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New fuel filter solves rough cold idle and hesitaion

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Hi everyone.

I just wanted to share this in case anyone else is having this issue.

Background, stock 2004 turbo tip with 80,000km.

I've been chasing really rough cold idle (engine surges and almost stalls) and "jerky" acceleration on this car since I bought it (at about 50,000km). Sometimes it would also stall when coming to a stop (it's an auto so it's a PITA when it happens).

I cleaned the MAF, and checked for boost/induction leaks. Everything was good there. No errors in durametric.

I also made sure the battery was fully charged (interestingly a marginal improvement, but nothing concrete).

As part of the 80,000 service, I replaced the fuel filter, and bingo, instant improvement, perfect cold idle and nice smooth power delivery right up the red line. I've never had the car driving so nicely!

Fuel quality in Australia is renowned for it's poor quality, and 80,000km (64K miles?) is the recommended replacement interval, but I'll definitely be replacing it more often. I recon every 40,000km would be more like it here.

As a side note I've never replaced the fuel filter before, but it was much easier that I expected, took about 30 minutes in total, the hardest part was getting the plastic quick connector off the input line. The best tutorial I found was at ECStuning. I bought a Mahle branded filter, it's a perfect fit.

I have a short video of the rough idle, and I'll try to include it later.




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Good point, unfortunately I already tossed the old filter and it was garbage/recycle day the next day, so it's gone :-(

It was the only thing I did to the car on that day though.

I should clarify, I'd done the oil and other bits a the previous week as I'd ordered the filter separately and it took longer to arrive, so it was done on a separate day (I keep a "stock" of oil filers/crush rings etc at home).

I'd done the battery charge test a few weeks earlier, and the boost leak test about a month ago.

I did the spark plugs/drive belt today.

I still think it's a "Fair" bet that the filter was contributing to the problem, but unfortunately I can't absolutely confirm it now....

(I should know better, I used to be a scientist!).



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