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98 OBS running rough 2.2 5sp


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Glad to see the USMB is Back!

 

98 2.2 Impreza 5 sp 262K with about 160K on the engine.

 

It's been running rough for a while, noticeable at idle, with more shaking the a smooth Subaru engine should have. Until the last few days, there have been no codes over the last 8 months I've noticed this.

 

The codes posted P0301 and P0303, miss fire on 1&3.

 

I've checked and done the following to get it running right.

- New NGK Plugs,

- Air Filter

- Swapped Plug wires

- Fuel System Cleaner

- Checked for vacuum leaks

 

None of these fixed the problem, although slight improvements were noticed. This has been a very slight problem until the last day or so.

 

With the codes showing, I pulled the plug wires one at a time, all produced a drop in RPM.

 

I pulled the injector plugs one at a time, #3 produced little or no change in idle. Ohm the injectors, all were 11.7 Ohms.

 

I had another coil, so I swapped them, no change.

 

I had a set of 2.5 injectors, so I swapped them, slight change still rough.

 

I can hear a Pop Pop in the exhaust.

 

I'm going to do a compression test and check the timing marks tonight.

 

What else am I missing?

 

Thanks, Larry

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i chased something similar a little while ago on my 96 Leg. EJ22 and i turned out the connectors for the fuel injectors were swapped so obviously it was injecting fuel at the wrong time....worth a quick check....as for the plugs and wires im assuming you you used OEM?....to check for the vacuum leaks did you do a vacuum test?...if not i would do a vaccum test and see what you get.....

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I'm not sure you're missing anything - be interesting to see if one side has slipped valve timing. You could try holding a small stip of paper to the tail pipe. If it tries to 'suck in' that could mean a valve is open when it shouldn't be. I dunno if that trick works if timing is off by just 1 or 2 teeth though.

 

Maybe there is a fuel pressure/delivery problem?

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When you say you "swapped plug wires".... what exactly did you do?

 

The EJ engines like new plug wires about annually. OEM or NGK are recommended.

 

1/3 use the same side of the coil (wasted spark ignition) so that vaguely points to an ignition failure - I would normally suspect the coil but you swapped that out.

 

GD

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I pretty much have it down to #3 not firing due to lean fuel. I thought I had it a few times when I did the following, but the problems comes back on #3 cylinder.

 

Cleaned all the Engine Connectors

Cleaned the MAF and then swapped in one I had (seem to help the most)

New Subaru Plug wires, no change

 

Pinch the fuel return line and the RPM increases some so I'm going to tee in a pressure gauge and change the filter. My Manual says 2.6 to 3.3 PSI for fuel Pressure is that correct?

 

Full system voltage at the Injector 14.2 Volts engine running. When I have the rough running at Idle pull the #3 injector plug has no effect on the RPM.

 

The plug is white as can be, lean. More after I test the fuel pressure.

Thanks for the ideas, Larry

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