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nabilc
nabilc,
Category: Honda
Satisfied Customers: 3498
Experience:  Manager/co-owner at Autotronic
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Civic: 1990 honda civic. Randomly the check engine light goes

Customer Question

1990 honda civic. Randomly the check engine light goes on and the car barely runs. It makes a missing sound and can't move very well at all. Then if I turn off the engine and restart, the light goes off, and the car runs fine again, until the next time it happens.
Submitted: 1 year ago.
Category: Honda
Customer: replied 1 year ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  nabilc replied 1 year ago.
Hello and Welcome! I'm Billy and i will assist you with your inquiry. Feel free to ask if any further info is needed.
Did you to retrieve the fault codes (as the check engine light is on)?
Did you check anything or replaced any parts yet?
do you have the manual or auto transmission?
Customer: replied 1 year ago.
When the check engine light is on the red light stays on. When the check engine light is off, the red light goes off.
Customer: replied 1 year ago.
automatic transmissionI have not replaced anything yet except a new distributor because it sometimes seems to miss.
Expert:  nabilc replied 1 year ago.
Which red light other than the check engine? (what does it look like)?
Customer: replied 1 year ago.
The red light is on the ecu under the pasender foot rest.
Expert:  nabilc replied 1 year ago.
Hello,
Since you are having the warning lights, i will attach the method by which you can retrieve the fault codes:
https://drive.google.com/file/d/0B6Zgf4dbmODzR0JhaFVwNmFoVlE/view?usp=sharing
Kindly get the fault codes and get back to me, as having the fault codes, we would be able to conduct some checks and hopefully pinpoint the culprit.
Regards,
Billy
Customer: replied 1 year ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 1 year ago.
Like I said, the red light does not blink at all, it remains solid, so would that be a zero? I also noticed that if the CEL light goes on, and I turn off the engine and start it again, it runs fine. And I think that it is in "limp" mode when the CEL light goes on.
Expert:  nabilc replied 1 year ago.
Hello,
Indeed it is the limp home mode, or reduced performance.
But when you get the check engine light, did you try to turn the engine off, and then turn ignition on (without starting), and watching the light below the carpet for blinking and count as indicated?
Customer: replied 1 year ago.
Yes, I did that and after turning off the engine and turning ignition on, light blinked one time. So, since it says "oxygen content" I figured I must have to replace oxygen sensor. But it still did the same thing after replacing sensor.
Expert:  nabilc replied 1 year ago.
Hello again,
In this case, we need to check the sensor wiring (to engine control module), here are the details:
https://drive.google.com/file/d/0B6Zgf4dbmODzU2dVYXFNZm1QS0E/view?usp=sharing
Kindly get back to me with your findings, or if further assistance is needed so we proceed accordingly.
Regards,
Billy
Customer: replied 1 year ago.
Hi Billy, This is puzzling. If it is a problem with the wiring, then why when the CEL goes on and it starts running in limp mode, why if I shut it off and then start it right back up, the light goes off and it runs fine again?
Expert:  nabilc replied 1 year ago.
Hello,
This is exaclty what wiring problems cause.
When a problem is detected by the ECM (engine control module) it sets the fault, triggers the light and limp home mode. When you restart the fault resets, until it is detected again. A loose connector would cause this, a faulty wire would cause this, etc...
Plus, having replaced the sensor itself, all you have between the sensor and the module (which is detecting the fault) is the wiring. I would check that first (as being most likely) before getting to other things.
Regards,
Billy
Customer: replied 1 year ago.
your link said to inspect pressure regulator. Where is that, how to inspect it?
Expert:  nabilc replied 1 year ago.
Hello,
The pressure regulator is mounted on the side of the throttle body, it has the fuel pipe that returns to the tank. It controls fuel pressure (as wrong fuel pressure woudl cause wrong mixture and wrong oxygen sensor reading). Having a fuel pressure gauge would ease this test: before the regulator, the fuel pressure should not exceed 36 psi.
It has two fuel pipes on it (from the throttle body, and to the tank), and a vacuum hose connected at the intake manifold.
regards,
Billy
Customer: replied 1 year ago.
Also, how do I do this testing, since I do not have the "test harness" required? Do I just put power to the wire connected to the O2 sensor, and follow that wire to the ECU and make sure power is getting through? Is the only way to do that is to take apart the wiring harness and unwrap the bundle of wires? It tested good from the sensor to that major juncture. Now I have to test from there, down through the firewall, and into the area where the ECU is located. You sound familiar with this old car.
Customer: replied 1 year ago.
Ok. I know that I have continuity from O2 sensor to ECU (white wire). Do I need to do the test about holding the rpm at 4000 for 10 seconds, and reading for voltage? Could it be the ECU is bad? Should I go buy a pressure tester to test the fuel pressure regulator? What direction should I go next?
