Fouled plugs, rough idle, lack of power
 

For the past few days I've been having an intermitent problem of a rough idle. Bad shaking, lack of power. Yet if I drove it around the engine would just come back to normal for a time. Happend when I put in some gas from a local gas station. Figured it was just bad gas. Filled up with different gas (same grade) and the symptoms went away. Felt good for about 4 days. No rough idle, no lack of power. Everything was normal.

Then yesterday on my way back from work, the symptoms showed up again. Lack of power, rough idle. So I took out my spark plugs. Monster fouling. Lots of carbon build up. I cleaned out the plugs and re-installed. Tried to go to work today and the engine ran fine. No problems until I got onto the highway. Then the symptoms came back. Rough idle, lack of power. Basically feels like I'm running on one rotor. Pulled off on the side of the road right as the car died. I pulled off because I kept hearing a metal noise like a lp banging against something--I wasn't sure what it was so I got off as quickly as I could.

On the side of the road I waited for the engine to cool. I pulled the plugs again, and inspected. No fouling (There shouldn't be anyways I hadn't gone more than 10 miles), and they weren't coated in anything--oil or otherwise. I let the engine cool a little more and removed the pressure cap from the radiator to see if I lost a coolant seal and I seemed to remember that an easy way to check if I lost a coolant seal was to open that cap and crank to see if I got any bubbles/splatter. Nothing bubbled or splattered, so I assume my coolant seals are okay. Next I pulled the plugs and turned the engine over by hand. I got 3 strong "whistles" from the front rotor, and I got little "psssshhh" from the rear. I kept turnign it by hand and I eventually got 3 strong "whistles/psshs" from both front and rear.

I called into work today to let them know what's going on so I plan on doing a compression check in an hour or two, and if that checks out, looking for a vacuum leak. Is there anything else I should look for?

something recent that might affect this might not: I ran out of gas about 2 weeks ago. I doubt it has anything to do with anything since I had replaced my old fuel filter with a new one about a month or two before that. Another thing is that I continue to get condensation in my oil tube, but I clean it out regularly and it hasn't had much trouble with it recently. I think it was oil in the line I replaced.

The car itself is an S4-NA mostly stock (only suspension modifications)
Gutted Cats
Recently cleaned (<10,000 miles) injectors
Silicon Vac Lines replaced same time as injectors.

Cliffs: Car ran fine after having an intermitent problem of Rough Idle and lack of power. Today car died on highway refusing to restart. Heard metalic noises from the front of the car (which didn't happen at all when I nursed it back home). Coolant seal seems good (unless I opened the wrong cap and did that test wrong). Compression seems useable--will know for sure later today. What's wrong with my car?

If you are intermittently losing compression on the rear rotor that would explain the loss of power and rough idle. Perhaps one of the rear rotor apex seals is sticking due this carbon build-up that was on your plugs.
How many miles on the engine?

I'd have to figure it out. New engine went in at 70K. My Odo reads 111k... about 40k miles on it or so. I don't see how it could be carbon.... I redline it once a day at the least. Could be. I do have some sea foam I could try to dump into it. But I recently did a sea foam treatment (Litterally about two days ago or so).

Checked engines compression:

Front: 100-110 PSI, 30+ PSI individual
Rear: 100-110 PSI, 30+ PSI individual

(Last time I did a compression test my engine tested around 85-90PSI, 30+ psi individual. That was about a year ago or so.)

Check your injector clips to see if one is possibly backing out.

Change your Fuel filter.

intermittent ignition problem?

Fuel filter, I kid you not, was changed no less than 5000 miles ago, if even that. I'm leaning more towards loose plug for the injectors, but I haven't confirmed it. I worked on it a little bit. Replaced my crapped out Master Cylinder for my Clutch. Checked the compression, and fixed my oil leak on my oil cooler (annealed my crush washers). Put it all back together and did a test start. It started right up. healthy as can be. I'm concerned that it will do it to me again though. I also noticed that the oil level is pretty low so I'm going to drop in a few quarts and see if my problem still persists.

Have driven over 120 miles with out problem.... Could it just have been residual gas? I haven't touched anything on the engine besides just checking compression.

could have been, did you run out of gas recently? In older cars, especially ones that have sat, it is common to have them suck up gunk that has settled on the bottom of the tank. Have you checked voltage to the fuel pump?The resistor pack?

I did run out of gas recently, but I didn't have tons of gunk for it to suck up. I'll get to drive it awhile today. So, we'll see how it all works out.

just thinking out loud here but take a soft hand and while cars is running wiggle the engine harness from the tps to the injectors and all the way to the firewall... trust me
i have a small crack in a few wires in the harness under the uim and it would act like a blown motr sometimes and then it would run fine after i wiggled it so i just rewired everything from pass side firewall to injectors and sensors, really wasnt a big deal for me but i dont have top mount ic or any extra carp on my motor like emiisions and b.s.

pm and let me kow if thats what it was before you go crazy over replacing parts.

you can call me if you have anymore ?'s
6154731965
wes carlock just do so before 230 pm central time otherwise ill be at work.
good luck

Sorry I haven't gotten back to everyone quickly. I'm going on a few days now without problem. I'm starting to wonder if I just had my idle set much too low and when my temperatures increased the BAC didn't know what to do which put me in limp mode. Just a thought, not sure if it's true or not. Ever since it happened last and I adjusted my idle to be higher than where it was everything has been running just fine.

As for the harness i'm holding off on redoing anything with that as I plan on going standalone in a few months. I'll be getting a custom harness made with bulkhead connectors so I figure as long as the harness holds up for that time I'll be fine. I also plan on running the harness differently, but that's a completely different story.

Alright, this problem has reared its ugly head again.

I recently did a sea foam treatment and changed my oil. I'm now having the same problems. I filled up a gas station I normally fill up at and i'm getting the problems all over again.

I messed around with setting my idle and the BAC and I got it to idle correctly yesterday and I didn't have any problems. Took it to work this morning without incident, then on my drive home the problem reared its ugly head again.

I've tried re-doing the idle and what not, but the problem still persists. Can anyone offer any help?