Frustrated! Another hesitation thread

[mattgold]

Greetings all. I have a '99 ej20tt manual, 175k km, and I am getting really frustrated with an annoying hesitation/jerkiness when driving. Most noticable while the engine is warming up, the throttle response seems hesitant and sometimes quite jerky, often scarily so when in 1st gear. Once warm, the hesitation is most noticable doing 2-2.5k rpm in traffic and you're trying to adjust your speed slightly - the throttle will seem to 'stick' and then suddenly open.

 

Could this be caused by running a wet oil air filter (I know, I know), and if so, what has that damaged/screwed with?

 

The wet oil air filter was in for around 20k before I noticed the hesitation, then I changed back to paper. Since then, the car has had (@171k);

 

New cambelt/tensioners/idlers/plugs/air filter

Coil packs checked and cleaned

New MAF

Upper engine cleaner (OEM, inlet manifold onwards)

Oil change

 

One thing I have noticed during all this; usually after each of the above was done (and even just trying CO contact cleaner on the old MAF) the engine would seem fine for a day or two, and then gradually get worse. Could this just be my imagination???

 

When I purchased the upper engine cleaner from the dealer, they recommended spraying into the throttle body, which entails removing the intercooler. Needless to say, I was not so keen to do this, but now I am thinking that I should have? Changing the oil is about as mechanical as I get.

 

At 143k I had the CEL come on several times when climbing hills (5th gear, 3k rpm) , and when taken to (a different) dealer, they pulled codes 12, 32, 61, 62, 63, 64 and 67 !

 

They suggested it was a wastegate issue, couldn't find any problems with solenoid valve connections, but couldn't reproduce the CEL. Needless to say, the CEL re-occurred And I haven't had a CEL after the oil change at 150k

 

IF it was the wet air filter, what else should I test/clean/replace? TPS? Clean throttle body?

 

OR what else should I look at? (Keep it simple, post pictures preferably )

 

Matt.

[tcspeer]

I did not see in your post where you changed the plug wires, I think I would do that next. You said you changed the plugs, many times the wires will be damaged when you change the plugs.

Greetings all. I have a '99 ej20tt manual, 175k km, and I am getting really frustrated with an annoying hesitation/jerkiness when driving. Most noticable while the engine is warming up, the throttle response seems hesitant and sometimes quite jerky, often scarily so when in 1st gear. Once warm, the hesitation is most noticable doing 2-2.5k rpm in traffic and you're trying to adjust your speed slightly - the throttle will seem to 'stick' and then suddenly open.

 

Could this be caused by running a wet oil air filter (I know, I know), and if so, what has that damaged/screwed with?

 

The wet oil air filter was in for around 20k before I noticed the hesitation, then I changed back to paper. Since then, the car has had (@171k);

 

New cambelt/tensioners/idlers/plugs/air filter

Coil packs checked and cleaned

New MAF

Upper engine cleaner (OEM, inlet manifold onwards)

Oil change

 

One thing I have noticed during all this; usually after each of the above was done (and even just trying CO contact cleaner on the old MAF) the engine would seem fine for a day or two, and then gradually get worse. Could this just be my imagination???

 

When I purchased the upper engine cleaner from the dealer, they recommended spraying into the throttle body, which entails removing the intercooler. Needless to say, I was not so keen to do this, but now I am thinking that I should have? Changing the oil is about as mechanical as I get.

 

At 143k I had the CEL come on several times when climbing hills (5th gear, 3k rpm) , and when taken to (a different) dealer, they pulled codes 12, 32, 61, 62, 63, 64 and 67 !

 

They suggested it was a wastegate issue, couldn't find any problems with solenoid valve connections, but couldn't reproduce the CEL. Needless to say, the CEL re-occurred And I haven't had a CEL after the oil change at 150k

 

IF it was the wet air filter, what else should I test/clean/replace? TPS? Clean throttle body?

 

OR what else should I look at? (Keep it simple, post pictures preferably )

 

Matt.

[mrCharlie]

A very off chance that could help is the neural position switch.

 

I replaced mine trying to track down a very frustrating stalling problem, and instantly cured my car of a lot of weird jerkiness and hesitation. It's not especially hard to replace or expensive (~$25), and easy enough to test (do a search or check a service manual for how, don't trust me--though my old one seemed to test okay).

