Sorin Busi

I have already taken my car to two shops; total cost so far $250. Progress:none.

I have a P0172, Car has a rough idle.

I have replaced the plugs (new NGK iridium), the air filter, and flush the cooling fluid. I am "lucky" to have two identical cars, so I swapped sensors from one to another: MAP, EGR, IACV, even the O2 sensor on bank 1. None of those changed anything.

Some suggested to it may be a defective injector or I may need valve adjustments. My car has 128k.

The last mechanic, suggested to replace the timing belt. He estimated it at $2200 but of course he's not sure it will fix the problem. The timing belt has been replaced 15000 miles ago.

Few more notes:
Short Term Fuel Trim Bank 1: -23%
O2 Bank 1 voltage slightly above 0.6V, usually 0,74

Short Term Fuel Trim Bank 2: +10%
O2 Bank 1 voltage variable between 0.12v to 0.75, with an average of 0.35V

If I keep the engine at 3000 RPM, both O2 Voltage between 0.3 and 0.6. The STFT B1 is actually going down at around -6%. B2 is always positive, less than 10%

Absolutely any comments and suggestions are highly appreciated.

How can I measure the Fuel Pressure?

Sorin Busi

Little documentation about Short Term Fuel Trim(s):
P0172 and P0175 - OBD-II Trouble Codes

Sorin Busi

The URL was cut off:
repairpal.com/OBD-II-Code-P0172-and-P0175

Tonyware

When looking at fuel trims it is important to also look at the long one. Can you get some numbers for that and both banks?

Regardless, you could invest some time watching the following two videos (part 1 and 2) explaining short and long fuel trims and the conditions that make them go up or down.

Secret of Engine Problem Diagnosis- Fuel Trims Pt.1 - YouTube

Secret of Engine Problem Diagnosis- Fuel Trims Pt.2 - YouTube

But the fact you did the timing belt not long ago may hint something went wrong there. Can you look thru the peep holes, if at top dead center the markings align on both cylinder banks? Any excessive valve ticking noise?

Fuel pressure is available as an OBD II value but Honda for some reason doesn't publish that. In the case you suspect a bad fuel pump... again watch the videos.

One way or another, it may be a good idea to take it to an Acura dealership for proper diagnosis. They have access to the Honda Diagnostic System and whatever they write down on paper as far as what the diagnosis is, they are accountable for it.

Sorin Busi

Hi Tony and thank you for the info. I am getting better and better on this subject, unfortunately my car does not. Today I took it to a shop to be fixed. They said it is definitely the valves needing adjustment. Paid 550 for it and after the procedure nothing changed. Well, I maybe should send them the videos you sent.


Thank you again.

Sorin Busi

Really informative videos. My condition is P0172 (running reach). LTFT B1 is -18% at idle, therefore this is the new base. The computer adjusts down the fuel (adding less fuel trying to maintain 14.7:1 ratio). However, since STFT B1 is also -25% when it should have been 0 (because the new zero was set), that means the adjustment is not enough and it still trying to compensate.


Now, at 2500RPM the LTFT B1 goes to -8% and STFT B1 goes to about -12%. Bank 2 is in normal range, LTFT about 4% always. This makes me think (based on the video explanations) that is NOT the fuel pump or fuel delivery; am I correct in concluding this is rather an exhaust air leak? It looks so. If it was intake air leak it would have been P0171, running lean.

Tonyware

Just a wild guess... if you can remove the top O2 sensor from the rear cat and throw a flash light in it to see if all looks ok, like a bee beehive, or it has collapsed. Its pretty crowded back there at the engine bay, haven't seen up close an RLX J engine to see if there is any space or they have curved the cat enough not to be able to see. Alternatively, a shop can lift the car up and look at the rear cat from below by removing the j-pipe. Just a guess...

But the safe bet is to take it to an Acura dealer, state the problem and let them figure it out. As I mentioned before, they have the tools to do a proper diagnosis. Hope the one in your area has a couple of ace mechanics who know J engines inside out. BTW, just because they do the diagnosis doesn't mean they fix it too! If you can cut your costs by buying the parts yourself on-line and taking it to a cheaper rate shop that would be ok too... assuming you know someone good!

Sorin Busi

It seemed I did not update this thread. The conclusion: the timing belt mechanism was off by one tooth. Everything was smooth after readjusting it. I read another thread (user some_dude89) who experienced the same problem. Hopefully this will help someone in the future.

All the best to all - I love the acurazine crowd !!

miner

Thank you for updating this thread Sorin

miner

Thank you for updating this thread Sorin.