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hesitation unknown

Good morning. Well, I posted here a few weeks ago with an unknown issue that I thought might be the transmission. It was diagnosed by those here and a tranny shop as other issues. At the recommendation of the shop, I replaced cap/rotor, I had just done plugs and wires and skipped those for now. At the advice of this group, I replaced the fuel filter, that seemed to have done the trick. Now my problem is back.

I'll describe it as I did before, at highway speeds only, I get a hesitation. It feels like all the power just drops out of the engine. I get no spike up or down in oil pressure, voltage, rpm or temp. I have no check engine lights flashing or staying on and no other idiot lights showing. What I feel is something like pulling a trailer with electric brakes that all of a sudden start pulsing. It only happens at highway speeds and typically only after 20-30 minutes of driving.

Any thoughts?? I did check the ground strap and see no rust/decay/fraying.

Thanks.

Reply to
JeffD.
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A plugged up air filter on the gas tank vent will cause symptoms like that.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

"JeffD." wrote:

Reply to
Mike Romain

OK, that kind of makes some sense. Another issue, not described makes this seem even more likely. When I remove the cap to fill the tank, I often get a lengthy vapor pressure discharge. Where is the air filter for the vent hose?

Reply to
JeffD.

It is under the hood and is on the bottom of the charcoal canister. The canister looks like a coffee can with tubes out the top. It is a $2.00 filter and is a real pain to change. The canister doesn't come apart so the filter has to be dug out. The second one is easy though...

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's
Reply to
Mike Romain

Must bang head against brick wall! Forgot to mention it's a 92 XJ, 4.0 FI HO. It appears that the evap canister is a single molded plastic unit, not the coffee can style. Next thoughts?

Reply to
JeffD.

I guess they didn't like it that we could just change the two buck filter eh.

I would be taking the tube off that goes from the canister to the air filter box and be seeing if I could blow or suck through it with the gas cap open.

On mine I check the filter by driving with the gas cap loose. If the hesitation goes away, bingo. Mine doesn't have a check engine light to go off though.

Mike

Reply to
Mike Romain

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