Stevius

I have a '99 Lexus ES300 and im getting codes P0171 engine to lean bank 1, P0300 multiple random missfire, P0301 Cylinder 1 missfire, P0303 Cylinder 3 missfire, and P0305 Cylinder 5 missfire. The first code I got was the P0171 code and the others came afterwards and have been intermittent. When i first got the codes I went through and cleaned my MAF sensor, took out my oil control valves and the filters and cleaned it but no change so far. My timing belt and water pump was changed at 132,000 miles and im currently at 190,000 miles. It runs fine for the first ten minutes or so and then slowly begins to degrade. It will start to idle really rough and then begin to loose power and jerk while accelerating. Its at that point it throws the missfire codes. Im thinking the oil control valve but when i took that apart everything looked good and the filter was still in pretty good shape. Is there a way i can test the oil control valve to see if thats the issue and is there anything else im missing.

clintbw

When this happened to me, it turned out to be a vacuum leak. Once the car warms up and the engine expands, it pushes open the already exposed leaks and you get poor performance. Check all of your vacuum lines, and connections between each device in the intake system (manifolds, plenum, air box, etc.) Hope you figure out what's wrong.

310V6

When is the last time you changed the fuel filter?

Stevius

Thanks for the replies. Just changed the fuel filter a few weeks ago. I'll check for vacuum leaks today and let you know what i find.

Stevius

Ok so did some checking for vacuum leaks and didnt find anything, but after I finished working on it I decided I would take it out for a drive and it ran much better. Usually the issues start after 10 minutes or so but this time i drove it around for 30 minutes or so and the only thing i noticed was a slight hesitation under heavy load. When i got back i checked my engine codes again and was still getting the previous codes because i hadnt cleared them but now im getting P0306 P0171 P1349 under pending faults. The only thing i did different before driving it this time was that I had it running for 10 - 15 minutes while i was looking for vacuum leaks. I cleared the codes and im going to see how it runs over the next couple of days.

Stevius

Ok so hooked up my OBD sensor to it and checked the o2 sensors and the fuel trim sensors. for the fuel trim sensors Bank 1 sensor 1 seems to be stuck at 19.5 until it warms up and then it fluctuates between -8 to 8 with occasional spikes to -20 or 20. Bank 1 sensor 2 is constantly stuck 96.5 with no fluctuation. Band 2 sensor 1 is between -8 to 8 at all times. for the o2 sensors bank 1 sensor 1 stays around .6 with occasional fluctuations to .7. Bank 1 sensor 2 is anywhere from .0 to .5 and fluctuates considerably. Bank 2 sensor 1 is around .6 with occasional fluctuations to .7 same as bank 1 sensor 1. Bank 2 sensor 2 gives me no reading for o2 or fuel trim. Any advice on what to do from here? Im just confused since this seems to be a completely different issue that what i was originally having and that has completely disappeared. Could it be that the culprit is a bad o2 sensor thats causing the fuel air mixture to be off and would that cause intermittent random missfires? Thanks for any help.

01LEXPL

iTrader: (10)

Honestly, get the OCV's, both [which i highly recommend getting for 100$ ish from rockauto]. Cheaper than new O2's anyways...

I would explain in further detail but don't feel like it, read my posts here;
https://www.clublexus.com/forums/es3...171-p0174.html

Also, I wouldn't bank on the O2's yet. for them to be read properly they need to be in closed loop, if your car is misfiring... it's not going to give an accurate reading.

Hayk

iTrader: (1)

Sounds like a fuel delivery issue. You mentioned it happens under load, which is a symptom of poor fuel pressure. It could have something to do with your fuel filter change.

01LEXPL

iTrader: (10)

^ mine did the exact same thing... when it was super cold [prior to 'warming up'] it ran fine, half the time the CEL didn't even come on!

Once it got close to operating temp, **** went bonkers, sputtered, underpowered, just as OP describes.

Stevius

The weird thing is the original problem has completely vanished. I have driven it the past 2 days with no missfires even under a heavy load. i cleared my engine codes and now all I am getting is the 1349 code which I never got previously. The missfire codes have vanished and they had been happening daily for the past couple of weeks. I've also noticed that the bank 1 sensor 1 and bank 2 sensor 2 both seem to have pretty similar readings while driving now while the bank 1 sensor 2 is still stuck at 99.6 for the fuel trim and .0 while driving for the o2 sensor. When in park o2 sensor goes to .5. I'll try new OCVs and see if that fixes it.

kornpeef

on this engine i have seen alot of cracks or tears in the intake rubber pipe. normal they occur close to the throttle body on the bottom. I would remove the rubber intake between the airbox and the throttle and give it a good once over. and check the throttle plate while your in there and give it a good cleaning with some brake kleen and a rag. i suggest not spraying the throttle body directly but spray the rag and wipe the dirt off.