prkirby

Alright, I'm going to try and be as thorough as possible on where I'm at in the troubleshooting process. Any help, pointers, general ideas on where to research further would be greatly appreciated. I've put A LOT of time into this swap and troubleshooting, and I don't want to give up and take it to a shop yet.

A bit of backstory:
Had an 01' XJ 4.0L automatic that served me well for about 8 years. The head cracked on it a few years ago, so I had a reman dropped in by a shop. Ran great, other than of course all of the small fixes, cooling system overhaul, etc that I had to do. Unfortunately, the Rust Belt finally started taking it to its grave, piled on with all of the other electrical and creature comfort fixes I had laid out ahead of me, I started looking for something with a clean body to make my long term project. I found a '93 XJ with a manual in North Carolina that had ZERO rust, and was owned by an old mechanic, was in great shape at a great price. The only problem was it was burning a good bit of oil during idle, and he said valve covers were probably shot. I thought "Well I've got a reman in the '01 with only 40k on it, doing the swap myself will be a fun project to jump into the deep end with"

Fast forward a few months, starting to burn up oil like crazy and I decided it was time to make it happen. Ripped the engine out of the '01, and after a few weekends, had it all settled in the '93 and 'running'. However, I noticed some immediate serious power loss, trouble accelerating, started hating any hills at all in 5th, etc etc. This thing had plenty of power before, in fact I could get the wheels to chirp on it if I felt like being 'that guy'.

So, here is my trouble shooting process, part swaps, and where I am at currently. Any pointers to move forward with troubleshooting would be greatly appreciated.

Current Symptoms:

• Occasional to consistent backfiring, it doesn't seem to correlate to temperature.
• Power loss, trouble accelerating
• Occasional stalling coming to stops, lower RPMS
• Rich smelling exhaust
• A 'Chuffing' sound out of the exhaust, is the best way I can explain it. It sounds like port chuffing on ported subwoofers that very consistent, if that's helpful at all.
• Shakey / especially week at lower RPM's, between 800 and ~ 1500 seem to be its least favorite.
• Plugs 5 and 6 seem to be getting light oil deposits.
• Tachometer seems to be a little flaky, especially on start up (however, the CPS is new, see below).

Troubleshooting / issues fixed up to this point:

• The very first thing I realized, was that I accidentally overfilled oil by almost a quart like an idiot. Drained the quart out and got a substantial amount of power back, but it was still rather lacking, and I was still getting backfire.
• Swapped in the TPS from my buddies YJ that was known working, no noticeable difference.
• Checked all ground points with a multi to make sure was reading consistent voltage drops from the battery across all, seemed to be good. I did not however do a deep clean of them, since the readings were happy.
• Distributor, ignition coil, plugs, and plug wires are all basically new, purchased just before the engine swap. Rotor cap is new and seems to be happy.
• Unplugged my O2 sensor just to see if it made a difference, nothing that I could tell.
• Checked for any intake vacuum leaks via brake cleaner method, can't find anything at all. Seems to be happy.
• The intake manifold was filthy from the old block, so I brought the new one over and gave it a deep clean. No difference.
• Rented a fuel pressure tester kit, all was to spec.
• The inside of the bell housing was pretty rough when I did the swap, gave it a clean, but decided it couldn't hurt to swap the CPS after reading about its effect on timing. No difference.
• MAP sensor seems to be fine, IE haven't noticed any leaks or anything by it. I figured it probably isn't that since it was working fine with the old block.
• The catalytic converter was super rough on the inside and falling apart, so I decided to delete it for troubleshooting purposes. No difference.
• IAC motor was pretty hagard with sludge from the old block, so put a new one on and didn't notice a difference. If anything, it seemed to make the backfiring more consistent / worse
  • (did this at the same time as putting in a new set of plugs so I could witness buildup better, since the old 'new' ones were in the old block for a month or so and were already dirtied up a bit)

I'm kinda of at a loss at this point. No check engine lights, no hidden codes. When I put the new block in, I followed the hanes manual protocol to find TDC and align distributor to fire on plug 1. I thought alignment looked the same as the distributor on the old block, so I thought all was well, IDK. As side note, the '01 block was using a coil pack, the '93 does not. Not that that should make a difference.

Potential next steps / thoughts I have:

• On the '93 wiring harness, there is a plug for a 'coolant temp sender' and then the plug for the coolant temp probe that goes into the thermostat housing. The 'coolant temp sensor' is a single wire plug that had a spot for the sensor on the rear drivers side of the block. The head on the '01 block does not have that spot. From what I've read, and what I've seen from wiring diagrams, this plug is only for the dash gauge, so I have it unplugged for now. It seems like the other sensor actually talks to the ECU, and controls the aux fan if needed. But if I'm wrong, that would be great because apparently the ECU uses the coolant temp to adjust fuel/air ratio and timing. But I have a feeling that's unrelated.
• I suppose I could go through and give my grounds a good hearty cleaning, but I don't really thing that's it. Can't hurt.
• I've flashed the ECU after each sensor swap I've done. Doesn't seem to help at all, in fact sometimes seems to make it worse.
  • (I used the method found on a different thread: https://www.jeepforum.com/forum/f11/...sed-xj-899735/

Sorry for the long post. I want to be thorough so no one has to waste time asking what I have / have not done yet. Any help would be greatly appreciated of course. Thanks!