Here are the symptoms, what is the illness?
06-11-2009, 01:57 AM
#1
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Here are the symptoms, what is the illness?
First the patient..
83' n/a, 97k miles.
1. Low idle that sometimes gets a bounce upon inital startup. This only happens when the air temp is in the moderate range (45-80 degrees). Once the engine gets warmed up it idles a bit high, but steady at 1000rpm.
2. An occasional hesitation when accelerating, nothing too bad but feels similar to a turbo lag (I know it is a N/A), you are expecting a steady pull but there is a dead spot for a second, then it pulls. The rpm do NOT change or rev when this happens and the clutch wear still measures in the good range so I am ruling out clutch slippage for this.
3. When I pulled out the plugs today they seemed a bit too white so I'm thinking it is a bit lean.
4. I'm only averaging about 18mpg. This is with a 70/30 split of city and highway driving. Mostly shorter trips of less than 30 min. at a time and I like drive it hard. A few mountain drives but very little actual 65-80mph highway cruises.
So there you have it 944 gurus, what is the prognosis???
83' n/a, 97k miles.
1. Low idle that sometimes gets a bounce upon inital startup. This only happens when the air temp is in the moderate range (45-80 degrees). Once the engine gets warmed up it idles a bit high, but steady at 1000rpm.
2. An occasional hesitation when accelerating, nothing too bad but feels similar to a turbo lag (I know it is a N/A), you are expecting a steady pull but there is a dead spot for a second, then it pulls. The rpm do NOT change or rev when this happens and the clutch wear still measures in the good range so I am ruling out clutch slippage for this.
3. When I pulled out the plugs today they seemed a bit too white so I'm thinking it is a bit lean.
4. I'm only averaging about 18mpg. This is with a 70/30 split of city and highway driving. Mostly shorter trips of less than 30 min. at a time and I like drive it hard. A few mountain drives but very little actual 65-80mph highway cruises.
So there you have it 944 gurus, what is the prognosis???
06-11-2009, 01:21 PM
#5
Three Wheelin'
Either of them. Heat expands things and sometimes makes them work properly (or better). I had an issue with my AFM not sending the proper voltage at certain portions of the barn door's swing when it was cold. It was almost to spec when it was warm.
If you search for "frwik afm" I'm sure you'll find the link I dug up on this. He used to have it on his site, but it looks like it didn't make it when he redesigned it. I found a link to the old site in archive.org that shows you the process for checking the AFM tracking and how to fix it (without any extra parts! woohoo!). Do the test cold would be a good start, and then try it when the car is warmed up and see if it acts the same way.
06-11-2009, 02:28 PM
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I am no expert, but my 84 suffered the same symptons untill it died and wouldnt start.
Turns out one of the wires running to the ECU started shorting the speed and ref sensors.
This is all according to my mechanic who did fix it.
May not be the issue with yours but just thought i would mention it as something to look at if the above does not work.
Turns out one of the wires running to the ECU started shorting the speed and ref sensors.
This is all according to my mechanic who did fix it.
May not be the issue with yours but just thought i would mention it as something to look at if the above does not work.
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06-11-2009, 06:53 PM
#9
Three Wheelin'
06-11-2009, 08:02 PM
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You can get a whole pressure test kit at an auto parts store or Harbor Freight but I doubt they have the right fittings for the 944 fuel rail.
The cheapest dial tire gauge you can get, some tubing, perhaps a hose size adapter, and some hose clamps will work but keep the gauge above the height of the rail so it does not fill with fuel. I have used a cheap oil pressure gauge too. the really cheap $2.99 dial gauges often have an NPT fitting hidden by a barrel where you fit them to a schrader valve. Take that off and screw it onto some hose, then clamp. Instant, cheap fuel pressure or boost gauge.
Be ready for leaks.
I would tend to suspect an air metering problem. AFM or a split in the intake plumbing perhaps. Could also be excess fuel from a torn FPR or damper, that would also explain the poor fuel economy but not the clean plugs. It probably runs better after warmup because it's getting into closed loop and compensating for the issue to some degree.
-Joel.
The cheapest dial tire gauge you can get, some tubing, perhaps a hose size adapter, and some hose clamps will work but keep the gauge above the height of the rail so it does not fill with fuel. I have used a cheap oil pressure gauge too. the really cheap $2.99 dial gauges often have an NPT fitting hidden by a barrel where you fit them to a schrader valve. Take that off and screw it onto some hose, then clamp. Instant, cheap fuel pressure or boost gauge.
Be ready for leaks.
I would tend to suspect an air metering problem. AFM or a split in the intake plumbing perhaps. Could also be excess fuel from a torn FPR or damper, that would also explain the poor fuel economy but not the clean plugs. It probably runs better after warmup because it's getting into closed loop and compensating for the issue to some degree.
-Joel.
06-12-2009, 01:28 AM
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FPR's are actually pretty cheap and easy to replace. You could try a fuel pressure guage first.
http://www.pelicanparts.com/catalog/...pg4.htm#item21
http://www.pelicanparts.com/catalog/...pg4.htm#item21
06-12-2009, 10:13 AM
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I have a simple test kit but it lacks a fitting for the 944 fuel rail. There is a kit for sale at Harbor Freight this weekend for $10 that appears to have more fittings than mine, you might take a look at it.
If you take the cap off the test port, do not lose the ball bearing that seals it.
If you need help I might be available Monday after work.
-Joel.
If you take the cap off the test port, do not lose the ball bearing that seals it.
If you need help I might be available Monday after work.
-Joel.
06-12-2009, 12:43 PM
#15
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I have a simple test kit but it lacks a fitting for the 944 fuel rail. There is a kit for sale at Harbor Freight this weekend for $10 that appears to have more fittings than mine, you might take a look at it.
If you take the cap off the test port, do not lose the ball bearing that seals it.
If you need help I might be available Monday after work.
-Joel.
If you take the cap off the test port, do not lose the ball bearing that seals it.
If you need help I might be available Monday after work.
-Joel.