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Discussion Starter #1
Hello to my forum friends.

My 2.4L 2005 CRV Auto has something it's trying to tell. It runs well in urban areas but at highway speed when power is required for more than 30 seconds, it peters out until the accelerator is released and re-applied at about 1/2 throttle. So on long hill-climbs it can only manage about 70 KPH. The exhaust is blacker than it should be. When it plays up, the fuel consumption histogram in the instrument cluster is immediately 100% illuminated, suggesting that the computer is throwing every possible CC of fuel into the motor.

There's a bit of history to share: I've just bought the car from someone who obviously wasn't mechanically minded, and a new motor (180,000Km) was fitted about 1,300 Km ago. The car has now travelled approx 240,000 Km. The MIL globe had been removed from the instrument console (a dastardly act, probably by a mechanic, and the last owner probably knew nothing about its removal). The OBD-2 download records distance traveled since MIL was illuminated as two figures - about 53,000 Km (dig it, dig it!); and 1,300 Km. I guess that relates to engine number one, and engine number two. OBD-2 has just two errors stored, both P0172. I do wonder if the previous owner should thank his mechanic for the failure of his first engine, which was working with its vital monitoring and warning system effectively disabled.

My first instinct was to replace the in-tank fuel filter, which showed signs of having been in the tank for a very long time. Good start, but that hasn't fixed the problem. The second try has been to clean the MIL sensor and I haven't yet test-run the car to see if it's fixed. I doubt that will be the trick, because the motor showed no other symptoms of a dirty MIL sensor. In general, the car is running very well.

Here are relevant data from the OBD-2 output: 1. Fuel system 1: CL; 3. Calc Load: 55.68%; 4. Coolant Temp: 84.0 degC (The car had been parked for 1/2 hour when I made this download); 5. STFT B1: -31.25%; 6. LTFT B1: -19.54%; 7. MAP: 56KPa; 8. Eng Speed: 1584.18 PRM; 9. Veh Speed: 42 Km/Hr; 10. Spark Adv: 24.5 BTDC; 11. IAT: 29.0 degC; 12. TPS: 19.60%

OK, there's something wrong, for sure. Both short and long-term fuel trim figures suggest that the computer (it's a drive-by-wire motor) is doing everything possible to lean-off the mixture. I suspect it is getting a bad signal from one or more of the key sensors, such as the pre-cat O2 sensor or the TPS. But the car is running as sweet as a nut with the exception of the black exhaust, failure when power is required, and of course that pesky MIL indicator lamp which is conspicuously missing in action....

Any advice on what to test next and how to do so would be gratefully appreciated.
 

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Welcome to the forum! Moved to Gen 2 Section.
 

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2006 EX AWD
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I agree with your assessment of STFT and LTFT saying waaaaaay too much fuel being dumped thru the engine. You didn't mention history of spark plugs, might be an easy way to start.
Their visual condition might also give clues (is only one plug wet with fuel or several?). Not to get ahead of ourselves, but I'd also do a fuel rail pressure leakdown check. could have leaky injector or o-ring.
 

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2005 and 2006 EX AWD
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I would be looking at the upstream O2 for malfunction ,you could unplug the upstream o2 and drive it ,it will stay in open loop preset perimeters for air fuel mixture to verify a bad O2,contaminated fuel could do that also ,E85 will make it go lean though + fuel trims,a bad fuel pressure regulator could cause high fuel pressure and go rich too but not likely on the CRV,if you watch the data while accelerating hard it will go into open loop it sounds like thats when it smooths out until it starts reading the B1S1 O2 again so probably just a bad O2
 

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Discussion Starter #5
Thanks, folk. Here's an update. With help from a friend, we checked fuel rail pressure, performance of sensors and live data for air:fuel mix. All appear good. Remember this car runs as sweet as a nut except when power is required for more than about 15 seconds. So at this stage I suspect a partially blocked cat. The car has a replacement engine and we don't know how the last engine died. But there's a chance it damaged or blocked the cat before it died. Does anyone have experience with partially blocked cats in the 02 to 06 CRVs with the K24A1 motor, please?
 