 

I don't suggest this as a first-line check, but it might be worth considering. My experience is that it was an obscure component which made no sense to be causing my problems, but apparently has some importance relating to throttle response and mixture, especially when the car is in open-loop mode (ie warmup and (I think) wide-open throttle). Before I replaced the switch, throttle response was very non-linear, almost like an on/off switch. Gas in and it would hesitate then surge, letting off the gas resulted in the RPMs falling too quickly, or stall if I was out of gear. When the car warmed up, all was pretty much fine. I don't floor it often enough to know how it behaved under those circumstances.

 

Might be worth checking out- but I'm sure others will chime in with some more likely suspects.

[mattgold]

A very off chance that could help is the neural position switch.

 

I believe I read your thread on the neutral position switch, but for some reason I was thinking that was only an AT thing. I'll go back and search the archives again.

 

Probably is a long shot though.

 

M.

[mrCharlie]

My car is a manual, but yes, it likely is a long shot.

 

Best of luck!

[mattgold]

I did not see in your post where you changed the plug wires, I think I would do that next. You said you changed the plugs many times the wires will be damaged when you change the plugs.

 

I did suggest to the mechanic that the wires needed changing, but he was adament that was not necessary. Two things make me believe that it is electrical/spark related; (1) The jerkiness is similar to what I have experienced with other cars having distributor/ht lead faults (2) the problem 'seems' worse in wet weather.

 

Looks like I might have to get the car hooked up to a computer and analysed...

 

M.

[tcspeer]

I have never tried this but others here have suggested spraying a light mist of moisture on the wires after dark and check for some jumping fire. I would not spray it when the engine is hot.

I did suggest to the mechanic that the wires needed changing, but he was adament that was not necessary. Two things make me believe that it is electrical/spark related; (1) The jerkiness is similar to what I have experienced with other cars having distributor/ht lead faults (2) the problem 'seems' worse in wet weather.

 

Looks like I might have to get the car hooked up to a computer and analysed...

 

M.

[mattgold]

OK, so finally got around to having the car looked at, and it turned out to be the O2 sensor after all - it was really leaning out the fuel mixture to the point of stalling. Here is a link with a picture of the sensor in the exhaust manifold:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=73753

 

Boy am I happy to have the subby back to its old self....

 

M.

[OB99W]

OK, so finally got around to having the car looked at, and it turned out to be the O2 sensor after all - [...]

Congratulations on getting the problem resolved, and thanks for getting back to us. O2 sensors often become "suspect" by around 100,000 miles (converting from kilometers, that's about where your car was at).

[mattgold]

Congratulations on getting the problem resolved, and thanks for getting back to us. O2 sensors often become "suspect" by around 100,000 miles (converting from kilometers, that's about where your car was at).

 

I have a feeling the O2 was replaced shortly before I bought the car but I don't have the paperwork to refer to, but this makes me believe that in this car the sensor isn't lasting much more that 80k km. But then again this car has had other 'issues' so that complicates things Anyway, I know what I'll be thinking of replacing when she gets to 250k km....

 

M.

[unibrook]

My fix turned out to be the front 02 sensor. Here is my review from a diff thread: I have a 2001 Forester L with 85k miles on it. I have been chasing an intermittent hesitation under load problem for the past year since 80k miles. Only occurred when engine was warm. The front 02 sensor had been replaced once at 40k miles. I suspected it again this time, but since the only codes thrown had been cyl's 2&4 misfire ( p0302 & p0304) I assumed it must be ignition related. So I replaced plugs and wires 8 months ago...no effect. Did the dollar bill test over exhaust pipe, it was fine. Misted the coil, no sparks. I mentally sort of ruled out the fuel filter since it only happened when the engine was warm. Finally, a week ago while cruising on hwy at 65 mph, I felt the hesitation again (I wasn't even accelerating this time) and a new code was thrown....p0172. AutoZone read it for me, I described the symptoms to the guy and asked if he thought it might be the front 02 sensor. He said, "absolutely." So I decided to replace it next. Cost me $100.75 incl tax for the oem part# 22791aa00a from Cityside Subaru. I asked the Parts guy there if his experience was that this model engine needed a new front 02 sensor every 40k miles. He said, "no, these sensors are good for 100k miles." Well, bullsnot on that. I replaced the new front 02 sensor in 1 hour reaching from the top over the passenger side of the engine using an adjustable wrench. Be sure to use the thread lube so you can get it out easily next time.....after another 40k miles. I took out the air channel assembly first for better access. That seems to be the fix. No further hesitation since. Car runs like new.