Rich Bank 1 + Cylinders 1, 2, 3 misfires at startup

[Drewmcg]

Can a clogged/bad Catalytic converter on the Bank 1 (passenger) side cause a rich bank one error (P0172)? If so, how does this happen? Thanks.

Note: This is not one of the causes I've seen discussed on generic OBD code sites, e.g., https://www.yourmechanic.com/articl...-code-system-too-rich-bank-1-by-blake-griffin

 

[Drewmcg]

Not sure whether this answers my own question--but this Ford Tech Makuloco video (albeit different Ford engine) shows a bank 2 LEAN code (P0171) due to a clogged cat:

I guess that suggests that a clogged cat would NOT cause a RICH code, right?

 

[lincolnshibuya]

i think the clogged cat is more of a symptom rather than the cause. too much fuel (rich condition) can overheat the cats

 

[Number4]

Tread carefully. Sounds to me like your are jumping time on bank 1.

 

[Drewmcg]

Thanks for the caution/thought No. 4. I recently replaced the timing chains and timed the engine using the OTC tools, so have wondered about the same. Thing is, there is no misfire any time at higher rpm/load. In fact the engine runs smooth and strong throughout the range (no rough idle or anything). These 4.0 SOHC Cologne V-6's do not have variable cam timing like some of the 4.6's or the newer 3.5's used in the Ford Edge 2007+. So unless any timing issue has to do with the PCM advancing/retarding spark, I'm not seeing how it could be a timing issue (e.g., wouldn't that issue persist at higher rpms/under load?).

This is acting like a fuel (or fuel + air) issue on Bank 1. I'm planning to pull the intake and the fuel rail for closer inspection after putting a fuel pressure gauge I just bought on to verify that the pump (which is relatively new) is supplying the proper pressure at startup (which it almost certainly is, given the way it starts right up, runs smooth, and there is no issue on Bank 2). I had replaced all six fuel injectors, but mixed some new with some rebuilt that I do not (now) have total confidence in.

I have already replaced Bank 2 cat ("spliced" in new one) and eliminated the third, rear cat that had debris stuck in it from the failed Bank 2 upstream cat. I did not replace both front cats b/c my scan tool told me that Bank 1 was working fine. But given the persistent bank 1 rich code, I wondered whether this was a mistake. However, the Fordtechmakuloco video makes me think a clogged cat would only result in lean, not rich, bank one code.

I'm open to re-timing bank 1 head (still have the tool). I don't believe I'd need to re-pull the engine to do so, and want to pull that valve cover anyways b/c of a small oil leak dripping on the manifold. But I just don't "get" how it could be a timing issue based on above analysis.

 

[Drewmcg]

Okay, I FINALLY found a post that seems to confirm that a clogged cat CAN cause a RICH condition (P0172 or P0175) on that bank: http://www.explorerforum.com/forums/index.php?threads/4-0-rich-one-bank-lean-on-other.381377/

As referenced above, Ford Tech Makuloco's analysis of a clogged cat causing a LEAN code seemed to contradict this: how could a clogged cat cause both lean and rich codes?

I'm thinking of pulling the front O2 sensor on bank 1 and clearing the code, and seeing if it comes back. Theory being, if the open hole avoids the backpressure on bank 1 that (theoretically) is causing the rich condition, it won't come back. Hopefully, my Cylinder 1, 2, and 3 misfires in first 1,000 revolutions will go away, too. If so, I replace that cat and I should be good to go.

I've been been contemplating pulling the plenum, pulling apart the fuel rail/injectors, and maybe even re-timing that bank--all alot of wasted work if this is the cause.

Crazy part is that the truck runs great--starts up quicker than any vehicle I've owned; accelerates smoothly, idles smooth. This could be the new plugs, wires, coilpack, timing chains, pcv valve, fuel filter, fuel pump, etc., etc., that was all done as part of an engine swap. Must be (if I'm right, which is a big "if") that the PCM/OBDII system is sensitive to even a little backpressure at idle, causing rich bank condition/random misfire bank misfires....

