Random inconsistent miss issues

[lawsoncl]

Originally Posted by maxbraketorque

Did I say cheap Chinese or suggest a low cost sensor? I'm sure some OEM CPS sensors last 300K+ miles, but the reality is that the OEM sensor can go bad without a hint of warning at much lower mileages, as it did with mine that only had 110K miles the vehicle. I agree that the CPS is not likely to be the cause of his issue and I even noted that in my response, but I was just trying to provide some potentially helpful advice. I'm beginning to think that I choose the wrong forum to discuss XJs.

Easy there. I'm just pointing out that the quality of aftermarket parts sucks. People who don't realize this can actually cause themselves more headaches when they start blindly replacing parts with poor quality replacements. There are plenty of examples on this forum of new parts being bad right out of the box, and the person thinking "well that can't be the problem because it's brand new".

[LedSled]

Alright so I went and bought a noid light set to confirm what I thought was the issue but noid light is blinking as it should be so now I’m back to square one

[LedSled]

It also seems to idle lower. Around 600 rpm. Any suggestions

[lawsoncl]

Originally Posted by LedSled

Alright so I went and bought a noid light set to confirm what I thought was the issue but noid light is blinking as it should be so now I’m back to square one

How's the wiring look where it transitions between the engine to the firewall? It's not uncommon for the wiring to become chaffed or frayed inside, particularly if the motor mounts are bad. Often it shows up only when the engine moves during acceleration. I'd wiggle and shake that harness and see if it stumbles at idle.

[four_shot]

^^This. It is a known issue . The injector harness will chafe where it bends around the fuel rail.

[LedSled]

Originally Posted by lawsoncl

How's the wiring look where it transitions between the engine to the firewall? It's not uncommon for the wiring to become chaffed or frayed inside, particularly if the motor mounts are bad. Often it shows up only when the engine moves during acceleration. I'd wiggle and shake that harness and see if it stumbles at idle.

Was one of the first things I checked. Harness looks fine. No chafing

[LedSled]

Ok so here’s what I’ve checked so far. Wiring is good from pcm to injectors. Did notice a chafed spot on the pigtail connector on the number two injector but it’s not causing an issue. I will replace it after I fix the current issue. Clean IAC and replaced TPS sensor. I noticed an improvement in driving with the new TPS but the miss and noise is still there. I’m starting to think something internal. Possibly lifters or valves.. Or I’ve heard of head gasket issues causing misfires. Will be checking fuel pressure and cylinder pressure this weekend. Maybe that will tell me something. Any tips or ideas are welcome. Thanks

[RCP Phx]

You keep saying the harness is good, but what have used to verify this? I don't see any values posted so........

[LedSled]

Originally Posted by RCP Phx

You keep saying the harness is good, but what have used to verify this? I don't see any values posted so........

I checked wires for chafing on the harness from pcm to injector plugs all was good except for the number 2 injector plug had some chaffing near the plug. I don’t think that would cause a cylinder one miss and I plan on fixing that after I resolve the current issue. I checked positive side of injector for 14v constant power and I got a little over 14v. Used noid light to check pulse ground side, and noid light was pulsing as it should. To me this would tell me that the harness is fine. If there is anything else I should check on the harness please let me know.

[RCP Phx]

First you were not checking for wire "integrity", second the individual "triggers" are negative (the important ones), the injectors share a common positive.

[LedSled]

Originally Posted by RCP Phx

First you were not checking for wire "integrity", second the individual "triggers" are negative (the important ones), the injectors share a common positive.

Not sure what you mean by “integrity” but I checked wires for continuity and resistance between pcm plug and injector plug. All had continuity and less than 0.5 ohms resistance. Not sure if that’s what you meant. And yes I said I checked that in the previous reply. I check positive side of injectors for 14v and I checked negative side with a noid light. The noid light was pulsing, like it should, so the grounding was working correctly from what I can tell. If this isn’t what you meant please explain. Thanks

[RCP Phx]

I was referring to "insulation integrity" that's where it started with mine.
A little long, but some good info..... https://naxja.org/forum/showthread.php?t=1145993

[LedSled]

This weekend we ran several tests but got nowhere
First we ran fuel pressure test and got a steady reading from idle to wot of 53psi
Next did a spark test on the coil pack and had good spark at the number one plug.
Next we ran compressions test and got these values.

#1. 155
#2. 166
#3. 159
#4. 174
#5. 166
#6. 156

So compressions seems to be good

Lastly we ran a scope into the cylinder and everything looked great for an engine with 227k miles cylinder walls were clean piston was clean.