I need help.... I just cant make this work.

[Br0wn0ne]

So, ill try to keep this short but ive been at this a long time.

So i built a stroker. Let's start with saying im far from inexperienced in automotive. Ive been doing it as a career now for well over a decade. Anyways, picked up the 4.6L clegg kit. 8.8:1. Clearwater cylinder head. Comp cam 163-201-5. 24lb injectors

So it seems to run fine. Above 4k it starts to stumble and fall on its face. It feels like it loses a couple cylinders. Once I let off it will smooth out after a second or two. Timing looks good. Fuel pressure looks good. It throws codes for cyl 1 or 6 when it acts up. Ive swapped plugs, coil boots, and injectors around. It doesnt follow. Also tried a new coil rail. I cant make a change in this. Im running out of idea. Im about to pull my cylinder head and send it to the machine shop as a last ditch effort. Its a new head. All new springs. When it acts up with a vac gauge attacked the vac tanks and starts banging around all over. So idk if its valve float? Maybe guide is slipping out? Maybe thats normal for these. Idk. When its cold it doesnt have a issue. But as soon as its warmed up, it acts up.

Also its a 2002 with a 5 speed. Dont think I mentioned that.

Thanks for any input. Im jusy at a loss.

[mpgMike]

I know you said you tried a different coil pack, but cylinders #1 & #6 fire from the same coil. I'd still be looking at coil issues. Furthermore, heat will cause a weak coil to get even weaker.

[Br0wn0ne]

I know you said you tried a different coil pack, but cylinders #1 & #6 fire from the same coil. I'd still be looking at coil issues. Furthermore, heat will cause a weak coil to get even weaker.

They are? I didnt know that. Ill try another coil and maybe check the harness and connector then. Honestly I didnt even think of that with them being on opposite ends. Thank you. Ill dive back into that this week.

[Gorilla]

The 4.0 is a weird double firing spark setup. I have doubts that it's the cause, since it runs well on closed loop and doesn't seem to throw codes until you romp on it, but it is the common thing in a 1-6 misfire.

Issues on opposite ends suggests not a vacuum or exhaust leak.

It could be way off on the fuel tables causing it to go very lean or very rich on open loop. Ideally a wideband O2 in the merged exhaust would give you some more accurate indication on that. But not as to why 1-6 specifically causes an issue.

The fuel table looks like this (stock-ish);


There is a pretty big step up in pulsewidth right at 4000rpm if you're at sea level, and then if fuel enrichment hadn't been adjusted, they're usually set to add fuel around 11 seconds. And mine as it came stock was way too rich at my altitude (6,000 ft) running around 11:1 when it finally kicked in. I've gotten it dialed into to go to 12.8 pretty quick and stay there stable, in part by having fuel enrichment kick in pretty quick, but dialing back the enrichment a good amount.

Another possibility is that your fuel pump isn't keeping up with the flow demands, though it's hard to monitor that while driving without investing in some added bits. The TJ 4.0s run at all different fuel pressures and injector specs depending on the year, so that might take some digging. The Walbro 255 for our system has been recommended to me if the stock (Bosch) pump can't keep up.

NRT makes a fuel rail with a port for a fuel pressure gauge, which you could do as an electronic gauge feeding into the dash.

[Br0wn0ne]

The 4.0 is a weird double firing spark setup. I have doubts that it's the cause, since it runs well on closed loop and doesn't seem to throw codes until you romp on it, but it is the common thing in a 1-6 misfire.

Issues on opposite ends suggests not a vacuum or exhaust leak.

It could be way off on the fuel tables causing it to go very lean or very rich on open loop. Ideally a wideband O2 in the merged exhaust would give you some more accurate indication on that. But not as to why 1-6 specifically causes an issue.

The fuel table looks like this (stock-ish);


There is a pretty big step up in pulsewidth right at 4000rpm if you're at sea level, and then if fuel enrichment hadn't been adjusted, they're usually set to add fuel around 11 seconds. And mine as it came stock was way too rich at my altitude (6,000 ft) running around 11:1 when it finally kicked in. I've gotten it dialed into to go to 12.8 pretty quick and stay there stable, in part by having fuel enrichment kick in pretty quick, but dialing back the enrichment a good amount.

Another possibility is that your fuel pump isn't keeping up with the flow demands, though it's hard to monitor that while driving without investing in some added bits. The TJ 4.0s run at all different fuel pressures and injector specs depending on the year, so that might take some digging. The Walbro 255 for our system has been recommended to me if the stock (Bosch) pump can't keep up.

NRT makes a fuel rail with a port for a fuel pressure gauge, which you could do as an electronic gauge feeding into the dash.

