Blackcherokee290

Hello everyone,


I have a 2000 cherokee classic with 4.0L I6, and is a CA emissions. Has about 168,900 miles on it. Decent Oil Pressure. I have a rough idle issue that occurs only in drive or reverse at a complete stop, which is made waay worse with the A/C on. The RPMs seem to hang low at 500 and theres a stumbling vibration, nowhere near as bad as I went through with the heatsoak misses, but still noticeable. The CEL keeps coming on with P0432 (main cat bank 2 below threshold).


Heres a description of my fight with idle issues:


150,580 miles – Replaced ignition coil with autozone duralast and 6 new bosch spark plugs
150,605 – Throttle body and IAC removed and cleaned then reinstalled
150,692 – Removed and replaced all 4 O2 sensors with rockauto NTKs
154,051 – Added gumout “regane” high mileage fuel system cleaner
154,204 – Timing chain replaced
156,878 – DTCs: P0302, P0202 – then erased
157,667 – Removed fuel injectors and cleaned (backflushed with seafoam, air compressor, and battery). Replaced injector #2. Installed TSB heatshield and had PCM reprogrammed by dealership for heatsoak issue (TSB:18-039-03). All 6 fuel injector O-rings replaced as well.
157,730 – Removed and replaced TPS and IAC motor with mopar parts. Then used Autozone fuel pressure gauge: 0 PSI 30 minutes after shutdown, 20 PSI at first key-on (no start), 44 PSI at second key-on (also didn’t start it), 46 PSI at hot idle
157,835 – Compression test: At 3 cranks, all 6 cylinders were within 140 to 150 PSI. At 4 cranks, all 6 cylinders were within 150 to 157 PSI. Removed and replaced all 6 spark plugs with regular champion double platinum copper core and gapped to .0035”. I added 1/3 a can of seafoam to the full fuel tank.
159,845 – P0432 (after hot trip to desert) and manually erased
160,279 – P0432 and manually erased
160,889 – P0432 and manually erased
163,420 – Replaced all 4 O2 sensors again with NTKs from rockauto
166,000 – Complete cooling system overhaul and new serpentine belt. Also installed extended idle switch. Fixed some vacuum leaks on the passenger side.
168,000 – Got back from Northern Nevada (went thru death valley, outside temps around 123F). A few weeks later I was sitting idling with extended idle on for about 50 minutes in park when the RPMs jumped and went racing everywhere and then idle switch stopped working for awhile (I posted a thread on this but I still haven't figured it out- don't mean to double post things). Ever since then the idle has been crappy. I went home and disconnected idle switch and reset the ECU with no change in the idle.
168,319 – P0432 and this time I used a program to read the FF data


I typed it out exactly as it is on the screenshot……


Frame Number: 0
Fuel System 1 Status: CL
Fuel System 2 Status: CL
Calculated Load Value: 5.9%
Engine Coolant Temperature: 207F
Short Term Fuel Trim – Bank 1: 0.0%
Short Term Fuel Trim – Bank 3: -40.6%
Long Term Fuel Trim – Bank 1: 3.1%
Long Term Fuel Trim – Bank 3: -36.7%
Short Term Fuel Trim – Bank 2: -4.7%
Short Term Fuel Trim – Bank 4: -43.8%
Long Term Fuel Trim – Bank 2: 2.3%
Long Term Fuel Trim – Bank 4: -35.9%
Intake Manifold Absolute Pressure: 15.1 inHg
Engine RPM: 640 RPM
Vehicle Speed Sensor: 0 mph

I know diagnosis over the internet is really hard but I just need some pointers. If I have to replace the cat I will try to learn how to....or just pay a shop if it's during the semester. I know I need to get it smogged soon, so the CEL has got to be figured out....as does the idle.

Blackcherokee290

Bump....


I have never bumped a thread before but since its been 1 week and 500 views I figured its time.

OH and check engine light went off on its own for 1 day, then BAM its back and same code....been on for 4 days straight

CCKen

Frame Number: 0
Fuel System 1 Status: CL
Fuel System 2 Status: CL
Calculated Load Value: 5.9%
Engine Coolant Temperature: 207F
Short Term Fuel Trim – Bank 1: 0.0%
Short Term Fuel Trim – Bank 3: -40.6%
Long Term Fuel Trim – Bank 1: 3.1%
Long Term Fuel Trim – Bank 3: -36.7%
Short Term Fuel Trim – Bank 2: -4.7%
Short Term Fuel Trim – Bank 4: -43.8%
Long Term Fuel Trim – Bank 2: 2.3%
Long Term Fuel Trim – Bank 4: -35.9%
Intake Manifold Absolute Pressure: 15.1 inHg
Engine RPM: 640 RPM
Vehicle Speed Sensor: 0 mph


I don't own a '00/'01 XJ California emissions XJ but I do have a 2001 diagnostics manual, and it does not refer to a 'Bank 3 or 4'.


Are you able to pull up and any diagnostics trouble codes?


Edit: There is no P0432 listed.


By what I see STFT and LTFT for your bank 3 and 4 shows that those/that banks are running way too rich. Trim in the -30's and -40's is insanely high.


Here's a pic of the CA emissions exhaust. Can you correlate?

Blackcherokee290

Thanks for the reply CCKen,

Yeah I dont really know what the FF data really even means, I have ideas but dont know why there are 4 banks of FT.

