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Join Date: Feb 2007
Location: Bettendorf Iowa
Posts: 18
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HIGH! Idle
On my 88 944 N/A I have a very high Idle. When ever I start her up she runs around 2100 rpms. But all of a sudden she'll go back to the average 900rpm. Does anyone have any ideas on what can be causing this. Thanks, Josh
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Joshua Federico 1988 944 N/A mint condition 1993 pontiac sunbird conv. (P.O.S) |
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03-06-2007, 09:22 PM
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Josh, does it stay at high idle until it warms up a bit or is it at high rpms and then goes back to low rpms then back to high? It could be a few different things depending on what it's doing.
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Tom 1990 944S2 Cabriolet 2002 Chevy Silverado 2500HD 2003 Maroon Ford F350 dually |
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03-06-2007, 10:52 PM
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Jumper between pin B and C on the test plug and reset the idle.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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03-06-2007, 11:06 PM
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I'm with Bill
Join Date: Jun 2005
Location: Scottsville Va
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Quote:
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Electrical problems on a pick-up will do that to a guy- 1990C4S |
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03-07-2007, 01:39 AM
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Does this happen when she is warm, or only after the first start-up in the morning?
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1983 944 RHD Original. Uses all my spare cash! 1947 Morris Sold 1972 Benz Sold 1975 Benz Sold 1976 Benz Sold 1977 Benz Sold |
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03-07-2007, 03:18 AM
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Certified Rennwerker
Join Date: Oct 2002
Location: Kansas
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It can be adjusted as SoCal mentioned. The test plug is on the passenger side near the brake booster do as Socal stated and reset idle using the adjustment screw on the throttle body, not the throttle stop or the A/F screw inset in the AF meter. With the jump wire in, the ISV is bypassed and you can rest the idle then remove the wire and the idle should remain at the setting made.
Also look for vacuum leaks as a cause. From the post it does hit 900 rpm which is the normal idle spec so I feel the cause may be a leak of perhaps the TPS...black switch under the TB. Dal
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PCA " I've been everywhere, done everything......just can't remember any of it!" 
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03-07-2007, 07:05 AM
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Location: Bettendorf Iowa
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It primarily does the rapid idle when I start her up in the morning, but it doesn't do it as bad after it warms up.Thanks i'll try jumping it to rest it, and if that isn't the problem i'll look for some kind of vac leak.
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Joshua Federico 1988 944 N/A mint condition 1993 pontiac sunbird conv. (P.O.S) |
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03-07-2007, 12:00 PM
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Certified Rennwerker
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Location: Kansas
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This is a diagram of the test plug, apprx the size of a silver dollar. The adjustment needs the engine temp to be around 90, basically start and idle a minute then test...on a cold engine to start out. The second pic is the adjustment screw and it takes very little turning to change so go in increments. Helps to have a helper watch the tach for the desired range while one adjusts.
Dal  
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PCA " I've been everywhere, done everything......just can't remember any of it!"
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03-07-2007, 12:21 PM
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A bad Idle Speed Valve can be the culprit as well. That things is located under the intake manifold. Typically they get dirty and ive heard some people clean em out with brake cleaner and cured the problem.
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88 928 S4 Black, Black and Grey Interior Alpine head unit & amp, Bazooka Tube, Viper 5704 Smart Start GPS tracking, Devek Headers, Flowmaster 40 3" with Resonator, Auto Authority chips. Custom Luggage Cover. Traded - 86 944 Turbo Guards Red. RIP - 85.5 944 Guards Red |
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03-07-2007, 07:34 PM
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Location: Peachtree City, GA
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Should this procedure be used after changing DME units? I just changed mine and the idle is too high. Out of instinct I adjusted the throttle position screw. Looks like I have to set it back (anyone know the rough position? 2 turns after contact? Something like that?). Any help would be appreciated.
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05-14-2007, 06:03 PM
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Politically Incorrect
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Location: Hoover, Alabama
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From my experience, I would try this:
1) Throttle stop screw in 1/4 turn after contact. 2) Reset the TPS. 3) Idle speed screw out 2 turns after contact. 4) Jumper pins B & C on diagnostic plug. With engine hot, RPM should be reasonably close to 900. If way too high back throttle stop out a little and reset TPS again. You shouldn't have to turn the idle speed screw more than about 1/2 turn either way to get to target idle speed. ALWAYS reset the TPS after you touch the throttle stop screw. After some trial and error and dissassembly and reassemly, I ended up about 1/8 turn in after throttle stop contact.
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Edek '87 924S '91 535i |
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05-14-2007, 06:39 PM
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Location: Peachtree City, GA
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How do you reset the TPS?
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Mark '83 Porsche 944 NA '90 Porsche 944 S2 |
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05-14-2007, 07:12 PM
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1983 Porsche 944 2.5 liter
