Need help Identifying hesitation
05-20-2009, 03:32 PM
#1
Track Day
Thread Starter
Join Date: May 2004
Location: Hercules, CA
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
Need help Identifying hesitation
My 89 964 acts up occasionally. 
The idle is irratic going back and forth from 800 to 1200 rpm. I can feel the engine hesitate when I accelerate. Sometimes at freeway speeds it would jerk like it's missfiring. When the engine is in this irratic stage my stereo sound goes in and out too. It happens on fm stations as well as cd or mp3's, so I know it's not interference thru the antenna. Sometimes restarting the car clears everything up. Sometimes it runs for a while then goes into this limp mode. Everytime it happens or starts I know because the radio start acting up too. I've changed the DME relay and it didn't help. Any ideas? Alternator? Distributor? TIA
The idle is irratic going back and forth from 800 to 1200 rpm. I can feel the engine hesitate when I accelerate. Sometimes at freeway speeds it would jerk like it's missfiring. When the engine is in this irratic stage my stereo sound goes in and out too. It happens on fm stations as well as cd or mp3's, so I know it's not interference thru the antenna. Sometimes restarting the car clears everything up. Sometimes it runs for a while then goes into this limp mode. Everytime it happens or starts I know because the radio start acting up too. I've changed the DME relay and it didn't help. Any ideas? Alternator? Distributor? TIA
05-20-2009, 04:00 PM
#2
Rennlist Member
Just an idea, but you might want to check the fuel pump. I was having the same symptoms as you, except I don't listen to the radio! Anyway, I changed out the DME relay and no effect. I checked the dist. belt and it was okay, checked the dist. caps okay as well. After not smelling any fuel coming out of the tail pipe on start up. I knew it was the fuel pump. Mine had been going for close to 5k throwing check engine lights, missed acceleration, rough start up, irratic idle speed. Now after replacing and cleaning the ISV valve the car runs like a freak and idles smoothly. My pump died at 100k miles, depending on mileage maybe the culprit.
05-20-2009, 04:16 PM
#3
Do you have original coils? These have been showing their age.
I had similar hesitation or really miss type problems that were cured with new coils. The coils are around $50 US each and would be good candidates for changing due to age anyway; assuming they are old, of course.
It sounds like it could also be spark plug wire breakdown problems. Have you tried spraying a mist of water on the wires at night in a dark place? If you see sparks jumping they your wires are in need of replacement.
I had similar hesitation or really miss type problems that were cured with new coils. The coils are around $50 US each and would be good candidates for changing due to age anyway; assuming they are old, of course.
It sounds like it could also be spark plug wire breakdown problems. Have you tried spraying a mist of water on the wires at night in a dark place? If you see sparks jumping they your wires are in need of replacement.
05-20-2009, 06:56 PM
#4
Nordschleife Master
Has your car had the wiring harness/air flow meter plug done as set out in the technical service bulletin?
https://rennlist.com/forums/964-foru...rness-mod.html
I used to get a hesitation (usually going down hill) so I checked if mine had the mod described in the thread above. I found it had been partially done and the breather pipe next to the plug had come out of the clip on the rear wall (the bulletin is aimed at making sure there is a gap between the AFM plug and breather pipes). After correcting this I've yet to have the hesitation re-occur.
https://rennlist.com/forums/964-foru...rness-mod.html
I used to get a hesitation (usually going down hill) so I checked if mine had the mod described in the thread above. I found it had been partially done and the breather pipe next to the plug had come out of the clip on the rear wall (the bulletin is aimed at making sure there is a gap between the AFM plug and breather pipes). After correcting this I've yet to have the hesitation re-occur.
