[GRLPWR]

Similar symptoms - for me it ended up being decouplers missing from injectors.

[badsector]

Originally Posted by GRLPWR

Similar symptoms - for me it ended up being decouplers missing from injectors.

What are those?

[DJtoad]

Originally Posted by GRLPWR

Similar symptoms - for me it ended up being decouplers missing from injectors.

I take it the injectors had been replaced earlier? I would never take the car back to whomever did that work. Hopefully the tech who discovered the issue also checked to be sure the injectors had been properly coded because there's a good chance they weren't.

[GRLPWR]

Originally Posted by badsector

What are those?

If I can explain this correctly, they're like o'rings that help absorb vibration. Since they were missing, it caused a vibration, which then caused a tab to break from another part (can't remember the part name), therefore causing the injector to turn/swivel, causing misfires/limp mode/shudders. Ok, something like that.

Originally Posted by DJtoad

I take it the injectors were replaced earlier?

Yes, a few months prior to me purchasing the car. After numerous visits to several shops and then to a dealership, they finally diagnosed the problem. I was able to track it down to work done by another dealership. I was also able to get them to reimburse me of the deductible I had to pay. And, yes, they were coded (both times). Guess sometimes these things (decoupling element) get stuck on the injector and a careless or overworked tech will overlook them.

[Blzn335]

I have the same symptoms. Mine is at the dealer now. Replaced spark plugs, injectors, and decouples. Still doing not fixed. They've had her for a few days. Hoping theyll do intake cleaning. Will post results

[badsector]

One more question.

How exactly does the carbon build up on the intake valves cause this? Just guessing if the valve does not open all the way the fuel/air mixture causes misfires?

[superjay]

it does not close all the way, and the aperture is smaller. Also, the injector gets caked in carbon so you get random spray patterns, and less fuel in the cylinder. Also, the valves become heavier so they don't move as quickly as they should.

[badsector]

Originally Posted by superjay

it does not close all the way, and the aperture is smaller. Also, the injector gets caked in carbon so you get random spray patterns, and less fuel in the cylinder. Also, the valves become heavier so they don't move as quickly as they should.

Ah, I see. Thanks.

Yea I thought the injector cleaner worked but it's still bucking, although not as bad. Asked the dealership and it's going to cost me $550+tax to get it walnut shell blasted.

[Blzn335]

Just got my car back from dealer. After replacing plugs, coils, decouplers, injectors, lpfp, and hpfp, none of it fixed the problem. They finally did the walnut blasting. Runs like a champ now. Smooth hard acceleration and it even really smoothed out the idle too.

[r3dbimmer89]

To bring this thread back to life I had somewhat similar symptoms except mine werent as extreme as the OP. Took it in last week and it was a faulty fuel injector along with a contaminated spark plug. All covered under the California Emssions Warranty so I didnt have to pay the CPO deductible. Car is running like new again...much smoother idle, start ups, and take off. I just knew the carbon build up was the culprit but I guess not...