Any ideas why my 98 Legacy L with EJ22 has developed an intermittent stumble at highway speed?  It happens when engine is warm and maintaining a steady speed.  A single, instantaneous stumble might occur twice during a two hour road trip, but I know it's not going to heal itself.  Feels like more than a single cylinder misfiring once.  Could it be electrical even though there is no CEL?  Past experience with clogged fuel filter on other cars has been loss of acceleration.  This thing still accelerates as well as ever.

 

We're having a heat wave - might get to 40* - so I'm going to go for a drive and see if I can make it happen.

 

My wife prefers this car over our near new Accord, but I don't want to turn her loose with this issue.

 

Thanks for your advice.

Dave

Could be the AFM starting to fail. Once had similar symptom with  my 95 and in my case, it was the AFM. 

Edited March 9, 201412 yr by john in KY

Could be the AFM starting to fail. Once had similar symptom with  my 95 and in my case, it was the AFM. 

 

Just to clarify--by "AFM" you mean Air Flow Meter, correct?  In other words, MAF or MAP?

I had something similar with my 99, with 2.5 motor. I suspected a small amount of water in the fuel tank. I added 1 gallon of E-85 fuel, then finished refueling with unleaded 87 gasoline on a near empty tank.. I figured the ethanol would absorb the water, and it did.

I had a similar problem and it was a dirty TPS.  I used some Radio Shack lubricated contact cleaner to fix it.

Thanks for the tips!

 

Rooster, your description of the symptom is better than mine.  I burn enough ethanol that water is probably not the cause, but that is what it feels like.

 

Will clean the TPS next and then on to the AFM.  I was wondering about the AFM, but most of the posts talked about stumble at idle.

Yeah it could be the MAF (aka AFM) too.  They get bad solder joints, you need to take the lid off with a sharp knife to resolder it.  I had this happen too, but it wouldn't just stumble it would cut out and jerk, and it would throw a code.  But it's certainly possible.

Removed the TPS today and sprayed it with contact cleaner, but I don't think I could really see the contacts.  They seemed to be encased in the plastic housing.  I'm now debating to wait and see if that fixed it, or to go ahead with the MAF (AFM).

 

Thanks again.

Yeah the wiper is inside, can't see it.  There is a gap between the rotating part and the housing that I sprayed into while turning it back and forth.  Also need to make sure it's adjusted right or the engine will jerk slightly when going from decel to accel while cruising.

Good to know, presslab.  I liberally sprayed contact cleaner in the "crack" and exercised it as you recommend.  I scribed the sensor and the mounting location so I could reinstall the sensor in the original position.  It ran fine afterwards.

 

I really appreciate you guys taking the time to get into the details with me.  I am trying to use searchable terminology (TPS and MAF don't pop up on search) so others can find this in the future.

80 road miles yesterday with no stumbles. I am going to chalk this up to spraying contact cleaner into the slip joint in the throttle position sensor.  will post back if I have additional symptoms.

 

Thanks for the help!

It sounds like the start of a fuel pump going bad.

 

Something to keep in mind.