C2 Turbo

As i approach 4000 RPM ( any gear) it starts to shake or feels kinda choking or carbon in the plugs feel but once i have gone pass 4500 rpm the car feels fine ?
Plugs were changed about 4 years ago at around 24,000 miles and the car currently has 38,000 miles. Any ideas besides the plugs ? Sounds electrical to me ?
Thanks

maverick

Fuel pump or fuel transfer pump; plug wires. Mine is having similar issues. Just had the WUR rebuilt and a Tial waste gate installed. Air control valve has gone out but have bypassed since I'm in Red Hot Texas!

Francisco Martinez

Assuming this is at WOT, If it smokes when shaking and then runs fine, then you are have an overly rich condition on boost. But then something must be causing that overly rich condition all of the sudden.

Metal Guru

A boost leak will cause that condition. Check the silicone hose to the intercooler and that the intercooler is seated on the o-ring on the throttle body and that the o-ring is not damaged.

SA Mike

+1

C2 Turbo

Drove it today and it seems like the hesitation is only in 3rd and upward gears and not in 1st and 2nd.
Fuel pressure pump or the regulator sounds possible.
Boost leak ? ...then why does it pull strong after 5000 rpm ?
Rich condition ? No smoke at all however checked the oil level today and looks like it might be slightly over-filled..could that cause it ?
Thanks for all the tips.

Francisco Martinez

You do not necessarily need to be smoking to be rich enough for hesitation, I have had this happen to me when tuning the mixture, this cold be caused by bad WUR among other things. If you can rule this out, like the others said, a small boost leak reflected to the control signal of the wastegate could be causing an overboost surge, when the turbo runs out of breath it picks up again over 5K rpm. But if this was the case, the overboost protection should be activating, do you have it grounded or the lines swapped with the boost sensor? I have seen this a lot and this is one of the causes of the digital boost gauge not reading correctly. If this is the case, this is very dangerous for the engine, this has never happened to me on the turbo 3.6 but did happen on my ex Renault R5 Turbo II. Slight overfill should not cause this, at least never done it to me and I have occasionally overfilled a little. I did have a friend do a real overfill once and he had oil coming out all the wrong places..very scary but nothing happened to the engine.