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.
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.
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 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.
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.
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.
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.
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....
Have you checked the new plugs for fouling or any visable defects?? Also, you might want to swap back to your original wires to make sure your new set doesn't have a bad wire. I had that happen with a Ford Ranger. It drove me nuts!!
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!
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.
Does your idle pulse all the time? Mine only acts up after a really hard drive! My current theroy is that maybe my intake manifold is heating up and warping causing a vacuum leak!
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.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Subaru Impreza GC8 & RS Forum & Community
3.1M posts
79.1K members
Since 2001
A forum community dedicated to Subaru Impreza GC8 and RS owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, turbo upgrades, maintenance, and more!