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2005 and 2006 EX AWD
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how does it run at full throttle,did you check the fuel pressure under load? fuel pressure when it drops power,check engine vacuum at 2300 rpm does it hold vacuum or keep falling down would indicate a restriction ,if it runs good at WOT then rule out restriction
 

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Discussion Starter #7
Thanks, Dave. We checked fuel rail pressure at idle and increased idle to 3000 RPM. Steady at 450 KPa or thereabouts. No dips at all. But remember that high idle uses much less fuel and produces less exhaust gas than full power at same revs. Problem occurs under 3/4 to WOT under load at about 3500 RPM to 4000 RPM. I don't like (perhaps don't understand) the idea of testing a motor at WOT with no load applied. If the fuel rail pressure was low, wouldn't the OBD2 live data show a lean mixture? The air:fuel mix stayed perfect on OBD2 when malfunction occurred during test driving. Thanks again, Dave. I appreciate your support. PS I changed-out a well out-of-date fuel filter at the start of my mystery hunt and that made no effect on the occurrence and severity. If it were a weak fuel pump I would have expected to see a difference, or see flagging fuel pressure when changing RPM under no load conditions.
 

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2005 and 2006 EX AWD
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check the fuel pressure while driving put the gauge under the wiper dont turn on the wipers, WOT open will not read offthe O2 sensor so that can tell you if the engine makes good power then its only when its in closed loop driving ,Vacuum? if the problem is only under load test it under load.
 

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Discussion Starter #9
check the fuel pressure while driving put the gauge under the wiper dont turn on the wipers, WOT open will not read offthe O2 sensor so that can tell you if the engine makes good power then its only when its in closed loop driving ,Vacuum? if the problem is only under load test it under load.
Thanks again, Dave. Much appreciated. I took the car to an exhaust specialist today who has a reputation for knowing everything about cats. Great bloke - won't supply a cat to another mechanic unless he diagnoses a problem first. Cited examples where mechanics blamed a cat for stupid things they should have picked-up. He went over the symptoms and looked at the car and reckons it doesn't sound to him like a blocked cat. The car is in his garage overnight so when cold in the morning he can remove both sensors and put a camera in through the holes. If front and back of the cat look OK he's prepared to conclude that the problem lies elsewhere. So that threw me back to thinking about more improbable but plausible causes and I wondered if this fuel pump is starving under full load (which was my first intuitive guess). I remembered that we only tested fuel pressure at low and high idle, and not under WOT and full load. So I like your thinking (again). Bendigo, where I live, is the third largest city in the State (Victoria, Australia) yet many of the "good" tradies will go out of their way to look after mugs like me for very little or no payment. Reputation and service are more important values here. Sometimes makes me feel lucky to live here. Thanks again, Dave, I'll post a progress update when I have more news. Cheers S
 

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very good sounds like you found a good mechanic ,probably a bad upstream O2 if it runs good when you have your foot to the floor, if it runs good with your foot to the floor and fuel pressure is under 55PSI and vacuum is normal under load ,its also due for valve adjustments tight exhaust valves that are out of adjustment will let unburnt fuel into the exhaust too if it hasnt been done at 100K check them anyway not knowing the history,after 130K or so especially the exhaust valves go tight they should be about .012" on a cold engine, also the converter is probably damaged from unburnt fuel so whatever destroyed the converter needs to be fixed , LET us know , yes Kev it could be a mass airflow meter sensor but the 2005 should not have one(speed density) on the U.S. model 2007 and newer have the MAF design ,
 

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another thing I just thought of is if someone changed the engine and its been a problem since they could have mixed up the O2 location ,they have different connectors but I think they are long enough to put in the wrong hole ,they are both close to each other on the CRV,probably the vale adjustment or O2 or both
 
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