Recently, when cruising in 3rd or 4th around 2500-3500 RPM my vac gauge needle floats back and forth about every 3 secondsin increments of 4Hg. It stops if I push the car or if I let off the gas completely.I've hadno CEL. Only otherproblem I'm having is boosting (gotta push the car harder then normal to get in positive boost). My idle is pretty steady, around700-750 RPM, and my vac readsa steady 21-22 at idle.I thought maybe the plugs could be causing the issue, so I replaced them, no go. I checked the resistance on the high tension leads, the readings were fine. I wasn't able to test the coil packs (probes weren't long enough) so thats still a possibility I guess. I'm going to check the purge solenoid valve when I get home. Wanted to see if anyone else has any ideas on what could be causing this issue?

 

Here are some pics of one of the spark plugs I pulled. From a distance it looked ok. Once I took macro shots I realized somethings f'ed up.Firstthing thats obvious is the specks. Second thing is the green coloration of the strap.I think I may alsosee some pitting on the electrode. Anyone notice anything else?

I don't think the specks are aluminum since I don't seem to see any shine under any light. Could that be from anti-seize compound seeping into the cylinder? And what's up with all that crud on the threads?

Anyone have any insight into what could have caused this? I haven't had any indications of overheating. My oil level hasn't dropped any over the past 3000 miles. Just for ****s I'm going to try and do a compression test this weekend.

Edit: will upload pics in a minute, they're too big.

 

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i think that the plugs look fine, just a little worn. always a good move to replace them though. i have lost tips in my motor that scored the cylinder walls and tilted valves. i would see if there is a leak in any of the intake lines around or after the intercooler. you could be losing a little air that is metered already by the MAF which would make you run a little rich after the air/fuel mixture hits the chamber. if this gets worse, it will cause the cars front end to dive as soon as the turbo boosts.

if you have to change the coil packs, i recommend getting packs off of a 1.8 L and going to a salvage yard and pulling a valve cover off of the same motor. it will all fit yours. this is a very small mod, but it will stabilize the voltage and make you idle smoother.

 

Looks like coil packs are fine and compression is fine. I'm starting to lean towards the EGR vavle sticking since it happens during low accell/cruising. So, my question is... does anyone know how to test the EGR for proper operation without removing it?Are there some wires I could tap to monitor voltage?

 

all that you need to do is put a brake bleeder on the vac line that controls it. start up the car and pull a suction on that line. when you can't pull anymore, the car should have died already. if it doesn't die, there is an EGR difficiency which you could probably remedy just by cleaning it.