bradly garrett

Start off im not a writer. Spelling grammer and punctuation is wrong
1999 jeep grand cherokee laredo 4.0 4x4

Bought jeep 4 years ago immediately computer went bad i tried 3 computers finnaly got the correct one jeep ran fine.
Broke tranny about 1 year after tore it down rebuilt it jeep ran fine.
Crank positiin sensor went bad replaced it jeep ran fine.
2 months ago Took jeep on a trip running great broke a piston obvious tapping noise still ran great. Tore into motor found piston replaced everything in bottom end pistons rings seals bearings crank cam lifters rods. Had engine block honed. Put all back together put in jeep started up did break in rpm for half an hour notice a slight rattle sound plus miss relized crank shaft possition senso slightly off got a new one. Jeep ran great.
Drove for about 1 week 60 miles did good.
Then saturday morning woke up started it missing bad not running good through codes.
0180 fuel temp
0765 shift solenoid
015d 02 censor
0353 coil 3
Didnt make sense so i cleared them jeep started up drove good 2 more days. Then monday morning no start cranking but not starting. New code
1391 crank position sensor
Ok re placed sensor again maybee it went bad china made junk. Then tried to start and cranking then backfired blew airbox into 10 pieces. At a complete loss at this time not sure what to try and do. Fear it may be computer again. Spent alot of money at this point and dont have money to just throw at it and hope. Any ideas.

Noah911

I am not sure what would be causing this, but it sounds like like you may have too lean of an air-fuel mixture? The intake ratio is skewed in favor of air, causing an expulsion out the airbox when unburnt fuel ignites in the intake manifold for some reason..?

Why would the engine have had too little fuel and a lot more air? Not enough fuel supply, and/or dysfunctional engine timing for some reason?

dave1123

A backfire is always caused by ignition on an open intake valve. From the sounds of yours, the manifold must have been flooded with fuel and the throttle held open. I'm thinking an injector that didn't seal off properly. Not much to go on, but should point you in the right direction.

bradly garrett

Cam position sensor is the current code thrown after air box blew out. . .

Noah911

Camshaft Position Sensor. That could do it.. If that sensor is not installed and set correctly it won't be timed properly. If it is out it could cause firing on the wrong stroke and backfire out the intake. Doing the work you have had done, did the camshaft position sensor ever get messed with? Even if, it still doesn't make sense though since it has started and run great previously.

dave1123

It could have failed and shorted internally, sending an ignition signal to the wrong coil.

Noah911

How about the wiring harness/wires in the engine compartment? There has been recent work done in there.. It is possible that something has become amiss with the wiring like pinched or frayed wires causing some arcing or a short.

zj rider

My 97 zj ran great and then would crank but not start replaced cam sensor ran for a day then same thing. It turned out to be the plate on the distributor was bent under the pickup

bradly garrett

Got this jeep to run. Turned out to be a combination of the cam sensor and crank sensor. Since they were both cheap off brands from differnet stores. One came from auto zone and the other from o riley they werent in sync together i replaced both with mopar parts and it fired right up. Running good. Thanks everyone who replied hope this helps others

Noah911

Thanks for updating. I'm glad you have your Jeep running good again now!