3.3 turbo not revving smooth

[tonypeoni]

Just got my trubo back from the mechanic and it still has a slight miss. It occurs in the 2000/2500 and again at 3000/3800 not noticeable above 4k. This is only noticeable when free revving the engine. In gear its barely noticeable if at all. I was wondering how smooth a 3.3 turbo should be? Is it kinda a lumpy motor when revving out of gear? Ive asked my mechanic if my cdi box is on the way out and he thinks it could be the case but not likely nor the fuel pumps nor a bent valve ect. He thinks I have a injector hanging. Ive tried fuel system cleaner to no avail. Please help

[equality72521]

Curious to see what you find as I have a similar problem.

[tonypeoni]

Originally Posted by equality72521

Curious to see what you find as I have a similar problem.

I see your in indy too! lol The gas around here is truly bad.. That could be the cause. My e46 M3 was took out by bad gas according to the BMW dealer. Both BMW and Porsche mechanics stated that getting good gas in the city is becoming a problem. I think mines a combination of a few things.

[jwasbury]

I'm going to make a guess that its ignition related. This is only because when I had a miss at light throttle (none on boost or at idle), I first assumed intake leak, then fuel and chased those things for months. After replacing all seals, testing WUR and checking fuel pressure, and replacing injectors ($$$), the problem persisted. Only then did I buy a timing light and checked spark timing. Way way off...too far advanced. The distributor hold-down nut wasn't tight and the dizzy had 'walked' off time. I was happy to find the problem, but shocked at what it turned out to be. I thought with the timing set so advanced, I'd have experienced symptoms on boost, but the car ran great under every scenario except light throttle cruise.

The lesson I learned is that I should go through the basic "tune up" list any time I have an issue. Had I checked off all the items on that list before zeroing in on a fuel injector problem, would have saved myself $600 on new ones. I suppose I have a spare set now though (for the day they are NLA). Maybe you and your mech have already gone through all of this? How are your plugs? Wires? Cap/rotor? Green trigger wire from dizzy to CDI? Do you know anyone that you can swap CDI boxes with to rule that out?

[RarlyL8]

Who is your mechanic? He can hear and test your car out and experience the issue in action, we cannot. If he thinks it is injectors have them tested and cleaned. Not really money wasted if they are old.

[s5uewf]

I had a slight stumble between 2400 and 2900 and it turned out to be the plug wires leaking at the distributor cap. New cap and wires resolved. I'm sure it was leaking spark throughout the range, but that is where I noticed it.

[911st]

Do you have a wide band and any AFR info? This might suggest if it is fuel or timing related.

I do not know if it is relevent but the rpm points referanced are about where boost starts and about where full boost would be. However, if we are talking about reving w/o load it would not fit.

I would first check the intercooler seal, look for leaks, inspect the dist cap, check for smooth timing advance with a timing light, and go on from there with testing the CIS pressures...

+1 on having injectors cleaned and tested anyway.