2000 Ls idles rough


paulott
06-24-2012, 08:05 PM
Hi, I have a 2000 Ls 3.9 V8 125,000 miles that started idling rough.I checked for codes and got p0171 (bank 1 lean), p0175 (bank 2 rich) and p0307(cylinder 7 misfire). I swapped cop and sparkplug from cylinder 7 to cylinder 5 and erased the codes.I ran the engine for a while and rechecked the codes to see if the misfire followed the cop and plug. They did not. I still get p0171,p0175 and p0307 (cylinder 7 misfire). What do you think the problem may be.

shorod
06-24-2012, 11:28 PM
When you swapped the spark plug did you notice any signs of moisture or oil on the plug ceramic or the CoP boot? The misfire could explain the rich condition on bank 2, a misfire would be a likely culprit of the lean code on bank 1. But as far as the source of such a vacuum leak or the reason for the consistent #7 misfire, you're going to have to do more digging. A cylinder leak down tester may help you determine the source of the misfire, unless the issue is a bad fuel injector. A careful inspection or smoke test could help you find any vacuum leaks.

-Rod

joegr
06-25-2012, 10:22 AM
If one of the secondary timing chains jumped a tooth (due to worn out tensioners), it could cause those symptoms. Do you get a slight rattling sound at the front of either valve cover on cold start up?

Sometimes the PCV plumbing cracks and can also cause your symptoms. You can spray some engine cleaner around on the engine while it is running and if the engine changes speed, you've found the leak.

danielsatur
06-25-2012, 11:45 AM
Don't forget to clean the breather tube + port from the valve cover to your throttle body, this port supplies air for engine when the throttle plate is closed.

joegr
06-25-2012, 05:58 PM
Don't forget to clean the breather tube + port from the valve cover to your throttle body, this port supplies air for engine when the throttle plate is closed.

Actually, the throttle plates don't close completely, and the IAC (or Idle air bypass valve) provides most of the idle air. There is a tube (on the V8) between the IAC and the main air intake tube. The PCV system does not provide enough air to run the engine even at idle.

paulott
06-30-2012, 08:52 AM
The secondary timing chain tensioner plastic slide is missing and the chain jumped a tooth. Would the missing piece be down by the crankcase sprocket, or would it end up in the oilpan?

joegr
06-30-2012, 11:12 AM
The secondary timing chain tensioner plastic slide is missing and the chain jumped a tooth. Would the missing piece be down by the crankcase sprocket, or would it end up in the oilpan?

Yes, one of those places. It probably won't cause any more harm it you don't find it. The oil pan is easy to drop, so I would do at least that much.

paulott
07-01-2012, 08:17 AM
I am going to drain the oil and strain it to see whats in it.

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