Damaged Camshaft Position Sensor? 97 4.0

[Mud Mixer]

97 4.0 5sp
Check engine light cam on. Jeep ran ok but wouldn't restart.
Couldn't retrieve codes via Key/Display method. Flat towed it home. Code P0340.

Pull the cam sensor and find it destroyed. Put an old spare in, engine fires right up. Sounds like a rod knock now but it's the Distributor. (for sure)

Anyone run across this before? I'd pull the Distributor but it pouring rain.

Thanks in advance.

 

[Chris]

Well you certainly found your issue.

It’s not uncommon for the shaft or gear in the distributor to wear out with age. It would be worth pulling the distributor to inspect it further.

Make sure to check for any excessive play in the shaft and that the gear isn't damaged, as that could lead to further issues if ignored.

 

[Mud Mixer]

Pulled it and found it was the source of the noise. Removed the pickup, the shaft was much harder to turn than it should be.
The half moon was bent and contacting the pickup. Straightened it with some needle nose pliers and patience.
Disassembled it and found the bushings in good shape but lacking lubrication. Zero side play.
Scotch Brite cleaned the shaft. Brake cleaner inside and out. Super Lube grease in the bushings. End play was about .025".
Put it all back together, runs like New. At idle it always had an intermittent minor miss every 2 or 3 seconds. That's gone now.

 

[Mud Mixer]

 

[Mud Mixer]

That's all there is to it.

 

[hear]

Sounds like you got it all solved, well done.

The "half moon" is the tone ring that triggers the hall effect sensor. Notice it is a simple on/off 50% "duty cycle". The later jeeps (05 & 06 for sure) had a 6 position tone ring which is much more precise. For the earlier style, I would guess that your pliers fix is perfectly fine, so long as it clears the gap on the sensor. I would be a little concerned about why it got all banged up in there if there was no side play on the shaft, but the proof is in the pudding. If it runs clean & quiet now, you're probably good to go. Nice job on salvaging an otherwise fine factory part.

The dizzy on my 97 went a while back, and I tried really hard to source the bushing because I had tons of play on my gear and I wanted to re-use the OEM unit if possible. But I failed in that quest so now I have an aftermarket. (Duralast, which will make many people cower in fear, but it's been like 3+ years an zero issues).

Also....where did the magnet go that had been in the cam sensor? It had to have fallen to the bottom of the diz enclosure. Did you find it? Or did it get chewed up along the way?

 

[Mud Mixer]

It's a mystery why the tone ring contacted the pickup. The Magnet was stuck to the upper cast iron bushing. I found replacement bushings on McMaster-Carr. I should have measured the OD for future reference but they have a great assortment. The lower bushing is Bronze. I'm also guessing at the shaft size. GM SBC's have 2 different shaft sizes, a .500" and a .493". Nothing a reamer can't fix.
I do have a lathe in the garage but since there wasn't any real wear, I put it back together and it worked.
From the amount of buildup on the shaft, engine oil must lubricate the upper bushing somehow.
According to my code reader, idle timing is at 16 degrees before disassembly and 17 degrees after the repair.
Does this sound about right?

 

[Mud Mixer]

 

[saharagirl]

97 4.0 5sp
Check engine light cam on. Jeep ran ok but wouldn't restart.
Couldn't retrieve codes via Key/Display method. Flat towed it home. Code P0340.

Pull the cam sensor and find it destroyed. Put an old spare in, engine fires right up. Sounds like a rod knock now but it's the Distributor. (for sure)

Anyone run across this before? I'd pull the Distributor but it pouring rain.

Thanks in advance.

View attachment 643700

Hey Mud Mixer, I'm having the same code pop up on my 98 Sahara. Where can I find this part to replace it? I also wanted to change the crankshaft position sensor and I went to the dealer to get the mopar brand and the one they gave me wouldnt fit to my jeep so I had to return it and got a $20 one from amazon. That one did fit. But I would still like to get the best quality crankshaft position sensor and now also change tyhe cam shaft position sensor. Do oyu know where I can get it? please let me know!

 

[Chris]

Hey Mud Mixer, I'm having the same code pop up on my 98 Sahara. Where can I find this part to replace it? I also wanted to change the crankshaft position sensor and I went to the dealer to get the mopar brand and the one they gave me wouldnt fit to my jeep so I had to return it and got a $20 one from amazon. That one did fit. But I would still like to get the best quality crankshaft position sensor and now also change tyhe cam shaft position sensor. Do oyu know where I can get it? please let me know!

I'd suggest going through Rock Auto.

 

[macleanflood]

Mopar, Standard Motor Products and Napa Echlin all seem to have better success rates.

-Mac