90 accord, random sputtering and code 43
 

Hello,
I am still trying to figure out this problem. This car is running great except randomly this starts to happen:
- it starts to lose power
- Pressing the gas produces no additional power and misfiring. Letting off the gas produces a slight power boost
- Eventually the computer throws a code 43 (lean downstream) and *immediately* the driveability problem goes away.

I am guessing that the TPS is at fault but wondering if anyone else had suggestions how to isolate the problem. I would think it was crud in the gas tank except for the fact that the problem clears up simultaneously with the computer throwing a code.

sounds like maybe an 02 sensor problem to me...considering the problem goes away when you throw the code. sounds like the ECU is going into open loop once you throw the code and begins to run better because its now running off of the fuel tables instead of the 02 sensor.


Modified by brads94accord at 5:31 AM 2/13/2007

Re: (brads94accord)
 

OK, so how do I get the frozen O2 electrical plug apart without destroying it? >_<

Re: 90 accord, random sputtering and code 43 (runderwo)
 

code 43 is written as 'Fuel Supply System' But it usually means the O2 sensor is reporting a rich condition.
The real meaning was lost in translation from Hondaeese to Americaneese.

All the basics need to be in order, plugs, air filter, Dist rotor, etc. Then check if the O2 sensor is staying high .6V and more all the time.
I don't rule out a bad/lazy O2 sensor but would say to check all the cheaper/easier stuff first.

Re: 90 accord, random sputtering and code 43 (hondadude)
 

I would test the O2 sensor but the electrical plug is frozen together. Will soaking it in PB blaster get it loose?

New plugs/wires, new air filter, new distr cap/rotor, new fuel filter, PCV valve, failsafe thermostat all from Autozone.

I don't think it is fuel delivery because it clears up when the code is thrown.

Re: 90 accord, random sputtering and code 43 (runderwo)
 

Yes you are correct; I was just saying what the code number is written as in the Service Manual, the real cause of the code is never the fuel.
PB Blaster is really hard on rubber parts, but I've never soaked plastic with it;
WD-40 is a safe bet. Or try to warm the connector up and then try again.
Sometimes the little catch doesn't release all the way and you have to slip a small pick in there and release it?

Re: 90 accord, random sputtering and code 43 (hondadude)
 

OK, got it loose and replaced with Bosch... still code 41 after ECM reset.

I have 13.39 V at the open pigtail, and 10 ohms on the heater circuit.

What could it possibly be?

This is a really dumb reason for the computer to go open loop anyway, so the O2 sensor doesn't heat up quickly, fine, but then the computer is just making it worse by going open loop...

Getting it loose was a real chore! Can't use a usual O2 sensor socket because of the location, and a 6 point line wrench was rounding it off. I ended up with this thing that's kind of a crow's foot, but instead of a wrench it's a short socket with a cut in it. That, combined with getting the pipe red hot all around the sensor with a propane torch (normal "warmed up car" didn't seem to help loosen it), and spraying with PB blaster while red hot, eventually got it loose. Had to use a 18 inch breaker bar with the ratchet... and blow out the flames occasionally https://honda-tech.com/forums/images...s/emsmilep.gif But that tool I mentioned was the real life saver because it was the only thing that would "bite" the OEM sensor without wanting to round it.

Re: 90 accord, random sputtering and code 43 (hondadude)
 

Hi, I also have a 1990 Honda Accord (EX) and I continue to get the same code (43) and also 41. Like someone said, 43 is Fuel Supply System. 41 according to my printout from the shop is O2 Sensor Heater. I don't know where that is located. I had the O2 Sensor itself replaced on the same day that I had a brand new Cat, Exhaust line and Muffler installed and I have taken the car to a few places and the same two codes always show up. Someone told me that the O2 Sensor Heater is inside the Cat, but that was replaced also. The car runs great except for that, and I have the same experience where the car seems to run better after the engine light comes on. Just last week I replaced all the Spark Plugs, wires, cap and rotor. I didn't do the coil however becuase it was another 70 something dollars and I didn't have enough money. Very odd that no shops I've taken the car to can find the source of the problem. Can anyone confirm where the O2 Sensor Heater is located and whether or not codes 41 and 43 are related? Also how do I check if the engine is running too rich? Thanks, I just discovered this forum today.

