dillon410021

'88 944 turbo with mtune.
I have a low vacuum issue. When warm, I get 10-15 in vacuum at idle. It seems that when cruising, I let off the gas and the vacuum will go to -20 for a split second then to about 15 but if I feather the gas just slightly, it will go back down to -20. Its real weird. also, at times the idle will stumble going back to idle. It takes a couple seconds to even out.

As far as the hot start problem, It will start up fine but have a hunting/ surging idle at ~600rpm for several seconds then even out.
The tps, isv, and o2 sensors are all new. reference sensors are older but are properly spaced.

-maybe the dme temp sensor as that is old.
-vacuum lines are new
just weird issues


Any and all help is appreciated.

Rogue_Ant

Definitely check the DME temp sensor...
Also, if you haven't, then reset the idle:

http://www.clarks-garage.com/shop-manual/fuel-08.htm

Additionally, you can try adjusting the fuel a little by changing the FQS. Try going from position 0 to 1.

dillon410021

OK, I will reset idle again. And as far as the temp sensor, can I test at sensor or do I have to do it at DME? Also, I remember you saying the timing will change vacuum but would it do what mines doing where I get more vacuum as soon as the tps clicks

dillon410021

ok, I looked and the dme temp sensor is new, it was the gauge sender that is still old. hmmm what else make a hot start surge

Rogue_Ant

Dillon, have you tried adjusting the FQS?
Idle issues are usually related to the TPS, and/or wiring...

Also, do you have any logs that I could take a look at?

pr951

Quick and easy fix for me was to resolder the joints on dme relay.

Had those ghost-ring looking cracks on solder joints and this was a newer dme relay. So maybe heat/current would expand the bad joints and cause a bad connection only when warm.

Black51

Exhaust leak?

I have similar vacuum, and fairly somewhat running when 'cold', and I also smell exhaust in the cabin.