And yes there is a DTC (the CEL cycled off today, it seems aggressive driving turns it off...then idling under some accessory load turns it on). I am including a screenshot of the OBDII reads. Regardless of CEL, it still shudders and idles poorly, sometimes at 900 RPM and sometimes around 300-400 particularly in gear.

I looked at your picture and that is the same configuration as my exhaust, although I believe there is another catalytic converter further down the line but I'm not sure of that.

CCKen

Yes, the California exhaust does have an unmonitored downstream Catalytic Converter.


That app you are using may not realize its dealing with an XJ with only four O2S'.


Anyway, give this a try: Get a can (or two) of Chrysler Combustion Chamber Cleaner and run it through you TB to see if it will clean out your combustion chambers and purge all the nasty crap out, and in the process, clean out your downstream devices, like the Cats.


I've used it in the past and it does work.


Follow the instructions on the spray can.


See what happens.


When you see Short Term Fuel Trim, you are looking at the PCM's response to the O2S' in that bank. A negative number indicates the PCM is pulling fuel off (fuel injector band width) to compensate for a rich mixture (that the O2S' are detecting). A positive number would show that the PCM is adding fuel for a lean condition.

Blackcherokee290

Okay called the local Chrysler dealership and they said they cant buy Mopar combustion chamber cleaner any longer due to CA environmental laws. Why this is I have no idea.... I checked amazon and its restricted shipping but I still can get it since its 48 state shipping only. I read on a few forums that seafoam in the fuel can splatter the cats or the O2 sensors with crap and since I'm on my second set of new O2 sensors I don't really want to do that again. Although all I did last time was put seafoam in the fuel tank, I never did put it straight into the TB and use it like this:

http://www.jeepforum.com/forum/f13/m...leaner-945851/

Still, I'm up for trying it since its not going away.

And yea now that you have explained it, I can see how the PCM is definitely trying to correct for a rich fuel mixture (based on the O2 readings only?) by backing off the FT. Maybe I'll try data logging some sensor data while I drive.

EZEARL

Read the page but note post #48:


https://www.cherokeeforum.com/f2/spa...190691/index4/

CCKen

^^ Good idea.

CCKen

Don't use seapuke.

Blackcherokee290

Ezearl, thanks for that link, and I skimmed the thread and read the post you suggested. I'll give that a shot this weekend if I have the time. When the can of the combustion chamber cleaner arrives I will go ahead and use that too. I really appreciate you guys giving me some advice....I'll let you know what happens. If anyone else wants to chime in or something go for it.

Blackcherokee290

OK so the Mopar Combustion Chamber Cleaner finally arrived in the mail. Hopefully going to give it a shot tomorrow. As CCKen advised I'll follow the directions on the can.

Oddly enough the P0432 check engine light turned off again (for like 4 days now wtf) but it still idles like crap in drive with the AC.

I will report back with what happens in the next few days.

BTW....whats a air pump? The cleaner can says:

Remove air cleaner (I'll warm it up with the cleaner on....dont want to leave it off for the entire warmup since I'll be outside under a tree), run engine until at temp, if equipped disconnect air pump. Spray all linkage controls to insure against sticking. With engine running at medium idle (750RPM) spray entire can directly into throttle body. Keep engine running just fast enough to prevent stalling. Avoid excessive engine speed. When can is empty, turn off engine and let stand 5-10 mins. Restart and run at low speed for 5 mins to completely expel cleaner. Reconnect air pump hose to engine if equipped.

CCKen

The air pump referenced is a Leak Detection Pump (maybe). Some vehicles had an air pump to pump air into the exhaust/Evap system. The Leak Detection Pump only pumps air into the Evap system to test for leaks.

Blackcherokee290

Ok so I did the mopar combustion cleaner last night. Kept spraying it into the TB and feathering the throttle to keep it idling. No smoke but some burning type smells and the CEL was flashing and threw all kinds of codes. Let sit 10 mins and it had trouble but it started on 1st crank. Let it idle for 10 mins, no smoke, then drove it like i stole it.....and the mpgs went UP! I used to get 11.8 mpg if i drove decently, and now i get 15.2 if i drive it like a nutcase, maybe a second treatment is in order haha. I went ahead and erased all 6 DTCs.

Still stumbles and runs rough at idle in gear with A/C though, primarily when up to operating temps (i think this is because it transitions to closed loop?)

So yea better accels, better mpgs, engine sounds healthier, idle still weird. One thing i noticed is theres like a particular speed (1-3mph) when i roll to a stop when the engine just "clicks" into crappy idle.

CCKen

You may want to test your TPS. Below are the test procedures. Use a safety pin to back probe the connector. Make sure the pin is bottomed out in the connector adjacent to the wire.





Safety pin:

CCKen

The above tests are done using a digital multimeter.


You can do a sweep test (looking for dead spot on the TPS variable resistor) using an analog multimeter, set to 5 volts DC scale.


Ref. above test chart - Back probe the Orange/Dark Blue tracer signal wire. Connect meter (+) probe to pin. Connect (-) probe to the braided bonding strap at the firewall or to the battery negative post.


Turn the ignition switch to ON?RUN (engine off). Slowly advance the throttle from idle to WOT. The meter needle should follow the throttle movement without hesitation. Hesitation indicates a dead spot in the TPS variable resistor.





I did this test and found a dead spot at just above idle on my OEM TPS.