Hi guys, so I've go this Honda Accord LX, 1998, V6, 222K miles. She's my baby, and she's sick

The following items are relatively new but are all up for speculation:
plugs (NGK, just re-gapped them a bit ago, all looked equally burnt)
wires
cap
rotor
EGR valve (cleaned out)
IAC Valve w/ gasket
MAP sensor
fuel injectors (refurbs from ebay)
rear O2 sensor

note: I've done the EGR port clean out and tube extension.
When it was running fine it was getting 23 mpg highway, now it gets 15 max, and it's getting worse.

Symptoms:
1. takes a few seconds longer to start (possibly unrelated, not really an issue to me as is)
2. seems to bog down during normal driving conditions. Have to push the accelerator down further and further until it finally revs higher and launches the car forward.
3. Using cruise control on the highway, set to 65 mph, accelerates to ~67 mph, bogs down until it coasts down to around ~64 mph, then accelerates again. She's basically surging but I may not be too understanding of the definition of it.


Codes: P0171: System Too Lean (Bank 1) P0170: Fuel Trim Malfunction (Bank 1)

I was able to catch a P0130 randomly (Sensor Circuit Malfunction (Bank I Sensor 1)) but it quickly disappeared.

I initially suspected a vacuum leak but have sprayed all gaskets in and around the intake with carb cleaner, no changes in REVs. I have not done a smoke test.

I pulled and plotted some data. First, highway driving. (It may be better viewed if downloaded and opened in excel) The first tab is all the data. The second is driving on cruise control around 63 mph and having the car hold the speed great. Right before this on the graph you can see i was coasting in neutral, just down a big hill for about a mile (trying to save some gas). The third tab is the same cruise control situation but the car is surging trying to keep the set speed. Check out how everything is just going up and down, what the heck.

https://www.dropbox.com/s/su8n5tg6ug...20PM.xlsx?dl=0


At this point I'm thinking it's an electrical issue, either the O2 sensors, the main ignition switch wiring harness, the vtec solenoid, or the ECM itself.. others have suggested the thermostat, vacuum leaks, and the cat being clogged.


If the vtec solenoid was infact stuck, it'd lead to bad timing. When it bogs down at low speeds under load, the sound coming from the tail pipe is rough, possibly from the timing issue. It sounds thin and like coughing, like a slower "chh, chh, chh, chh", like it's barely chugging along, then i press the accelerator a bit more and it launches me forward with a nice vrooomm.

The intake boot had a crack in it but i taped it up for now. The engine runs a tiny bit better but I have a strong feeling it's not a vacuum leak issue based on how erratic it is. Soon after I taped it up the surging came back. In fact, when the car is cold it'll run fine for about a mile then start acting up. Each time I reset my codes or the ECM totally, the problem goes away for about 5 miles, then slowly comes back more and more until it throws the lean code.


I'd like to fix this an I am a mechanical engineer, it's just driving me crazy.. If you need more data pulled at a particular time or while I'm doing a certain action let me know!

The second and third data is some acceleration data from stand stills. You can see how the RPMs and speed will drop while the throttle position stays the same, then once i press the accelerator down more, the RPMs and speed quickly pick up.

https://www.dropbox.com/s/n1lz79kvoz...ccel.xlsx?dl=0
https://www.dropbox.com/s/36l9cmul66...ccel.xlsx?dl=0

This fourth document is all the work that's been done to the car since my family has owned it (minus some oil changes and inspections).

https://www.dropbox.com/s/hewgsyy9wxl1914/work.pdf?dl=0


I hope you guys can help me figure out what's going on! it's quite a doozy I know

Thanks,

-Andrew

 

Hard start and P0171 can result from low fuel pressure. Suggest checking fuel pressure first.

I managed a smoke test using a cigar (almost choked to death!) pushing smoke through vacuum line w/ open end intake duct (removed from air box) and blocked w/ rubber glove. If glove expands indicating holding pressure, your system is tight. Don't forget to open throttle plate.

good luck

 

ill give it a shot. ill probably get a new intake tube as it is. mine is cracked to ****. but i didnt think that was the problem as it's before the throttle body.

 

wait did you use the cigar to blow smoke into the intake etc to try and find the leak using positive pressure? or did you get it lit and move it around the seals while the engine was running to see if it'd suck the smoke in?... a bit confused by your statement

 

Positive pressure (all intake/exhaust valves closed) looking for smoke. If you can pressurize and hold pressure on the glove, there are no leaks.

good luck

 

I will talk to the doctor when I get a chance, a master tech I work with part time. I don't have the books with me right now but have dealt with similar code scenarios before. In the mean time here is was what can give you:

1. Vacuum leak or fault PCV valve or leak at the PCV
2. Faulty injector, but a trained eye as it seems you have should be able to see symptoms on the plug or plugs
3. MAP sensor - if you have the shop manual follow the diagnostic procedures
4. Faulting front O2/AF sensor

Yes it could be a clogged cat. If you drive at night and drive it for a while stop at a dark location and see if it is glowing, although at this point I am not leaning towards that being the culprit. In the meantime if you have a sticking injector(s) run some BG44k cleaner through the tank with the tank near 1/4 full to increase its strength. Rarely it could be a FIAC valve that is dirty or gummed up, so there is no harm in throughly cleaning the throtle body and ports with the car running. If you have a fuel gauge it may be worth running the car and watching what the pressure does. I will get back with more when I can. There are several others on this site that I am sure will chime in before I can get back.

Finally, welcome to the HAF community and great post. Great details. Do you have a scanner (I.e. Snap-on) that you can freeze frame data?

 

One additional thing you should do is listen to each injector by using a piece of hose to your ear. I sounds like if it is an injector it will be one of the from ones since codes lean towards bank 1. They should have a nice smooth regular clicking sound.

 

Switched out the Fuel Pressure regulator.. That didn't do it.
Patched a small leak in my exhaust, but i dont think that was a real issue as it was right before one of the mufflers at the end of the system. ended up switching the O2 sensor right in front of the main CAT and then reset the codes. drove great to work today, hopefully the issue has been fixed!

 

Thanks for posting back and hear that #4 in my post above my be the culprit. You won't know until the car goes through its drive cycle but at least for now it seems better.

Thanks again for the update.

 

So it threw a P0135 code.... Before I switched the sensor out I was getting about 200 miles per tank. Now I suspect ill get ~300 a tank because it's running so smoothly, even with the P0135 code thrown, and i've gone 60 miles and the fuel gauge has barely budged. Now unless I nicked a wire in the harness of the sensor i'm not sure why this would happen. But the thing runs great. Despite the P0135 code and the lack of the two original codes she runs great. I contacted the vendor of the sensor to see if i can return it as I suspect it may be faulty.. they have not replied. I purchased the correct O2 sensor, I hope they sent me the correct one.