Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 924/944/968 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Mar 2000
Location: Riverdale, GA
Posts: 363
Send a message via Yahoo to Cebu
Question RPM flux on Startup

86 944na (stock), On first engine start after sitting overnight,the engine stumbles for approx. 3-sec and then smoothes out with a steady 900 RPM. There is no RPM hesitation on acceleration or starts the remainder of the day.Vehicle accelerates smoothe and strong to red line. Only after car sits for 12 plus hours does the RPM surge from 9-1100 on start. Items replaced,Fuel filter,fuel pressure regulator,fuel pressure damper. All imputs are appreciated.

Old 06-01-2001, 07:34 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
Join Date: Jul 2001
Location: Portland, Oregon USA
Posts: 16
Unhappy

My '86NA does it too. It started about a week or two after I installed a Europroducts DME chip, but I don't think that's what's wrong. Anyone else have issues after installing one of these chips? I haven't replaced anything fuel system related yet, but I am going to replace the O2 sensor next week to see if my full throttle performance get's better. I'll let you know if it helps.
Old 07-12-2001, 08:50 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Magnus_944's Avatar
 
Join Date: Jul 2000
Location: Sweden
Posts: 278
Post

It could be a leaking injector.

/Magnus
Old 07-12-2001, 10:48 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
fty fty is offline
Registered User
 
fty's Avatar
 
Join Date: May 2001
Location: LI NY
Posts: 1,689
Send a message via AIM to fty
Post

I have the same problem..does it all the time bobs from 600-110 then flattens out after a couple mins...
Old 07-14-2001, 09:03 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
Join Date: Feb 2000
Location: Kingsport, TN
Posts: 2,925
Post

My '86 with MAF has a low speed rough idle for the first couple of minutes. It has not gotten any worse or better in 3 years. I just live with it. It does not fluctuate; it merely idles too low for the first couple of minutes.
Old 07-15-2001, 08:06 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
Ehab's Avatar
 
Join Date: Mar 2001
Location: Somerville, MA
Posts: 466
Post

When it fluctuates, that is an indicator that the mixture is either too rich or too lean for that period of time, or a leaky injector flooding a cylinder. I know this because I can cause the idle rpm to fluctuate by setting the A/F mixture using the AFM bolt.

Coppari ... sounds like your Aux Air valve needs cleaning/tuning, or replacement if faulty. My idle starts at 1100 when cold (steady), then slowly drops to 950 as the engine warms up.

e
Old 07-15-2001, 11:50 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
MAS MAS is offline
Registered User
 
Join Date: Jul 2001
Location: Victoria, BC, Canada
Posts: 608
Garage
Post

"... My idle starts at 1100 when cold (steady), then slowly drops to 950 as the engine warms up."

Same with my 87 924S.

-Zog
Old 07-15-2001, 01:43 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
Join Date: Apr 2001
Location: Twin Cities, MN USA
Posts: 148
Garage
Post

The variation in initial idle speed is due to the action of the Idle Control Valve (the ICV is in 85.5+ cars, while a Auxillary Air Valve (AAV) is in previous cars). As the speed drops the computer signals the ICV to open slightly, causing the RPM's to rise. If it overshoots the valve is closed slightly reducing RPM. Some initial hunting is normal for this engine.

Old 07-16-2001, 08:04 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 02:47 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2020 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.