Mechanics

RPM IDLING ISSUE

1992 Honda Prelude

Engine Mechanical problem
1992 Honda Prelude 4 cyl Front Wheel Drive Manual 375000 miles

Engine - H22a with JUN stage2 cams
ECU - piggyback with Unichip

Recently my RPM drops too low, abt 500RPM. It usually sits at 900RMP on idle. I brought it to a workshop and has check on my spark plug. All 4 of them are burned out completely. I have then changed them.

We checked the car again and the idleing is still at 500RPM and there are quite a lot of black smoke out.

This morning as I was driving off, the car has a silght " pulling" effect. It seems like there is something stopping the car to move smoothly as usual. And on the 1st through 3rd gear, the car does not drive as smoothly as it used to be. The exhaust is also coming out with a very low gurggle sound during low RPMs when driving off.

When I let off the throttle at abt 60kmh, I will feel the car having the same pulling effect.

Please advice.
Avatar
Drian_pang
October 28, 2010.



Hi drian_pang,

Symptoms indicates a possible fault with the ECM which is causing the engine to run rich.

Do you have any trouble codes?

KHLow2008
Oct 29, 2010.
Hi KHLow2008,

I have a A/F ratio and it does shows it is running rich on idling. But after the car is moving or so, it is showing stoich. Even after driving off and stopping at lights, it shows stoich then after. But at times it can run rich. So, it is not always consistent which I have live with it.

I have got a Unichip as piggyback as I have the JUN stage2 cams on it.

Tiny
Drian_pang
Oct 31, 2010.
Stage 2 cam requires the idling speed to be higher than standard and you can try setting it at 1000 rpm and see if it works.

Get the throttle body and IAC cleaned to allow more consistent air flow which should stabilise the idling.

KHLow2008
Nov 1, 2010.
Hi again, thanks for your reply thus far.

A friend of mine commented that my H22a now sounds like the boxer engine from the WRX, which it should not. He also suggest that there are " misfiring" I am going to get it checked out by someone proffessional locally. But if you have anymore thoughts, please let me know i.E. Like what to check or what I need to explain to the mechanic when I see them.

Thank you again,
Adrian

Tiny
Drian_pang
Nov 2, 2010.
Hi Adrian,

When misfiring occurs, the idling speed would be affeced and the engine would not idle smoothly.

Check the spark plugs and wires. Note if any oil or water are present in the plug tubes. They would result in misfiring.

KHLow2008
Nov 2, 2010.
I have got the mech to look into it but it seems that everything is good.

What can be the problem if I got too much fuel in the combustion chamber?

Tiny
Drian_pang
Nov 3, 2010.
Too much fuel could be due to : 1. Bad MAP.
2. Faulty PCM.
3. Faulty TPS or out of adjustment.
4. Excessive fuel pressure, faulty pressure regulator or clogged return lines.
Above situation would result in all spark plugs showing signs of being rich, ie sooty.

5. Misfiring, when sparks fails to ignite.
6. Faulty fuel iinjector,

5 and 6 would normally occur on specific cylinders only.

KHLow2008
Nov 3, 2010.
Great! Thanks for much of your advice. Looks like it is time for me to go to Malaysia to get this sorted out. Workshops in SGP are useless!

Tiny
Drian_pang
Nov 3, 2010.
What abt a faulty O2 sensor? Will that cause the car to run this way?

Tiny
Drian_pang
Nov 4, 2010.
A faulty O2 sensor would cause rich or erratic running but it would not occur as very sudden. More of a gradual change.

Is the O2 sensor showing any code?
Did you get the O2 sensor data stream while in operations?

KHLow2008
Nov 4, 2010.
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