dmauterer

Have a high mileage 1995 S90 Q V6. All vital signs are great. Just installed NGK wires and plugs. No oil usage either. Engine pulls hard to about 4500 rpm and then cuts-out quickly. About 5000. miles back installed new timing belt; pump; idler pulleys and sensors. At the time I checked all coil packs. Runs great but will not rev higher than 4500. rpm. Could valve springs be an issue? I have not checked all vacuum lines lately. Engine does have a KN cone inlet filter with a custom conn. to Air inlet meter. Has a relatively complete new exhaust from dealer. Last VAGCOM showed no codes(OBD1). This problem seems to have cropped up very recently. Engine does have excellent compression readings at all cylinders and runs very smooth to rev limit. Is there a setting in the ignition computer for rev limit? I do have a spare_good ignition Hitachi computer.

CRAZY_RUSSIAN

check if your switch over valve is working properly, vac lines and clean your MAF (and get rid of that K&N. it dose have a rev limit, but its at higher RPMs.

Luxus Panzer

quick way to check the I.M. changeover valve....

Zip tie the valve open and take it for a boot, if problem goes away then it is something is not opening your valve.

good luck.

dmauterer

Is this changeover valve located in the throttle body which has a small butterfly and a large butterfly. I have cleaned mine a few thousand miles back. I remember the action is mechanical linkage aka 2 barrel progressive carb style.

CRAZY_RUSSIAN

yep...
lol, it dose look like a progressive webber carb :-D