Stroked98Xj

'98 Cherokee, 190k miles on body and trans. 4.7L stroker with ~10k miles. It's been running great and pulls like a tractor until suddenly last weekend it throws a P1391 code and runs like crap. Hard to start but always does in 1-2 trys (was always a 1 crank engine until a few days ago). It spudders and chokes on itself (missing?) when you're driving it and it doesn't like any more than 1/4 throttle.

Here's what's new as of March 2014:

• Napa Distributor
• Napa Cap
• Napa Rotor
• Napa plug wires
• Champion spark plugs
• Napa coil
• SCT Tune 173hp 299lb-ft torque to the wheels

The engine swap happened in 2013 and has been a blast to drive ever since. OEM exhaust header, Magnaflow high-flow cat, Magnaflow muffler, O2 sensors are in their proper places and were new during engine swap. LS6 injectors.

Since the P1391 code suggests cam or crank position sensor, we've replaced both. Crank sensor came from Napa, cam position sensor came from Jeep dealer. Replaced both of them this evening with no change in symptoms. I disconnected the battery during this work, and engine code was not present during first run of engine. It came back right away 2nd time starting. When you rev engine in Park, it hiccups after 2000 rpm and I don't try it much past 2500 as it starts to fall on its face. Also replaced IAC sensor tonight too just because I've been having an intermittent high idle problem, but that's a moot point for the P1391 code.

49PSI fuel rail pressure immediately upon key on. Fades to ~42psi after a minute. Didn't drop below 30psi for the hour or so the gauge was hooked up.

What else to try? A buddy of mine suggested I disconnect the cam position sensor and try cranking the engine over, but it would just crank and crank never starting. What did that prove? Anything?

Need other suggestions to try. This is a daily driver so my wife and I are sharing vehicles and it sucks.

Stroked98Xj

Here's a picture of the rotor timing in relation to TDC. I didn't verify it's #1 yet at TDC, but let's say for arguments sake the timing chain jumped a tooth in either direction, how far off could the rotor be?

Yes the engine is pink...it's my wifes engine and she built it almost all herself. Yes it's dirty....she likes puddles.

Turbo X_J

Fault codes point to problems in a circuit not necessarily a component. Have you checked the harness in the engine compartment for chafing and/or broken wiring and corroded connectors?

Not to open a can of worms, but the OCOD probably isn't helping anything.

Stroked98Xj

OCOD?

CCKen

Generally, when rebuilding an engine, the timing chain and gear set are replaced. 1/2" max play in the chain.


Anyway, here's how to check if your distributor is timed correctly:


Remove the electric radiator fan so you can get a direct view of the timing chain cover timing marks and the vibration damper timing mark.


Remove the distributor cap, rotor, and cam sensor. Replace the rotor.


Rotate the crank damper to align its timing mark with the zero (0) mark on the timing chain cover. See pic below.


See if the rotor is pointing near #1 cylinder cap terminal. If it's pointing at #6 cylinder, rotate the damper 360 degrees until it points near #1. See pic.


With the timing marks dead nuts aligned, see if you can insert a 3/16" pin punch or drill bit thru the plastic disc in the distributor and down through the alignment hole in the distributor base. If you can, the distributor is in time. If not, the distributor was installed improperly or the timing chain has jumped. See pics.


Damper/cover timing marks aligned:





Punch installed in the 4.0 hole in the plastic ring:





Distributor installed with pin punch installed. Note the position of the rotor relative to #1 cylinder cap terminal. Modified cap shown:





.

SteveMongr

OCOD = Orange Can Of Death. Also known as Fram oil filters.

I enjoy CCKen's posts because I always learn something!

Stroked98Xj

Engine has been running great for a year. Good gas mileage, fun power, smooth operation.

What other checks or tests can be performed to rule problematic parts out?

Stroked98Xj

Still fighting this. No resolution or updates yet. We just parked the Jeep for awhile until this weekend.

Any other suggestions to test?

CCKen

Here's some possible causes for P1391:




DAMAGED TONE WHEEL/FLEX PLATE (CRANKSHAFT)


INTERMITTENT CKP SIGNAL LOSS WHEN WIRING IS WIGGLED


WIRING HARNESS INTERMITTENT


INTERMITTENT CMP SIGNAL LOSS WHEN WIRING IS WIGGLED


SENSOR CONNECTOR/WIRING


SENSOR CONNECTOR/WIRING


CAMSHAFT POSITION SENSOR


CKP SENSOR CONNECTOR/WIRING


CRANKSHAFT POSITION SENSOR

CCKen

Did you ever verify distributor timing like I outlined in post #5?

Dirtdiggerjr

Thanks CCKen solved my issue. Saved me a lot of headache and time! Not to mention cash!!!

CCKen

Cool, but what did you do to save you a lot of headache and time/cash?

sycoglitch

lol talk about vague booking

Dirtdiggerjr

Sorry guys and girls new to this. My 97 xj was chunking the p1301 code ( cmp or ckp signal intermittent condition explanation) got to looking at CCKen pictures and noticed my sixth cylinder was firing off the #1 spot on the distributor. The plug wires were on opposite sides from the spots. So I put cylinder 1 at top dead center and pulled the distributor cap to find out the holes with the punch from CCKen picture didn't line up. It was 180 degrees out. So I pulled the distributor lined up the holes a set my punch in them to keep them lined up. Put the oil pump to 11 o'clock and put the distributor back in the right way. Hooked everything up the right way not opposite like it was. Reset the ecm fired it up and the p1301 code has been gone every since then.

CCKen

Thanks for the follow-up.


Good work.


Help yourself to a cookie, you deserve it.