'90 Accord EX - Check Engine Light & Very Poor Performance

[BS13]

I believe I have a really tough one here. I’ve had problems starting about two years ago and the problem is now getting worse quickly.
Quick summary: Check engine light code 43 – Problem with O2 sensor or fuel related problem. Over the past two years, I’ve:

• Bought, swapped and or replaced the ECM three times,
• Changed out the O2 sensor about 6 times – Bosch “burns out” almost immediately and the Honda OEM O2 Sensor last 3-4 weeks,
• Replaced coolant temperature sensor three times,
• Coolant temperature connector – replaced,
• Swapped MAP sensor,
• Swapped throttle body for TPS,
• Changed fuel injector resistor,
• Checked fuel pressure – good with 41psi
• Taken the catalytic converter out – looks good w/daylight coming through,
• Drove car without converter – drove poorly
• Checked wiring from O2 sensor to computer – seems good
• Replaced O2 sensor connector on wire harness side
• Had a complete tune up in November ‘06 with new plugs, plug wires, rotor, cap and air cleaner

Up until November the car ran pretty good even with the check engine light on although slightly diminished few economy at about 21-22mpg. There was a very slight engine miss detected only on smooth roads. Normal around town mileage was 24-25 with highway getting close to 30-31 mpg. The car has a manual tranny.

The tune up shop had the car and could not find the source of the check engine light problem. At that time we were getting check engine light codes of 41 which I believe are O2 sensor heater circuit problems.

I took the car to an auto electric shop and they could not trace the problem either. At that time I was using the Bosch O2 sensor because they were a 1/3rd the price of the OEM sensor. After numerous replacements, the sensor was lasting less than hours. Then I tried the OEM sensor and bingo, I thought I had the thing fixed. Not! Three weeks later the engine light came on again. After two more weeks, the electrician gave up and gave my money back.

As time has progressed, the car has started running more and more poorly. I am on my next OEM O2 sensor with no codes yet. It’s been about a week. But it will come and when it does, it will be code 43. Plus in the last couple of weeks the car cannot get out of its way. Significant, I mean big time, loss of power and fuel mpg maybe not even 15. The engine is obviously running very rich.

Oh, one other very important thing. The car runs great during the first minute of operation! The car starts to warm up going into closed loop mode and performance goes into a dark hole.

I took it into another shop and I watched and supported the mechanic. That was when we were swapping a lot of the parts from another ’91 Accord. No luck. Notta!

Now I’m driving one of my back up cars. I’m thinking about taking this car to the Honda dealer but I not quite ready to take it in the billfold yet. Does anyone have any suggestions? I need to put either me or the car out of our misery soon!

[StealthSonic]

Does your car have original exhaust modifold (header?)

I had this issue before with O2 sensor on my 2000 Accord.
I have 3rd party Header and cut O2 harness.

High Performance header usually has 90 degree O2 sensor possitioning and it sits under the car. Its supposed to be bad because the heat travels upward and the O2 sensor is getting cook and it slowly destroying the silver in the O2 sensor's tip. If that's the case you can bring to Midas and etc and have them re-drill (reposition the sensor to 45 or 0 degree.)

Make sure that isn't cut wires on the harness, though that doesn't really give alot of problems if cut wires rejoined correctly (not with just electrical tape) Voltage in O2 sensor is very little, bad connection or high resistant can damage the O2 sensor.

I had bosch sensor before but I ended up returning it because it doesn't come with harness and the color of the wires doesn't match my car (my model has 4 wires). I then went to the dealer and bought an O2 sensor and that worked for about a month and it died. I ended up taking the O2 sensor from my 2nd Accord and it works until now (almost 2 years.) I also re-ran O2 wires with the shortest possible route with heatsheild installed and used less resistan wires. That fixed my problem.

I than went back to the dealer and complained to them about the issue and they told me that the best way to get O2 sensor is to give them the VIN#. Apparently there are CA version of the sensor (CA has hight emission restriction) Make sure you get the exact O2 sensor from the dealer.

I hope this help abit.

[jeffcoslacker]

The first thing I check with runaway overfueling is the fuel pressure regulator...if it's blown, it'll throw way too much fuel regardless of what the ECM and O2 are telling it about fuel trim.

Since you have a fuel pressure gauge, hook it up to the rail, turn the key on, and pinch/clamp the return line...the reading should jump a bit then quickly return to the proper value...if it shoots way up, the FPR is blown....

