Air in fuel system
Hello, so this vehicle runs well just has an issue with the mil being illuminated. The intake has been smoked with no leaks exhaust has been smoked with no leaks. Bank one upstream and downstream sensors and exhaust manifold have been replaced with Nissan OEM parts. This was before what’s happening now. After clearing self learn short term and long term fuel trim start climbing on Bank one to 25% short term 0% long-term and Bank 2 to 15% short term addition 0% long-term almost immediately on start up, fuel injectors have been cleaned and tested on an ANSU machine. Next thing that will be replaced is the fuel pump. This is being done because air appears to be being pumped into the returnless system by the fuel pump module any thing that I might be missing? Your kind help is greatly regarded.
check your MAF sensor voltage and compare it to the known good MAF voltage.
Just went a few rounds with the p2099 on a vehicle where customer has all three cats replaced in an attempt to pass emissions. This vehicle would toggle between p0430 or p2099 as cat monitor was difficult to set. Bank 2 cat post O2 would normally sit at about 200mV unless I was driving it hard. You may want to check exhaust for leaks again. You need 5-8psi according to what I read as I smoked…
… It is ASNU machine… Air in the fuel column is a bad thing. … Dan H. … Hobbs … South Texas …
… I fail to see anything in my reply that would draw 4 (or more) negatives… nothing I said was false or misleading… Dan H.
Hi Dan, I think there are some who don't actually read and comprehend at times.
Might as well just accept it, it is the way it goes.
The misspelling did not get noticed by some. ASNU USA
Hi Chester, Your information does not add up to replacing a fuel pump. Bank 2 CAT is rich and bank 1 is lean. There is an imbalance that is likely leading to a timing issue. Do a cam and crank signal test with a scope and see what is going on. Doing a cranking compression test may also give you a clue. Depending on mileage, a fuel pump may be needed, but the information does not support that.
Unless I am reading wrong, both banks are lean. One adding 15 and the other 25.
Glenn, P2099 — Post Catalyst Fuel Trim System Too Rich Bank 2 confused me at first by its definition. When I looked at my post cat O2S, bank 2 was always lean. Thought PCM may be an issue - then decided to get into it. What it actually means is the PCM has to add too much injector on time to get rear O2 to go rich. Never read description in SI, but the possible causes i.e. exhaust leak at rear…
Does the idle seem rough on initial startup after fuel trim learn is cleared before stf trim corects ? I would have jumped straight to injector balance/pressure drop test with 3 different pulse widths after no mechanical problems where found, also what it the Mas reading?
Have you …en the vehicle after clearing/resetting self learn at highway speeds? Monitor short/long term fuel trims. If you have a continuous lean with no …ability issues I would be suspicious of the MAFS. Nissan has had issues with these for years. If you had air in the fuel system, one would think that under heavy acceleration that the engine would crap out. Fuel pressure should be 51 psI.
Why was the exhaust manifold replaced? Is code P2099 new after the exhaust manifold replacement? I believe you have an exhaust leak, which may be causing the P0171. Also, if you think there is air in the fuel in the fuel line, add fuel and see if the bubbles go away.
Hello, thanks all for your responses. Just finished driving this vehicle for permanent DTC’s. This is required for California smog. Baseline problem for this vehicle was bad welds at the bungs for the AF sensors.
Hi Chester, Was this factory exhaust or aftermarket issues? Any pictures?