2001 S40.
· Here are the symptoms:
o Error code P0026
o Rough idle for first minute after starting when engine is cold.
o After leaving the highway/freeway and coming to complete stop, car will severely hesitate when attempting to accelerate.
o Overall, car runs sluggish.
· Troubleshooting so far:
o Replaced upper O2 sensor. No change in performance or error code.
o Unplugged battery, allow computer to resets. No change…
o Replaced fuel filter about a year ago, assuming not an issue.
o Replaced spark plugs about a year ago, pulled again recently, look fine.
o Pulled MAF, looked very clean. Still cleaned with MAF spray. No change in performance. Unplugged MAF wire while car running, died instantly. Tells me MAF working.
o No “sucking” noise that would indicate a PCV Trap problem.
o Used carb cleaner spray on running engine to attempt to find vacuum leaks. None found other that one listed below.
o Found large air intake hose to the turbo loose. Tightened up. Car ran very well for a day, then went back to previous symptoms.
· I've been attempting to correct this problem now for a couple months. There seems to be an endless amount of advice out there - most of it requires replacing expensive parts. Before I dump any more money into this problem I would like to have a better idea of what is going on.

 

Remember, free advice is worth exactly what you paid for it...

I did a google search on that code and got Intake Valve Control Solenoid Circuit. Now that sounds good except the 2001 does not have VVT on the intake cam, only the exhaust cam. Other hits talk about low voltage causing this code to pop up. Overall, it's very hard what to make of it. What you don't want to do is start replacing parts without diagnosing it more.

I found your description interesting on the intake pipe being loose. After tightening it ran very well for a day? Could it be you stopped a leak after the MAF? Could you have moved something like a battery ground that worked it's way loose after a day? Did the check engine light go out when it ran well? Have you cleared the codes with a code reader, not just disconnect the battery?

 

Don't mess around with gremlin's to long. f you try a few things and can't figure it out, pay a pro to check it. Try to understand that some of their guides tell them to throw parts at it as well. Doesn't sound like you've spent ANY money on the problem yet but that air valve may be a consideration. Sounds like an air problem to me.

 

Hudini,
what other grounds (other than battery) could be worked loose? Is there something else I should be looking for?

I thought I had the problem solved after tighting the air intake hose to the turbo. The car ran better than ever, it would jump when I barely touched the gas!. But after a day or two it returned to running sluggish. I did clear the code with a reader. After a week the error came back. I'm baffled with this one.

rspi,
Most of my research has pointed to the Mass Air Flow being the focus. It seems to solve the problems sometimes. I have read posts from others expressing frustration at buying a ~$185 MAF and it not solving the problem. I just want to make sure I've exhausted all other free fixes before I begin dumping my hard earned money into the car.

Thanks for your responses. Please let me know if you can come up with any other suggestions.