1998 Forester S, 5 spd, 102 K

 

Data:

 

• Engine has serious stumble after the first time I turn it on and drive away in first or after upshift to second gear.
  
• Stumble feels like running out of gas.
  
• Gas tank full; also happened as tank ran down to under five gallons onboard.
  
• Recovers/stumble ends when reved in neutral to above 4K a few times.
  
• Never occurs after first occurance. Once it has sumbled and recovered the stumble does not return for duration of drive.
  
• Does not matter if engine is hot or cold; does act slightly different when the engine is cold--seems to do for shorter time and less severe.
  
• Engine starts perfect with no throttle pedal needed. When warm, the engine spims at 1200 rpm, then drops to 800 (or so, I haven't got a secondary tach to check exact engine speed).
  

 

My first thought was the fuel filter but it doesn't show during any other time. Now I think it is somehow choke related, but....?

 

Any ideas out there why this may be happening?

 

Randall

Do you let the car warm up or just drive off?

 

I had similar issues. If I let the engine warm up, it wouldn't do it.

 

You may want to try changing brands of gas.

 

I never found out what was causing it....it eventually went away or went away when I did all my swaps.

I just drive off! Hell, yes!

 

Did you have this same trouble when the car was warm, too? Seems strange to me that warming it a bit would keep this from happening when the car is already warm.

 

What swaps did you try?

 

Thanks.

 

Randall

Had a similar issue on my 97 Legacy. Turned out it needed new Ignition Coil / Wires. It would stumble only when cold for the first few mins when it was still partly humid in the engine bay. Once it warmed up, the water evaporated and everything was fine. The stumble also went away once the engine was revved.

 

When I was replacing Ignition Coil ($100 at dealer), I noticed that Cylinder 2 wire had its lead retract into the the rubber sleeve. Looked like I pulled on it too hard and the lead retracted.

 

Well, anyway, once that was replaced, back to normal. I would check those parts to make sure.

I just drive off! Hell, yes!

 

Did you have this same trouble when the car was warm, too? Seems strange to me that warming it a bit would keep this from happening when the car is already warm.

 

What swaps did you try?

 

Thanks.

 

Randall

 

No, only after the car would sit overnight or for extended period of time...AND....if you just put the car in gear and kept your foot on the brake, and didn't touch the gas pedal.....it wouldn't do it. I say that because I brought it to the dealer and they just started it up and did what I said, and it never reproduced the problem. Once you touched the gas pedal is when it would stumble, and then it'd be fine.

 

I really don't know what the issue was.

 

So on yours, do you get the problem when the car is "warm" as well?

 

My car was originally FWD AT & normally aspirated. It's not AWD, MT, & has a turbo legacy engine. So way too much stuff has changed....however I have supspicions it might have been auto transmission related.

So on yours, do you get the problem when the car is "warm" as well?

 

Yeah, it happens when it is warm. I can get it to do the stumble everytime I start it, warm or cold, even moments after shutting it off when warm or cold.

 

lightly

 

Randall

Hmm.....have you done any routine maintenance on it recently, plugs, wire, filters, etc?

Hmm.....have you done any routine maintenance on it recently, plugs, wire, filters, etc?

 

No I haven't, but I did rinse the motor area the other day and since then...:-\

 

Last night I did the "what have a I changed" scenario in my head. The rinse! So I cleaned all the plug wire connections and a couple key grounds and it seems to have stopped stumbling. I'll know more today after my wife drives it all day. We'll see if that was it.

 

Maybe just a bit of moisture in the electron highway.

 

Randall

If you didn't do it, disconnect all the electrical sensor connectors, blow them out with compressed air, and put dielectric grease in them.

So I checked all the plug wires and they seemed fine. Replaced the fuel filter, still no joy. Still having the problem. It happens in every gear, one time and then doesn't again for as long as that drive lasts.

 

Based on other posts I have read, I will try the following:

 

Remove and inspect plugs

 

Remove and clean TPS (have a procedure)

Test the TPS (have a procedure)

Clean contacts to TPS (electric contact cleaner and dielectric grease)

 

Check connections on knock sensor.

 

Reset CPU (do I just disconnect the battery for X time?)

 

Randall

Yeah, remove the battery cable for an hour or so.

Yeah, remove the battery cable for an hour or so.

 

 

Resetting the CPU didn't do it. On to the next.....

 

Randall

I had a problem with intermittend stumble. Someone suggested MAF sensor. So I removed it and cleaned with a spray cleaner (dont touch it) just spray. Let it dry and replaced. After this the stumble has not come back. Knock on wood:o).

I had a problem with intermittend stumble. Someone suggested MAF sensor. So I removed it and cleaned with a spray cleaner (dont touch it) just spray. Let it dry and replaced. After this the stumble has not come back. Knock on wood:o).

 

Thanks, I'll try that, too. Did you use Brakleen or electric contact cleaner or....?

 

Randall

use brake cleaner

 

Things are looking good. No more stumble after five days.

 

I cleaned the MAF sensor with Brakleen, cleaned the MAF sensor connection with electric contact cleaner and lubed with dielectric grease; cleaned the coil to plug wire connections with electric contact cleaner and lubed with dielectric grease; cleaned the TPS connection with electric contact cleaner and lubed with dielectric grease.

 

Seems to have fixed it.

 

 

Randall