Expert:  nabilc replied 1 year ago.
Hello,
You need to check the continuity from ECU to O2 sensor directly (one lead of the multimeter at the eCU connector, and the other at the O2 sensor).
Yes, the voltage reading is also essential, however, and yes the ECU could be bad, but we need to exhaust all options before we get to that conclusion (process of elimination).
You can go to autozone (or equivalent), and have them test your fuel pressure (at idle and at around 3000 rpm). No need to by a gauge only for this test.
Regards,
Billy
Customer: replied 1 year ago.
Ok. I checked for continuity with the multimeter, and that's tested out fine. Is the pressure regulator the only other possibility besides the ECU?
Customer: replied 1 year ago.
I called Autozone. They said they don't do a pressure test, but they do rent out the gauge. I can buy it for $159 and after I am finished I can bring it back for a full refund within 90 days. What a deal!!
Expert:  nabilc replied 1 year ago.
That would be great!! Make sure there are no hidden tricks...
If the pressure regulator is good (you have pressure within norm, and pressure increases with rpm, not to exceed the values indicated), i would next check for any vacuum leaks or exhaust leaks, as these two would also cause o2 sensor false readings.
Customer: replied 1 year ago.
Is there a good way to do that, testing for vacuum leaks.....do I need a special tool for that? I just went out and started it up and it is running really bad. RPM going way up then way down.
Expert:  nabilc replied 1 year ago.
Hello,
First, i would clean the throttle body. I would also clean the idle air control valve. Using carb cleaner and a toothbrush is the easiest way for me.
Then, to check for vacuum leaks, i usually start apraying water bit by bit, around the intake manifold (all the relevant hoses).
If the idle changes when the water is applied on some place, you've found your leak.
While at it, i would remove the vacuum hose from the pressure regulator, make sure it is not draining any fuel (the vacuum hose that connects to the intake manifold), check the brake booster hose to manifold as well. Those are all locations prone to fault and leak.
Regards,
Billy
PS: the idle suggests a problem with the idle air control, so i would start with that.
Customer: replied 1 year ago.
I don't want to end our connection till I resolve the problem.
Expert:  nabilc replied 1 year ago.
Hello,
The conversation should stay open. Just check, get back to me, and we'll proceed....
Regards,
Billy
Customer: replied 1 year ago.
Today while I was driving the check engine light went on and instead of turning the engine off and starting it I let it stay on and it resolved itself and the light went off as i pused the accelerator. Is it possible that the check engine light has a short and it's causing the engine to go into limp mode. This thing that's puzzling me is that it so intermittent it seems like if there was a leak it would be bad all the time wouldn't it?
Expert:  nabilc replied 1 year ago.
Hello,
Being intermittent and "self healing", the problem you have is most likely caused by wiring problems. I would check the engine wiring harness and connectors (mostly at components, connectors and ECM).
PS: sometimes leaks aren't constant, as the leaky parts if small, being temperature dependent, the small leak would expand and contract with temperature, vibration and other factors.
But i would double check the wiring first in this case.
Regards,
Billy
Customer: replied 1 year ago.
Ok. This is what someone else told me. Is this true??Your problem is with the connection. You cannot cut, splice, or mess with the pigtail or connector on the oxygen sensor. Even getting WD-40 on the pigtail will knock the sensor out--they are extremely sensitive. I would buy a new OEM oxygen sensor that fits perfectly. Take the connector that fits with you to get an exact match.The O2 sensor they sold me did not have the correct end on it, so I snipped the one from my old sensor, and soldered it to the new sensor. This guy says I can't do that. Is that true? I will keep looking for wiring problems.Thanks,Sue
Expert:  nabilc replied 1 year ago.
Hello,
O2 sensors are too sensitive: true.
You can work with the connector, however, you need to be extremely careful, know what you are doing, make sure the O2 sensor can still get air through the wire...
The main thing here would be that the sensor gets air through the connector, and if the wiring is tight (due to soldering, taping etc..) the O2 sensor will not get the air (this air is used for reference to be compared with the exhaust gas), it will make problems.
Regards,
Billy
Customer: replied 1 year ago.
so are you saying that if I cut the wire and soldered on the other connector from the old sensor, that it is not going to work right? If so, then how come there are so many universal sensors that come with stuff to crimp on your own connector?
Expert:  nabilc replied 1 year ago.
Hello,
I'm saying that the universal sensors come with specific connectors that still allow air in to the sensor. While soldering, you need to make sure that within the wiring loom of the oxygen sensor there is still place for air to come in.
Regards,
Billy