icsmike

When i start the 928 it want to surge or hunt for an idle. Not a big hunt but just a few hundred RPM's it sounds like someone is reving the pedal from 800-1100 up and down. Not consistent just after first start up. I also noticed that i cannot get it to start after the first or second try it acts like it burns what fuel is available and it needs more. This might be related to my hood ding problem....


I wonder if its a IAC or vacuum leak?

AO

It's probably either a big vacuum leak or an intake leak that the ISV is fighting. Hence the idle fluctuation.

Mike Frye

From some discussions the other day about my car:


https://rennlist.com/forums/showthre...ferrerid=45339

This weekend Adam and I looked at a few things and we think it might be related to the O2 sensor. I've got to look further into it, including replacing it with a new one.

For mine, it wasn't a problem until I re-did the top-end, but I'm not sure that there were no vacuum leaks before that, so it might be that there was more than one problem, and it had been tuned to deal with all of them. I don't even know if the TPS was adjusted properly before this, so it may have been idling low, but at 20 deg. BTDC which would have masked a rough idle/start condition.

Now I've tested the TPS and the ISV is new and seems to work OK.

If I figure it out I'll let you know. Please do the same, as there were several responses to this from people who are just living with it, and I think it might be a symptom of something that could cause a lean condition at high RPMs which could be BAD.

icsmike

Thanks fellas. This also happened after I had the top end apart.

surfdog4

did you figure this out? I too just finished redoing the intake including the vacuum lines and now have this issue..mine does it after it warms up though..gradually climbs rpms and then drops dramatically..i was pretty careful checking for leaks as i went..and it seems to run fine with throttle application

icsmike

Nope.

Big Dave

I've got this symptom, too. Still haven't figured it out. My MAF is new. I've got a new O2 sensor to install next.

michaelathome

That makes 4 of us.

Michael

sharknoob

.............5 i had same thing on my 944 the old belt had the cam 1/2 tooth off .....changed the belt timing marks lined right up runs great . mine is ever so slight that i was going to look into it till i changed the belt this winter

surfdog4

i'm beginning to believe my problem is related to the vacuum limiter..doing to try and dive in this weekend to find out..but i don't think that helps you guys because i think it was deleted in '83 (at least for automatics)

Big Dave

Noticed another symptom has emerged. It wants to stall while in gear if I'm coming to a stop and after I'm stopped. Pop it in neutral and it's ok. In gear at a stop, the revs keep dipping and it eventually stalls. I finally have another daily driver, so it's time to dive in I suppose.

shmark

Mine "pulses" at idle, maybe a 50rpm fluctuation. My last 928 did exactly the same thing, never thought much of it, other than I think on an early car it's movement in the air meter. Nowhere near the hunting you have, but not rock-steady either.

Stan.Shaw@Excell.Net

Add me to the list of those with this (90 GT). It started after I had the intake refresh done, replacing almost everything that is ever likely to fail. It has gotten worse, requiring me to "pedal" a bit when stopped (I am sure people think I am just enjoying the sound ).

In my case there was no tension in the timing belt after it was replaced. I am wondering whether when it was tensioned to correct that problem, if it affected the timing marks. Haven't pulled the covers off to check as I hate re-work when there is plenty new work to do