Codes P0171 & P0174 (Too lean bank 1 & Too lean bank 2)
I have checked all vacuum lines, sprayed carb cleaner around MAP sensor, Intake manifold gaskets, between throttle body and manifold and around all vacuum points. All are tight. I've cleaned the MAF sensor and throttle body. Ive read that fuel filter might need changed, but 95% of posts for Too lean on both banks point to vacuum leak. Anything I'm missing here or should I go for the fuel filter next?
Just as a little history - My employees car. She drove it to failure last year due to overheating. I replaced her waterpump and thermostat last year and it ran well. Started having issues this winter and she didnt tell me till it alkmost wouldnt move. It was throwing over a dozen codes. Just replaced all sparkplugs and one ignition coil and oil change etc. Also found the front valve cover to be loose and fixed that. Runs like a champ now, but has those two codes still. Am Guessing the fuel filter does need changed as she hasnt maintained well and it does have 109,000 on it, but really want to find the code issue.
Well, you seem to be doing all the right things ...but too lean on both banks could be the MAP is faulty and cleaning it didn't do the trick. Replace it..easy for me to say I know they are a hundred bucks..but maybe it can be tested before you put out that much for a 'maybe'
Codes P0171 & P0174 usually means unmetered air is getting into the engine. Not detected by the MAF. You said you already cleaned it, but a vacuum leak is always the culprit when it comes to these codes. Could be a faulty hose, or an intake gasket. Some mechanics will "smoke" the car to find the leak. The way I usually find them is start the car, and get under the hood and start moving the hoses around and you'll here a hiss. Also look for collapsed hoses and loose hose clamps.
If there are no intake leaks, the next step is to replaced the air filter and clean the air flow meter. If the problem persist the front oxygen (O2) sensor may need to be replaced. --- Here's a link to Jaguar specific codes - there are some TSB links at the bottom. --- http://engine-codes.com/p0171_jaguar.html
Considering the repair history and mileage, and that it is a consistant hard code, it could be the O2 sensors are fouled and not responding quick enough. I worked on a 1981 Cadillac 6-8-4 engine where the check engine light would flicker while driving but wouldn't set codes. Most notable symptom was that while driving with the light flickering you could use the AC control head (used to control diagnostics) to force 4, 6, or 8 cylinder operation without going into diagnostic mode. I found out, several years later from a Cadillac Service Engineer, that the sluggish O2 sensor was putting the computer into a factory production line diagnostic test mode(negative voltage on the sensor input accessed by the worker from a green connector under the hood). Checking fuel pressure will give you an idea about the fuel filter or imminent failure of the fuel pump. Clogged fuel tank venting could also cause a reduced fuel pressure. A couple of fouled injectors could also be causing it to run lean. In 1984 I ran into a whole slew of Oldsmobiles that consistantly fouled injectors when using Texaco gas. I think a clogged air filter would give a rich condition.
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