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Half tech, half MJ, couple questions on XJ


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Ever since I got my '88 Cherokee, it's had a major sputtering problem. Last night, about 5 miles into my drive home from helping my mom run the laundromat, the truck backfired real hard and began running perfectly. It doesn't have a cat on it, so I know it couldn't have been clogged, so that's out the window, but still leaves me curious as to what it might have been. My initial thought was it had bad gas, as it used to be a farm truck and this is the first full tank of gas I've had through it since I bought it. So, what is everyone's opinions/ideas on why an '88 Cherokee 4.0 would do that?

 

Next question. I know all abut the wonders of Seafoam from running it through the gas tank and oil in Baby on occasion, but now I am wanting to run some through the tank and directly through the motor of the XJ when I get home on Monday, but what vacuum line is it under the hood that is to be used to thoroughly clean it all out? A pic would be of great help in this case.

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Could have been a blocked muffler. The backfire might have been blowing through the blockage.

 

After hitting a deep pothole my Geo ran like crud. Floored it up a freeway on ramp, and it sounded like a hard backfire. After that it ran fine, albeit loudly. Turned out the pothole jarred loose some rusted mufler part that ended up blocking the exhaust. The backfire was the muffler splitting open along the weld seam making another exit for exhaust gas.

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mvusse, the muffler is brand new, and it still runs quiet. It was included in the purchase of the XJ. dasbulliwagen, thanks, I'll definitely look into that one as a viable option, as I'm quite sure it's the original one yet; the 'EMISS MAINT' light has always been on since I got it, so I know I need to disconnect the little box under the dash, at a minimum.

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The muffler might have been new, but it may have had tenants.

 

Many years ago, I had a similar problem with my Hudson pickup. (Yes, Hudson used to make pickups. 1947 was the last year, and I had one). I had done an engine swap, had it running nicely, put a new exhaust on it, then parked it for the winter. Next spring I started it up at it ran HORRIBLY. Sputtered, stuttered, and kept wanting to die ... and did.

 

Finally, I got thoroughly frustrated. I started it one more time, and as soon as it caught I floored it.

 

POW!

Flames shot out the tailpipe, and all of a sudden it was purring like a kitten. Mice had bult a nest in the tailpipe (or muffler), and the nest was building up sufficient back pressure that it was like the proverbial potato in the tailpipe. It took flooring it to build up enough Moxie to blow the nest out. If yours was parked for awhile, it could have been the same problem.

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could it be carbon build up on the pistons?

 

i know my father owned a 66 Bonneville ambulance (yes the ambulance used to haul out the injured motorists on the saltflats)

he would bomb down the roads in it, and one day it it had this "backfire" which blew out all of the carbon buildup on the pistons and the rpms went right up and ran like a bat out of hell after,

also my sisters bf's grandmas car had the same thing happen to it lol there was a black spot of suit on her driveway for every cylinder

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Viable options, and appreciated. The thing is, even before I put the muffler on, it was running like crap, felt like it was almost down a cylinder. After putting the muffler on it, it was quieter, yes, but still ran like crap. When it backfired like that, was almost a transition phase for it, as ever since, it's still running great. I'm still thinking it was just bad gas, as it was a farm truck for the past 8 years, and the nearest place for gas for them was about 30 miles away. I'd still like to run some Seafoam through it though, just to see if that will open it up even more, but I'm going to need a pic of what vacuum line to use to suck the Seafoam up through, and if possible, a proper procedure to do so.

 

Thanks for all your advice so far, if anyone has any more, keep them coming.

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Very doubtful that it was carbon build-up in the cylinders. Fuel injection has almost done away with that problem. Most carburetors ran rich which contributed to the problem. We know that Renix injections tend to run lean.

 

I would guess there was some critters in the exhaust somewhere. Usually fuel related sputtering doesn't clear up with a backfire. It usually will just go away as you run more clean fuel through it.

 

Seafoam should go into the line to the brake booster. Pull it off on the booster end.. and just dribble it in as the engine runs. You don't want enough going in to choke out the motor.. but it will sputter some and be prepared for large, LARGE quantities of nasty smelling smoke.

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Could have been a blocked muffler. The backfire might have been blowing through the blockage.

 

After hitting a deep pothole my Geo ran like crud. Floored it up a freeway on ramp, and it sounded like a hard backfire. After that it ran fine, albeit loudly. Turned out the pothole jarred loose some rusted mufler part that ended up blocking the exhaust. The backfire was the muffler splitting open along the weld seam making another exit for exhaust gas.

 

the only time ive blown a muffler was on my old mj when we were stuck at the camp in some deep snow (2wd) and since i was new to this i let dad drive . well he got mad and floored er. all of a sunnder black stuff came outta the tailpipe and it got louder turns out he revved it up soo much he blew the bottoe out of my still semi good muffler. and then next summed i landed on it on a big rock.... end of story the muffler is long gone now

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Many years ago, I had a similar problem with my Hudson pickup. (Yes, Hudson used to make pickups. 1947 was the last year, and I had one).

 

For those of you who have never seen a Hudson pickup. This one's a beautiful 47 with a turbocharged biodiesel-fed 7.3-liter Ford Power Stroke V-8 under the hood :eek: :eek:

 

6a00d83451b3c669e20120a6780de0970c-800wi

 

Never had a Hudson, but did have a 55 1/2T Studebaker pickup for awhile.

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Wondering if Petes gonna hammer that muffler back into shape B4 he wraps it with duct tape and puts it back on. Had a '42 Hudson PU. one of the last ones made B4 WII. Swapped it straight across for a '27 Harley JD. Neither one of them ran so not sure who got the best, or worse, of that deal.

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nope. i did keep it for garage decor though. In its stead is a full bore race "muffler". :D one that doesn't really fit he original pipe. :shake: gotta by an adapter for that one of these days.

 

 

It was free so how could I not use it?

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Sorry for not getting back on this, I've had a lot to deal with lately. Thanks whowey for the help on location, I'll have to wait a bit before I can do it though, as I have a funeral to go to this week for a friend that passed on Thanksgiving morning, as well as a young cousin that is currently in the hospital, and I'm not feeling the best.

 

The XJ has still been running great though, so I'm hopeful that a basic tuneup along with the Seafoam will be the full cure.

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