AccordEX1991

Can't seem to find the fault code description for a 1991 Accord EX.

Codes available are only for 90-98 Prelude.
Code 41 - Primary Oxygen Sensor - Heater circuit malfunction
Code 43 - Fuel Supply System defective or malfunctioning fuel supply system
Are they the same for Accords?

Thanks.

hondadude

Yes you have the codes correct; The O2 sensor is probably the cause of the code 43. If it's heater doesn't get it hot enough, the sensor lies to the ECU about the A/F mixture.
Here's a link to help you check out the O2 sensor;
http://img139.imageshack.us/im...7.jpg

cam22a

Yep they'll be the same. Could be a faulty o2 sensor causing both.

AccordEX1991

Thanks for the responses.

I already replaced the O2 sensor, because I got a code 41 before.
I checked the 100k mile old sensor heater element and it read about 4 ohms so I replaced it with a new one.
But I never checked 12volts DC on the heater wire connector. Perhaps I should have done that first. Maybe the heater power supply is dead. I'll check it tomorrow with a digital meter.

How about the fuel supply problem? What sensor reads this fault? Could it be injector resistance or just the effect of missing O2 sensor heater circuit??

Thanks again.

hondadude

Okay the "dreaded" code 43
This code description got all screwed up in translation, from hondaeese to Japaneese then to Americaneese.
What it really means is the O2 sensor is seeing unburned oxides; AKA the engine is running in an overly rich condition.
So ya gotta start with all the basics, Plugs, wires, air filter, then move to stuff like fuel pressure regulator diaphram, fuel pressure leak down test, making sure all the injectors are sealing good. Timing, intake valves adjustment...ETC....ETC....
Just thinking about code 43 has got me heading in to get another shot of Makers Mark
I'd say get your O2 sensor HEATER CIRCUIT problem straightend out first.

AccordEX1991

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hondadude &raquo;</TD></TR><TR><TD CLASS="quote">Okay the "dreaded" code 43
This code description got all screwed up in translation, from hondaeese to Japaneese then to Americaneese.
What it really means is the O2 sensor is seeing unburned oxides; AKA the engine is running in an overly rich condition.
So ya gotta start with all the basics, Plugs, wires, air filter, then move to stuff like fuel pressure regulator diaphram, fuel pressure leak down test, making sure all the injectors are sealing good. Timing, intake valves adjustment...ETC....ETC....
Just thinking about code 43 has got me heading in to get another shot of Makers Mark
I'd say get your O2 sensor HEATER CIRCUIT problem straightend out first.</TD></TR></TABLE>

Thanks.
I'll check the heater circuit first. Isn't it that the heater circuit is only needed on cold start up to get the sensor to operating temp fast and start sending A/F signal?
Once engine is at operating temp, heater circuit should not be needed anymore.
My gas mileage is alittle lower. City driving is 22mpg and highway is 25mpg.
I should be getting at least 30mpg highway.

I checked the fuel pressure regulator diaphragm. It's good, no fuel came out of the vacuum line.

New plugs, magnecor wires, new ignition coil, rotors and cap.

AccordEX1991

Heater circuit is fine. Two white wires.
I got 12V when I turn ignition switch to ON.

Anybody knows which 4-wire connector in the engine compartment is the O2 sensor?

AccordEX1991

Ok, here is the update.

I disconnected the new O2 sensor plug under the engine before the cat.
Hooked up the digital meter to the heater circuit. Turn ignition ON, I got 12VDC.
Disconnected all electrical connectors in the engine compartment and sprayed contact cleaner on all of them.
Disconnected battery to reset all codes, then drove the car.

Drove fine initially then stumbled at 2500RPM. CEL lit up then stumbling disappeared.
It drove fine and was able to drive the car back home.

Put jumper on blue connector and check for computer faults.
CODE 43.
So CODE 41 cleared itself by cleaning all connectors.

Still left with one code, CODE 43.
Wonder what's setting off this code.
Any ideas?

Thanks.

amckee

What brand of O2 sensor did you use? I tried a Bosch once only to have to replace it with a Denso to clear my 43.
As a side note, 2500 RPM is the point at which the EGR is enabled.

AccordEX1991

I bought a Bosch sensor with the plug from O-Reilly.
When you replaced with Denso, did it clear your code 43?
I wonder if O'Reilly will accept O2 sensor returns.

