Strange and horrible sounding '87 Renix 4.0 I6
 

Hey all. Thanks for reading.

I'm having a really hard time figuring what my 4.0 is doing. It sounds really horrible when it's running. Almost as if it's not running on all cylinders/misfiring. 1987 Cherokee Laredo, Auto, 4.0 I6, lifted.
Recently changed spark plugs and oil. Also checked fuel injectors, all are working properly.
I made a YouTube video to give y'all an idea of the sound.

Your video doesn't work. But when you changed the plugs did you change the wires, cap and rotor?

That's odd. Video works for me. No, didn't change the wires, cap, or rotor. I'm tight on money right now and already had the plugs.

Here's the link to the video to watch it on YouTube, not on here=http://youtu.be/fnZMIlqwgVI.

Go back over your spark plugs wires and make sure they are on the right plugs from the distributor. I always mark the wires with masking tape so they don't get messed up. When I change wires, I only change one at a time. I know it sounds stupid but getting one plug on the wrong wire really messes it up. Also, make sure the boot has a connector in it that fits the plug nice and tight. Sometimes they get mashed and don't make contact.


What plugs did you put in and what did you have before? Sometimes you can get a bad plug out of the box although that's not my experience with plugs. I use cheap Champion Coppers in my '87.


As the saying goes -"Timing is everything"


The diagram is from Fixya.com.

I replaced them with champion coppers, can't remember what the old ones were. I'm pretty sure I checked the wire sequence when I did the plugs.

That diagram, like many others seem to be, is misleading.

#1 is actually at the 5 o'clock position on the cap when the distributor is clocked properly.

Yeah, all the diagrams are like that. But, #1 on my jeep is at the 5 o'clock position.

double check the firing order man. And reseat the boots on the plugs, sometimes the rubber of the boot itself can stop it from pushing down onto the actual spark plug.

My #1 is at this position. I think it's the screw positions that are causing the problem with the pics. If you are looking at the engine, #1 is 90 degrees from the line of the engine (furthest point from the engine).


Best way is to find TDC and confirm.

Here. Use this one made by EZEARL:

Ok guys. Checked all the wires and everything, they are all correct, I might triple check them though, just to be 150% positive. But, if they are right, I still don't know what it's doing. I might just pull all the plugs and check them. But until I do, I've got a slight tidbit of an update, I think I might have an exhaust leak somewhere at the manifold. Could that cause it to do what it's doing? And I'm assuming y'all can watch the video?

You could take the exhaust manifold completely off an engine and it would not cause a misfire.

How was it running before you changed the plugs? Make sure that you have the proper gap .035 You may have a bad wires and or cap and rotor?

I don't know if it's misfiring or not. I'm worried about the loud sound. Can y'all watch the video or not? That's the best way to get an idea of the sound. Before I changed the plugs it would just run like I had heat soak symptoms all the time. It wasn't making the horrible sound though. Just chugging real bad. I set the gap as close to .35 as I could. Could excess heat cause those to go bad?

if you could, take a video from each plug location and follow the wire back to the cap. do that for all 6. then we can at least tell you the wiring is correct and tell you what else to check.

ps i watched your video, and aside from a couple times it sounded rough, the sound wasnt great to show the problem, i had trouble hearing it most of the video honestly.