95 Grand Cherokee missing at high speeds
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Model: Cherokee(SJ)
95 Grand Cherokee missing at high speeds
I have a 95 Grand Cherokee 5.2 that I've been working on. It's been giving me a good bit of junk and I ended up needing to replace the computer. Well, today was the first day I got it up to highway speed. At speeds under 50 mph, it did fine. But soon as I started getting close to 60 mph, the engine started missing. Right at 60 it missed a bunch and the car shook a lot. Didn't die, but at least a few cylinders weren't firing. Once I got up to 70, if I was still accelerating it did fine, but as soon as I let off the gas or just gave it a constant amount of gas, it started missing. It missed worst around 60. Now, if I was going 70 and let off the gas, once it got below 50, it quit missing, and just slowly decelerated like expected. Just now when I went to turn it on, I had to give it some gas before it started. While still in park I got it up to 1500-2000 rpms and I could feel it missing.
So, thought it might be timing. I did just have the distributor replaced by a shop. But when I looked into it, apparently as long as the distributor is pointed at cylinder 1 at TDC, the computer does the rest. I talked to a friend and he said maybe coil or plugs and wires. I don't know how old any of those things are. My fear is that it's a bad computer. I've already bought and had to warranty 2 computers because they were bad. Not all of them gave me the same problems. The original problem was a no start problem. The first replacement computer did the same. The second one had a bad voltage regulator and was overcharging the battery at at least 19 volts.
So, all that being said, is it simple as plugs and wires, or is it yet another bad computer?
Thanks for the help,
Jedidiah
So, thought it might be timing. I did just have the distributor replaced by a shop. But when I looked into it, apparently as long as the distributor is pointed at cylinder 1 at TDC, the computer does the rest. I talked to a friend and he said maybe coil or plugs and wires. I don't know how old any of those things are. My fear is that it's a bad computer. I've already bought and had to warranty 2 computers because they were bad. Not all of them gave me the same problems. The original problem was a no start problem. The first replacement computer did the same. The second one had a bad voltage regulator and was overcharging the battery at at least 19 volts.
So, all that being said, is it simple as plugs and wires, or is it yet another bad computer?
Thanks for the help,
Jedidiah
Old fart with a wrench
Joined: Nov 2010
Posts: 14,398
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From: Manlius, east of Syracuse, NY
Year: 2000 XJ Sport & WJ Laredo
Model: Grand Cherokee (WJ)
Engine: 4.0L
Check the distributor for a worn out shaft bearing. You said it's been replaced, but I doubt with a new one. If the shaft wobbles at high speed, it could cause your missfiring.
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Joined: May 2015
Posts: 818
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Year: 1994
Model: Grand Cherokee
Engine: 5.2L Magnum V8 220hp 285ft-lbs
What is the spark plug condition? How long since the timing chain was replaced? Have the spark plug wire resistances been measured? Does the distributor cap and rotor pass a detailed visual examination? How does the coil look / measure? How is the coil electrical ground?
The TSB 18-48-98 for the spark plug wire routing should be implemented. There are additional small retainers specified in the TSB.
The TSB 18-48-98 for the spark plug wire routing should be implemented. There are additional small retainers specified in the TSB.
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