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Discussion Starter #1
Hi all, I have a 2000 Intrepid RT with the 3.5 L engine.

I keep getting error code 172, (right bank too rich) every 500 or so miles.

The following have been changed to fix the problem but has not.

1. Both Upstreem O2 sensors
2. All 6 fuel injectors
3. Gas Cap
4. Air Filter

No other code is generated and the car runs great other than a slightly rough idle which it hasa always done since new.
It has 120,000 miles on it and just passed an emission test with flying colors.

Im stummped, any ideas?
 

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2000 said:
Hi all, I have a 2000 Intrepid RT with the 3.5 L engine.

I keep getting error code 172, (right bank too rich) every 500 or so miles.

The following have been changed to fix the problem but has not.

1. Both Upstreem O2 sensors
2. All 6 fuel injectors
3. Gas Cap
4. Air Filter

No other code is generated and the car runs great other than a slightly rough idle which it hasa always done since new.
It has 120,000 miles on it and just passed an emission test with flying colors.

Im stummped, any ideas?
could it be a lack of air getting to that side, air leak? vacuum leak? if you get less air in there the car will run richer, just a thought
 

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I've taken a look at my Powertrain Diagnostics manual for 1/1 Fuel System Rich. Here's the list of possible causes it indicates.
Catalyst plugged
Powertrain control module
Engine parts tolerance
Injectors stuck open
MAP sensor
O2 sensor (upstream)
Fuel pressure regulator
Wiring harness/connectors.

It talks about monitoring the mixture with a DRB III tool etc. which you probably don't have access to. It also talks about performing tests on component systems in the order below. I'm sure these tests are performed with the DRB III tool also.

Coolant Temperature Sensor
Throttle Position Sensor
MAP Sensor
Engine Mechanical Systems
Evaporative Emission System
EGR System
Intake Air Temperature Sensor

I don't know if any of that info helps but it was all I could dig up.
 

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Personally, I can't see how the MAP sensor or fuel regulator could be bad without it effecting both sides - but that still leaves a few things. The cat didn't occur to me - I guess I assumed that would show up as a code, too ...
 

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Discussion Starter #6
I forgot to add:

changed all 6 coil's and sparkplugs. (old plugs had perfect look to them, no rich deposits.)
No air leaks, all new gaskets (when injectors were changed)

All that is left is the downstream O2 sensors (I may reverse them and see if the problem moves) (but they are just for cat effiency and never flags a code for that.)
Map Sensor, but why always the right bank?
PCM, could be, maybe one of the coil drivers is failing on the right bank.
Engine itself is in great mechanical shape, always mobil 1 and burns no oil and compression is spot on.
funny thing was, the emmission test, the guy was amazed how well the car performed, all things were right on spec.
I wish it would throw another code just to help me out, but never does. Never a sensor code :(
 

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Woober Goobers!
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I was just passing on the information I looked up in the Powertrain Diagnostics manual. It's the same one the dealer mechanics would refer to. I agree with you on anything attached to the manifold that's defective should affect both sides. I'd tend to think a wiring problem or intermittant connection. And the PCM could be crapping out intermittantly. How often does this code show up? once a week? I assume it wasn't there when you did your emissions test? Maybe the wiring/connections to your upstream O2 sensor. I'm just a backyard mechanic. I thought the manual information would be helpful, however some items in there didn't make sense to me.
 

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I assume you've tried simply resetting the computer?

I'm not sure what you mean about the coil driver. I just checked through the FSM and the only thing I see in the coil circuitry that isn't fuse, PCM, or coil is a capacitor for each bank. Is that what you're talking about?
 

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Discussion Starter #9
pcm drives the coils, wondering if one of the drivers in the PCM is going.
It happens about every 500 miles or so.
Yes, I reset the pcm, its how I clear the code until next time.
You would think if it was a bad sensor connection, I would get a sensor code, but nope, its always 0172.
May have to give it to the dealer, but so far they have no idea either.
 

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D76G12 said:
I assume you've tried simply resetting the computer?

I'm not sure what you mean about the coil driver. I just checked through the FSM and the only thing I see in the coil circuitry that isn't fuse, PCM, or coil is a capacitor for each bank. Is that what you're talking about?

the pcm has 6 transisters (drivers) that control the ground side of each individual coil.
 

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Discussion Starter #13
Ok, here is the update:

Dealer could find nothing wrong, DRBIII found everything ok. Emissions were perfect.

Replaced MAP sensor (which contains air temp sensor)
Swapped O2 sensors left to right (both upstream and downstream)
Cleared code and 300 miles later it came right back "0172" (right bank rich)

So now this is what has been replaced:
All 6 injectors
All 6 Coil's
All 6 spark plugs with stock plugs.
Map Sensor (and air temp sensor)
PCV Valve
AIS motor (and TB Clean)
TPS
All O2 sensors
All vacumm lines have been checked. Maniforld vacumm is in spec.
All electrical connectors were cleaned.
Gas Cap
Compression was checked, spot on.
Computer code was checked and is up to date.


All that is left is Cat converter, EVAP and The PCM itself.
Cat Converter is not to suspect because it does great on emissions (very clean).
It seems to happen when I come to a stop and idle for a minute or so, never does it while driving.
Anyone know a good witch doctor?
 

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Discussion Starter #16
Dealer checked the EGR, it was working properly. Idle is ok which is a sign of bad EGR.
EVAP is not the problem, bypassed it and the darn 0172 happened again.
SRV is currently dissabled (via plugging nipple on right side of manifold) and car actually seems peppier. Maybe the SRV Valve is acting up and causing an air leak at times on the right bank intake manifold.
Will run a few days and see if the wonderful code reappears.
Car ran perfectly for 115,000 miles, now it has this 0172 and really being a pain.
Chrysler enginners in Auburn Hills are wondering if its a bogus code and not running rich on the right. They are looking into it too.
 

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Discussion Starter #17
Finally fixed!!! Problem was the cam timing! When the changed the timing belt, they got the right bank off (retarded) by 2 teeth. It was one tooth outside the two timing dots.
I released the tension, adjusted the belt and set both cams the same and the problem is solved. Run perfect (even better than when new and far better performance too!)
Stupid dealer!!
 

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D76G12 said:
How are the plugs ...?
That is what I was thinking, check the plugs, make sure they are gapped correctly and they are good plugs.
 

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wrench said:
That is what I was thinking, check the plugs, make sure they are gapped correctly and they are good plugs.
Damn, should have read the whole thing before posting
 
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