Welcome to the North American Subaru Impreza Owners Club Thursday October 23, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Service & Maintenance

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Thread Tools Display Modes
Old 01-06-2002, 11:57 PM   #1
Scooby Newbie
Member#: 11957
Join Date: Nov 2001
Location: ithaca ny
1999 impreza 2.5rs
midnight black pearl

Default serious idle problems on 99RS

alright, heres the problem, i have a 1999imprezars with high mileage 76k to be exact. about a month ago it started idleing very rough after it sat overnightor for a couple hours and the engine cooled down. i would start it and it would jump to about 1500 to 1800 rpm then go down to about 500rpm and the whole car would shake. so i took it to the dealer and they said nothign was wrong with it.(BS) i then too it to a private mechanic and they said it was a number of things all of which have been replaced.(new fuel pump, O2 sensor,spark plugs and wires) none of which solved the problem. then they took the temp of the engine and realized it was about 70 degrees off so they replaced that and that helped. i then took the mechanic for a ride with the computer hooked to the ecu andit said that the fuel line was staying open when it should be closed. the mechanic said that the car will adjust and that this shoould fix it. now about a month later it has all started agian any suggestion as to what this problem might be?( i apologize for the length of this post but to properly explain the problem i had to explain everything) thanks for you help
* Registered users of the site do not see these ads.
pearlblack2.5rs is offline   Reply With Quote
Old 01-07-2002, 12:04 AM   #2
North Ursalia
Miss You Mom
Oct 1940 - Feb 2008

Super Moderator
Member#: 809
Join Date: Jan 2000
Chapter/Region: NESIC
Location: NH, Land Of Many Trees
2000 2.5 RS, '14 For
92 5MT SVX


When was the last time in those 76k miles you changed the fuel filter? Did anyone test the engine vaccuum (as it affects the fuel pressure riser) and the fuel pressure yet?

North Ursalia is offline   Reply With Quote
Old 01-30-2002, 12:57 AM   #3
Scooby Newbie
Member#: 5376
Join Date: Apr 2001
Location: Markham, ON, Canada
1999 Impreza 2.5RS


This is happening to me too for the past few winters.

Do you have any follow up on it?

I have around 50k on my car right now, just replaced my fuel filter, but didn't help...

I'll try to do the pressure check asap...
s is offline   Reply With Quote
Old 01-30-2002, 01:33 AM   #4
Scooby Specialist
Member#: 1234
Join Date: Apr 2000
Location: Vancouver, Canada


Check the intake pipe for cracks or air leaks. Since it is a 99, air leaks that bypasses the MAF will casue weird idle problems. Also check your idle air control and see if the throttle body is clean.. Might be dirty.
Avenger is offline   Reply With Quote
Old 03-01-2002, 12:11 PM   #5
Scooby Newbie
Member#: 162
Join Date: Aug 1999
Location: Phila, PA
1999 Impreza RS
Silverthorne Metallic


I am having EXACTLY the same issues right now!! I took it to the dealer and they said it was the O2 sensor, which I replaced myself. On a whim I just put in some STP Total Fuel System cleaner, but I am still waiting to see if that does anything.

Did you ever figure out what this is?

Girl'sRS is offline   Reply With Quote
Old 03-01-2002, 01:51 PM   #6
Scooby Newbie
Member#: 6831
Join Date: May 2001
Location: philadelphia
98 impreza 2.5RS


i started getting that on my 98... changed out the spark plugs and everything was smooth again
fabulous12 is offline   Reply With Quote
Old 03-05-2002, 04:15 PM   #7
Scooby Newbie
Member#: 6436
Join Date: May 2001
Location: Holland, PA
1998 Impreza 2.5RS

Default Throttle body

Have you tried cleaning the throttle body? It seems like an obvious thing to try... Gunk from the PCV system collects below the lower lip of the throttle plate and restricts airflow. This makes the IAC valve go crazy.

Use intake cleaner or Chemtool Carb Cleaner.
vvk is offline   Reply With Quote
Old 03-29-2002, 12:43 PM   #8
Scooby Newbie
Member#: 162
Join Date: Aug 1999
Location: Phila, PA
1999 Impreza RS
Silverthorne Metallic


Ok, I think I solved it. When my fiance was changing my oil he noticed that the engine had a slight knock. I put in a tank of 93, (I usually use 87). The idle smoothed out immediately. Well, since I dont want to pay for 93 forever, I tried 89... seemed fine. And I just put my first tank of 87 back in and it still seems fine. Im keeping my fingers crossed, but I think the higher octaine did the trick.
Girl'sRS is offline   Reply With Quote
Old 03-29-2002, 09:11 PM   #9
Scooby Specialist
Member#: 1415
Join Date: May 2000
Location: Anytown, USA
2005 OBS 3.0R
'12 SantaFe


Common items to check: (also gonna repeat what others said)

1. Corrosion on coil pack leads
2. Pull plug on MAF and reseat it
3. If at all possible check fuel pressure. Maybe FPR is going bad?
4. Check throttlebody for build up of gook
5. Check PCV valve
6. Check for leaks in intake. Any leaks after the MAF is gonna make it run funny.
7. Replace fuel filter
8. Check vacuum or look for cracks in vacuum hoses, listen for leaks.
9. Reseat all electrical connections

And so on...
spshultz is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
CEL / low idle problem on STOCK 05 2.5RS 2.5impreza Normally Aspirated Powertrain 22 08-25-2014 06:57 PM
Uneven idle problem on my snowblower nitrohuffer Off-Topic 11 01-12-2005 03:15 PM
high idle problem on 93 1.8 in a 95L scobaru Normally Aspirated Powertrain 2 12-16-2004 11:28 PM
Serious brake problems-Anybody else with "sensitive" ABS on a Forester? wadejg Forester Forum 6 02-03-2004 10:20 PM
idle problem - with A/C on svxxx-26 SVX Forum Archive 7 11-21-2000 06:43 AM

All times are GMT -4. The time now is 07:16 AM.

Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.