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Jeff A.
 
Join Date: Oct 2003
Location: CA southbay
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944 not running right?

More in the continuing saga...

Well, I had a few other questions and they all got worked out. I replaced the water pump, belts, and hoses on the 944 i just picked up. It started up easily and seemed to run OK in the garage. I finally toOK it out for a drive, the first time I've driven it since I towed it to my house after buying it a few weeks ago. Here's my current problem; it runs rough and stumbles for the first 15-20 minutes and then cleans up and runs decent (and I'm thinking it will not pass the CA smog test). Things I have noticed; it idles OK when first started but at about 8-900 rpm but stumbles when rev'd up or the engine is loaded to drive off. when rev'd up it stumbles but the rpm's do increase and the rpm's drop quickly back to the idle rpm when the accelerator is released. The temperature hits the first line in about 5 minutes when started cold and stops rising but the car still runs rough until the 15 or so minute barrier is reached. When started up warm, it still takes time to run clean. Once it runs clean, the rpms drop slower to about 1050 rpm.

I'm not that familiar with the 944 engine (yet). I put on a new distributor cap but still have the same old plugs, wires, and rotor. It doesn't seem that these items would provide the intermittent poor-good engine performance, just make it run poor if they were the cause but more likely the fuel injection is the culprit?

any ideas for the rest of the board?

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Jeff A.

'88 944
'99 Vanagon
'03 Pilot
Old 04-28-2008, 09:22 AM
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Sounds odd to me, start cheap though! Have you replaced the fuel filter? if not now's a good time. Then i'd try to check the injectors. You can actually pull the injectors (if you do you'll prob need to put new o-rings on...they're cheap) and put paper towels under them and see if they are all firing right while a friend cranks the motor.

So how long has the car sat/been imobil?
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Brian

'86 944 NA
'94 Jeep Cherokee 3" and 31's
'86 Chevy C10 425hp
'98 Dodge Neon (the wife)
Old 04-28-2008, 07:02 PM
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my car does not stumble but does not idle well until warm. This is because I bypassed the ISV. Sounds like it is running rough until the oil warms up which takes longer than the water. It's probably vacuum related. Could be whole host of things brought on by sitting for a long time.
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'88 944 240,100 miles -race car
'05 Boxster 110,000 - Daily Driver
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Old 04-28-2008, 07:09 PM
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Jeff A.
 
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good input. the car sat for at least a year before i towed it away. i like the oil getting up to temp idea. what uses this info?
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Jeff A.

'88 944
'99 Vanagon
'03 Pilot
Old 04-28-2008, 07:50 PM
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I'd check into the fuel system. I'm really not sure as the way it acts as it warms up though. But if it sat for a year it's quite possible that you have some varnish/build-up in the fuel system.

Also, if I'm not mistaken there should be a temp switch that tells the DME if the car is hot or cold and the DME will compensate by richening or leaning out the mixture.

Also my check the AFM, but the fact that it runs OK after warm makes me think it's not the AFM
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Brian

'86 944 NA
'94 Jeep Cherokee 3" and 31's
'86 Chevy C10 425hp
'98 Dodge Neon (the wife)
Old 04-28-2008, 07:57 PM
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Something worth mentioning, just because it just happened to me today ... Check the intake manifold gaskets, or any other vacuum leak for that matter. My #1 gasket just sprung a big leak for no good reason and it idles like crap, since it's basicly idling on 3 cylinders. Test the Air flow meter as well. ( http://www.frwilk.com/944dme/afm.htm ). If you can, check the fuel pressure as well. Also check the DME engine temp sensor, screwed into the engine, between the intake manifold and the driver side balance shaft housing. It has two contacts. It should be: 15-30 deg C-1.45-3.3K ohms, 80 deg C-280-360 ohms. A pot of water on the stove and a thermometer works great for checking it.
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Old 04-28-2008, 08:04 PM
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I agree with bholmes. It might be worth replacing the DME temp sensor. It's a whopping $12 i think. Also all the other things mentioned are good (and free) places to start.
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'88 944 240,100 miles -race car
'05 Boxster 110,000 - Daily Driver
'74 911 Targa - long term project
Old 04-29-2008, 11:29 AM
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Jeff A.
 
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Well, mystery solved. I simply completed changing more of the easy stuff: rotor, plug wires, plugs and presto! it runs really well! I picked up a fuel filter today as well but will put it in tomorrow for the heck of it. I'm so jazzed... now that it runs well, I'm gonna smog check it to complete the registration this week, then start on my long list of other comfort, electrical and looks items. Great to be back.
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Jeff A.

'88 944
'99 Vanagon
'03 Pilot
Old 05-03-2008, 10:01 PM
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....
 
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tune up's do wonders...
glad you got it fixxed

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Old 05-04-2008, 09:54 AM
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