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2000 Lexus RX300 lean on bank 2 only
08-07-2016, 04:08 PM
Post: #1
2000 Lexus RX300 lean on bank 2 only
2000 Lexus RX300 runs lean on bank 2 only. No misfire. Had P1150 and a P1440 evap code.
3 month ago this came to me with exhaust leak at front flex pipe. At that time it had the above codes plus p0171 (too lean bank 1) and at that time fuel trims were neg for bank 1 and pos for bank 2. Cleared codes and fixed exhaust leak.
So now it's back and I've replaced both upstream A/F sensors, and smoked the intake but did not find any vacuum leaks. After a test drive, LT fuel trim for bank 2 is at 12 to 14 pos. Bank 1 is near zero. Does a valve timing problem effect fuel trim? I'm wondering about ocv problems. With no misfire, and no vacuum leak, I'm at a loss for what's going on here.
Also, other places online I see front bank (radiator side) as being bank 2. But I see that head sits closer to the crank pulley end than the other, indicating to me it is bank 1. Confirm? Cyl 1 should be at front of crank which would be bank 1? Thanks!
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08-08-2016, 10:48 AM (This post was last modified: 08-08-2016 10:51 AM by Rupe.)
Post: #2
RE: 2000 Lexus RX300 lean on bank 2 only
Here's a rather lengthy article on a similar issue where the guy found an externally operated vacuum pot with a worn shaft allowing a vac leak only at certain times, like deceleration and idle. It didn't show up in a smoke test with the engine off, which sounds like your situation.

http://www.clublexus.com/forums/rx-2nd-g...codes.html

Let us know is this helps.

Edited to add: I have never seen an engine where #1 bank was not the closest to the damper pulley, although I do recall an older one (in the 60s?) where you set timing from #2 cylinder.
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08-10-2016, 08:11 AM
Post: #3
RE: 2000 Lexus RX300 lean on bank 2 only
Thanks Rupe. I had actually already found that. Can't figure out what vehicle / engine that is, but looks different then what I have here. Plus, that leak was driving fuel trims for both banks. I'm having trouble on 1 side only. But something I did notice yesterday... the fuel rail in the back sits considerably lower than along the bank in the front. Wondering if I'm just seeing injectors getting clogged on that side only? I'll let her run it a while and see what happens... her inspection month is a long way off, when the SES light becomes an issue. Might be easier to diagnose if it gets worse. Or maybe it will go away? : )
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08-10-2016, 10:01 AM
Post: #4
RE: 2000 Lexus RX300 lean on bank 2 only
If you suspect an injector issue and have plenty of time perhaps a double dose of some cleaner in the fuel tank may help? It's cheap, easy, and on a 16 year old car that may buy you some time. After a week or so you can check the trim levels again.

BTW, I have seen a leaky EGR play hell with some engines. Don't forget that's inert gas and may act like an internal vac leak but only screwing with the cyls closest to the valve. It would never show up on a smoke test.
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08-11-2016, 08:13 AM
Post: #5
RE: 2000 Lexus RX300 lean on bank 2 only
I'm not a big fan of adding cleaner to gas tank. I just envision anything it cleans out of the tank, line, filter,... gets sent to the injectors.

EGR... LOL... GM TBI comes to my mind. I went round and round on one of my own vehicles before figuring that one out. EGR leak drops vacuum at MAP and it won't idle for crap! No MAF so it's got nothing else to go on. It makes it idle too rich, but then the misfiring makes O2 sensors read lean so ecm adds even more fuel. This is the stuff the "code reader / parts store diagnostic fans" just don't understand...

Anywho, I'm gonna record the current fuel trims at idle, and at various rpm's. Then check it again later. Maybe make sure she's buying quality brand gas and tell her try some techron if she likes. My fear is that it gets worse to the point of misfiring. It could be running on half the engine and the entire exhaust fall of and this woman would be oblivious to having a problem. I'm not exaggerating. That's just how she is. But she'll come back when light comes back on if I insist. Maybe I'll pursue the evap code if it's 1st to return. That could be a vacuum leak as well, but I'm pretty sure that is an unrelated problem.
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08-11-2016, 09:42 AM (This post was last modified: 08-11-2016 09:43 AM by Rupe.)
Post: #6
RE: 2000 Lexus RX300 lean on bank 2 only
Jimmy, you seem to be sharper than the average tech. I'm sure you will eventually straighten it out and have a good story to tell us. In the meanwhile I am going to take a LONG weekend off. Good luck!
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