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Engine pulsates at idle,need help

3K views 30 replies 12 participants last post by  dohtohrhi 
#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
 
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#5 ·
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.
 
#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
 
#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
 
#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
 

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#14 ·
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.
 
#16 ·
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.
 
#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
 
#22 ·
I have this exact same problem with my car.......I have alot of aftermarket stuff on it though. If I reset my ECU it will run fine for about 4 days. Then it starts up again! It seems like it happens after a hard drive!!! I have not pulled my codes yet. I'm gonna soon! RallyeX plaese keep us posted!
 
#23 ·
Yesterday I changed the injector on cyclinder #3
the problem went away for a little bit. Late last night it started doing it again.I'm still trying to figure it out.

I also had my left rear wheel bearing go out last week. I replaced it with the Legacy bearing wich is a tapered roller bearing.


RallyeX
 
#25 ·
The engine pulsates after it has reached operating temp. The engine idles at 800rpms while you are sitting still. Then the rpms drop to about 400-500 rpms, that is when it starts to pulsate. Once the rpms are up the car runs good.

The flat spot at 3500 to 4200 rpms is really bad.


RallyeX
 
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