bucking below 2000 rpms under load

[subarusaver]

Hello all,

 

My 93 Legacy wagon 5 speed ,237000 miles 2.2 ej22 newly re sealed by myself...Complete re seal..heads machined,all gaskets...no leaks ..

Approx 3 months ago.Just Today it started jerking in fifth gear....I did notice an odd sound when it was real cold here (10 degrees or so)..sounded like a fan blade rubbing plastic just under the hood in front of the steering wheel (or maybe like a piece of plastic rubbing the tire)..it did not last long enough to chase....or find..Now the problem is it misses ONLY under a load and ONLY a SLIGHT load......it idles fine......runs like a race car!!  no problems to 6500 rpms!!!  but when I lug it or put it in high gear at LOW engine speed(2000 rpms),it misses terrible...and jerks...

 

No Engine codes,

 

Sprayed everything with brake clean to check for vacuum leaks

???????

 

Any ideas?

 

Thank you for any help

[sparkyboy]

A faulty knock sensor will cause those symptoms. They often fail after a long time

My 92 leggo did the exact same thing and my knock sensor had a huge crack

[subarusaver]

THANK YOU!!!!

Consider this one FIXED!!  The car runs ALOT better!!! I did not realize just what the knock sensor does,I do now and the car really does run like a new car!!

The old one was and had been cracked ..THANK YOU!!!

[sparkyboy]

Hooray!

[subarusaver]

NOT SO FAST!!!  

 

Okay, it worked great the day I installed it, NOW it seems to be having the same(not as severe) problems coming back..If I try fifth or fourth gear at 1200 rpms, it starts the jerking again......I removed the new sensor, cleaned and wire brushed the block, sprayed it clean with brake clean,put it back annnndd .... it didnt help....

 

 

NOW WHAT??? maybe cam or crank sensor???

[sparkyboy]

Balls! I guess never celebrate too early huh?

Sorry, i should have mentioned that the knock sensor has to be installed in a certain orientation and has to drop down onto the engine block...let me look at mine and I'll tell you how mine looks. If you look close it's not perfectly flat iirc.

Beyond that, i don't suspect the cam or crank sensor, those control spark and fuel injectors so you would know if one of those are bad because the car won't start.

1200 rpms is pretty low where the engine isn't making much power and that bucking could just be the drivetrain.

However she ran great yesterday? Weird...

Has the idle changed at all?

The idle air control valve might be starting to get gunked up if this problem comes and goes depending on engine temp.

She could just need a tune up at this point

Edited January 29, 2018 by sparkyboy

[subarusaver]

When I did the reseal(in November), I pretty much polished everything inside,lapped the valves, cleaned  the intake and exhaust ports,cleaned the intake ,

new spark plugs(double checked the gaps .040 I think)..I did not change the fuel filter or the air filter(It's fairly new)..It seems like the knock sensor is alllllmost working perfectly but failing just a bit....It ran fine before this latest incident..and recently,the idle DID catch my attention before the knock sensor replacement...It just had an odd lope or something..BUT the idle is probly between 500-700 rpms....

[sparkyboy]

It might be worth it to remove the idle air control valve and spray everything with carb or brake cleaner while opening and closing the plastic valve with a screwdriver or your finger. Just be careful with the gasket or have a new one handy. 

Coolant flows through that valve so they can get pretty gunky after a while

Typically it will make the idle jump from 750 rpm to about 1200, then settle back down repeatedly until the coolant warms up enough for that plastic valve to free up a bit.

I imagine that if were really stuck, it would let in too much air and cause some bucking at lower rpm  

I understand that some guys can use sea foam to clean the iacv without removing it from the intake manifold, but I have never tried that approach.

[subarusaver]

Update.....

 

Since it has been raining for the past two weeks here ,I decided to just drive the car and pay attention..

The issue seems to be gradually becoming more prominent...or regular..

 

Definitely noticed at first start up,(for at least two minutes) it will NOT stumble or sputter at all.....

 

As soon as the engine gets a hint of warming up(just when the temp gauge starts to move)  the problem is present.

 

After it warms up a little,very little, I notice a definite putt putt putt rhythm when idling , and if  I pat the gas , I can feel it shake .Once idled up, its smooth

 

until under a load at lower idle...

Also I have been able to get it to flutter and cut out under heavy acceleration..

The check engine light did come on once and went off quickly...

 

Any more Ideas?

 

Thanks!!!

Edited February 17, 2018 by subarusaver

[1 Lucky Texan]

it seems we're always suggesting Engine Temp Sensor, could be I suppose, especially if the car smells or seems to be running rich.

 

The sensor might be keeping the ECU incorrectly informed that the engine is still cold when it isn't and too much fuel is being injected.

 

 

Live data could 'prove' that theory if you don't want to throw another part at it.

[heartless]

if you have had the CEL come on, go get codes checked - it will have stored something (even if it is not currently on, there should be something)

That could point you toward whatever the culprit is...

 

beyond that - don't lug the engine? shift to a lower gear...

[sparkyboy]

Would a faulty fuel pressure regulator or throttle position sensor cause an issue such as this?

I know you said you cleaned everything, so i assume that the throttle body is clean.

Maybe that slight miss at idle is an injector clogged or something, a faulty iacv will cause a surging like idle, but typically won't make the car idle lower than 750 or 800 rpm.