EGR has been cleaned already 5k miles ago.
When I start the car, it idles good with CEL off.
Drive around, it surges at around 2500 rpm but idles fine.
It surges until the CEL light is ON, then it drives and accelerates smooth.
Drives smooth with the CEL ON, until you turn engine off and back on, the cycle repeats.

What could it be?
Thanks.



Modified by AccordEX1991 at 9:00 AM 7/25/2007

amckee

when you say it surges, do you mean that it stumbles and catches itself repeatedly?

AccordEX1991

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by amckee &raquo;</TD></TR><TR><TD CLASS="quote">when you say it surges, do you mean that it stumbles and catches itself repeatedly?</TD></TR></TABLE>

Yes. it stumbles and catches itself repeatedly until the CEL light comes ON, then it runs smooth, until I turn the engine off and the cycle repeats.

I was out of town for a week and did not get a chance to troubleshoot. I may take a look again sometime this week.

Thanks.

AccordEX1991

Update:

I changed the plugs from Bosch to Denso and also changed cap and rotor.

The stumble at 2500 rpm disappeared. sigh!!

After driving for a while, the CEL came ON again. CODE 43 again.

CODE 41 is totally gone though.

What else could trigger CODe 43? Miles per gallon is 24 if that helps. It's a little low. Usd to get 26 city.

Thanks.

amckee

You might keep resetting the ECU and see if the engine cleans itself up now that you've cured your misfire. If it doesn't go away, I'd look at replacing that Bosch O2 with a Denso or NTK. hondiscountparts.com is the cheapest I've found on O2 sensors.

AccordEX1991

I'll try that route if the code 43 does not go away.

By the way, the Bosch plugs seemed to be firing good. Plug tips were all very light brown. No sooty plug. But the Denso plugs, rotor and cap cured the misfire though.

Thanks.

AccordEX1991

Update:

The misfire came back yesterday while driving home from work.
Then it smoothed out again after the CEL light came back ON.

This is driving me nuts.

I have a spare ECU so I changed it for kicks since I am really frustrated and thinking about selling the car. hehe.

This morning I drove it to work and it drove fine but the CEL came back ON.
But the misfire is gone. At least, it drives really smooth. We'll see what codes were thrown this afternoon.

AccordEX1991

Update: July 31, 8:00 PM

Drove the car home from work with no misfire. Ran smooth, but CEL came ON.

Checked ECU code again. Code 43.

Checked injector resistance, all measured 2.55 ohms.
I will get a noid light and check if injectors are firing.

I will back probe the O2 sensor and measure voltage signal and see if it's running lean or rich.

Will give update this weekend.

AccordEX1991

Car still runs smooth and not misfiring at all. ECU replacement cured the misfire.

Still throwing ECU code 43. CEL comes ON after driving about 5 miles. I checked all injectors and resistance values are all 2.55 ohms. No open or shorted intjectors. Checked the ballast resistors as well. All good.

Valves were adjusted 2k miles ago. No valves ticking.

I will check the timing.
What is the factory distributor timing?

Thanks.

AccordEX1991

Update: 8/2/2007

Drove to work for 12 miles this morning, CEL did not come ON. Yeehah!

I think the O2 sensor residuals whatever you may call it, cleared up after driving for a while after the ECU replacement, and O2 sensor started to work the way it should.

Just wanted to give an update. CODE 43 is a bitch to resolve. But I think it is resolved.

I will open up the failed ECU and check the circuit board for the injector transistors and see if I can find some obvious component failures.

amckee

12 miles is a short commute. You really should take it on a long 75 mph haul. I have a 92 EX with 256,000 miles. I bought it 7 years ago with 103,000 miles. Back then it got 28 mpg. Now I get about 26, but I have less interstate. I took several trips to the gulf coast after the hurricane to rewire some flooded houses and still saw no better than 27. I've heard of other people getting 30, but I'm skeptical. 24 is too low, I think. Do you have a vacuum gauge that you can hook up to the intake manifold. It could reveal alot.
I think that you are barking up the wrong tree checking injectors and resistors. Most problems with these 4th gen accords are common among them all, and you just dont see injector problems on stock engines with stock ECU's. You say the EGR was cleaned 5000 miles ago. Did that include cleaning the small port that run the length of the intake as well as the four smaller ones that terminate in each of the four intake ports? Last year I removed and cleaned everything down to the head and was surprised at both the amount of carbon in the EGR ports and the state of all the gaskets and seals. All rubber orings and seals on the injectors as well as all the valves on the intake were hard, brittle and cracked, or just flat instead of round. Your car has reached the age where rubber parts start to fail regardless of mileage.

