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Discussion Starter · #1 ·
2001 S40.

Here are the symptoms:

Error code P0026
Rough idle for first minute after starting when engine is cold.
After leaving the highway/freeway and coming to complete stop, car will severely hesitate when attempting to accelerate.
Overall, car runs sluggish.

Troubleshooting so far:

Replaced upper O2 sensor. No change in performance or error code.
Unplugged battery, allow computer to resets. No change…
Replaced fuel filter about a year ago, assuming not an issue.
Replaced spark plugs about a year ago, pulled again recently, look fine.
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.
No “sucking” noise that would indicate a PCV Trap problem.
Used carb cleaner spray on running engine to attempt to find vacuum leaks. None found other that one listed below.
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.
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