Code P0340 and my TJ won't start

[SkylinesSuck]

Driving along minding my own business, the jeep bucks a couple of times over a minute or two, then starts missing multiple cylinders, then dies. Code P0340 comes up which is........

Camshaft Position Sensor A Circuit (Bank 1 or Single Sensor): A rationality error has been detected for loss of camshaft position sensor (no fuel sync).

Cranks fine, doesn't start. No power is going to the coil during cranking which I assume is because the PCM is not telling it to fire. I replaced the camshaft position sensor inside the distributor, as well as the crank position sensor on the bell housing. Still the same thing. I can clear the code and after it cranks for about 3-5 seconds, the code comes back. Also, over the past few weeks, I've had an intermittent P1391 code (Intermittent Loss of CMP or CKP) that is probably related. I could clear that one out but it would come back after driving for about 10-20 minutes. Not showing the 1391 code now, just the P0340.

[gradon]

I had an intermittent 1391 until my cam position sensor was synced correctly.

[SkylinesSuck]

I might try syncing it later, but it has been running fine for a year or so with the current distributor setting, well before I started getting codes.

I checked for worn/frayed wires and everything looks good. I checked the resistance in the wire that caries signal from the camshaft position sensor (CMS) to the ecu, the crank position sensor (CPS) to the ecu, and the throttle position sensor (TPS) sensor to the ecu. All have .002 of resistance when the multimeter is set to 2k on Ohms (2 ohms?).

Also, both the CPS and CMS show infinite ohms no matter which leads I touch together on the 3 pin connector. I *think* that's correct judging by what I saw on how to check a crank position sensor (b & c terminals should show infinite resistance) and somebody mentioned it should be the same for the camshaft sensor. This is the test I am referring to (although the connector doesn't look exactly the same, but it is a 3 pin).........



TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.



As for power, both CPS and CMS are receiving 5.1v on the a & c terminals with the key position to "run". O yeah, and the "b" terminal on both CPS (crank) and CMS (camshaft) sensors show .002 resistance when grounded to the engine bay with the key in the "off" position and .057 in the "run" position.

[dwg86]

Have you pulled the cam position sensor? Check for a sheared roll pin in the gear, or worn cam gear.

[SkylinesSuck]

I did change the cam position sensor. The was a bit of up and down play and a little torsional (twisting) play on the shaft the rotor rides on, but no more than 10-15 degrees of rotation I would say. The dizzy itself is locked down tight still.

[SkylinesSuck]

So it turns out the distributor gear ate itself for breakfast. Probably due to the high volume oil pump giving it to much resistance (that's all I can figure any ways). Since the dizzy wasn't spinning, obviously it wasn't moving the rotor and cam position sensor. Kinda weird how it ate itself though. All the gear teeth on the dizzy show wear, but it ate a nice little crescent out of the gear so it wasn't engaging the cam, but I couldn't spin it freely when I just grabbed the rotor and turn it back and forth since it hit the other still half way intact gears.

Grabbed a dizzy from a '91 Cherokee in the junk yard and it looked the same as my '98 TJ's (both HO so it should work). In the process of trying to get it indexed correctly now.

[dwg86]

There has been a couple of guys on Hesco's web site that have been chewing up dizzy gears. The only reason I have seen distributor gear wear has been from lack of lube, cam walk, or different pitch teeth on the dizzy gear compared to the cam gear. I have only seen this on AMC V8 since the cam gear is removable from the cam, and installed after the timing chain. Some mfgs were making new cam gears with the wrong pitch.
Did you install a new cam in the engine? Is the spring and pin in the end of the cam? Is the little button on the inside of the timing chain cover still there, or is it worn down? Check to make sure the little hole that feeds oil to the cam/dizzy gear isn't plugged. The dizzy gear is only lubed by drain back oil from under the valve cover.
You can make a pressure fed oil line to the dizzy gear pretty easy. You have to drill a hole in the block right by the dizzy gear and run an external 1/8 copper line and a "T" fitting from the oil pressure sending unit to the dizzy gear. I made on my stroker for insurance purposses, because I have heard of some Jeep 6's eating cam gears. I had already made a dizzy gear oil line on my amc 401, so I knew it wasn't a big deal.

Here are some pics of the line going into the block. I ended up using a .020 hole for the "squirter" for the cam/dizzy gear. I installed a piece of .020 stainless steel wire in the end of the copper line (cam gear side), smashed or crimmped the line and then pulled the .020 wire out. http://www.jeepstrokers.com/forum/viewt ... r+oil+line

[dwg86]

A couple of pics down in this thread are some more views of the oil line.
http://www.jeepstrokers.com/forum/viewt ... ne&start=0

[SilverXJ]

One other thing to consider is the distributor shaft may have froze, which sheared off the teeth on the gear. I had that happen once on the stock cam sensor on my 2000. Everything was fine and it just died. The shaft froze in the housing and the teeth sheared off.

[SkylinesSuck]

dwg86--that looks interesting and I've seen your write up before. Next time I do a rebuild (which hopefully won't be any time soon) I might give that a shot.

SilverXJ--with the old dizzy out now, it spins freely, but I know what you mean. The whole reason for my stroker was the old 4.0 spit the dizzy out of the freaking block due to a seized shaft. Scary stuff.


So I got everything back together, changed the oil, and started it up. It runs, but after about 10 seconds, it develops a galloping idle and will eventually die after a minute or two. Also, it pings it's ass off after about 40% throttle. That could be due to the 1/4 tank of 87 octane that we put in it (with nothing but fumes in the tank to begin with) just trouble shooting, or it could be that I have an adjustable crank sensor and it's not where it should be. It's pretty much in the middle of the slot though. Anywho, the first problem is the real one. I've played around with the dizzy slowly moving it back and forth trying different position around where it was originally set when I indexed it. It makes the idle smooth sometimes when I move it, but then it starts right back up. Also, it dies (obviously) when I move it to far, so I've found the two extremes of running and tried everything in between as far as I can tell. Could the indexing still be my problem, or is it a engine will run/not run kinda thing? I looked for vacuum leaks, but couldn't hear or see anything.

[SkylinesSuck]

Oh yeah, and no codes anymore.

[dwg86]

I would say it's your indexing, (cam and crank sensor). You might want to take it to a dealer and have them put in on thier DRB. My cam sensor was out 17 degrees. The dealership adjusted it for free. It took about 5 mins to do.

[SkylinesSuck]

Sweet. I'll give it a shot in the morning. Hopefully they don't try to charge me for an hour of labor or something gay like that. I'll let you guys know. If anybody has any other ideas about the hunting idle, please let me know in the mean time

[SkylinesSuck]

Not cool. They want to charge me a $90 shop fee for 1 hour's worth of labor to use the tool. Gay.

[gradon]

That would be the norm, dwg's experience was the exception. You'd think they could give you a break and charge a 1/2 hr for their 15 minutes.