[nattywrx]

Hey guys, my buddy has a 99 RS that we are trying to diagnose. Just recently, the car started idling funky and stalling/dying out.

I pulled one of his coilpacks and found oil in the chamber. I told him we had to take care of that asap since that may be the cause of the problem. So today, we replaced the valve cover gaskets as well as the spark plug gaskets and switched out the spark plugs with new ones. However, the spark plugs we got were the super cheap champion copper ones. We also did a fresh oil change & filter as well.

We put everything back together, started the car up and it started idling fine. After a few minutes however, it started idling really bad, rpm's dropping very low and fluctuating and the motor was shaking violently as if it were coughing trying to stay running. That is how it was before as well.

I took the car for a drive and noticed it also started to hesitate at about 3k-4.5k rpms. It felt as if the power would cut out for a second or two before it would come back. It would also have hesitation when cruising and would buck back and forth at a certain rpm if trying to accelerate slowly.

It idles fine for a little bit, then all of a sudden drops into that phase where it is barely runnning and idling very rough. Rev it a little, it will idle good for a minute, then again go back to idling very rough and wanting to die.

I think we will change out the spark plugs for some better ngk's, and see if that makes any difference. Any ideas on what it could possibly be?

Will also probably clean the MAF and see if that does any good. Change coilpacks possibly? o2 sensor? pcv valve? It kind of sucks that there could be so many possibilities.

Hopefully we can get down to the bottom of this soon and figure out the problem asap.

P.S. - Engine seems to be running very rich. There are no CEL's. He does have an exhaust and headers.

Thanks guys! - Natty

 

[SL33P3R]

Having the same problem on my 00' rs. Mine idles fine, and in neutral goes through the rpm band fine. But under load, it shakes and shudders and is ridden with hesitation (again at 3k rpm, or anything passed 1/4 throttle). Got so bad I parked it before any real damage was done, and driving like a granny was getting old.

I have no CEL, sparks and plugs are good. And if it helps, the problem slowly came about, at first i thought my clutch was occasionally slipping. Curious if it is fuel delivery, but like i said it soars through the rpm band in neut.

Sorry to leech on your post without an answer, but I figured this would be better than a new thread since our issues are so similiar.

 

[marioc1028]

free bump for same problem on my 00 rs!!

 

[Jack_Stalk]

http://www.rs25.com/forums/f13/t66391-hesitation-look-here-first.html

Search is your friend.

 

[marioc1028]

lol saw that after i posted...

 

[Impreza99RS]

Try cleaning out the IACV (Idle Air Control Vavle) with air intake cleaner and brush it out to remove any excessive gunk that is stuck in there! if this doesnt solve your problem for your idle then you have more problems, possibly 02 sensor. For the misfiring it could be anything 1st check for moisture in the plugs that could cause the misfire.

Hope this helps

Impreza99RS

 

[chaz2.5]

Have the exact same problem with my 99. Been through the hesitation thread several times with no avail to what the culprit is. Everything from intake, MAF, IACV, wires, plugs, coil pack, wiring... etc....... Nothing worked. I believe my issue is internal. Car is losing oil, but no leaks, piston rings perhaps? All I can say it's I feel your pain and hope you find the culprit and it's an easy, inexpensive fix. Mine is resulting in a swap.

 

[94gtstang50]

Also just started having this issue, gotta clean out the IACV, so excited to do it in this 20* weather...

 

[SL33P3R]

Figured I'd update. I didnt want to buy parts guessing what it was so I started with what I thought it was. I checked the Knock Sensor, after some reseraching I discovered these little bastards have been the culprit numerous times. They will not throw a CEL.
Upon inspecting the Knock Sensor, to my dismay it looked totally fine. No cracks, wires fine. Just a little carbon buildup. So by force of habit I just took some emery-cloth and brakleen and sanded off the carbon. The knock sensor is $150 and again, I wasnt about to buy a part that i didnt know for sure, especially when it visiually looked fine.
My car sat a little longer....because I didnt think I fixed anything. A week later I drove it around to keep air movin through the interior and chargin the battery.......and all was well. No sputter at increased throttle, nothing. I have my suby back.
Not sure if this will help anyone. But I guess carbon build up on the knock sensor is very evil!

 

[skatershawn]

Figured I'd update. I didnt want to buy parts guessing what it was so I started with what I thought it was. I checked the Knock Sensor, after some reseraching I discovered these little bastards have been the culprit numerous times. They will not throw a CEL.
Upon inspecting the Knock Sensor, to my dismay it looked totally fine. No cracks, wires fine. Just a little carbon buildup. So by force of habit I just took some emery-cloth and brakleen and sanded off the carbon. The knock sensor is $150 and again, I wasnt about to buy a part that i didnt know for sure, especially when it visiually looked fine.
My car sat a little longer....because I didnt think I fixed anything. A week later I drove it around to keep air movin through the interior and chargin the battery.......and all was well. No sputter at increased throttle, nothing. I have my suby back.
Not sure if this will help anyone. But I guess carbon build up on the knock sensor is very evil!

Awesome Pawsome man.. I find it a bit useful!! Just keep us updated on how it continues to run, if all is well after a few days or so!