Gary C2

I am experiencing hesitation during the first second or so during a hard accel either out-of-gear or in gear. Also it doesn't seem as snappy when accelerating regardless of engine speed or load. The car is a 1990 C2 w/50,000 miles. It's a 90 so I can't check codes.

This problem cropped up a week ago. It occurred suddenly...not over time. When at idle, out-of-gear and stomp on the throttle, the engine doesn't respond for a while. The hesitation appears after it warms up, not when it's cold. The hesitation seems like it lasts a second. Otherwise the engine seems to run fine.

Things I have checked:
1)Distributor belt (It was replaced 3 months ago)
2)New fuel filter
3)Fuel pressure is 45-50psi regulated.
4)Checked cylinder temp sensor
5)Checked air intake sensor
6)Checked idle switch and function
7)Checked full throttle switch (did not notice and difference at part throttle when actuated. I did notice some effect when actuated at idle)
8)Checked air filter
9)Checked 'freeness' of the airmeter flapper.
10)Checked O2 sensor. Approximately 0.55 volts at idle when warm. Drops to approximately 0.250 volts during an accel and then returns to 0.55 volts. The hesitation is still there with the O2 sensor disconnected.


Any ideas on what the problem could be? Thanks for your help.

Adrian

Dear Gary,
Did you happen to disconnect your battery for any reason.
I would recommend a DME reset and see if the problem remains.
To reset the DME, turn igntion to run but do not start. Put foot on the accelerator for 11 seconds minimum flat to the floor. I leave it on for longer to be sure. Release pedal then turn ignition off. Then restart 964 and go for a minimum 15 minute drive. Try to drive over as many ranges as possible. Do not switch the engine off or stay at idle for too long.
The other way to do this is to disconnect the battery, reconnect then go for a drive.
If this fails to help I suggest a visual inspection of the knock sensors. If one of these is playing up the symptoms are similar. To check the knock sensors you need a timing light and a hammer (just kidding). Have someone sit in the 964 and put the RPMs at 2500. With the timing light, line up the timing marks. Then with the hammer or other knocking device, lightly and I mean lightly tap the knock sensor. The timing will advance and retard with the tapping and then removal of the tapping. The marks should move apart and then return to where they were. If the timing marks do not change then the knock sensor is kaputski,
Ciao,
Adrian
911C4

PS: The other possibility is a mechanical problem in the throttle body mechanism. Maybe the cable connecting the pedal to the throttle body. I would check the connections at both ends.

Iant

Gary,
My 90C4 was having the same kind of symptoms and it went into the shop last week, after being connected to the computer it was found to be running to rich. The solution has been to bypass the oxygen senser and fit a coding plug, and to my delight it runs much better now!! I thought before it went in it might cost me a few quid but they did that, fitted a new heater flap motor(and supplied) and did a brake fluid change for under three hundred pounds. Anyway, just thought i would share my solution with the group as there seems to be alot of posts re rough running/poor porformance.