Bucking, surging, hesitating, WOT condition

[ajfsgrl08]

First info on the car.

1999 Legacy L 2.2L 5 speed. Car has a MAP and Both O2 sensors are wideband. Front O2 has been changed with OEM replacment. Coil, plugs, wires, knock sensor all have been replaced with OEM parts.
The engine is a mongrel. Top end (heads/Im) is the 1999 parts. The bottom end (block, pistons, rods, crank) is out of a 1996 Legacy L.
The car has a High flow cat, and much less restrictive muffler than stock. I have done the "defouler" mod to the rear O2 sensor to compensate for the exhaust.

The car ran fine/normal for several months. Recently the car started to surge while driving down the road. Just cruising along on level ground, holding even on the throttle, the car will start to lightly surge. The speed doesn't change, nor does the rpm. It just feels as though you stepped down on the throttle in the smallest amount and then let off to the prior position.

The car did this for a month or maybe 6 weeks unchanged. Then in just the last week or so, the car has started to become sluggish when climbing hills, and the weirdest part is last but not least. While driving along at a steady speed, on level ground, the car feels as though you slammed your foot to the floor and then let off the gas, then again slammed your foot to the floor and then off again. Sometimes it does it twice, sometimes three times. A quick blip of the throttle and the car will run normal again, aside from the slight surging problem.

The car has not thrown any codes. Although it always seems to take a month of running like shit before it will finally throw a code.

As I said the car runs normal. Starts cold fine, high idles cold fine, idle drops back as it warms up fine, starts and idles smooth when warm. Runs fine under WOT, no bucking or skipping all the way to redline.


:sigh: :smt026 :smt026 :smt026

[Huffer]

Check your Throttle Position Sensor...

[chuckthefuk]

What ECU & Harness are you running? 96' or 99'?

You could have a bad throttle cable.. when they start to fail they get sticky or seize temporarily.. This could be the bucking your experiencing. 5MT subaru in general have a bucking issue from factory at low speeds....

-Chuck

[green97gt]

Both O2 sensors are wideband. Front O2 has been changed with OEM replacment

oh yeah?

[ajfsgrl08]

I thought about changing the tps, but have not had a chance to test it, the car has not thrown a code for it, and I don't really want to throw either $130 or $ 260 (2 different ones availible from Subaru) at the car in hopes that this is the problem.

The car is slowly getting worse with the surging. It is to the point now where it is doing it about 75% of the time when driving. It is now doing it when climbing hills as well as on level ground.
About the only times that it doesn't do this is rolling down a hill or when the engine is not up to normal operating temp.

When the surging first started, if felt just like the A/C compressor was kicking in and out. Now it is about twice as bad.



The ECU and harness is the original ECU and harness from the '99.

[Huffer]

Clean the TPS.

And your OEM O2 sensors are narrowband, not wideband.

[ouch1011]

Don't the phase 2 engines use a wideband front O2?

Test the TPS before throwing a new one on. Also, if the car has EGR, try unplugging the vacuum line from the EGR valve, plugging it and going for a drive, see if it changes the problem at all.

[ajfsgrl08]

Actually I thought at first that the car used narrowband O2 sensors. That is until I had to replace the front one and remove the rear one from the pipe when I redid the exhaust. I gave Subaru a call to get the new one and at first they wanted to tell me that the car used 3 wire sensors front and rear. I had both of the sensors in my hand and when I gave the part numbers to the parts guy he was very confused. He checked the computer and sure enough, both front and rear are wideband. He said he has never seen this on anything older than an '01 (not that there is that much difference between a '99 and an '01).

As I said in my original post the car is a very odd setup. Verymuch a mongrel. Inpart dure to be (engine wise) and inpart due to subaru (the rest of the car).

I had thought about unplugging the EGR, just haven't tried it yet. Haven't had much free time in the last few weeks. I was mainly looking for peoples opinions, just to add to my own so I have a sort of checklist to go down through when I finally get to testing some of this stuff.

[ajfsgrl08]

Well, the haynes manual is useless.

This is a stupid question, but where is the EGR valve and solenoid located on an EJ22? A picture would be great.

I looked for a conventional looking EGR valve and could not find one.

[Lachrymologist]

https://sl-i.net/FORUM/images/imported/2010/01/IMG_36051-1.jpg
It should be under the transducer circled in the above picture.

What you said about the sketchy feeling in the gas pedal and sluggish hill climbing... Sounds exactly like the symptoms my car experiences when it throws CEL P0325, knock sensor circuit. Maybe check to ensure your knock sensor is positioned correctly (sensor terminal 45-60* relative to the rear of the engine bay) and still in good shape.

[ajfsgrl08]

Well I figured out the surging problem, finally!

Upon smelling hot brakes a couple of times, I replaced a sticking front caliper and the surging has dissapeared completly.

Upon thinking about the situation, the only explanation that I can come up with is that being all wheel drive, the sticking caliper was causing a pressure differential in the driveline between the front half and the rear half, and the surging was the center differential slipping to releave the pressure. :shrug: Maybe I'm wrong on this one, but it makes sence. Any thoughts?

[ajfsgrl08]

I retract my previous post. :evil: :smt011 :smt021 :smt017

The majority of the surging is gone. The surging is verymuch deminished vs before the caliper change. Only a slight surging persists, about the same as the A/C compressor kicking on and off. I can only get the car to surge now while holding speed between 58-60 mph on level road. After a drive of more than an hour and paying close attention to the car, those were the only conditions where I could get the car to surge.

Damn!!!!!!!!!!!! :smt017 :smt017 :smt017 :smt013 :smt013 :smt013

[silver_s13]

Wideband O2 sensors have 5 wires, not 3. You have nothing more than a heated narrowband O2 sensor if it only has three. Well, that and an idiot parts guy at your dealership.

[ajfsgrl08]

Wideband O2 sensors have 5 wires, not 3. You have nothing more than a heated narrowband O2 sensor if it only has three. Well, that and an idiot parts guy at your dealership.


At what point did I say that the car uses 3 wire sensors? If you reread my previous posts you will see that the car does infact have wideband front and rear sensors.
The car also does not have an EGR. I could never find one, and upon having my local subaru parts guru look up the specs with the vin, the car indeed does not have one.


Well, it has been awhile, and the car is still surging. Since my last posts I have changed the filler neck/cap and check valve that is on it (car kicked a p0440, code gone once filler neck etc were changed). Changed front wheel bearings and got car lined up. Also changed the center diff.
Immediately after changing the filler neck/cap/valve, the surging got considerably worse. Not in intensity, but in frequency. It surges when holding even on the throttle anywhere above 45-50 mph. Gas tank doesn't hold a vacuum. Or atleast something with the purge system isn't alowing a vacuum to be held in the tank.

No codes. No sticking brakes.

Thoughts?

IAC?
MAP?
TPS?
Purge control solenoid?

I have monitored the car while driving and surging with ROMRaider and everthing seems to be working fine and within specs. :smt021

[Garrison]

My bet would be the tps. I had very similar problems before I replaced mine. Also, if you're considering going ebay tps sensor, don't. I went that route and the spring tension of the ebay sensor was vastly different and I had to tighten the spring tension manually.

Good luck with it.

[r3v_v3ng3]

:smt017 Try checking the throttle cable