Howdy,
This forum help me a bunch when I needed a shock fix a few years ago (installed air-shocks thanks to someones recommendation) and once again, I'm looking for a little help. In short, the idle will drop and the engine cuts out. This happens primarily when the engine is cold and I shift from 2nd to neutral and coast to a stop. I also notice, primarily in 2nd when driving slowly, the car runs with a wicked shudder basically rocking forward until the RPMs go up. I had a drop in gas milage from the 38-40 mpg that I usually get to 32 mpg. This seems to have gotten better since I've tried addressing the issue. Any ideas?

Here is the background. I left the car sit for 2 months while I was in China. I came back and noticeed a massive rat/mouse nest in the cabin air filter and engine air box. I cleaned those out as well as I could and still had these issues but had to drive from Wisconsin to Utah. On the drive I ran some fuel injector cleaner. There were no apparent issues driving 70mph and gas milage improved to 36 mpg or so but once I was back in Utah and drove the car when it was cold, the same idle issue. Research suggested coil packs. I removed them all and they look fine - none of them are obviously burnt out - not that I know exactly what I'd see if they were. I put some dieletric grease on them and plugged them back in. I drove another 500 miles at highway speeds without issue only to have the same idle issue this morning when I fired up the car and drove it while cold.

Idea? Maybe something blocking an air flow sensor? I don't know where that is, I'm thinking that might be the next thing to check out. What else should I consider? I took it to a garage and they checked for engine codes but nothing came up. Like I said, the car generally runs fine when warm. Also, when the idle starts dropping out, if I try to rev up the engine, it doesn't respond, the idle just plummets and the engine cuts out. It makes me think the rats clogged up the air intake and the sensor is preventing the fuel. Any idea will be appreciated!

Thanks for the time and help!

 

Some more info that may be useful: 2008 Manual with 130000 miles. I change the spark plugs, coolant and brake fluid 20000 miles ago, but other than that, I haven't really touched anything.

 

The coil pack life is 80 to 120 K miles average. IMHO They are like plugs they are a maintenance item on this car and there is no real sign of failure. You might get a cracked or corroded one once in a while that makes the issues worse..

I strongly believe its a long term heat related issue since they sit about 8" from the exhaust system behind the intake.. So if your all highway miles the airflow through the engine bay helps keep them cooler than sitting in traffic. (totally my wild theory I have NO proof)

At 130K you should have recently done Plugs, Coil Packs, Valve adjust if you don't do your own work make the mechanic scratch the labor for the coil packs and plugs because they have to pull them to do the valve adjust any-way.

 

All the Coil Pack topics recommend a valve lash adjustment for warm-up issues.

Due to the rats-nest I would also clean the throttle body and butterfly, and do the ILP (Idle Learn Procedure)

PS: I left our plugs in, the two times I adjusted the valves. Keeps debris out!

 

Question:
what happens to the idle if you rev up the car in neutral to 3000 rpm then release the throttle??
(The engine must be warm about 70 to 80 degrees C)
Does idle falls to less than 500 rpm, then goes back to normal within second or so??? (~700 rpm)

 

Doctor J - The idle usually does exactly what you described when the engine is warm - in neutral when I push it to 3000 rpm it drops low then recovers at 700 or so. When the engine is cold, however, and I shift to neutral and notice the idle dropping and I give it gas, the idle just drops out and the engine cuts.

Thanks for all the advice, I'm not knowledgeable enough to adjust the valves, so I'll have to take it to a mechanic.

 

Thanks! This may sound more like needed valve adjustment ("tight" exhaust valves cause larger valve overlap)
Please have this checked and post the results!