Dieseling

My 1990 Jeep YJ, 258, has started dieseling after shut off. Does it about one half the time. I think I have the idle and sol-vac solenoid set OK, but maybe not. I tried disconnecting the vacuum and power to the solvac solenoid figuring that maybe the carb was being held open a bit by those, but the problem still occurs. The car does not Ping. Any thoughts. Aloha Joe Maui HI

Reply to
Joe and Joann
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Reply to
L.W.( ßill ) Hughes III

Aloha Bill Thanks for the input. It appears that on my carb, based on what I understand to be the instructions for setting the idle, the solenoid can only increase the idle in two stages above the curb idle. The first increase is caused by a the electrical part of the solenoid, the second by a vacuum signal. It doesn't seem that this sol-vac device can ever drop the idle below curb idle. Am I thinking about this incorrectly?

Also, The problem occurs when engine is hot so even if the choke pull off is bad, the choke shoud be well off by then. (Choke does work.)

Will look into the carb kit. Any other ideas?

L.W.(ßill) Hughes III wrote:

Reply to
Joe and Joann

Do you have AC or an automatic? If so you need the solenoid, otherwise it has no function except to get in the way...

The idle should be 500 rpm with the solenoid unplugged and then you set the solenoid for the 750 idle. If you have an automatic, it should be in drive while adjusting.

Then you could just be carboned up from too many short drives with low octane.... Just FYI, the owners manual for the 258 with the BBD states high octane might be needed to stop the ping or load rattle if the engine is run hard, hot and loaded. The computer uses a knock sensor for low octane gas.

You can decarbon the engine. I was taught to use a pint of ATF to do this, others swear a pint of water works also. I know first hand that the ATF treatment will make the inside of the combustion chamber look like new.

I get the engine warmed up and remove the air filter. While keeping the rpm up with my hand on the throttle linkage, I slowly pour the ATF down the carb keeping it revving enough not to stall. Once the ATF is all in, I shut off the engine for a few minutes, then start it up and go.

Warning! This will make a thick white cloud of smoke. Neighbors are likely to call the fire dept. if they don't know what's up.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Aloha Mike Thanks. No A/C and manual transmission. The tag under the hood says 750 for the lowest idle, however, I suspect that the 500 number you mentioned would might help the dieseling. . I am not sure how well it will idle at 500, but it idles fine at 750. Easy enough to try for sure.

If you use water instead of ATF, do you still turn off the engine when it is in? Any particular kind of ATF? Joe

Mike Roma> Do you have AC or an automatic? If so you need the solenoid, otherwise

Reply to
Joe and Joann

The 500 idle is for when there is no power or vacuum to the solenoid. When running, the solenoid holds the idle up.

The idle solenoid is there to jump the idle up when you put it in drive or when you turn on the AC. It has no other function. Some folks put a switch on the power to it and unhook the vacuum. They then use it as a switched fast idle.

Any type of ATF works, I always seem to have Dexron around. I would also shut it off after a water pour. It shocks the carbon, so the cool down might be part of it.

Mike

Joe and Joann wrote:

Reply to
Mike Romain

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