(FIXED) 2009 Honda Accord power loss, P0171

Hello everybody! Have a non Honda like issue here.... 2009 Accord 4cyl. 75k on the clock. Extremely well maintained. Woman came to shop saying it runs terrible. She came out to the car with me and sure enough... extended crank... started on 1...then 2... then finally all 4 began to hit and the car idled. Mash the throttle and the engine attempts to slowly rev- pops out the air box and will barely make it past 4500rpm. She was lean for sure so. Only codes stored in memory are a p0171 and P0300. Here is some data:

-STFT +46.9 at all times
Maf- (nice and clean) 2.8gps at idle, 1.25v at idle- hits about 3v when it makes a feeble attempt to rev
AFR- 16.2 at idle- hits 27:1 under snap throttle. If I blast some propane into intake- I can get trims into the +20 range and AFR drops back to 14.5ish.
Fuel Pressure- 50psi
Injectors at idle 3ms- snap throttle 15-17ms

I checked for vacuum leaks even though in my opinion this is way beyond a vacuum leak- found nothing. I honestly thought for sure I was going to have low fuel pressure but not the case. Even under snap throttle bogging- fuel pressure stays at 50psi. I did a quick current ramp of pump and I need a little assistance as to what I'm seeing. Am I correct in thinking that pump rpm is right around 8000? Does the waveform look ok? I was expecting to see less rounded humps. I asked the lady if there was any chance she filled it up with E85 but she doesn't remember putting gas in the car in the past two weeks. I took a sample and its brown in the jug and smells like gas so I'm not sure on that front. Thanks for any advice!

Hello fudgie,
Does your shop have previous history with the vehicle? Does she maintain her car on time, specifically oil changes?

The K24 timing chain in her vehicle has a tendency to stretch due to lack of oil changes affecting mechanical timing. Generally speaking it should trigger a P0341 (cam out of phase) but I have had ones which only triggered a P0171 and/or P030x.

Pull the timing cover off and check the timing. Good luck sir

and if you have an in-cylinder pressure transducer, this would be a perfect occasion to use it

FIRST THING I DO WITH ALL VEHICLED SOON AS I TOUCH THEM I DO A RELATIVE COMPRESSION TEST THEN DIG INTO TIMING COVER sorry for caps not yelling

I just had one of these in the other day with a jumped timing chain. All I had was a p0300. Thing wouldn't rev either. If you don't have an in-cylinder pressure transducer you can grab both cam sensor signal and the crank signal and see if they are off.

Here is a known good you can reference with.

CH1 (yellow) = CKP
CH2 (green) = Intake CMP
CH3 (blue) = Exhaust CMP

Thanks everybody for the help. I'm working on being scope savvy- but at my current stage I would question every waveform I'm looking at so I did what I always do. Took off the cam cover and timing marks are dead on. I have serviced since new and it looks perfect in there. Its a start stall when cold. Will not accept throttle. If you ease into it- you can get it to about 1500. As it warmed- things seemed to settle down. After about 10 minutes of idling. Had 97 misfires on #4, 3 on #1. STFT +46.9. LTFT 0.00. Maf voltage 1.27. AFR 16.1. Lambda 1.0. B1S2 .020. Whack the throttle and it behaves like a car with a bad accelerator pump and mains that are too small! Once it hits 3000 rpm- afr was 28.9:1. Flashing mil with misfire codes for 1 and 4. Kills injector pulse on those cylinders. Key it off and then back on- back to the above specs at idle. It had about a 1/4 tank in in it so I pumped it out and replaced it with fresh fuel just to rule out possible e85. No improvement. Injectors are at 3ms at idle and about 17ms under a snap (where it barely revs and lean pops). Checked all grounds and they are perfect. No com problems with any other modules. No codes anywhere else. Any opinions on fuel pump ramp? Thanks again for help!

what do the trims do at a steady 2500 rpm's? if you can get it to hold there

STFT maxed at 46.9. LTFT stays at 0. AFR at 2500 is approaching 20:1 and its struggling. The only time I have been able to bring stft down was by the addition of propane to the manifold and it dropped it back to roughly 20%. For giggles- I removed upstream O2 just incase I was dealing with an exhaust blockage and it made no difference. If I had no diagnostic tools- I would have gotten the canon out and fired a pump into it, but based on what I see- pressure is always 48-50psi and the pump appears to be turning around 8000 rpm if I did things right looking at the ramp. Thanks again everybody

That fuel pump waveform looks OK to me. You're on a pretty fast time scale, so it's not unusual to see rounded peaks like that. 8000 RPM sounds a bit fast, but there are newer pump designs out there that spin faster than what I'm used to. *shrug* If the pressure is in spec, and you saw good flow when you pumped the tank out, then I wouldn't sweat it.

Why is it so crazy lean... I was thinking about a skewed AFR sensor, but that doesn't explain the start/stall when cold. Your MAF reading at idle sounds exactly right, but maybe it's worth disconnecting it? It can't run much worse, right? :lol:

I have unplugged the maf and no difference at all. The front AF was completely removed from car when I was checking for exhaust restriction. No difference. Does 3ms at idle sound about right? 15-17ms on a snap? I looked at both injector and coil waveforms and they look ok when comparing to Pauls book. I had another 4cyl accord in to compare too but it ended up being that earth dreams di engine.

Might sound a little dumb, but how are the plugs?

Ok- car is fixed. After ruling out absolutely everything else- Checked pressure drop on each injector and bingo... we have a winner. Surprisingly enough- local dealer had them in stock. I pumped out the fresh fuel I put in there just incase there was some type of contaminant- took 10 minutes to swap injectors and car is running aok. Thanks for all the assistance!

Wow. :ohmy: Did not see that coming! Well done fudgie - I dunno that I'd have thought to check that.

Just curious, do you recall what the injector drop numbers were? I imagine they'd all have to be plugged to some degree to get the symptoms you found...

Yea, I am with Tyler on that one. That was the last thing I would suspect. Any chance you could post the pressure drop results for our curious minds?

Last thing any of us would expect but it kind of makes sense.

I ruled out everything else. I confirmed cam timing visually. Injector and coil waveforms look good. Ran vtec and vtc tests with scantool- all reported normal. CTS, IAT all reported exactly what I would have expected on cold start up. The only way to bring down pegged stft was to add a lot of propane in booster hose so I knew AF sensor was responding. B1S2 reporting full lean at all points when hot. Fuel pressure was a solid 50psi. #4 was the biggest offender, #1 second followed by 3 and then 2. I was always getting misfire counts on #4 especially on start up. Not a dead miss- maybe 100 counts over 5 minutes of running. Most setting on start up. What I found weird was the dealer having them on the shelf. The whole time I knew it was a fueling problem but working on imports for 20 years- I have only changed injectors once and that was on an 88 Volvo 740t. It was a good reminder for me that just because "they never have problems" doesn't mean that they cant and I need to keep an open mind.

fudgie wrote: The whole time I knew it was a fueling problem but working on imports for 20 years- I have only changed injectors once and that was on an 88 Volvo 740t. It was a good reminder for me that just because "they never have problems" doesn't mean that they cant and I need to keep an open mind.

Truth.com right here. Injector issues are waaaaayyyy down on my suspect list when it comes to imports, especially Asian makes. Very nicely done, sir.

They stock them at the dealer. :lol: Kinda reassuring to hear that, huh? Recently, I was a little bit nervous about recommending replacing the turbo on a Ford Edge, until I heard they're on backorder. :woohoo: