus the VVT-I code.

Update:
I went to lunch today and after about 5 mins of driving, i looked down and there was no CE or VSC light...all clear. I wish i had something better to offer to those that have had or are having similar issues. I have to agree with Sha4000 about the issue being related to the MAF. The temp when the issue started was 25-30*. Today, it's around 45*. With that being said, i 'm going to clean the MAF and hope that it doesn't show up again. Sha4000, keep us posted on that OCV. Thanks all!

-Brandon

when was the last time you replaced your spark plugs? that is the first thing i change (regardless if it needs changing or not) when i get misfire codes. at that mileage i hope you have replaced it at least 3 times in its lifetime.

Yes I would check spark plugs like timmy has stated. I had literally just changed my plugs less than 10k before my issues so I thought they were not likely the culprit but after running my torque app to check fuel trims and doing lots of reading I cleaned the maf and that solved the problem. Even now with the P1349 I was skeptical and attributed it to the temp since it was like 19 degrees at the time. So I cleared the code several times to see if it was a fluke but the codes kept coming back immediately.

Thanks guys. Changing the spark plugs is something that I have been wanting to do along with a laundry list of other things. It's just puzzling that only the odd number cylinder's were misfiring? Again, thanks for you input.

-Brandon

That is why I did not think the plugs were my issue but with your mileage and depending on when you last changed them, it would not hurt and is not that expensive. Check your air filter too, when that gets clogged problems arise.

Good deal. I'm going to try and get to that this weekend. What's the recommended gap?

Clarification needed. Did you mean to say 300 rpm? Or is the idle really that high?

You are right, it does seem odd to get all misfires on one bank. So maybe it is OCV or cam sensor related? Other issues would not tend to pick out one bank.

I'm almost sure he meant to say 300rpm but It's good you caught that randal.

well on my 99, 1349 was my OCV was dirty, cleaned it with carb cleaner and cleaned the chamber also and the light went away, about 3 or 4 years now, no other lights..

Update:

I did mean that car idled down to 300rpms and not 3k, sorry about that. This past weekend, the CE and VSC OFF lights came back on. The car had the exact same symptoms. It happens once the car is at operating temp and then that's when it becomes intermittent. Tonight, I changed out the plugs with Dezo Iridium's and it's the same. This leads me to believe it's one of the sensors acting up, and I can't put my finger on it. I unplugged the MAF and the car dies, so that's good. Whichever sensor it is only affects the driver side plugs and coils. Randal, I will be checking the OCV when I return home from work tomorrow. Any and all help is greatly appreciated!