Chargrod

1984 944

Runs great. No complaints. However, when coasting there is a surgey-ness that occurs. Not at idle at a stoplight or in traffic. Only when coasting.

Thoughts?

Jfrahm

Surging off-throttle is usually from gulps of unmetered air:
Cracked intake tube (J-boot) after the AFM
Cracked elbow to the idle air controller
Cracked IAC hoses
etc.

Chargrod

So a vacuum leak after mass air flow sensor essentially?

c

Chargrod

To be specific this only happens when coasting say up to a stop sign as the RPMs get closer to the idle level at lower speeds. It does not occur when coasting a faster speed or at idle at full stop.

C

Tony5

Engine surging or driveline lash? Two very different problems that could be described the same way by someone that doesn't know how to tell the difference. Low speed coasting is definitely a place driveline lash will show up.

Chargrod

IS there a reliable way of differentiation of these two maladies?

I was considering something like a dirty intake, idle maladjustment with the screw or the other air adjustment next to the throttle body, or Throttle position sensor, loose belts or even MAF. Am I way off base?

C

Tony5

I'm trying to think of a good description I can put into words. It's definitely a feel type thing, spend enough time wrenching on cars and you get better at understanding problems.
Are there any mechanical clunking noises to go with the surging? Does the surge correlate with rpm?

walfreyydo

I would describe driveline lash as a slight delay when you get on or off the gas, but should resolve after that slight delay. Its definitely something that is felt with throttle but also when engaging the clutch/taking off from a stop.

Surging would be if you have the throttle held steady (or closed) and the car wants to continue accelerating even after a time delay. This could be related to a vacuum leak.

Jfrahm

Hmm, when you describe it like that it makes me think of a torn clutch rubber damper.

walfreyydo

Another possibility is you have an issue with the AFM itself, so recommend doing the voltage test and re-tracking the arms if needed. How to do that is on Clarks.

Also, the post above me is a bot/scammer and should be reported - trying to get post counts up so they can likely scam people on marketplace