Running really rough. Need some help.

First time posting, long time trawler of the threads.

I'll try to keep this short, it's been a project.
Backstory:
91 Cherokee automatic with a rebuilt donor 4.0L from between 92-94.
I was having an over heating problem when ever it ran. Changed the temp sensor, water pump, and radiator in the last 2 months. Finally decided to say screw it and use YouTube to guide me through a head gasket change.

Used a felpro gasket kit. Got the gasket on keeping everything bagged and tagged. I did not do a valve job... Long story short it's put back together in one piece with all the bolts and hoses in place.

The problem:
Engine won't idle but does start and runs when kept above 1500 rpm. Not firing on cylinders 4 5 & 6 (back 3) Spark plugs on those 3 are getting wet and properly gapped but have no carbon on them. Contacts on distributor were cleaned. Not sure what to do next.

you have no spark on those back 3? Have you used a spark tester, or just going by what you see on the plugs? Also, when you installed the new gasket, did you have the head surfaced?

I'd find TDC "1" and make sure the rotor is pointed near number one on the distributor cap. It usually ends up a little past number one.

Put a compression gauge in number one spark plug hole, turn the motor over by hand until the compression gauge starts to build pressure. Align the zero timing mark and see where the rotor is pointed.

You also have to be careful that you actually have number on the distributor cap as your starting point.

Double check the wires running to your injectors and make sure they are plugged into the proper injectors.

This is a starting point, it gets more involved the deeper you check into things.

But do the easy stuff first, like making use you are getting good spark to all the plugs. I usually open a used plug up to around 0.060 and hold it onto a good ground and look at the spark. Not pushing your crotch against the fender while you are testing the spark is likely a good idea.

Remember the firing order for the spark plugs is cast into the intake manifold.

CompleteCherokee said:

you have no spark on those back 3? Have you used a spark tester, or just going by what you see on the plugs? Also, when you installed the new gasket, did you have the head surfaced?

Click to expand...

I have sparks from all the plugs. I pulled them out and saw that they all arced. No I did not have the head resurfaced. I checked it against a flat piece of board and it was smooth without any bumps waving or warping.

8Mud said:

I'd find TDC "1" and make sure the rotor is pointed near number one on the distributor cap. It usually ends up a little past number one.

Put a compression gauge in number one spark plug hole, turn the motor over by hand until the compression gauge starts to build pressure. Align the zero timing mark and see where the rotor is pointed.

You also have to be careful that you actually have number on the distributor cap as your starting point.

Double check the wires running to your injectors and make sure they are plugged into the proper injectors.

This is a starting point, it gets more involved the deeper you check into things.

But do the easy stuff first, like making use you are getting good spark to all the plugs. I usually open a used plug up to around 0.060 and hold it onto a good ground and look at the spark. Not pushing your crotch against the fender while you are testing the spark is likely a good idea.

Click to expand...

My sparks are orange in color, I need to get a noida tester next I suppose. I made sure to triple check the order on the distributor. It's correct and starts at 1. The injector wires are also properly running.

I guess my next step is to pressure test it and hand rotate. Thanks.

Check the inside of the cap and make sure it is clean and dry.

Orange spark not good. Seems you are not getting enough juice to plugs. Is it possible that you have broken 3 plug wires, stepped on them, or some such? There is a resistance test to check values as per inch length of each wire. Sure hope you get the rest of help you need to make your XJ work correctly.

BTW: Just another back-yard mechanic tip: Rather than using a "board" when making a quick check as per head surface levelness, use a sheet of glass. Spray head gasket surface with WD-40, (not in any way affiliated), place glass on head to check to see if there is an even wet bead. If so, lightly press one's finger in various locations to see it there is a dramatic difference in the way the wetness changes. If no changes seen, then probably good to go. I have filed on head surfaces, (only on my vehicles), several times with good results in order to insure good gasket seal using the above method. (Be sure not to allow filings to go anywhere but into the trash bucket). Also, in the past it used to be standard, (I still do), to accomplish an in-service check of head bolt torque values after about 500-750 miles. Google that, or look into an FSM.

Let us know when you meet success please.

Hey guys. Still having troubles with it. I've done as has been discussed so far, I just poured a quart of rizlone in and it seems to have helped a bit. This is the link to a video of it. Take a gander see if you guys can come up with anything.

http://youtu.be/IC6LxFgTfz8

if you have orange or yellow spark, as mentioned that needs to be addressed

New plug wires have not changed anything. How can I address the spark color?

You could change the coil.

But I would test compression with a compression tester first. You are wasting time and money if you still have low compression on those last three cylinders. Many auto parts places loan them out. Or buy one. $20?

if the spark is yellow or orange, and you've changed plugs & wires and verified they are in perfect condition & plugs are gapped properly, then you have an issue with the coil

The coil is a moot point now. I gave in and took it to a mechanic for diagnostics. He said I have a dead cylinder.

So my question is this. Do I have him investigate further, or do I junk it? Maybe possible engine transplant?

A dead cylinder could be lots of things:
no spark
weak spark
broken / worn rings
broken piston

Did he clarify what he was meaning?

No he didn't clarify. He said he tried to turn it over heard a dead cylinder and stopped. "Didn't want to waste my money" and I need a new engine.

Anyone want this project and lives in the north Orange County area? I'll sell it really cheap. Is it time to go buy a wrangler off a lot?
I'm a college student so this isn't an appealing option to me, but I need transportation to school ASAP.

Get another mechanic to take a look. You can't tell squat about a dead cylinder by listening, unless you threw a rod and it was clanging around.

Since it isn't ODBII, and the computer doesn't tell you what to replace, he is probably at a loss. Find another mechanic.

So I got it in another local shop. The guy said it was probably a stuck or bent valve. He is going to fix it got 1100$. I'll keep you guys updated as to its success and what was ultimately the problem. I appreciate the help from all of you.

the sad part is just because someone is a mechanic and has some certifications, that doesn't mean they are good or know what they're doing.

This is very true, I've spent some time looking for a decent mechanic. The guy I've left it with seems rather competent. He called me this morning to let me know I bent two rods and the valves.
I had a feeling that's what I did when I was putting the block back on.