[subarusaver]

ANOTHER UPDATE: Today,   I plugged the black test connectors together to get the stored codes and got this:

 

31 Throttle sensor

32 Oxygen sensor

24 Air control valve.....I am assuming  'Idle Air Control Valve' The notes on Legacy Central say this about the IACV ;

 "Prevents abnormal engine speed using "fuel cut" in relation to
engine speed, vehicle speed, and throttle sensor position".         Sounds enough like my issue.

 

according to Legacy Central ode List here http://legacycentral.org/library/literature/codes.htm

 

 I do not have a lit up check engine light, so I will follow the procedure in the Legacy central link and see what that turns up...So Far I'm leaning to Sparkyboy's idea about it being the IACV.....It seems to be going that way..

Edited February 18, 2018 by subarusaver

[sparkyboy]

If I recall, when my iacv needed cleaning there was no check engine light

Anyway, be sure to let us know the results!

[Bushwick]

I was gonna say O2 sensor before seeing your codes. Once an O2 is failing, it can cause it to run wonky. If oem is still in there, it did it's job until now. Would consider replacing that, reset codes, and see if anything returns and go from there. Consider getting a higher quality O2 to avoid possible headaches.

[subarusaver]

UPDATE 2/23/18  

 

After filling up with 92 octane ( my daughter told me she had put low octane in it last fill up) I put a bottle of Lucas octane boost/not street legal..injector cleaner in it .

Noticed positive results within the first 50 miles...The problem is still present.. not as severe but still very much there...Tonight, I pulled the Idle air control valve,marked it well,took the top off and cleaned it real good(it was pretty dirty)..Put it back in place and at first the idle was staying around 1500 rpms and just as before, it performs perfect until it gets a HINT that the engine is beginning to warm up,then it has the slight miss at idle when I pat the gas pedal, and stumbles when in a strain  at lower idle (still seems ok at full throttle with an exception of some fluttering just not consistent)...I really hate to keep changing parts,but the check engine light is not activated, since I did find STORED codes in the ecm ,I unhooked the battery to wipe them off...I did unhook the NEW knock sensor while it was running and ...it acts the same...Would the o2 sensor cause the putt putt idle?

 

Thanks for any input!!

Edited February 24, 2018 by subarusaver

[subarusaver]

Question...When I did the re seal, I changed all the timing components...Before this issue started, there was a weird sound from the engine compartment.

The sound was like an inner fender rubbing against the drivers front tire it only happened a few times,and went away too fast to find.It did seem to be keeping up with engine speed...Is it possible the belt or cam jumped a tooth? and would this be consistent with with my issue?

[rocketman]

Mine jumped a couple of teeth,so I put a belt gaurd on it,never happend again,mostly for standerd trans cars.

[GeneralDisorder]

Check the TSP for dead spots. Ideally with a graphing volt meter or oscilloscope. I've seen the early TPS units with high mileage get dead spots where they sit during part throttle cruise. And you have a code for it.....

 

GD 

[subarusaver]

I THINK I FINALLY FOUND THE ISSUE!!!!!!! After getting the crap knocked
out of me two or three times, I FINALLY thought to check the coil. (I
had laid my hand on it to rest my arm while checking the idle air
control valve plug)......After reading lots of info on checking coils
and diagnosing coil issues, I found an old forgotten technique, go out
at night, raise the hood , crank it up, look for sparks....LOTS OF
SLIGHT SPARKS around the front side of the coil, especially as it warmed
up.One of the plug wires lit up when I sped the engine up as it was
missing.....Pretty sure this is the issue....so simple, I overlooked
it...I will close this post with final results either way..off to Rock
auto for a coil and some ngk wires!!! Thanks everyone for every
suggestion!!!!

[heartless]

my old 95 had a bad coil... but it was throwing misfire codes (it was also an OBDII system, so..)

 

would be fine in dry weather, but any hint of dampness would cause it to act up.

Once I found the sparking coil, I swapped it out with a used one from my old retired 90 Legacy and it ran great.

[Bushwick]

Glad you found it! Be sure to run the car a good 30 minutes or so at highway speeds or similar, to allow the O2, cats, etc. to get rid of any junk that might be in/on them from the weak spark (guessing it was running rich? to some degree) and IF it runs a little rough at first, it should hopefully clear up after the drive. Hopefully you don't get cat codes down the line, or raw exhaust fumes like a cat-less engine out the tail pipe when warm, which points to cat breakage.

Edited May 20, 2018 by Bushwick

[turboguzzi]

not to hijack, but out of curiosity...

 

i have an early leg SW like you. what device do you use to get the codes?

 

Tnxs

 

Y

[heartless]

not to hijack, but out of curiosity...

 

i have an early leg SW like you. what device do you use to get the codes?

 

Tnxs

 

Y

 

on the 90-94s there are a pair of single wire test connectors up under the dash - usually to the left of the steering column - sometimes still taped up in the harness so not easily seen. there is a pair of green ones, and a pair of black ones. each pair has a specific function.

I used to know what did what, but it has been a while... a search should turn up the info, however

[subarusaver]

IT'S FIXED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :bouncy: :bouncy: :bouncy: :clap: :clap: :clap: :banana: :banana: :banana:!!! The new coil and plug wires did the trick!! purrs like a kitten til you step on its tail,then it runs like a wildcat!!!

 

Thanks all for all the suggestions and help!!