All gears studder

[JPNinPA]

PCM is unlikely.

I'd first clean the grounds.
Check the temp sending unit.
Verify there are no intake leaks
CHECK Your plugs condition and model number.
Fix the thermo

Do the simple cheap items first and not many of these take this much time.

Good luck!

 

[Bond--007]

PCM is unlikely.

I'd first clean the grounds.
Check the temp sending unit.
Verify there are no intake leaks
CHECK Your plugs condition and model number.
Fix the thermo

Do the simple cheap items first and not many of these take this much time.

Good luck!

As always, thanks for the help. I'll post back once progress is made

 

[Bond--007]

UPDATE: cleaned all the grounds under the hood (some were in worse shape than others). Took the jeep for a test drive and the same hesitation was there. For sh*ts and giggles, I decided to remove the coolant temp sensor. It had a lot of build up on the end and was very dis colored. I had a new sensor I purchased online a couple days ago. I installed the new one and took the jeep for the test drive. No more hesitation in the run. Looks like it's fixed. I'll drive it to work the next couple of days to see if the issue returns

 

[Bond--007]

Ahhhhhhhh

:scratch: So driving home from work and the jeep started the "miss" again. It's not immediate after start up like it was prior to the coolant temp sensor change. It started about 2 miles down the road before I got on the interstate. Completed the following:

- Cleaned the grounds I could locate under the hood
- Changed the coolant temp sensor and cleaned the connection with electrical spray prior to assembling
- Cleaned the CPS, IAC, TPS, CKS, IAC & MAP connections and placed a little dielectric grease inside of each connection
- Installed the truck battery and had both the battery & alternator tested (passed)
- Removed the 3 connections to the PCM, cleaned them with the electrical spray, & placed a little dielectric grease inside
- Also did the PCM reset (remove the pos and touch to ground for 30 secs.....etc)


Not sure what else to check from here other than pulling the thermo and testing/replacing it. The part number on the Champ spark plugs I installed - shows
412
RC12LYC


Chasing this little gremlin all over the jeep is now starting to get under my skin :evil:


BTW, had the truck in for an oil change and they tested the battery. The battery passed (originally was in the jeep).... smh

 

[JPNinPA]

So it doesn't shudder when you first start like it did before the temp sending unit replacement.

Does it still stop when you reach operating temp?

The plugs are fine for a 97TJ. Gap 0.35
You could use 7034 double platinum but the double will not improve anything other than longer life.

In the long run fixing the thermo is a good thing and will limit how long the shudder occurs. But, it may not fix the issue.

 

[Bond--007]

So it doesn't shudder when you first start like it did before the temp sending unit replacement.

Does it still stop when you reach operating temp?

The plugs are fine for a 97TJ. Gap 0.35
You could use 7034 double platinum but the double will not improve anything other than longer life.

In the long run fixing the thermo is a good thing and will limit how long the shudder occurs. But, it may not fix the issue.

the shudder occurs later (~ 2 miles down the road) not at first start and take-off like before. Once it's up to 210*, the shudder doesn't occur and runs great. The other sensor I'm leaning towards now is the Intake Air Temp sensor. The reason for the thought process is when I removed the throttle body, everything was black from grime including inside the intake. If the sensor is fouled from grime, I'm thinking this could lead to the shudder since it is read in open loop against the standard stored tables in the PCM for open loop. Thoughts?

 

[JPNinPA]

The air temp sensor is possible. At some point I did ask if you cleaned it. You could try the unplug method on this and the O2 again.

Just check for leaks in the event something loosened. Spray carb cleaner or WD40 around the base of the TB. IAC, vac lines, intake at the head (cylinder by cylinder) then each injector then each plug. Small gaps can close up as the engine heats. Though this seems to be a open loop/closed loop issue.

The past few days its been 15-30 deg. It has taken about 2 mi for the engine to reach a full 210. The PCM does look for the engine temp to reach 65 deg then 160 deg within some time.


How did the plug you pulled from the engine look?

 

[JPNinPA]

BTW the resistances I posted are good for both the coolant temp and air temp sensors.

 

[Bond--007]

How did the plug you pulled from the engine look?

The spark plugs?

 

[JPNinPA]

The spark plugs?

Yes
Spark plug

 

[JPNinPA]

Again try disconnecting the O2. Then the air temp sensor.

