Fuel Trim Analysis?

[dizzysn]

I made another thread on this earlier, but noticed something new and want to get a bit more visibility on this.

Anyway - I've been chasing a vibration in the car that occurs around 1600-1800 RPM, smooths around 2000 RPM, but then gets worse around 2100 - 2300 RPM. Early in the morning the 2100 - 2300 RPM vibration feels almost like a rhythmic thud, but not during the rest of the day, which is weird.

This vibration is felt in the steering wheel, and sort of around the cabin as well, but not heard. Wide open throttle doesn't seem vibrate at all, and the car seems to have full power as far as the butt dyno can tell. There are no misfires, or check engine lights detected with Rosstech. Rosstech also doesn't report any faults that I can see. Engine mounts are possible, but seems to be difficult to diagnose without basically doing the entire job to get them out and inspect them, and I don't want to just throw parts at it.

A buddy asked me to look at my fuel trims, and this was at idle, and then going from idle to 1800 RPM and holding it. Does something seem a bit off here? Car is EPL stage 2, single upper pulley, gutted stock cats, DSG tune, stock downpipes, with Gibson muffler and Vibrant resonators.

Here's an attached photo at idle. The two trims being so different was my cause for concern.

[fastboatster]

pull the spark plugs and see how they look like. I'm having somewhat similar symptoms (well not me, my car lol) but also have an occasional idle vibration. I initially thought that this was due to spark plugs getting fouled with all the oil due to poorly functioning pcv/ccv system (burned a quart in 100 miles sometimes), but after pcv replacement which decreased oil consumption to nearly none, the situation improved but vibration is still there. Bottom line, all my spark plugs except for one look nice now, and I think I just have a dirty fuel injector in the cylinder where the plug is carbon fouled. So maybe some of your injectors are dirty/clogged, and perhaps the spark plugs and/or coils can be worn, too? I'm guessing fuel injectors, though. Wouldn't hurt to take a look at the plugs either way.

[Loe]

https://www.audizine.com/forum/showt...bration-Thread

[dizzysn]

https://www.audizine.com/forum/showt...bration-Thread

Only problem is I had it up on the lift and the exhaust wasn't moving when the vibration was happening, and neither was the motor, so I'm not 100% confident it's this. But I've basically ruled out everything else at this point.

- - - Updated - - -

pull the spark plugs and see how they look like. I'm having somewhat similar symptoms (well not me, my car lol) but also have an occasional idle vibration. I initially thought that this was due to spark plugs getting fouled with all the oil due to poorly functioning pcv/ccv system (burned a quart in 100 miles sometimes), but after pcv replacement which decreased oil consumption to nearly none, the situation improved but vibration is still there. Bottom line, all my spark plugs except for one look nice now, and I think I just have a dirty fuel injector in the cylinder where the plug is carbon fouled. So maybe some of your injectors are dirty/clogged, and perhaps the spark plugs and/or coils can be worn, too? I'm guessing fuel injectors, though. Wouldn't hurt to take a look at the plugs either way.

Plugs look great. Had new PCV and supercharger intercoolers put in about 6 months ago. No coolant or oil loss.