Engine misfire with check engine light staying on?

Hi,

A misfire can be caused by several things. For example, an engine vacuum leak or excessive or low fuel pressure can cause it to happen.

Since there are different possibilities, I would suggest starting by scanning the computer to see what diagnostic trouble codes are present. That should help point us in the right direction.

Note that this vehicle has an OBD1 system and doesn't require a scan tool to retrieve codes. Follow the directions in this link and let me know the results:

https://www.2carpros.com/articles/honda-car-1990-1995-obd1-code-retrieval-procedure-and-definition-table

Let me know what you find.

Joe

The engine light tells me Code 14 Idle air control valve or bad ECM.
I was right.
I didn't want to use the code reader because I want to learn from sounds and understanding how the machine works.

Hi,

Does the misfire only happen at idle? I ask because once you press the throttle, the IAC is bypassed, and air enters via the throttle body/throttle plate.

As far as the code, I attached the description and diagnostics specific to the code and this vehicle. Take a look through them and let me know if you are comfortable performing them.

Let me know.

Joe

See pics below.

When it's cold outside, when the wind temperature is below 15 degrees F, then the engine runs just fine until the electrical system gets a full connection from the car warming up and then the engine misfires.
Sometimes that would take up to 3 minutes until the engine starts to misfire.
If it's above freezing, then the engine misfires right away after starting the car.
When the engine started misfiring is when I was driving in a neighborhood.

After I changed the air filter, oil, and transmission fluids. The car seemed to be running just fine in idle until I put the car in drive and then I start losing power when I try to maintain a speed. When I am accelerating then the car runs normally.

After I changed the fuel filter is when the engine started misfiring when I turned the car on. The car still runs normally when I am accelerating but I lose power when trying to maintain any speed. That is when the RPM drops to 1500 and stays there until I start pressing harder on the gas pedal.

Why?
Does that sound like a ECM problem instead?
I don't have a voltmeter right now.

Hi,

If you lose power, I would check the fuel pressure. If you haven't already, here is a link that explains in general how it's done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Let me know what you find.

Joe

I changed the Idle air control valve because it was very dirty, and the car started up and ran but it was leaking antifreeze.
The hose to the IAC wasn't sealed properly by the clamp so I took the manifold apart and fixed the clamp.
Started the car and it ran but had a high RPM of 2.5 and still leaked antifreeze.
This time the antifreeze was leaking from the gasket on the IAC. I took the manifold off again and I took off the IAC to switch the gasket from the old IAC with the new IAC since the old gasket wasn't leaking and still looks and feels good. This time I added a little antifreeze to the gasket in hopes that it would stop the leak.
At the same time, I unhooked the hose from the radiator to the IAC and drained all the antifreeze and to make it easier to attach to hose to the IAC without so much space restriction.
I reconnected the hose to the radiator and refilled it.
Now the car won't even start. It will crank but won't start. The engine light won't even turn on when I put the key in the ignition to prime the settings without starting the car. Even when trying to start the car there is no engine light turning on.
The battery is okay, the crank is okay.
I'm assuming that the IAC is bad but I don't understand why it would start up before with misfiring, but it won't start up now after I drained and refilled the antifreeze.
Should I pour antifreeze down the hose from the IAC?
I'm assuming that the antifreeze isn't able to push itself back into the IAC.

Hi,

Will it start if you slightly press the throttle? Also, when you had the IAC removed, did you inspect where it went into the throttle body to make sure the air passage was clean?

Joe

No, it won't start if I press the throttle as I turn the key. I tried 4 times.
I even tried resetting the IAC with the trick of turning the car to the on position for a few seconds, off for 10 seconds and then turning the car on but it wouldn't turn on.

The space where the IAC is was slightly dirty but I tried wiping the dirt off with a paper towel but it wouldn't come off so I tried cleaning it with a scratch pad and a little antifreeze and wiping it down with a paper towel but the little amount of dirt wouldn't come off so I left it alone since it was running with the dirt on it.
The dirt is stained into the metal and won't come off.
The only other thing I did was, use a paper towel and wiped off the intake manifold temperature sensor since it was dirty on the inside.
The intake manifold is slightly dirty but that didn't stop it from running before. Plus, when I wiped off the temperature sensor, I also tried wiping down the inside of the manifold and most of the dirt is stained into the metal.

When I refilled the antifreeze, I used concentrated antifreeze. I know that I will have to drain the antifreeze again and mix it with water for a 50/50 ratio, but I didn't think that would cause the car to not start.
I'll take it apart again and take some pictures.

Solved the issue.
When I put in concentrated antifreeze, for some reason it didn't go up the hose to the IAC.
I drained the antifreeze and flushed out the radiator.
Then I mixed half and half water and antifreeze in a bottle and poured it in the radiator while the manifold was still off. The antifreeze started pouring out of the hoses to the manifold.
I put everything back together and the car still wouldn't start.
I took the manifold off again and inspected the IAC valve and found a hairline crack in it.
That explained why the car wouldn't start.
I decided to take the old idle air control valve and clean the dirty screen with a paper towel and put it on the manifold.
The car started up and after a few minutes, it started misfiring again.
I turned the car off and waited a minute, then turned the car back on and it ran for 20 minutes with no misfire.
Drove the car a few miles and no more problems.
Well except for the oil light flashing. There is no leakage and the oil light was flashing before the IAC started creating a problem.
There is no leakage and I believe the oil sensor needs to be replaced because I had 10W 30 oil in the engine before and when I changed it to 5w 20 like it should be then the oil light starts flashing when the engine gets warmed up.
Thanks for the help. Much appreciated.

Hi,

Thanks for the update. I'm glad to know you determined the issue and got it going. As far as the oil light, chances are you are correct. However, if you hear any ticking or knocking from the engine, there could be an issue.

Let me know if anything changes or if you have other questions.

Take care,

Joe

New problem.
My car misfires and loses power when trying to maintain speed.
When I start up the car, it misfires a few times and then calms down to normal.
As I accelerate it acts normal but when I try to maintain a speed then it misfires.
I tried getting a code, but nothing shows up and the engine light doesn't turn on until the engine continues to misfire while driving.
The battery, alternator and belts were checked out. Everything seems okay.
After I cleaned the IAC valve and put it back on, everything was running normal until I turned the heater on and then the engine started to misfire.
Now it continues to misfire when maintaining speed while driving.
I wonder if the IAC is actually going bad.

Hi,

That is very possible. The IAC receives a signal from the ECM when an added load is placed on the engine to increase engine speed to compensate for the load.

If you can, reinspect the connector. Make sure it is in good condition and tight. Also, remove the IAC and inspect it.

While the IAC is out, reconnect the wiring to it. Have a helper cycle the ignition key from off to on while you watch the pintle. It should move a bit each time the ignition is turned on and off.

See if that happens. Also, if a new one isn't too expensive, you may want to replace it.

One last thought, when the engine light does come on, immediately drive it to a parts store and have them scan the computer before it turns off. We need to determine if it is a specific cylinder or a multi-cylinder misfire. On the other hand, it could be something completely different.

Let me know.

Joe