 

[lincolnshibuya]

Okay, I FINALLY found a post that seems to confirm that a clogged cat CAN cause a RICH condition (P0172 or P0175) on that bank: http://www.explorerforum.com/forums/index.php?threads/4-0-rich-one-bank-lean-on-other.381377/

As referenced above, Ford Tech Makuloco's analysis of a clogged cat causing a LEAN code seemed to contradict this: how could a clogged cat cause both lean and rich codes?

I'm thinking of pulling the front O2 sensor on bank 1 and clearing the code, and seeing if it comes back. Theory being, if the open hole avoids the backpressure on bank 1 that (theoretically) is causing the rich condition, it won't come back. Hopefully, my Cylinder 1, 2, and 3 misfires in first 1,000 revolutions will go away, too. If so, I replace that cat and I should be good to go.

I've been been contemplating pulling the plenum, pulling apart the fuel rail/injectors, and maybe even re-timing that bank--all alot of wasted work if this is the cause.

Crazy part is that the truck runs great--starts up quicker than any vehicle I've owned; accelerates smoothly, idles smooth. This could be the new plugs, wires, coilpack, timing chains, pcv valve, fuel filter, fuel pump, etc., etc., that was all done as part of an engine swap. Must be (if I'm right, which is a big "if") that the PCM/OBDII system is sensitive to even a little backpressure at idle, causing rich bank condition/random misfire bank misfires....

that's a different scenario since there's another code that shows bank2 upstream oxygen sensor is stuck rich. The lean condition on a clogged catalytic occurs because there's decreased airflow going into the MAF in relation to the load (this is similar or close to having a dirty MAF sensor). I'd run Forscan and graph the necessary parameters on what;'s going on.

 

[Drewmcg]

Another wrinkle: My barometric pressure PID reads 7-9.5 hz. below what it should for my altitude (Southern Michigan) (https://www.fordf150.net/forums/viewtopic.php?t=69459 ). This after I had cleaned the MAF several weeks ago.

Question: Could this be causally related to my bank 1 rich/misfires issues? I.e., could a bad MAF be causing rich/misfire codes; or could a blocked cat cause the baro to be off?

 

[lincolnshibuya]

show us the graphs/live data on how your STFT/LTFT on both banks in relation to RPM,MAF voltage and Coolant Temp? set the test from 600-2500rpm both at startup (cold) and when warm.

If you have a clogged cats then you would have 50% less power but you're stating that everything is fine, it's just that you're getting a rich code.

 

[Drewmcg]

Yeah, I gotta figure out how to generate/post those graphs! (I have the forscan app/windows and a Bosch 1350 OBDII reader.)

Gonna replace that bank 1 cat today (<$350) and see what that does. If nothing else, that will be one less variable to worry about, and both cats should be good to go for a while!

I wish you didn't have to remove the transmission cross piece to get these Y-pipes in and out. Then I'd take the one off my doner vehicle and swap it on my XLS. But repairing all those bolts on two different trucks (or at even one) is just not worth it IMHO.

 

[Drewmcg]

Oh, and re baro: I swapped another MAF sensor in that I had from the same vehicle--it's even MORE off (by negative number) than the first one. If anything, this supports my thesis that backpressure from a clogged cat on bank 1 is restricting airflow into cylinders 1, 2, and 3--causing rich condition and random misfires (and skewing the baro by restricting air intake relative to throttle position, etc.).

We'll see once the bank 1 cat is replaced (a $400 expense as it turns out, unfortunately). I wish I'd swapped out the y-pipe for the one from the donor vehicle to begin with, but hindsight's 20/20 . . . .

 

[Drewmcg]

Put new cat in passenger side (wound up @ $350). No improvement in rich bank1 code or misfires on that bank (or in baro)--but at least I'm environmentally friendly now!

Plenum pull this weekend to explore fuel/air issues in Bank 1 and so I can replace a leaky valve cover gasket ....

 

[Drewmcg]

Update: Replaced Bank 1 fuel injectors last weekend (and used one of the ones from bank 2 that is showing normal trims). Same problem. So I do not see this as a fuel issue.

I guess I'm back to pulling the (new) plugs to see if I can confirm that its actually misfiring (I'm getting the flashing CEL occasionally--especially at stop lights, but want to eliminate the possibility of a bad PCM). My next attack will be to put new Bosch O2 sensors upstream on each bank. I already replaced these over a year ago with the Denso's sold at RockAuto, but am concerned with the strange readings I'm getting and wonder whether other problems are causing the Denso sensors to provide unreliable data to the PCM.

