CJ7 "missing" at highway speeds or under load - HELP!!

The cold air from a cracked exhaust manifold can easy warp an exhaust valve. A compression test with a little oil will find it:

But you're describing an ignition misfire, and I've cooked a set ofplugs in a quarter mile. You didn't say you replaced the ignition wires,which without the special pliers to pull them are easily damaged. God Bless America, Bill O|||||||Omailto: snipped-for-privacy@aol.com

How's your timing chain?

tw

it:

But you're describing an ignition misfire, and I've cooked a set of> plugs in a quarter mile. You didn't say you replaced the ignition wires,> which without the special pliers to pull them are easily damaged.> God Bless America, Bill O|||||||O> mailto: snipped-for-privacy@aol.comhttp://www.billhughes.com/>

Thanks for the advise on compression check - I'll give that a try; and I did replace the wires along with the plugs, I just forgot to mention.

-Shadow

Did you replace the plug wires? Spdloader

Good catch.

tw

As far as the timing chain is concerned - I have not a clue. Is this something I should check out?

Yes,when I replaced the plugs - forgot to mention ;)

Possibly you are running very lean. The plug condition can tell you a lot when you take them out. Under ideal circumstances, your plugs should be colored a light tan color. If they are perfectly white, and/or have little silver specks on them, your engine is running extremely lean.

This could be caused from low fuel pressure, low float level, or possibly something getting plugged up in the carb.

One other thing. If you haven't done it yet, you might want to look in to doing the Nutter Bypass. It will improve things very nicely.

Here is the how-to article:

Chris

I would replace the fuel filter, it is due.

I go through one or more a year when using my CJ off road. The dust and dirt collects under the cap and some goes in every time I add fuel.

I always carry a spare even.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > I have an 85 CJ7 that has developed a nasty habit of missing extremely

It's odd that while you were gone, a lot of the stuff that I knew you had experience with came up. I answered the ones I could but figured you would have some better input on some of them. I wasn't an epic substitute for you however, since I did not recommend that anyone check the ground strap at the back of the engine. Sorry. :-)

Chris

Mike Roma> I would replace the fuel filter, it is due.

Had fun out Jeeping, almost didn't come back.

And another gem for the OP, the air filter on the gas tank vent...

When that plugs up, he will get his symptoms. To test, open the gas cap when it happens and see if it is fixed right away. Mine even jumps rpm when the cap opens with a plugged filter.

The filter is $2.00 or so and fits in the bottom of the charcoal canister.

Mike

c wrote:

Thanks for all of the suggestions - I took it out this weekend without the gas cap on, but it still missed when going up a hill in

5th after it was warmed up. I read your response to another fellow's problem, and I feel I might have the fuel filter on upside down - could this be causing the problem? I also had my brother ride with me when I took it out, and he seemed to think it was a fuel issue, not a burnt valve as I thought. I have not pulled the plugs, but I can do that next weekend and see if it is showing signs of running lean. Thanks for all the help, and I welcome any more suggestions!!

-Tim

'Going up a hill in 5th'

OK, that can be a whole different animal.

You are trying to pull power in overdrive. Even with stock tires, this can cause issues with pinging.

First off, the fuel filter. Besides being upside down, they need to be changed every year or more often if you drive on dusty roads.

Second the 'miss'. Are you describing a timing knock or 'ping' that makes a rattling noise and bog under heavy load? Does it go away when you drop to top gear? (4th)

Even stock with the knock sensor working, the 82 to 86 CJ7 owners manual warns about this. The manual states when it misses under load, to run higher octane in it. If the higher octane still doesn't stop it, you are supposed to stop and lighten the load or slow down to lighten the load.

The owners manual also states 'not' to use any alcohol or ethanol mix at all in it. If it is an emergency, only use enough to get to real gas.

I have the computer put to sleep in my 86 CJ7 via the 'Nutter' bypass so I have no knock sensor to change the timing when it pings. Mine will 'not' pull power in any gear over 65 mph or over 3300 rpm if I use regular gas or gas full of ethanol. It will miss and bog and gets really bad gas mileage.

When I run 91 or 92 octane, the engine picks up and flies. 2nd pulls fast to 4400 rpm at 52 mph or so, 3rd powers up to 75 mph and 4th buries the speedo 'easily'. I was running in the fast lane last week coming home from camping fully loaded and had the speedo pinned at 140 kph for a while. Still got 11L/100 km or 23 mpg on that trip.

Mike

"I feel I might have the fuel filter on upside down - could this be causing the problem?" You're trolling aren't you!!!!!!!!!!!!!!

God Bless America, Bill O|||||||Omailto: snipped-for-privacy@aol.com