[jeffcoslacker]

What do the O2s look like when they come out? Sooted and choked, or burned up?

[BS13]

Originally Posted by StealthSonic

Does your car have original exhaust modifold (header?)

I had this issue before with O2 sensor on my 2000 Accord.
I have 3rd party Header and cut O2 harness.

High Performance header usually has 90 degree O2 sensor possitioning and it sits under the car. Its supposed to be bad because the heat travels upward and the O2 sensor is getting cook and it slowly destroying the silver in the O2 sensor's tip. If that's the case you can bring to Midas and etc and have them re-drill (reposition the sensor to 45 or 0 degree.)

Make sure that isn't cut wires on the harness, though that doesn't really give alot of problems if cut wires rejoined correctly (not with just electrical tape) Voltage in O2 sensor is very little, bad connection or high resistant can damage the O2 sensor.

I had bosch sensor before but I ended up returning it because it doesn't come with harness and the color of the wires doesn't match my car (my model has 4 wires). I then went to the dealer and bought an O2 sensor and that worked for about a month and it died. I ended up taking the O2 sensor from my 2nd Accord and it works until now (almost 2 years.) I also re-ran O2 wires with the shortest possible route with heatsheild installed and used less resistan wires. That fixed my problem.

I than went back to the dealer and complained to them about the issue and they told me that the best way to get O2 sensor is to give them the VIN#. Apparently there are CA version of the sensor (CA has hight emission restriction) Make sure you get the exact O2 sensor from the dealer.

I hope this help abit.

My car is totally stock except for the radio and the rims, nothing special. So, no, it is the stock exhaust mainfold. The electrician cut the harness to remove the old connector at the O2 sensor (4-wire). He didn't tell me he was going to do that but who am I to argue since he felt there could be a problem there. It was oily, I believe from a slight valve cover leak. Another connector was crimped back in place and everything seemed fine as far as the connection.

But you do bring up a good point about the OEM sensor. This is my second new one from the dealer. The first one they had my VIN so that part should have been correct. The next one came from the same dealer and parts person but I used my receipt for warranty. he could have mistakenly given me the wrong one however unlikely - I live in Houston. That second O2 sensor never made the car perform better even though the check engine light has not come on. I'll double check the part number by both receipt and part on the car.

Thx!

[BS13]

Originally Posted by jeffcoslacker

The first thing I check with runaway overfueling is the fuel pressure regulator...if it's blown, it'll throw way too much fuel regardless of what the ECM and O2 are telling it about fuel trim.

Since you have a fuel pressure gauge, hook it up to the rail, turn the key on, and pinch/clamp the return line...the reading should jump a bit then quickly return to the proper value...if it shoots way up, the FPR is blown....

Well, I wished I had a fuel pressure gauge. I got the readings from both the auto electrician and the last mechanic. In both cases the static pressure (no engine running) was nailed at 41psi. The mechanic also had a reading with the engine running. I was trying to stay out of his way so I could see exactly what the reading was. I think it may have been in the range of 28-33 psi but don’t hold me to that. The mechanic suggested and he admitted he was guessing that it could be the fuel pump because he had seen them do weird things on other cars. But as the pressure seemed ok I passed that off.

I’ll try the return line pinch test to see what it does. That sounds like an interesting possibility. Gotta locate a pressure gauge. It might be simpler to just replace the old pressure regulator.

Thx.

[BS13]

Originally Posted by jeffcoslacker

What do the O2s look like when they come out? Sooted and choked, or burned up?

Both the plugs and the O2 sensor look black with fresh carbon buildup when the engine is running poorly and the check engine light is on. It’s not as bad when the check engine light is off like it is now. But, I’ll check now anyway since the engine is running so poorly with no light on.

Thx again.

[BS13]

Originally Posted by BS13

Well, I wished I had a fuel pressure gauge. I got the readings from both the auto electrician and the last mechanic. In both cases the static pressure (no engine running) was nailed at 41psi. The mechanic also had a reading with the engine running. I was trying to stay out of his way so I could see exactly what the reading was. I think it may have been in the range of 28-33 psi but don’t hold me to that. The mechanic suggested and he admitted he was guessing that it could be the fuel pump because he had seen them do weird things on other cars. But as the pressure seemed ok I passed that off.

