Need help with rough idle and misfire

JSW

JSW

New Member
Joined
Mar 22, 2021
Messages
4
Location
North Port FL
I have a 97 TJ with the 4.0 and I am having an issue with a rough idle and a misfire type of jerking when driving. This problem however is intermittent. Here’s my story and what I’ve done.

Had the heater core and a/c evaporator replaced by a mechanic. The next day the Jeep died and would crank but not fire up. Jeep was towed home and the next day it started with no issues. I have replaced the following items so far
Plugs
Plug wires
Distributor cap
Ignition coil
TPS sensor (NTK)
Upstream o2 (NTK)
Cleaned the throttle body
Crankshaft Position sensor

My son just got home and said it did it all the way home, however I could not get it to duplicate the issue. I checked for vacuum leaks as best I could. Is there something that could have happened while replacing the heater core?? Or just coincidence.
 
Chris said:
Is it throwing any codes?
Click to expand...
Check engine light came on once and we went directly to Autozone but their reader said there were no codes. I’m thinking I need to use a better reader. Light has since turned off. I recently replaced the IAC and it was running great for a week and now we’re right back to idling rough at first start up and smooths out after driving for a bit
 
JSW said:
Check engine light came on once and we went directly to Autozone but their reader said there were no codes. I’m thinking I need to use a better reader. Light has since turned off. I recently replaced the IAC and it was running great for a week and now we’re right back to idling rough at first start up and smooths out after driving for a bit
Click to expand...

A better reader would help quite a bit, especially if it is one that can do real time data. That will tell you a lot because you'll be able to see the engine running in real time and this will help you nail down what exactly is causing the issue.
 
Simple and easy process of elimination.
Battery age, alternator output is?
Battery connections???

Plugs...what mfg did you use?

Throttle body was last cleaned when?

Fuel pressure is???


Start there


****Apologies on missing your TB cleaning.
 
Chris said:
A better reader would help quite a bit, especially if it is one that can do real time data. That will tell you a lot because you'll be able to see the engine running in real time and this will help you nail down what exactly is causing the issue.
Click to expand...
Borrowed a better reader. Still nothing. No codes and no misfires even though it was idling rough as he pulled into the driveway. Ugh.
 
JSW said:
Borrowed a better reader. Still nothing. No codes and no misfires even though it was idling rough as he pulled into the driveway. Ugh.
Click to expand...
It would help to have a nice reader with real time data. With that you could definitely tell a lot more in regards to what's going on in real time.
 
Thank you for the help. Ended up throwing a code for Camshaft crank P1391. Had already replaced distributor and Crankshaft position sensor. And of course I’m the middle of all of this the transmission went out on it. At the advise of some of these forums I replaced the Crankshaft Sensor with a Mopar one and haven’t had an issue since. So take it from me and save hundreds of dollars and a huge headache and use genuine parts. Ugh!!!
 
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