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after changing the head gasket, car shakes at certain RPM

2923 Views 5 Replies 4 Participants Last post by  Berserker
Hi, before i did the head gasket i accidentally bent intake valves on cylinder 4. I took off the head, brought it too a head machinist he changed the valves for me, and all of the valve stem seals, checked the cylinder 4 for leaks. I put on the head, fired up the car it was running nicelly except for the ticking, but it stopped after some time, because that was one of the hydraulic lifters. Drove the car out of the garage everything was nice. Put it into first gave it a little gas everythings good, a little more gas and starts shaking, and no power at all, let the gas pedal just a little bit and you can feel power coming back, and then if more gas starts shaking again, and a very bad smell of catalytic converter. Worst shaking happens up until 3-3.5kRPM when driving. When it idles, sometimes the RPM drop a little bit starts shaking, and then corrects itself and keeps doing that for sometime, until it runs nice again. If i start to rev it a little bit, it revs not smoothly 1-2kRPM, and then its like suppose too. Anyone what it can be? To me it looks like its something with air or fuel.
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Bad POS channel or coil. Pull the injector connectors one by one at idle, the one that doesn't make the engine stumble is your bad cylinder with weak or no spark.
Sorry i didnt mention what car it was, its a URS6, no check engine lights. The idle is fine. If i touch the gas pedal just a little bit to rev it its fine, press it half way and its start to stumble until a little bit above 1kRPM, and then you can rev how you want it, no shaking or anything. Could it be cheap spark plugs from autozone? or something? i unplugged injectors one by one each of them made the engine stumble.
You used cheap spark plugs from Autozone? Do change them...
put bosch spark plugs, same thing now it was kinda idling bad, disconnected each injectors and it seems to me that cylinder 1 injector, doesnt react as much as the others do.
Make SURE that you've hooked up and tightened the clamps on all the boost hoses.

I had a similar problem with the first head rebuild/replacment I did on a 200q20v. It would start and idle smoothly/rev fine, but any time I tried to drive it, the engine would torque a little bit, the turbo outlet hose would separate from the turbo, and the engine would stumble/die.

You might have a similar problem with a loose clamp allowing air out between the MAF and the IM.

Otherwise, if you've got a stumble at idle, start checking for a misfire. The UrS FAQ on quattroworld is really pretty good:" onclick=";return false;

Ignition system info:" onclick=";return false;

Coil diagnosis procedure:" onclick=";return false;
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