Peugeot 607 – one bank rich, bad starting, misfires

I wouldn’t try it. Remember, you’re talking to a group with wildly varying experience in diagnosing and fixing cars.

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The spark plugs are brand new. The old ones were equally worn out, so I guess it’s a problem with whole bank, not just only one cylinder.

Can you source a pcm? Are they plug and play? No security stuff?

One idea that’s driveway diy’er doable, swap the O2 sensors right vs left, see if the LTFT problem switches banks or not. It’s possible the computer only thinks the bank is too rich, but in reality it isn’t, so when the computer cuts the fuel by 25% to that bank it’s actually much too lean, and this is what is making the engine run poorly. If that were the case the spark plugs on the problematic bank would probably show signs of overly lean operation, the tips overly clean or white looking compared to the other bank.

I know you said you can smell gasoline odor from the exhaust pipe, but that’s normal on cold starts. Do you smell gasoline odor coming from the exhaust after the engine warms up?

I’m starting to come to the conclusion this problem is either ECM related, or to the valves on bank 1 somehow.

What if the electrical connectors got swapped, so bank 1 is reporting to bank 2?

That would be diagnostic too. Problem is the wires probably not long enough. Connectors may not match either.

Was the ERG valve ever inspected? Could it be stuck open? I think it would bring exhaust that has low oxygen back through the engine which would further decrease the oxygen content of the exhaust, causing the exhaust to appear too rich. It’s unlikely that this is the case but it’s just a thought since almost everything else has been tried.

Ah, the pesky erg valve.

I’m still a bit curious about whether or not the injectors on that one bank are pulsing or if they are being held open constantly as per the Volvo I mentioned. In the Volvo’s case it was all 6 being held open due to circuit board damage in the ECM.

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A noid lite kit would quickly answer that question

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I’m not sure if they’re commonly available where op lives?

op clearly knows quite a bit about vehicles and is probably capable of quickly figuring out how to use the noid lite kit, if he were to get his hands on one.

So far he seems to be doing pretty well figuring this conundrum out on his own :+1:

If there is an individual injector being held open due to an electrical malfunction, one spark plug would have tell-tail signs of the over rich delivery. The OP states that the spark plugs are new and is not interested in inspecting them.

That is right. Wires are not long enough for connectors to be swapped. I’m currently abroad so I will try the tips you provided when I come back. So far thank you all for your help.

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I don’t now if this issue has been resolved or not, but I learned that a mixture too rich problem can be caused by a faulty fuel pressure regulator, which leaks fuel in to the vacuum system which goes in to the intake manifold. The vehicle will run poorly especially at low load. The ECU can learn to correct the condition to some extent which makes it harder locate the problem.

In any case check all vacuum lines for the presence of fuel.

Hello. I would say that I’ve tried almost everyting, nothing helped. Eventually, car is starting to leak oil, so I’m propably going to get rid of it.

Have you taken it to a professional mechanic?

No, I have said that I’m trying to fix it by myself. It’s not worth it, the car is old and it has another problems. Visiting a mechanic would pretty much exceed the current value of the car.