ckkrause

I tried to describe the symptoms in an earlier post and was not successful, so I thought I'd try again. I have a '91 C2 w /88K miles and when I hold the throttle at a constant RPM, the motor surges and hesitates ever so slightly. The higher the RPM's the less you can feel it to the point that over about 3K RPM you can't really feel the surging. Acceleration and deceleration are not affected. The ICV is new 20K miles ago and is quite clean. Any ideas what may be causing this?

Thanks for your response!

-CKKrause

PC2

How old is your fuel filter? I had similar experience last year where I get slight hesitations at low RPMs (3000 ~ 3500), especially pronounced during inclines. I was able to trace the cause of the hesitations to a dirty fuel filter (1 year old, 12,000 miles).

ckkrause

PC2-

One reply, one victory!!! That was it...replaced the 2 year old fuel filter and...no surging!!!

Thanks for your reply!!

-CKKrause

pipster

Mine is doing something similar to this, did you notice it also while idling...

I only just saw this posting...so you know whats coming next !!

I have just changed my Coils today,

Do love these easy jobs - (apart from that damn blower needs to come off more times than a tarts knickers)

I'll be able to write a book soon !!! (lol)

The coils made a big diff with the feel of acceleration (not surprising as they are 108k old)

But did not fix the stuttering/pulsing..STILL !!!!

Checked the voltage against "Andrians" book which did show a sort of lower voltage than expected...Just under 13V when his book mentions 13.8-14.4 (the battery was fine ! with 12.6v) - Checked for AC leaking into the system (ALL OK)

I read a thread on "Renlist" today, about the fuel filter causing a similar issue with someone elses.. So I now have the filter and will be replacing this tomorrow...

If this don't fix it might be looking down the alternator route.

One strange thing was I took out the "dme relay" and swapped it with another I have, which temporarily fixed the issue....but after a 40 minute drive, the same stuttering/pulsing came back ! (so ruled DME relay out)

The list goes on...

Dissy Caps & Arms changed (one cap was cracked completely around screw)
Both Coils
Cat Oxygen Sensor
DME Relay
ECU Changed over
Battery All ok
Injector cleaner in petrol at regular intervals
Cleaned out the ICV (idle control valve)
Cleaned the carbon tracks on the Mass Air flow
Tightened up all the clips on the inlet manifold and pipes

bhensarl

Low voltage in a 964 wreaks havoc with everything it seems. The alternator looks like a likely culprit to me.
Brian

ckkrause

I lied...I started the car this morning and it is back to surging...BOOOO! I guess it's time to check voltages, etc...

-CKKrause

hawk911

Maybe we can just meet somewhere with all the cars that have this condition and get them all sorted at one time? Adrian- care to meet us there??

ckkrause

I checked voltages per Adrian's book and got about 12.6 v on the battery out of the car. With the motor idling the voltage was about 13.4 volts no matter what the RPM's. Adrian's book says it should be at least 13.8 V. Does this mean the regulator is bad or the the alternator assembly as a whole is bad? Thanks for your reply!

(I assume this may have something to do with the surging....)

-CKKrause

pipster

I have just swapped out the fuel filter (after removing lots of skin- damn those nuts are on hard !!), and the car seems to be very stable at idle and no surging yet - just been for a 20 minute drive and all very smooth !!

Think the meet up would be good, but problem, I'm in the UK and on my way to Australia...so probably not a possibility...lol

pipster

Looking at Adrians book the Alternator does look quite easy to remove...
I'm guessing recoditioned unit is the way forward ?

Anyone done this (DIY) ?

Just building up for the inevitable, after "ckkrause" message !!

ckkrause

OK..so I tightened up the grounds and charged the battery for a little bit. Then this morning...no surging. Driving home from work and still no surging...Too Weird!!

-CKKrause