I would get some more long haul miles on it before I did anything else, using the mileage as my guide. My mileage didn't return until I replaced the Bosch with a Denso. Lesson learned.
A vacuum gauge/pump would tell alot about the condition of your engine, and verifies the ability of all things that have a vacuum hose running to them to hold vacuum. I had a boost valve that wouldn't hold a vaccum. It's $30 well spent.

Thanks for the constant updates. It's no fun trying to help others if you never know the outcome.

AccordEX1991

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by amckee &raquo;</TD></TR><TR><TD CLASS="quote">12 miles is a short commute. You really should take it on a long 75 mph haul. I have a 92 EX with 256,000 miles. I bought it 7 years ago with 103,000 miles. Back then it got 28 mpg. Now I get about 26, but I have less interstate. I took several trips to the gulf coast after the hurricane to rewire some flooded houses and still saw no better than 27. I've heard of other people getting 30, but I'm skeptical. 24 is too low, I think. Do you have a vacuum gauge that you can hook up to the intake manifold. It could reveal alot.

I don't think I could get 30mpg either. I am shooting for 26. I will hook up a vacuum gauge. What vacuum reading am I looking for?

I think that you are barking up the wrong tree checking injectors and resistors. Most problems with these 4th gen accords are common among them all, and you just dont see injector problems on stock engines with stock ECU's. You say the EGR was cleaned 5000 miles ago. Did that include cleaning the small port that run the length of the intake as well as the four smaller ones that terminate in each of the four intake ports?

Yes the plugs were removed and cleaned the passages. Soaked the passages with carb cleaner and rodded it out.

Last year I removed and cleaned everything down to the head and was surprised at both the amount of carbon in the EGR ports and the state of all the gaskets and seals. All rubber orings and seals on the injectors as well as all the valves on the intake were hard, brittle and cracked, or just flat instead of round. Your car has reached the age where rubber parts start to fail regardless of mileage.

That's what I found out too. Injectors are all good.

I would get some more long haul miles on it before I did anything else, using the mileage as my guide. My mileage didn't return until I replaced the Bosch with a Denso. Lesson learned.
A vacuum gauge/pump would tell alot about the condition of your engine, and verifies the ability of all things that have a vacuum hose running to them to hold vacuum. I had a boost valve that wouldn't hold a vaccum. It's $30 well spent.

Thanks for the constant updates. It's no fun trying to help others if you never know the outcome.

I will drive it some more at higher speeds and see what happens.
</TD></TR></TABLE>

amckee

You should see 18-21 in Hg with a pretty steady needle on a healthy motor without leaks. If it's below 17, your sucking air somewhere. Hopefully you have a hand pump/gauge and can see if everything holds a vacuum. The EGR, MAP, cruise control, boost valve, IAB, brake booster all have to hold the vacuum that is applied. These type leaks are small. A large leak like a intake gasket would cause idle surge. I dont think your looking for a leak so much as looking to see if your head and rings are in good shape. Bad/cheap PCV valves cause vacuum issues as well. You need to 'T' into a hose that gets its vacuum from the intake side of the throttle body.

AccordEX1991

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by amckee &raquo;</TD></TR><TR><TD CLASS="quote">You should see 18-21 in Hg with a pretty steady needle on a healthy motor without leaks. If it's below 17, your sucking air somewhere. Hopefully you have a hand pump/gauge and can see if everything holds a vacuum. The EGR, MAP, cruise control, boost valve, IAB, brake booster all have to hold the vacuum that is applied. These type leaks are small. A large leak like a intake gasket would cause idle surge. I dont think your looking for a leak so much as looking to see if your head and rings are in good shape. Bad/cheap PCV valves cause vacuum issues as well. You need to 'T' into a hose that gets its vacuum from the intake side of the throttle body.</TD></TR></TABLE>

Thanks. I will borrow a vacuum gauge and pump. Vacuum hoses are all probably brittle and cracked. We'll see.

Hey But I am happy now. My gas mileage is already 26.9 or 27 on my last fill up.
184 miles on 6.82 gallons of gas city driving.

AccordEX1991

Hey just an update:

My CEL is still staying OFF pretty much most of my driving times.
No more codes 41 and 43. I believe the new used engine computer fixed it.
It runs really really smooth like butter. Hope to get another 50k miles before another electrical meltdown.

amckee

If your getting 27, I would just leave it alone. You don't have any leaks with that kind of mileage at 300,000. It's WAY too hot to be messing around under the hood.