Okay so I got another coil coming from MSD. Just in case. Im gonna check the harness and plug while im in there to see if I have a chafed wire or something.

I been debating putting a AFR wideband. With my year I have the two cats that come right off the manifold, so idk where to mount it where its gonna work properly. Down by the merge is gonna be post cat. Which ive heard doesnt work. Precast there isnt really any room to weld a bung in. Any ideas on that?

Ive checked my fuel pressure with a mechanical gauge at the rail (it has a test port) and I dont seem to be losing pressure when it acts up. So I dont think fuel pump is a possibility. Its pretty steady. I dont remember what it was, but somewhere around 45+ I think?

If my fuel tables are out of whack, then im going to need to invest in a tuner or something I imagine? What are you using for you fuel tables? I been thinking about investing in HP tuners but know that we are limited on the stock ECU's for what we can actually adjust.

Also, thank you for the reply.

[Gorilla]

I'd recommend placing it where the exhaust has come back together and bends towards the back. The bolt coming out of the passenger motor mount is pointing to the location where mine is installed and it has worked well. I did alot of research on the effect of the pre-cats and while there is some, it's not important enough to prevent you from getting usable data.



This is a post I made about the install (PLX) and getting the data into HP Tuners.
https://www.rubiconownersforum.com/thre ... nk.119317/

[Br0wn0ne]

Okay cool. Good to know. Ill tinker with it this weekend. If I cant find a wiring or coil issue. I might order up a afr and get that mounted to see what its doing. It might be hard ti spot a fuel issue before it starts missing. But ill likely be able to use the data down the road for tuning. Really hoping I can make some progress. I miss my wrangler and I have a ton of other upgrades to move on too. I have new axles, steering, lockers, ans gears waiting to go under it. But I want to get this sorted first.

[Gorilla]

Technically with HP Tuners VCM scanner you can see and log the whole thing. You want an AFR module with an analog 0-5V output to feed into the Prolink if you want real time logging, but even without the AFR you'd have a complete picture of the advance, and be able to see AFR and correlate to the injector pulsewidth. The logs look like this and you can see I've put the AFR feed up high. The rest of the data is logged to my laptop directly off the ODBII.

[Br0wn0ne]

Okay cool. I just yanked the head off. Mkstly.for piece of mind. Gonna have my machine shop check it out. Its the only.part of my recipe that I didnt do myself or have my.machine shop do. The head is a clearwater head so it came pre assembled to "factory spec" which my comp cam is rated for factory springs but who knows. Ill have the machine shop beef up the springs a little and give it a once over. If nothing else for piece of mind. I tried another coil from MSD and it still had issues.

While the head is out. Ill place a order with HP tuners. Prolly weld a bung in the exhaust for AFR since its easy to get out at this point.

Would there be any point in deleting (rodding out) the cats? With HPT I assume I can tell it to ignore the cats and such. O dont have emissions inspections in my state. They dont look clogged, but they dont look great either.

[Gorilla]

You can wire the AFR analog feed into this;
https://www.hptuners.com/product/pro-link-plus/

You can output in AFR, lambda or raw voltage. Whatever you prefer.

You need an MPVI3 to tune the 4.0L Jeeps with ODBII at the moment. For some reason they are not supported on the new MPVI4.

No comment on the cats

[Br0wn0ne]

Can you still get the 3? That throws a bit of hitch in my giddyap. I might have to reach out to them. Under non supported it lists 4.0 wranglers year range 97-01 and 04-06. Mine is a 2002... so it is supported? kind of weird way they have it listed.

[Gorilla]

I would reach out. It's very confusing. And I'm not certain on the availability of the MPVI3 from them, but I would assume you would be able to find them used as the MPVI4 has some significant improvements in sample speed and onboard memory and the MPVI supports the GM systems very well which has a much larger user base. I would be upgrading if the MPVI4 supported my Jeep or my 997.2.

[Br0wn0ne]

Yeah.... they said im not supported with no ETA for support. Well thats dissapointing... well now idk what to do. Any other experience with any other tuners? This puts me in a bit of a issue because I think you are right about my fuel tables needing adjust. Along with I need to tune out my cats as well. Or I guess replace them. Just not really where I wanted to spend money. Ugh. Really feeling like j can't win with this thing. I really need tk get this thing running right again.... now im just hoping the machine shop finds something with the head tk explain alot of this. Im at a loss.

[Br0wn0ne]

They recommend i try to find a mpvi3. They don't sell them, but said there might sk be some it there or used. So I guess ill start my hunt for that.

[mpgMike]

Take a look at rusEFI.com and their UAEFI stand-alone ECU. I'm using it on my '95 ZJ 4.6 stroker. It comes in around ~$200 US.