Subaru Impreza GC8 & RS Forum & Community banner

1 - 20 of 31 Posts

·
Registered
Joined
·
99 Posts
Discussion Starter #1
I have a 99 2.5rs,

I had a check engine light for a misfire so I put on all 4 new plug wires and ngk plugs, reset ecu and the car ran fine.

A couple of days later,
When the car is idling the rpms pulsate up and down.You can see the tach move a little bit. the car runs good once you are driving. But at idle it pulsates and then drops down to around 400rpms and throws a check engine light. then the rpms will go back up to about 1000 then drop again.

So I borrowed some parts from a friend.

I changed the coil pack, front o2. I put in a new air filter, fuel filter, pcv valve and changed all fluids. I also ran a tank of gas with injector cleaner.

So what could it be? Could it be a bad injector, tps.

Thanks
Jeff
http://community.webtv.net/Rim2001/Subaru
 

·
Premium Member
Two Mini Coopers!
Joined
·
10,629 Posts
Could be your MAF sensor going bad... but that is just a guess...

Sounds to me the ECU is trying to compensate for something - A/F ratio, improper mixture, coolant temp... who knows. Under warranty? Go to the dealer! :)
 

·
Registered
Joined
·
99 Posts
Discussion Starter #3
My car is out of warranty. I have 62,000 on it.

I'm not getting c.e.l. for the maf. I might try changing the injectors I have extra ones.

Any other ideas?

Jeff
 

·
Premium Member
Two Mini Coopers!
Joined
·
10,629 Posts
Drop by the dealer and pick their brain. You might be able to get some free advice.. maybe. :)
 

·
Registered
05 LGT limited
Joined
·
405 Posts
Before you spend too much moolah, pay the dealer the 70-80 bones to diagnose the problem, then fix it yourself. Better 80 for diagnosis than 100 or more for parts you may not need. If you've got free (spare) parts, by all means try that first.
 

·
Registered
Joined
·
99 Posts
Discussion Starter #8
Help

the only mods I have are 2.5 exhaust from the cat back with Apex N1, Upper air filter removed.

I don't know what code it is throwing now. I have to find out.

When the rpms drop below 600 it sounds like its misfiring.
As soon as I get on the gas it runs fine.

All the extra parts I have are from a friend. I still have 4 injectors to try.

I will check for vac leaks tomorrow.

Thanks for your input.

I will keep you posted.

Jeff
 

·
Scoobymods Guy
2010 Legacy 3.6R Limited
Joined
·
1,157 Posts
Are you sure all the hoses to the intake are secure and the filter in the airbox is in there right. I agree with the air leak theory,
 

·
Registered
Joined
·
99 Posts
Discussion Starter #12
not fixed yet

Here is what I've done

new ngk plugs, .041
new plug wires, all 4
replaced coil pack
replaced front o2 sensor
compresion: cycl # 1,3 200
# 2,4 210
new lower air filter
new fuel filter
all fluids changed
new pcv valve
checked all vac lines(no leaks)

I'm getting ready to adjust all the valves.

After that my final check will be to go to the dealer and have them check the maf.
Maf warrenty is 7/70,000. I have 62,000.

Nobody close by me has a 99rs that I can try there maf.

I will keep you posted on what I find out.

Jeff
 

·
Registered
Joined
·
99 Posts
Discussion Starter #13
Valve Adjustment

Not to bad!!!

2.5 hours to adjust the valves.

cycl. #1 int: .007 & .011
exh: .009 & .011
#2 int: .011 & .011
exh. .008 & .008
#3 int: .012 & .011
exh: .009 & .009
#4 int: .009 & .012
exh: .008 & .009

I set all intake to .007
and exhaust to .009


Can runs good except it still pulsates at idle.

I guess I will take it to the dealer to have the maf checked.

Any other ideas for me to try.


Jeff
 

Attachments

·
Registered
Joined
·
238 Posts
I had a similar problem recently. Check the airbox in/on the fender to see if it's loose or possibly cracked. Mine was loose and at startup & idle I could feel the engine pulsating as well.
 

·
Registered
Joined
·
99 Posts
Discussion Starter #15
Not fixed

I have checked all the vaccum lines and intake system.

I bought a hand held vaccum pump today. I am going to test the vaccum and componets this week.

Jeff
 

·
Premium Member
overdeveloped beater
Joined
·
8,335 Posts
Pull the codes!

Geez, you're doing nearly everything but the first step! If you don't have a tool to pull the codes, go have the dealer(or someone) pull them. Chances are the idle control motor is either going bad, getting bad contacts, or getting physically hung up as it tries to set the right idle speed. As soon as you touch the gas, the idle circuit is bypassed and the car runs fine, as you say.
 

·
Registered
Joined
·
99 Posts
Discussion Starter #17
pulled codes

I have pulled all the codes. The only code I have gotten is for misfire. I redid the pugs and wires, reset the ecu. So far since the reset no check engine light (about 175 miles).

The bad idle and what sounds like a misfire is still there.

So now I am checking the vaccum system.

I will also check the idle system.


Thanks
Jeff
 

·
Premium Member
Two Mini Coopers!
Joined
·
10,629 Posts
I believe it's inline with the TPS (Throttle Position Sensor) in the body of the intake. It opens the throttle plate slightly when things like the A/C turn on to prevent the engine from idling too slowly or stalling altogether.
 

·
Registered
1997 V2 GF4
Joined
·
335 Posts
do have a description of the exact codes your getting?

still sounds like a vacuum leak, and or a ignition system concern, cam/crank sensors maybe....these sesnors are what the ecu relies on for ignition timing....

if it is a misfire code it should be either

P0301
P0302
P0303
P0304

or a random misfire code....

grr need more info :)

Jay
 
1 - 20 of 31 Posts
Top