91L Festi has rough Idle

[ionfuel]

My 91L cold starts starts fine, runs good, averages 40MPG. Has 199k miles.

After driving for a while and come to a stop light/intersection, etc. the warm idle is a bit rough.

The plugs have less that 30k. Anyone have thoughts on what I need to check/look for to get the warm idle running smooth again?

I am not an expert mechanic, so any suggestions would be appreciated.

Thanks in advance.

Kevin

[m715]

The fuel we have available isn't helping, and the mileage is likely catching up with you too. Make sure you keep the oil changed every 3,000 miles due to the blowby you are likely starting to get. It really fouls the oil quickly and bogs the engine down if you don't. The other thing that is an easy and free fix, if the idle is *just slightly* too low with a warm engine is to bump the idle up just a little by removing the black rubber stopper on top of the throttle body and adjust the idle bleed screw inside the opening with the engine warmed up.

HTH

Michael

[ionfuel]

Thanks for the tip. What are your (or anyone's) thoughts on using synthetic oil (i.e. Amzoil)?

[FestYboy]

use it, it's more stable than dino oil and maintains its viscosity through a larger temp range.

[ionfuel]

Turned out I had a slightly bent intake valve and a burnt exhaust valve; replaced valves, head was machined, new plugs...man it purrrs like a kitten!

And to think I was getting close to 38MPG before; can't wait to post new MPG results using the fuel reformulator.

[FestYboy]

sweet!

[ionfuel]

Also forgot to mention that the work was done by the family mechanic/garage. Anyway he told he at the onset what he thought it was; and he was right (blowby/2 bad valves). He hoped that the pistons and rings would not need replaced. I was surprised (as I think he was) when I asked him about the condition of the heads; he said they looked like new! At 200k!