I’ll try the return line pinch test to see what it does. That sounds like an interesting possibility. Gotta locate a pressure gauge. It might be simpler to just replace the old pressure regulator.

Thx.

Well, this morning I went back to the mechanic and we tested the fuel pressure once again. It read normal although on the high side, that is 41psi with out the vacuum hose connected and about 30psi with the vacuum hose connected - of course, the engine was idling.

Then I crimped the return line and the fuel pressure jumped to 65psi. At idled the engine stumbled and almost died but didn't. It still seemed to me that this is what is supposed to happen to the fuel pressure with a pinched return fuel line. I bought a brand new pressure regulator, installed it and the car still runs poorly.

This thing is running so badly that I'm lucky to get across an intersection after being stopped by a light. Sometimes, I can't get the engine beyond idle when I ease on the gas.

Oh , my check engine light is coming back on. Code 43.

Thx for the suggestion, any others?

[jeffcoslacker]

Yours uses a barometric or MAP sensor to sense intake air quantity, right?

I don't think they had Mass Air Flow sensors in '90 yet...


Ever mess with it or check the vacuum line to it? If the line is split, it thinks the manifold vacuum is lower than it actually is, which tells it the motor is under load, and it will add fuel accordingly.

If the reading is not out of range, it will accept it without coding for that sensor.

[BS13]

Originally Posted by jeffcoslacker

Yours uses a barometric or MAP sensor to sense intake air quantity, right?

I don't think they had Mass Air Flow sensors in '90 yet...


Ever mess with it or check the vacuum line to it?

Yes, I have worked with the MAP sensor. The mechanic was messing with more than me. He checked it out and I was there watching. Later, when I was not there, he swapped one out from a '91 Accord (mine is a '90). No change or improvement.

I'm going to go remove the O2 sensor right now to see if I see anything unusual.

Thx for your input so far.

[BS13]

Originally Posted by jeffcoslacker

What do the O2s look like when they come out? Sooted and choked, or burned up?

I took out the O2 sensor and as expected it was black. But since the sensor was relatively new there was not a lot of build up on it. I could easily see the metal underneath.

Additionally, there was a lot of residual oil in the connector. I cleaned both the harness connector and the O2 connector with solvent and compressed air and then reinstalled.

I test drove the car and after about 45 seconds, it started performing poorly again. The problem is not solved.

[jeffcoslacker]

Sounds like as soon as it goes into closed loop, it's all over....

At least you can deduce it's an electronic control problem, not mechanical from that, most likely.

You may want to get a pin-out reading chart for your ECM, and start checking voltage readings at the pins, make sure everything is talking to the computer like it should...a dead or incorrect reading should lead you to the problem.

Sorry the FPR didn't help...it was a wild shot...but does cause that problem.

[BS13]

Originally Posted by jeffcoslacker

Sounds like as soon as it goes into closed loop, it's all over....

At least you can deduce it's an electronic control problem, not mechanical from that, most likely.

You may want to get a pin-out reading chart for your ECM, and start checking voltage readings at the pins, make sure everything is talking to the computer like it should...a dead or incorrect reading should lead you to the problem.

Sorry the FPR didn't help...it was a wild shot...but does cause that problem.

Yep, I agree with you completely. Any idea where I can get one of those pin out attachments. I've already very carefully spliced into the key wires for the O2 sensor at the ECM. I found nothing wrong. But I haven't checked the other sensors at the ECM. And I'm not getting other codes either. Funny when I disconnect some of the sensors, I get a code. I did that for the temperature coolant sensor. But other than code 43, I get nothing.

I may be going to the dealer anyway.

Thx again!

[jeffcoslacker]

I go to the local library....they have a subscription to Chilton's Online 5, then just print out the info I need.

I tried to find you one from another source I use for Honda info, but they only have pinouts back to 1992...

[BS13]

Originally Posted by jeffcoslacker

I go to the local library....they have a subscription to Chilton's Online 5, then just print out the info I need.

I tried to find you one from another source I use for Honda info, but they only have pinouts back to 1992...

Actually, I forgot to mention, I have a factory service manual. And I've about wore it out That is how I know which wires to attach to. But still, the wires are tiny and I'm afraid of cutting through them. The factory adaptor is the way to go.

When I talk to the dealer this week I'll ask if they have that ECM adaptor.They probably won't know what I'm talking about.

Thx