Plug wires in right order?

 

Yep, check the wires, plugs and all of that first. Make sure that you know where to put the #1 plug wire and then follow the firing order that is on the intake manifold. If that is not right, then you need to check you timing. If all of that is correct, then I hate to tell you what it could be but get back to us after you check everything else first.

 

Yeah I brought up to top dead center checked where #1 was and checked the firing order.

Give me all the possible bad things. Bad head is what I might I have but don't know how to check that.

 

Bad spark plug? compression test for head n rings , burnt valve maybe.

 

Getting my hands on a leak down tester. I'll keep ya posted. Thanks for all the suggestions.

 

My guess is depending on what your oil looks like(milky), you could have a cracked head which will not allow it to fire properly, a bent valve from too much carbon builup, collapsed lifter......I am not trying to freak you out but those are worse case scenarios.

 

Thanks. So today I did the leak down test. Although they were not the best they were all close. Got it all back together and turned it on and it idled around 800. Gave it gas and it spudered and popped out the exhaust. I noticed if I romped it would respond but if I slowly gassed it it would pop and backfire. Got so bad it blew some of the converter out!

 

Holy crap! If your compression is around the same on all cylinders but none of them lower than lets say around 130, then you should be ok on that aspect. Without being there to see and fidget, it is difficult but from this side of things it almost seems like your timing chain may have slipped a tooth or so.

I have ran many different engines and built many different engines and I have seen this same thing on a few different ones, doesn't matter what engine it is, if the timing is off, that is exactly what happens.

Maybe there is another obvious thing I am missing but it sure seems like it to me.

 

Do u happen to know what the timing is at idle. It put a light on mine and it was like 14 degrees btdc. I really don't think it's supposed to be there.

 

Yeah, I cannot remember but I thought it was 8btdc....but don't keep me to it....my book is not with me like it usually is.

 

Thanks for the help. Ill tear into the timing chain tomorrow and see where it's at. Is it like most where you line up the dots at Tdc?

 

From what an internet search told me it is supposed to be 8btdc at idle when warmed up to temp with an automatic trans.

 

Yeah, it is pretty easy and you do not have to remove the water pump to do it ok many people think that is the case but they are wrong. Just take the chain off and gears and put the gears on so the dots line up. The manuals show pics and make it a little easier to understand and makes it go a little smoother.....plus you definetely want to make sure you tighten those bolts back down to the correct specs or they could break or come loose on you and then you'll be in the hot tank for sure.

 

Sorry for the book that I write sometimes but there is something else that is pretty important too. Whatever you do, make sure you cut the tabs on the new oil seal where the oil pan/timing chain cover meet or you will never get it to fit right and will dang near torch your jeep out of frustration trying to figure out why you can't get the bolts in and it is leaking like crazy.

There are around 6-10 bolts on the bottom of your oil pan that go into the timing cover just FYI.

 

No problem. I don't mind the books. Do you happen to know where I can get a good reman engine? The engine I'm working is old and might need replacing.

 

Hmmm, this seems to be a pattern on here lately. If you have the money, the best place for a reman. is Jasper. They have good engines and awesome warranties. If that is not an option, I would trust Autovalue, Carquest, and Napa only.......don't go to autozone or advanced auto or there is a good chance of having a lot of issues and they usually don't last from what I have seen and heard.

Or, if you really want to have fun and have the time and resource you could do a mild stroker motor. a 4.7 stroker is plenty and has a ton of power and fun

Just saw that you were from california....dunno if the stroker engine is legal in your state but HESCO is from your state I beleive and they do all of that stuff.......they are one of the most expensive places out there too........you can build your own with a donor crank and stuff out of a 4.2 engine and save on money that way or you can just buy a kit for it.

 

I would to build a stroker. Need to find a good build sheet so I can start huntting down some parts. California does have some strict smog laws. If I do the stroker I'd have to register it in Texas. For now I just want to smog and title it. I haven't had a chance to look at the timing chain.

Ed

 

Checked timing. It's good. I'm out of ideas

 

Ok, is it possible that you have water in your fuel? Did you try to put dry gas in your tank and see if that does the trick for you?

 

No but at this point I'll try anything. Is it possible to have a clogged cat?

 

Well, after you telling me it backfired, I guess anything is possible......especially when you said it blew some of the cat out too.......your 02 sensors may be picking up some bad stuff......that is if you have 2 02 sensors and have a 96 and newer jeep.

 

If you are going to buy one, they sell high flow magna flow cats on car-stuff.com for $88 and that is pretty cheap compared to most that are $150+.

 

If the original motor did not backfire I don't think it would b a clogged cat. Might be a bent rod. How many miles on the old motor , and did you try to fix it to pass the smog test before you pulled it ? Sounds like you are going to spend alot of money , You could get a short block if the motor has good parts and go from there.

 

The exhaust was cracked bad on the last two so the original motors exhaust was not making it to the back. The only things I haven't changed is the water temp sensor, intake temp sens, map, and egr. Gonna pull egr today and see how it looks.

 

Could also be a bent valve or something simple like that, if there was a bent rod, the engine wouldn't be running. or it sure as heck would not idle.

 

Sanity check
Old engine ran but could not pass smog #4 cylinder no compression
Replaced with engine that was supposed to be good
Engine idles but backfires when given gas
All sensors from old engine and same issue
Is it safe to say that the engine has some sort of internal problem and not an electrical issue.

I can assume that if I had a bad sensor or ground the jeep would run rough.
I'm leaning more towards a flat cam. I've seen a 350 do that before.

 

I am not saying it is not a sensor but all the years working on the 4.0 engine and I have never seen a 4.0 backfire bad enough from a sensor issue to ever blow out the cat. like you described. I would look more towards an internal issue. The 4.0 engines are known to have cam issues for the #2 cyl causing a ticking noise when running that goes away or slightly goes away. What usually happens is the cam bearing in the area of the #2cyl gets worn causing the flat lobes that you are talking about and then the cam lobe starts to slap against the bottom of the lifter making it concave instead of slightly convex like it is supposed to be. The 4.0 engines also have issues with valves not seating right after about 150,000 miles or so depending on how the engine was taken care of and this will cause backfiring after a while because of low compression depending on how bad the valves are........if the valves get bad enough and cannot close, they can come into contact with the cylinder causing it to bend.

Just a little history on the 4.0 ok so you may know what to start looking for on your engine. Look for a lot of fluctuation in your oil pressure during rev. cycles, sometimes this is an indicator that your engine has a problem with the cam bearing.