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  #1  
Old 09-08-2009, 09:26 PM
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Gamesy Gamesy is offline
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engine shudder and bogs

lately my car has been starting to do a misfire type boging whenever i try to slowly accelerate. for example if i'm going say 80KM/h and slowly accelerate the revs dont really go any higher for a bit on the pedal but then the car shudders and bogs
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  #2  
Old 09-09-2009, 09:27 PM
Mephis Mephis is offline
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Re: engine shudder and bogs

Had this problem too.

Cleaned the MAF, Tweaked the TPS adjustment, Ran some fuel injector cleaner, reset the computer a few times and now it seems to be mostly gone.
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  #3  
Old 09-10-2009, 12:12 AM
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Re: engine shudder and bogs

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Originally Posted by Mephis View Post
Had this problem too.

Cleaned the MAF, Tweaked the TPS adjustment, Ran some fuel injector cleaner, reset the computer a few times and now it seems to be mostly gone.
whats TPS? i think my one spark plug coil isnt seated properly or the wire is fkd
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Old 09-10-2009, 09:24 AM
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Re: engine shudder and bogs

Throttle Position Sensor. (TPS)

It can be adjusted to read proper voltage when closed, .5 volts, or something, I think. Shop manual probably has details.

If it is out of whack, and gives more voltage, the computer will be skewed to think the throttle blade isn't in the position it actually is in. usually thinking it is slightly open, when it is closed completely.
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Old 09-10-2009, 09:45 AM
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Re: engine shudder and bogs

hmm i'll have to look into that, first i'll try taking a look at my one spark plug coil to see if its fully seated, these problems only started happening after changing the plugs and my front diff oil. maybe when the battery was unplugged the ecu reset and fkd up
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Old 10-24-2009, 10:41 AM
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Re: engine shudder and bogs

Did you ever find the problem? My 94 started doing similar last week and I've been trying to determine the problem. It happened suddenly, just started vibrating quite a bit when I started it one day. I've recently replaced the plugs so I decided to take a look at them again. They all looked fine but after putting everything back together, one of the cylinders was not firing at all. I found a bad coil and replaced it, hoping it would also fix the original problem. It didn't so last night I did a long driving test to get more symptoms. When the car is cold, the idle goes to around 1500 and the vibration is very noticeable. Once the car warms some, the idle drops and the vibration is less noticeable until the car is put into drive, then it is bad again. I drove the car as normal until it was fully warmed up, now the idle is close to 600 rpm and smooth. If I touch the throttle, to pull the rpm up but not enough to take off, the vibration is there. Now that it is fully warmed up I opened it up a few times. Acceleration seemed just as good as always although I thought I noticed a few jerks on the way up to 80. I cruised at 65 for some time, letting the tranny get warm and the torque converter lock up. Once it did I slowly pressed the accelerator down to speed up, but not going so far that the torque converter would unlock. It bucked badly when I did that, definitely showing the signs of a bad misfire. Back to the house trying similar slow acceleration as well as stomping on it. Even at 45mph with the torque converter locked, I could get it to buck badly when accelerating slowly. Stopped and reseated the igniter connectors but no difference. Once back in the garage, I put it in park and ran the rpms up. The vibration seems noticeable at all rpms and I could discern a noticeable misfire if I hit the throttle quickly. No CEL and no codes. I could not hear any vacuum leaks but I have not removed the intake.

I'm going to do more tinkering today, check the fuel pressure and the MAF. If anyone has any suggestions I would love to hear them.
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Old 10-24-2009, 04:01 PM
oab_au oab_au is offline
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Re: engine shudder and bogs

You could check the air box where it connects to the throttle bodies. The rubber joiners may be tucked up at the bottom, causing a lean condition.,

Next I would check the rubber boots on the coil to spark plugs to see if there are any black track marks running down the sides of them. If there are you can scratch them out and spray with a silicone oil.

Harvey.
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  #8  
Old 10-24-2009, 08:25 PM
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Re: engine shudder and bogs

Thanks Harvey,

I went ahead and cleaned the throttle body today while I was checking the MAF. I verified that the air path is all in good shape and connected tightly. I didn't get to testing the fuel pressure today but I was thinking a lean condition as you mentioned. I did get the oscilloscope out and tested all the crank/cam sensors, all good. Tomorrow I am going to pull all the coils and inspect them, I'm kind of leaning that way.

Mark
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  #9  
Old 10-24-2009, 08:59 PM
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Re: engine shudder and bogs

Quote:
Originally Posted by oab_au View Post
You could check the air box where it connects to the throttle bodies. The rubber joiners may be tucked up at the bottom, causing a lean condition.,

Harvey.
Harvey, good point, a Subaru tech told me that he was baffled, until he finally figured that out. It is easy to get the lip tucked, the snorkle still goes right up. I've had it happen to me, so +1 on bringing that up, someone will be helped by that.
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  #10  
Old 10-26-2009, 04:32 PM
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Re: engine shudder and bogs

I havnt really had much time to drive aroud much but ever since i ran some Seafoam through my car i think its been fine, next time i go for a drive i'll test and see if it still bogs.
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