My 4.0 is backfiring like crazy.

The PO recently instaled a new distributor. Is there an chance he installed it on the exhaust stroke and that is what is causing the backfiring?

 

Probably out of time

 

Pull the number one plug and put your finger in the hole and turn it with a wrench or bump it with the starter till you fell it start to push air out.
Remove the coil wire if your using the starter.
Then turn it by hand till the timing mark comes up on the balancer to TDC mark.
You can also check it with a long screwdriver and feel the piston top as you turn it by hand on the compression stroke.

Now pull the dist cap look where the rotor is pointing, is it pointed at number plug wire?
Yes, check the firing order on the cap and make sure its wired right.
NO, then pull the dist and rotate it where its just before the #1 electrode and slip it back in.
If the wires are right and your not starting, time to run a compression check and see if there is a dead cylinder with bad valves.
If you find a cylinder with low compression,
Squirt some ATF in that cylinder and check it again, got compression now, bad rings, if not its valve issue.
Now you have to pull the valve cover and make sure the rockers are working correctly.

 

Great, thanks! I will try that this weekend. Thanks again!

 

Ok, so there are no index marks on the harmonic balancer. How do I make sure it's at TDC?

This is what I've done so far:
- Replaced MAP sensor
- Replaced TPS and adjusted with multimeter
- Replaced/fixed vacuum
- Engine stalls when I put my hand over the throttle, so no vacuum leaks, right?
- Engine stalls/dies when I press on the EGR diaphragm
- Replaced, bolstered and cleaned grounds
- Fully recharged battery
- IAC connections new, IAC cleaned with TBC and IAC moves when the ignition is turned on.
- New, correctly gapped copper plugs
- New plug wires

PO replaced CPS and disty.

The little fella cranks fine, is idling ok, but is backfiring like crazy when there is gas applied. Guessing the last bit is to check timing- but need help since there are no indexes. Anything else I'm missing that would cause it to run rich/backfire to the point it cannot be driven?

It's so sad sitting in the lot... he really needs to be taken out for a spin......

 

Also replaced O2 sensor. TIA!

 

do this when you feel air coming out stick a straw in number one spark plug hole and turn the crank by the boilt in the center untill the straw reaches its highest point thats tdc compression stroke

 

fuel pressure ever been checked ,ever replace the dist cap???

 

Morning all:

I think we have found TDC. Dad held his thumb over # 1 and I cranked the engine with a 19mm socket. When it blew by his thumb we adjusted to the white mark on the harmonic balancer.

The picture attached is where the rotor is pointing. My index finger is pointing to the mark where the #1 wire is marked.

How do I adjust this so that the rotor is pointing at or .20 past the #1 wire?

I'm a little handy, but have never messed with distributors before. Thanks in advance!

Jan

 

Bump

 

are you sure no1 pistion all the way to the top of its stroke

 

I'm pretty sure, but not positive. Dad let me know when there was compression and we worked it until the mark on the HB was lined up. There are no numbers on the HB, so I'm working with the existing mark which is a white stripe.

The Jeep is running way, way rich, and everything else has been replaced/ clean/ or repaired. I'm thinking the distributor may be off a few teeth. The PO put in a disty, but I have no idea whether it was done/adjusted correctly.

I'm not an expert here by any means, so any thoughts or suggestions are greatly appreciated.

 

take a long skinny screw driver and in sert in no1 plug hole and turn crank nut watch screw driver handle for movement see if it need to go up or down to be at highest point. then check dampner and rotor.

 

The rotor should be pointing at that person's index finger.

 

correct dont think there at tdc maybe if dampners has slipped on rubber