Heres the run down 165,xxx miles 97 honda cr-v automatic 4spd. I tow a one axle car dolly with my 1800lb ek race car on it. Engine is the stock b20. It currently has headers, catback, and intake. I have replaced a number of things - cam seal, adjusted valves, full exhaust including cat, regular tune-up, fuel filter, fuel fill and return line closest to tank, axles, regular tranny flush, and a number of other things im forgetting.

Problem is I get the following codes under rare circumstances, currently the car runs fine and does even after CEL is triggered and cleared.

P0170 and P0171 - Fuel trim bank 1 and system running too lean.

First I only got the system running too lean P0170 - Cleared that no problems

Until about a week after when I went to go up a steep hill the car bogged until i hammered on the gas and the tranny kicked down. Sometimes this would happen and the car would sputter until I hit the gas/accel. It usually only did that when the gas was getting low, below a half tank. I replaced the fuel filter and have not had the bogging issue again nor any CEL

Again until about a month later I got those two codes. It happened coasting down a steep hill at around 50mph. Car was in full vacuum and it specifically threw the codes then. I am planning to replace the FPR and look for any vac leaks or exhaust leaks.

I am narrowing out that it is not the primary o2 because no other CEL was triggered for wrong voltage or whatever the case, along with the egr because there was no other CEL for it.

I am also narrowing out the fuel pick ups and returns seeing as how a honda dealership just replaced them.

Continuing to narrow out the valves as they were just aligned several months ago along with the plugs.

What else could be the problem besides the ones I stated: FPR, vac leak, or exhaust leak?

All input is greatly appreciated. I have done my fair share of research and seeing what other people now think. I havent found any instances where this was a problem on a cr-v only other hondas.

Thanks!

 

Tightened up headers, no exhaust leaks.

Look for vac line leaks, found none.

Gas cap, creates sufficent seal.

Injectors are not leaking.

Fuel pump primed and clicked up front as usual during startup.

No apparent problems when driving/idling.

I am gunna go with the FPR, then I am going to wait to see if the CEL returns. When it does I bought a pocket scanner and will scan that. If same codes I will clean the TB out and replace the gasket. And try again. IF CEL returns I will next look into the primary o2 and cat. It is an obx cat and I may be having a problem with that.

thanks!

 

I just went through this with my crv same codes and all. Ended up being the primary o2 sensor.

 

How often did you get the CEL?

 

What is the MAP sensor voltage at a fully warmed up proper idle speed, no AC or other accessories running, fans and such.

 

I agree, might be a o2 sensor.

 

The computer thinks the engine is running too lean and is lengthening the fuel pulse to compensate. So bad oxygen sensor is possible but so is a vacuum leak somewhere or another bad sensor or EGR valve.

It would help a lot if you put up on here what your analyzer is showing you apart from just the MIL code value itself. eg. manifold pressure, fuel trims etc...

Also, are the O2 sensor voltages fluctuating properly?

 

If the ECU says Lean but the emissions out the tailpipe are rich, then look closely at the O2 sensor, if the MAP voltage is somewhat off of 1VDC, then you need a valve adjustment. More info please.