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Unread 01-18-2002, 12:41 PM   #1
Hounddog
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Join Date: Jan 2002
Location: Arco, Idaho
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4.3 Vortec dies when hot

Hi, I'm new here.

I posted this info on other Jeep boards, but I haven't had any luck solving it yet. I was hoping that maybe someone here would be able to help. Thanks for giving it a shot.

I swapped in a 4.3L vortec with the 4L60E from a '94 Chevy Astro van into my CJ-7 last year. When the air temp is above about 90 degrees (won't be happening anytime in the near future ) the engine would just stop running. No sputtering, coughing, or loss of power prior to dying. After about 20 to 30 minutes of letting it cool off, it would restart and run fine for about 5 to 10 minutes, then die again.

No check engine light before or after it died, and no codes were stored. It would crank over, but wouldn't fire. I found that if I poured cold water over the dist. it would start alot sooner then if I just waited, but it would also die again sooner.

I swapped the coil and the dist. ignition module (I was in the middle of Montana at the time), but the problem is still occuring.

I haven't had any problems when the air temp is cooler. When the engine does die, the engine temp gauge doesn't show any increase over normal levels.

Some additional info that I posted later.

I checked the fuel pressure - it was good at about 58 psi. This is a CPI fuel injection setup. The spark was a very weak yellow spark when it had this problem.

I had someone tell me that it could be the weather-pak connectors. I guess that the theory is that because the connectors are water tight, that they are getting hot and separating. That is a tough one for me to believe it might be a possible cause. Have you guys ever heard anything like that?

I started trying the dist. parts due to the way it would start faster when I cooled it off with cold water. This engine has a little over 30,000 miles on it. It runs like a top the rest of the time.

This problem only occurs on the black top. When I'm on the trail, I haven't had any problems even when the air temp was over 100 degrees. Maybe the hot air isn't able to exscape fast enough when I'm at speed, and I'm over heating a component. My experience with electronics would lead me to believe that once overheated, it shouldn't work again.

Just to let you know, the fuel pump has about 4000 miles on it and is external style with the fuel filter upstream of the pump. I haven't had any problems with vapor lock, and when it dies, it doesn't give any advance warning by loss of power or sputtering.

I would have thought that a problem like this would have be sensed by the ECM, but no codes afterwards and no check engine light at all.

I appreciate you guys giving me input on this. I don't just want to start throwing parts at it, so its nice to hear what someone else thinks.

Any ideas? Thanks in advance.

Jamie

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'85 CJ-7 with '94 4.3L Vortec w/4L60E tranny. Line-X inside, outside, and underneath.
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Unread 01-18-2002, 02:49 PM   #2
Big92Jeep
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Join Date: Oct 2001
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For what it's worth

I had a 94 Formula with an LT1 5.7 in it. I had the same problem down here in Florida. After some research I found that my Mass Air Flow (MAF) Sensor was bad. I haven't spen't a lot of time with the 4.3L. But if there is a MAF between your air box and your throttle body it could be the problem. It measures amount of air, humidity, and temp of air flowing threw the intake. Mine didn't throw any codes either. It was just reading too hot.

I isolated the problem by borowing my friends MAF sensor off his LT1 and running it for a few hours. It simply plugs in so it's not a hassle to try.

I had my MAF sensor tested at a local speed shop. They told me that if it was bad it could read about 80-100 degrees hotter than the air actually was. So I replaced it and never had another problem.

There not cheap mine was about $200. If you do have one on that 4.3L I would see if I could find a friend with the same engine. Buy him a six pack. Swap it out and see what happens.

My 2ó

~RýCK
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Unread 01-18-2002, 04:27 PM   #3
Hounddog
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Thanks for the suggetion. I've got a spare manifold with all of the sensors including the MAF. When it gets hot enough to start give me problems I'll give it a try.

What kind of shop did you take your bad MAF to? Maybe I can pull this one off and have it tested now so I don't have to worry about being stranded later. It would make sense with it being able to run after cooling off (most electronics die when they overheat and will not work again). Thanks for the info.

Jamie
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'85 CJ-7 with '94 4.3L Vortec w/4L60E tranny. Line-X inside, outside, and underneath.
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Unread 01-19-2002, 09:41 PM   #4
Crash&Burn
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Hounddog:
How much did all that Line
X cost yuh
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1979 CJ7 (YJ tub) full cage, Currie 9inch rear with Warn full float kit, detroit locker, 456 gears both ends, Lockrite in front, T 18 trans, 360, 040 over, Isky cam, 2 into 1 Flowmaster exhaust

I'm not as good as I once was....but I'm good once as I ever was.
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Unread 01-22-2002, 03:00 PM   #5
Hounddog
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Crash,

I had the entire Jeep sprayed. The tub (inside and outside), dash, rollbar, fenders, doors, tailgate (all of them a dark red), and frame (which included the gas tank, skidplates, double-tube bumpers, nerf bars, and winch mount - all black) ran me about $800. Later I had the hardtop and the steel wagon wheels sprayed black for an additional $180. So I'm into it about $1000 total for the entire Jeep. I got this price quoted at an auto show, later he told me that it should have been about $400 higher based on the amount of product that he had to use to cover the entire Jeep.

It has held up very well to brush and trees on the body. The skidplates and nerf bars have peeled some due to contact with rocks on the trail, but I had expected that to happen.

If you have it sprayed on, I would suggest that you remove the body and fenders as a single piece (I took mine completely apart - made putting it back together quite difficult, had to trim it a lot) to have it sprayed, then reinstall as a single piece. Also be prepared to clean every stud/threaded hole with a tap-n-die set anywhere that the product is sprayed.

Give me a holler if you have any other questions.

Jamie
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'85 CJ-7 with '94 4.3L Vortec w/4L60E tranny. Line-X inside, outside, and underneath.
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Unread 02-15-2002, 03:51 PM   #6
Hounddog
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Quote:
Originally posted by Big92Jeep:
For what it's worth

I had my MAF sensor tested at a local speed shop. They told me that if it was bad it could read about 80-100 degrees hotter than the air actually was. So I replaced it and never had another problem.

There not cheap mine was about $200. If you do have one on that 4.3L I would see if I could find a friend with the same engine. Buy him a six pack. Swap it out and see what happens.

My 2ó

~RýCK

Hey Rick (Big92Jeep),

I was curious if you could tell me what the shop that checked out your MAF specialized in? Maybe that way I could see if there is someone around here that I could get to check out mine for me. Thanks.

Jamie
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'85 CJ-7 with '94 4.3L Vortec w/4L60E tranny. Line-X inside, outside, and underneath.
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