jenket944

The engine idles very roughly after startup, and it's noticeably worse on cold days. Typically revs at ignition up to 1200 and drops down to 600-800 before it comes back up to 1000 rpm. Sometimes it holds there, sometimes not. Problem is when the engine drops below 1000, one of the belts starts squealing like a banshee and I think it's because of slippage. Belt also starts squealing whenever I put a load on the engine (like running the AC). Tends to go away as the engine warms up. I typically just hold the throttle open to get the engine to 'idle' at 1500 for a minute until it's no longer cranky.

My question is what might be causing this. The engine runs with no problems once it's warm. I've got a tune-up planned soon - will be replacing the plugs, wires, cap and rotor, and the O2 sensor. If this doesn't clear it up, my next guess would be the idle speed regulator.

Any thoughts? It's really not a big deal but I figured I'd ask.

NV BOB

Intake manifold blown gasket for me. But could be any number of"things"

86 944 NA
84 911 Coupe

Zero10

Oh dear.. it could be many things.
I would start by checking for vacuum leaks. The engine is affected even more when the air is cold, as the air is denser, more of it gets in.
Next up, perhaps DME temperature sensor, or clogged fuel injectors?
Could also be the air temperature sensor inside the air flow meter.

It's possible it is ignition related, but I don't really think so.
Hope that gives you somewhere to start.
I don't really think it's the idle control valve.

The O2 sensor will not cure it, as it is not used until the exhaust warms up, which is a couple minutes. It could be the plugs, if they are really bad, but that should cause problems at all temperatures.
Let us know if it still has issues once you do a tune-up.

Melchior

Mine was doing the same thing all last week once the engine warmed up; RPM's sitting right at 1200-1500. I put some Redline Fuel System cleaner in it and it seems to be back at its steady 980 RPM. We will see how long it lasts. These cars are very mysterious...

Brett944Cab2

Dielectric grease any of the spring-clipped plugs under the hood you can reach, esp. the AFM. This has helped mine alot.

a little OT, although I still sometimes have the wanting-to-die problem - my belts don't squeal - meaning to me, maybe, that you need a tensioning ASAP?

Edit: rethinking, I'm pretty sure that's PS or some accessory belt, not timing or balance, but wouldn't hurt to think about a retension.

Heath

I've got this same problem since I let the fuel almost run out the other day...I'm thinking this is a fuel system problem....as in sucking up a lump of **** outta the bottom of the tank or something....

jenket944

I think I'm dealing with 2 separate issues:

1- a squealing AC belt, probably just needs tightening
2- the engine won't hold idle during cold start-up

Now that I think about it, the first problem started back in October when a bolt that holds the AC belt tensioner failed. My mechanic fixed it but I think he didn't put enough tension on the belt because it's been squealing ever since (does it worse in the rain). I'm taking it in to be serviced tomorrow. The tune-up might fix the idle issue. I'll get him to tighten the AC belt and see if that doesn't stop the squealing.

I considered it being a fuel issue, but I put in a new fuel filter recently and put new o-rings on the fuel injectors about a year ago (had to fix a leaky fuel rail). Didn't have the injectors rebuilt, so I might look into that later. But I've been on the track a few times and it never hesitates or misses once the engine is warm.

jenket944

I took it to my mechanic last Thursday. Turns out the belt squealing was caused by one of the bolts that holds the AC compressor in breaking in half. Shouldn't be too big of a deal to fix that, but will have to tap into that bolt and drill it out.

The engine runs a little better after the tune-up. I don't know if it completely resolved it, but it's noticeably better.

Thanks for the feedback, guys!