Fuel pressure help
02-17-2010, 05:37 PM
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Join Date: Feb 2010
Location: Houston, Tx
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Fuel pressure help
Hello I am new to Rennlist and a new owner of a 83 944 I bought so I could have a better car to track than my Audi. It's not a turbo, but too good to let get away. I have read many old postings and have learned a lot from all of you, but I still need to confirm some things.
I bought the car knowing it idled and ran poorly. It will not idle without help most times. And when driven it stumbles in almost all but mid range RPMs. The dependable shop that last serviced it before I purchased it stated they had checked everything and determined that the issue must be in the DME. PO did not want to replace it, gave up, and that is where I entered the picture.
It has fresh fuel, new fuel pump, filter, lines, injectors, etc. Before I would replace a DME I wanted to test the MAF, TPS, throttle body, and all checked out. So using the info from Clark's , I checked the fuel pressure. Engine off was 36psi (looks good). Then I started engine and checked but of course it will not idle without some throttle so I am not sure if I skewed the test. At idle it was about the same and was 33-36psi. (too high according to Clarks). After a 20min and even 1 hr later it is holding at 34psi.
So it seems the only issue is the Idle test and since the pressure did not drop do I have a regulator issue ? Or did me giving it throttle to maintain idle skew the data ?
Thanks.
I bought the car knowing it idled and ran poorly. It will not idle without help most times. And when driven it stumbles in almost all but mid range RPMs. The dependable shop that last serviced it before I purchased it stated they had checked everything and determined that the issue must be in the DME. PO did not want to replace it, gave up, and that is where I entered the picture.
It has fresh fuel, new fuel pump, filter, lines, injectors, etc. Before I would replace a DME I wanted to test the MAF, TPS, throttle body, and all checked out. So using the info from Clark's , I checked the fuel pressure. Engine off was 36psi (looks good). Then I started engine and checked but of course it will not idle without some throttle so I am not sure if I skewed the test. At idle it was about the same and was 33-36psi. (too high according to Clarks). After a 20min and even 1 hr later it is holding at 34psi.
So it seems the only issue is the Idle test and since the pressure did not drop do I have a regulator issue ? Or did me giving it throttle to maintain idle skew the data ?
Thanks.
