Slight miss at idle, poor MPG, sooty exhaust pipe, No codes. 250K

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Tozan

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The old girl is getting ... old 250k miles... lol

This has started happening in the last month...
I have a slight miss at idle when cold, it goes away after 30 seconds to a minute and does not affect acceleration or steady throttle. It goes away before I start driving down the road. I am not concerned with it but, include it in case it might be relevant. Runs smooth at cruising speeds too.

Power does seem a little soft sometime.. I am guessing this is related to running rich.

My average MPG has dropped down by around 3 MPG normally it is consistently around 16 and lately is around 12.5 to 13 MPG I live outside of town so my driving is very constant unless overlanding, hunting or out shooting.

The exhaust pipe is very sooty.

There are No codes triggered..

Some time the gas cap seems a little loose compared to the original that I lost a year ago. Can that be related if it gets loose and leaks?


OK, Some history.
It had been running rough before so I replaced plugs and wires and cleaned the K&N air filter a few thousand miles ago that roughness turned out to be a torque converter and it has run fine until recently.

I use injector / fuel system cleaner every 10 or 15k. V V T was turned off last year. I returned it back to the stock tune keeping the VVT off with no change...

I need to do a complete compression check and look at plugs I also need to rebuild the front end... But, it is hunting season right now so this will have to wait a couple weeks... lol
 
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Tozan

Tozan

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That's not my observation here for the past 6 yrs.
Well I wont debate the issue of VVT... I turned it off 50,000 miles ago so I don't think it is related to my problem..

If you have any ideas or things to look for relating to my problem that would be great...
 

j91z28d1

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sounds like a case of E% drifting high when running normal fuel.
 

Fless

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The other thing to check is individual cylinder misfires with a scanner that can show them by cylinder. Might give us a clue.

As @j91z28d1 noted, if it's a Flex Fuel system then check the alcohol percentage with a scanner, to see if it matches or is close to the fuel you're using.
 

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