Intermitant miss

[ALASKANMADMAN]

Back to my 99 TJ 4.0 AX15 all new and upgraded pretty much everything! After lots of recent upgrades it was running perfect but outta the blue at about 2750rpms in 4th gear its getting weird intermitant miss and more so under load with mild incline. Couple times when misfired watched Tach bounce from 3000 to 4000 real fast, while other times it just stumbles. Happened couple times in 3rd but other then that will get a backfire shifting up thru 2nd and 3rd then into 4th but very few times compared to the weird miss. All ready changed everything and was getting check engine light tps high and low. TPS is at about .7 as that's as close to .5 as can go and after clearing codes go cel again.....so, TPS is good and so is EVERYTHING else. My thought is the 26 year old ECM so cheeking if anyone else delt with ECM issues and has anyone come across and unlocked ecm in their journeys. Thanks in advance.

 

[TJ Jim]

Fuel pump

 

[macleanflood]

Check fuel pressure as mentioned. Clean and inspect grounds and battery terminals. I'd pull and clean or replace your CPS. Ohm check your coil. How do the spark plugs look? Ever change the o-rings on the injectors?

-Mac

 

[John’o]

This sounds like a Camshaft Position Sensor. If you are getting a blip at a specific RPM depending on gear. I chased it for 2 months until I figured it out. Cringed at 2700 in 3rd. Hit every time.

 

[ALASKANMADMAN]

Fuel pump

Nope. New and 52psi to rail

 

[ALASKANMADMAN]

Check fuel pressure as mentioned. Clean and inspect grounds and battery terminals. I'd pull and clean or replace your CPS. Ohm check your coil. How do the spark plugs look? Ever change the o-rings on the injectors?

-Mac

All check out and new

 

[ALASKANMADMAN]

This sounds like a Camshaft Position Sensor. If you are getting a blip at a specific RPM depending on gear. I chased it for 2 months until I figured it out. Cringed at 2700 in 3rd. Hit every time.

New distributor

 

[macleanflood]

All check out and new

New doesn't mean it works...what brand CPS?

-Mac

 

[John’o]

Crankshaft Position Sensor. My bad. Meant Crankshaft.
This one: https://www.amazon.com/dp/B006EFUF2I?tag=wranglerorg-20

 

[ALASKANMADMAN]

New doesn't mean it works...what brand CPS?

-Mac

Its a new Cardone distributor. No codes on it

 

[ALASKANMADMAN]

Crankshaft. Sensor.
This one: https://www.amazon.com/dp/B006EFUF2I?tag=wranglerorg-20

Has a new distributor as well. No codes

 

[John’o]

It is a different part from the distributor ring. It goes into your bellhousing

 

[ALASKANMADMAN]

It is a different part from the distributor ring. It goes into your bellhousing

You are correct. Sorry for the confusion on my part. That was replaced 3800 miles ago when new motor and tranny installed along with another new alternator and distributor. I don't get a code on it now but doing a driving code test with the snapon box but will pull it and bench test it as could be an issue anyway. Thanks man, all these posts lung transplant meds kinda hits ya like altzimers and some basic crap gets skipped right over. Good call