 

[Bond--007]

Yes
Spark plug

The plugs for 1 & 2 looked fine as well as the wires. The plugs for 3 & 4 looked fine but there was corrosion inside the boots for both plugs

Again try disconnecting the O2. Then the air temp sensor.

By unplugging the O2 sensor, this causes the EUC to go into OPEN2 loop according to the scanner. It seems like the issue is related to the primary OPEN loop mode and whatever sensors are read during that time. The secondary open loop (OPEN2) appears to bypass the initial sensors from primary open loop and operate directly from the ECU. From the research and web crawling, here's what I found from Warm-Up mode and the sensors involved

ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warmup, the powertrain control module (PCM) receives
inputs from:

- Battery voltage - Brand new battery installed on Friday Nov 21
- Crankshaft position sensor - Replaced on Sept 18
- Engine coolant temperature sensor - Replaced on Nov 20
- Intake manifold air temperature sensor - Replaced on Nov 20
- Manifold absolute pressure (MAP) sensor - Replaced Sept 18
- Throttle position sensor (TPS) - Replaced Sept 18
- Camshaft position sensor signal (in the distributor)
- Park/neutral switch (gear indicator signal—auto. trans. only) - N/A – Manual Trans
- Air conditioning select signal (if equipped) - N/A – No A/C
- Air conditioning request signal (if equipped) - N/A – No A/C

 

[JPNinPA]

That is all true.
Again

Again try disconnecting the O2. Then the air temp sensor.

By disconnecting the sensors should rule out internal or intermittent issues. Issues like bad connector. Internal short improper wiring. It only takes a min to disconnect while the engine is running rough.

 

[Bond--007]

**UPDATE**
Unplugged the O2 sensor this morning for my trip to work and unplugged the air temp sensor. The Jeep still hesitated and studdered as before but it wasn't as rough as usually (the hesitation usually won't stop until you let off the throttle, this time is hesitated but I didn't let off the throttle and it stopped)

 

[JPNinPA]

Just for clarification. Current issue is: the engine hesitates only when accelerating (not idling) while warming after cold start and a mile or so and continues until either the engine warms up or the engine idles?

Just correct and clarify as details are important.


PS where did you get the TPS from?

 

[Bond--007]

Just for clarification. Current issue is: the engine hesitates only when accelerating (not idling) while warming after cold start and a mile or so and continues until either the engine warms up or the engine idles?

Just correct and clarify as details are important.


PS where did you get the TPS from?

The issue summary provided is correct.

The TPS was purchased online as aftermarket w/ warranty Throttle Position Sensor

 

[JPNinPA]

The issue summary provided is correct.

The TPS was purchased online as aftermarket w/ warranty Throttle Position Sensor

If you have the old TPS put it back in to verify if this is the issue. From the description that it only happens while stepping on the skinny pedal and not at idle is likely a TPS issue. TPS end up having dead spots in them where the resistance does not change as you depress the pedal. So you end up leaning out the engine to a shudder. If you depress far enough you may go past the dead spot and it will act like normal. At idle the IAC sets the idle gas air mix.

You will read that the aftermarket TPS have been known to be bad right out of the box. It's worth a try to place the old one back.

 

[Bond--007]

I dropped it off at the garage I use for repairs I can't do on my own or don't have the time. I provided them with a list of what was completed already completed. I'll provide an update as soon as they have completed their diagnosis.

 

[Bond--007]

Took it to the garage and had them scan the OBDII. They came up with 2 codes stored in the memory, P0463 & P0132. I thought the O2 code was due to me unplugging it the other day. They then did a data log on the sensor outputs and it showed the O2 sensor data was very erratic (lean, rich, lean, rich, etc) whereas the downstream was steady. I contacted the company I bought the sensor from and they are sending a replacement.

info from the O2 box:
NTK
23506

just making sure this is the correct part number. Like I said in my previous thread, once I changed the O2, the jeep ran great for about 2-3 days

 

[JPNinPA]

Consider a intake leak on one cylinder will cause the erratic O2 sensor reading. Intake leak could be a cylinder, Injector, hung valve, or spark plug. Typically these things will continue past warmup. But smallleaks at the intake can seal as the metal expands. Just a thought.

Another possibility is the wiring is melted on the new O2. If the wiring wasn't secure or run too close to the exhaust it could melt.