Re: 90 accord, random sputtering and code 43 (Tupring)
 

maybe this might help you; Check for power to the heater circuit
http://img139.imageshack.us/my...7.jpg

Re: 90 accord, random sputtering and code 43 (hondadude)
 

Yes, I have battery voltage at the sensor plug. However, the OEM sensor reads 16 ohms while the Bosch reads around 10 ohms. Doesn't matter, both throw a code 41. I have not had any sputtering or stalling since immediately after the top end rebuild. It just gets crappy mileage....

Re: 90 accord, random sputtering and code 43 (runderwo)
 

So I'm being told that Bosch sensors are junk and to use the OEM sensor. Problem is, I have both a Bosch and OEM sensors that are throwing a code 41. Are both sensors broken or is the problem somewhere else?

Re: 90 accord, random sputtering and code 43
 

Ugh, the demon went away for a while but it's back with a vengeance. New 4-wire Denso O2 sensor, new fuel filter, cleaned out EGR valve + passages, but it still gives a noticeable power loss one the highway and throws code 43, then immediately starts behaving as if nothing was wrong.

I have a hole in my flex pipe so I don't think it's a plugged cat. The hole has been there longer than it's been throwing the 43. I don't think it's the problem but I have a new down pipe on the way anyway.

EGR passages were completely clogged. I cleaned it out pouring seafoam into the suction hole with the motor running until it drained faster than I could pour. Now when I pull vac on the EGR valve at idle the motor totally acts like it is going to stall but manages to stay running. Do I still have a clog?

I checked all around for vac leaks, found that the thing with the round plastic "hat" attached to the middle of the firewall, and the thing on the driver's end of the intake, both leak vacuum slowly. What are these things called and should I replace them?

How do I test the injectors for misting as opposed to dumping, can I pull the rail and have someone crank the (cold) motor while watching?

I am getting a multimeter that can log the O2 voltage which will hopefully help figure it out.

Re: 90 accord, random sputtering and code 43
 

I found a diagram that identified the leaking valve on the plenum as the "starting air valve". I still have not identified the leaking part mounted on the center of the firewall, does anyone know what it is?

Re: 90 accord, random sputtering and code 43
 

So that part is actually the valve that controls the vacuum powered rear motor mount. I went to the junkyard and out of a dozen of them I could only find 1 that did not leak. I could not find a starting valve that didn't leak.

I noticed a high (12 ohm) resistance between some grounds on the car. I sanded all 7 ground points (batt terminal, batt cable to frame, batt cable to block, ECM ground at thermostat, valve cover, PS pump, and driver's mount) and replaced all the screws. This brought the resistance down to tenths of an ohm.

I also checked the MAP sensor and replaced the vacuum hose to it.

So far no more code 43. I will let you know if I see it again.

Could someone comment on my EGR valve situation (under vac it tries to stall but stays running) as well as what I should do about the starting air valve leaking vac?

Re: 90 accord, random sputtering and code 43
 

Looks like the spurious trouble I have been having over the last few years was a broken/intermittent O2 signal wire. I rewired the whole O2 harness, checked for good O2 signal at ECM, and then drove 600+ miles and never saw a code. Mileage was around 30 mpg. So if you are having recurring code 43 problems over multiple O2 sensors, suspect the O2 harness wiring, not just the plug which itself can be a problem too.

Re: 90 accord, random sputtering and code 43
 

Maybe I was confused about the order of operations before. So, this came back in 2015. After checking the O2 sensor with a labscope and determining there was nothing wrong with it, and watching a bunch of other signals while driving and unable to find anything wrong, I cleaned out the EGR ports and runners with safety wire and drowned the whole EGR in seafoam overnight. It is now 2017 and it hasn't happened again since.

My theory is that clogged EGR ports on other cylinders are causing too much EGR to be diverted to one cylinder under some conditions, which is what causes the power loss and misfiring.

Anyway, if you're having this problem, I would say do a thorough EGR cleanout as I mentioned above before bothering with anything else.