Low on gas today and stopped at valero. not exactly chevron but not some no name independant either. I was in a hurry so only went half tank of premium. Car ran fine for my trip but i stopped at home to pick something up and when i restarted it runs like crap. Idle is all over the place and fluctuates from 1100 rpm to 200 rpm where it usually dies.

on the highway I can feel the power pulsing where I know the engine is losing hp. I figured maybe got some bad gas so filled the empty have of the tank with chevron premium and dumped a bottle of octane boost just for good measure.

Didn't do anything. Idle is still all over the place and I can feel vibration like I am getting misfires.

Any ideas? Fuel filter? Where exactly is the fuel filter?

 

fuel filter is in tank, not really designed for change. I have 150K on my G now and haven't needed to change the filter.

Has anything else changed at all? Any recent work or anything like that?

Could be bad gas...might have to run it through. Keep tank as full as possible so you keep reducing the amount of bad gas in the tank.

 

Sounds like bad gas. It'll pass. Hell, I had some after my burritos the other night. Talk about rough idle...

 

I hope it's just bad gas. Otherwise I am wasting half a day taking the kinetix off and putting the stock plenum back on to make a trip to the dealer.

Running like crap but not throwing a ses. I have a scanner but if it don't throw a code I'm blind.

 

Maybe its one of your filters and they are dirty as hell...

 

Sounds like a vacuum leak. Spray some carb or tb cleaner around the plenum and see if the idle changes.

 

I can't figure it out and it's pissing me off. check for vac leaks found none. It doesn't feel like a vac leak anyway. It's total random. most times it idles where it should but a couple times a minute is drops to 200 or 300 and I can feel the shuddering then it goes away.

same deal at higher rpms when crusing. fine most of the time but the random loss of power for a few seconds than back to normal. We had huge rain on tuesday first rain in 6 months or so. I'm thinking maybe the stations tank got some water.

if it doesn't get better after this tank I'm going to have to put stock plenum back on and take it in. grrr.

 

Water could be leaking in through the main harness gasket (just beneath the windshield on the pass. side) and onto/around your ECU. Have you had any wiring work done and was it perhaps punched through that area? Pull the pass. kick panel apart and look for moisture.

 

Rain ended Wednesday. Problem did not show up until Friday. Any kind of moisture would have been dry by then.

I did run a power wire through there last weekend for my sub so I will check to be sure. I siliconed pretty good but it's easy enough to take a look.

 

Pull the carpet up and feel around the floor boards...moisture will stay there for a long time. Also, moisture on the ECU connector could lead to corrosion which could cause issues after the moisture is gone. Hopefully if water did leak in, your ECU isn't fried. Bad design = Expensive lesson...ridiculous location for the main harness grommet and ECU.

 

finally got the ses light today.

Scanned and the code is P0171:

System too lean bank 1.

That's swell. could be several things; maf, pvc, manifold leak, vac leak.

I don't know where to begin

 

I think I would start with the air cleaner, checking for leaves, etc. and then move towards the manifold considering retorqueing all of the fasteners. If your air cleaner is oil based then I would go to the maf. A dealer could probably find this pretty quick looking at the output of the 02 sensors, etc. If concerned about warranty issues then take it initially someplace else to look at these outputs.

 

I have reduced possible causes to 3

Still considering bad gas but it is no longer the primary suspect.

I do run k&n so maf contamination is a possibility, but in my defense i only oil on the outside and I don't go crazy with it.

prime suspect is now manifold leak. Put the kinetix ssv on about 6 weeks ago. Flawless until friday. I did buy it used and didn't replace the cork manifold gasket. I just installed with the old one. I ordered a thermal new one today.

I'll give it to the end of the week and the tank will be empty for new gas and I will replace the gasket regardless

 

I was wondering what came of the situation? I let my car sit for a couple days just after fill up. A lot of rain has fallen in the area. Car runs fine then suddenly sputtering and eventually flashing service light. The problem is intermittent. Finally today while it was acting up I killed it while driving and restarted. Light stopped flashing and stayed on but car quit it's antics and runs strong. It has not repeated the problem yet after 50 miles. I stopped at local auto and had a scan of P03000 code "random misfire". I'm leaning toward bad gas. What was your result? I'm getting down to a quarter tank now.

 

when I installed the used kinetix ssv manifold a couple months ago i reused the crappy cork gasket it came with. Eventually it started leaking vacuum and that's what caused the issue. Replaced it with an aramid gasket from motordyne and problem solved. Car runs fantastic.

my code pointed to vac leak or maf sensor. Yours sounds like ignition.

A quick google search on your code says spark plugs, plug wires or dirty throttle body