If that does not work (I am not optimistic that it will), I'm not sure where to turn. I did put a newer-style harmonic balancer on this engine when I had it out of the truck--the one with the raised, thin metal tone ring. I wonder if I bent that ring somehow when re-installing the engine, and its throwing timing off? I have the old HB still, and could try to wrestle that on. What a pain that would be, though.

Other than that I'm out of ideas, other than to re-time bank 1. I sweat bullets to get that timing right with the engine out of the truck, however, and nobody has offered any explanation of how this could cause Bank 1 rich condition with no misfires at higher speeds when the engine starts and runs so well. And I've got a bad valve cover bolt on that bank that I don't know how I'm going to remove with the engine in the truck. Sheesh!

 

[Drewmcg]

Final update: At 2000StreetRod's and boominXplorer's suggestion I checked compression on each bank and then re-timed bank 1. My bank 1 compressions b/4 re-timing were 145, 145, 140 (bank 1) vs. 195, 200, & 206 (1-6) on bank 2. That seemed to confirm bad timing on bank 1.

I re-timed bank 1 (only), and it fixed all my symptoms. Whew!

Funny thing: I noticed that my baro was off (too low) with the right bank mis-timed. With two different MAFs installed, it was like 7+ too low for my area e.g., 149 instead of 156-58. I figured I'd have to eventually buy a new MAF sensor. But after re-timing bank 1, the baro is spot on (157-ish). I know this is a calculated (not sensor) figure, but did not realize timing could effect it.

Another thing: re-timing bank 1 fixed the goofy (lean) trims on bank 2, also! My long-term fuel trims on a 50-mile trip yesterday after re-timing bank 1 were like -1.0 bank 1 and -0.5 on bank 2. Sweet!

The truck does run noticeably smoother at idle, and seems to accelerate more powerfully (even sounds better).

I have no idea how I screwed up the timing on bank 1 initially. So much happier now with no misfires and no CEL! Many thanks to 2000StreetRod and to boominXploer!

 

[Bobbylew]

Glad to hear you got it solved! That gives me a direction to go!

 

[Drewmcg]

Glad my saga could help someone else.

Just got done putting the AJ1E Superior Transmission fix in for overdrive symptoms being caused (I think) by worn servo bore problem (transmission @ 185k miles). So far, the cleared CEL has not come back and 5th gear seem to work great (even had fun passing someone on two lane rural highway on way back from the shop where I did the repair last night--this 4.0L engine has great power).

These 2002 Explorers are sure great for DIY's!

 

[boominXplorer]

Good to hear all is now well!

 

[Drewmcg]

Thanks a ton for your help, Boomer.

 

[hahatherapy]

Final update: At 2000StreetRod's and boominXplorer's suggestion I checked compression on each bank and then re-timed bank 1. My bank 1 compressions b/4 re-timing were 145, 145, 140 (bank 1) vs. 195, 200, & 206 (1-6) on bank 2. That seemed to confirm bad timing on bank 1.

I re-timed bank 1 (only), and it fixed all my symptoms. Whew!

Funny thing: I noticed that my baro was off (too low) with the right bank mis-timed. With two different MAFs installed, it was like 7+ too low for my area e.g., 149 instead of 156-58. I figured I'd have to eventually buy a new MAF sensor. But after re-timing bank 1, the baro is spot on (157-ish). I know this is a calculated (not sensor) figure, but did not realize timing could effect it.

Another thing: re-timing bank 1 fixed the goofy (lean) trims on bank 2, also! My long-term fuel trims on a 50-mile trip yesterday after re-timing bank 1 were like -1.0 bank 1 and -0.5 on bank 2. Sweet!

The truck does run noticeably smoother at idle, and seems to accelerate more powerfully (even sounds better).

I have no idea how I screwed up the timing on bank 1 initially. So much happier now with no misfires and no CEL! Many thanks to 2000StreetRod and to boominXploer!

I'm having a very similar issue. You can retime bank 1 without removing the engine...Yes?

 

[boominXplorer]

I'm having a very similar issue. You can retime bank 1 without removing the engine...Yes?

Yes you can but you need the otc tool to set it correctly.