Thread: Car Still Running Rough *FIXED*

Basically, car's been driving fine up until earlier today. Was already probably 10 minutes down the road, almost to my destination. Felt a jump, ignored it thinking I probably hit a bump and was confusing it with the car itself. Car did it twice more after that in a row. Then it proceed to idle very rough at stop lights, RMPs and voltage were dipping pretty low. Upon acceleration, it was "skipping" and "jumping" again, as if the car wasn't getting enough fuel. Car died at a light, started fine, died again once I pulled it over. Started and ran ALMOST perfectly the rest the way to my destination. Jumped once more during that time and popped on the TCS light (no other lights).

At this point I was convinced I had a bit of bad fuel, so I drove it to the gas station after class, not a single problem. Filled it up and headed out....

Proceeded to start these shenanigans again at the next light. Didn't die, but was running poorly again. It stopped after a few minutes and ran normal the rest the way home.
My personal prime suspect at the moment is the fuel filter. Looking for a little help with this one.

Have you worked on your car recently?

Changed the alternator. That's it. Most certainly not an alternator problem.

Even new alternators can be lemons.

But. Fuel, air or spark. One is borked.
Check your MAF in particular. Check for vacuum leaks. Check fuel pressure.

And you've probably already checked under the hood to see if anythings been knocked loose. Hrmm.

Yup. As I said, it's consistent. It's not something that I can just show someone, I'd have to wait for it to happen and hope it doesn't stop doing that before I can film it or show it to someone

As I said in the chatroom, there are multiple problems that can cause the same symptoms, so it's hard to pinpoint over the internet. It could be injectors, FPR, coils, ICM, MAF sensor, etc. The coils and ICM can be checked for free at most parts stores. The MAF you can check by unplugging and driving it around for a bit (though don't go more than half throttle). Check for fuel pressure, and have the injectors checked for resistance as well.

im bettin its the maf... mine does that from time to time

Pulled the MAF, can't replicate the problem. Going to drive it tomorrow as well. If no more problems arise, I'll point fingers at the MAF.
And I kind of expected, but the car is a little less responsive and oddball with the maf unplugged, but my car is tuned so my tables aren't even close to stock anyway.

right. when i unplugged my (perfectly okay maf btw) maf, it would die when i let off the gas and start right back up. so even if it does it.... don't rule it out. you're looking for a change of any sorts.

Basically, it's not doing what it was doing before, so. Yeah.

So, it's apparently NOT the MAF. No store around here will check ICM or coils either.

Got a way to scan it?

Yes I do. I just did, and took a few notes. Until my buddy is off work, I can't drive and scan, but I did some idle scans. Unfortunately it wasn't acting up, but sooner or later I'll catch it.
I almost got it towed today it was running so awful for awhile. When it's running bad like that, it feels like it's being choked for fuel/air.

The only thing that didn't match what my scanner said was typical was manifold absolute pressure. My scanner said it should be roughly 12-20 in/Mercury(HG) and sitting at idle I was reading only 9 inHG. On rev it dropped to roughly 7-8 no matter what the RPM range was (between 1-4k RPM at least). Probably irrelevant as I'd suspect it would temporarily drop after letting off the pedal, but it saw maybe a 1/4-1/2 of the 4-6 range.

Spark seemed consistent, 20* spark advance at idle, increasing up 32* in the 3-4k RPM range.

Again, without the car HAVING the problem, the numbers don't mean a whole not, none of them do, so I have yet to rule anything out, except perhaps the MAF.

Edit: Also, maybe worth noting, it's not a hot/cold problem. Yesterday I had the problem randomly appear after 10-15 minutes of driving (car was fully warmed up by then) and today, it ran fine all the way to class from a cold start, but after 3 hours of class, problems appears immediately and I almost didn't make it out of the parking lot, and stalled it numerous times on the trip home. After 10 minutes or so it quit acting up.

32* of timing at WOT?

Am I reading that right?

In park, not WOT, 3-4k, I wasn't trying to piss off the neighbors with the rev limiter since I know it only goes to 4k anyway.
But yeah, 32* timing.

You can't really tell anything in park...

Go around the block or something and get some "under load" numbers.

I'll give it a shot. It's hard to keep an eye on the scanner while driving, its not like checking a scan gauge.

Edit: Anything I should keep an eye on in particular?

Well, I asked Nick...he said your timing shouldn't be that high anyways...I'd check out the LTFT's...and the misfires...see if you can see where the misfire is coming from if it registers via a certain cylinder.

If your LTFT's are pegging at +16.4...then you have a vacuum leak...that's what I'd pay attention to.

Alright, will do.