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1992 Honda Prelude RPM idling Issue

Tiny
DRIAN_PANG
  • MEMBER
  • 1992 HONDA PRELUDE
  • 4 CYL
  • FWD
  • MANUAL
  • 375,000 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.
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Thursday, October 28th, 2010 AT 8:46 PM

14 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
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?
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Friday, October 29th, 2010 AT 8:49 AM
Tiny
DRIAN_PANG
  • MEMBER
  • 8 POSTS
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.
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Sunday, October 31st, 2010 AT 8:22 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
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.
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Monday, November 1st, 2010 AT 10:12 AM
Tiny
DRIAN_PANG
  • MEMBER
  • 8 POSTS
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
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Tuesday, November 2nd, 2010 AT 2:55 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
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.
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Tuesday, November 2nd, 2010 AT 7:35 AM
Tiny
DRIAN_PANG
  • MEMBER
  • 8 POSTS
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?
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Wednesday, November 3rd, 2010 AT 12:29 AM
Tiny
KHLOW2008
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  • 41,814 POSTS
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.
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Wednesday, November 3rd, 2010 AT 7:49 AM
Tiny
DRIAN_PANG
  • MEMBER
  • 8 POSTS
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!
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Wednesday, November 3rd, 2010 AT 8:00 PM
Tiny
DRIAN_PANG
  • MEMBER
  • 8 POSTS
What abt a faulty O2 sensor? Will that cause the car to run this way?
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Thursday, November 4th, 2010 AT 2:34 AM
Tiny
KHLOW2008
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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?
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Thursday, November 4th, 2010 AT 7:02 AM
Tiny
DRIAN_PANG
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I have not got anyone to help me with the O2 sensor yet. I will ask when I get my car to the mech tomorrow.

Hopefully this will all solve. My FC is very bad at the moment.
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Wednesday, November 10th, 2010 AT 7:29 AM
Tiny
KHLOW2008
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A scan tool would help to understand the various sensors operations. Plug one in and go for a test drive and note the various sensor operations.

If your piggy-back is adjustable for the various rpm range, then some twiddling might be required.
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Wednesday, November 10th, 2010 AT 8:06 AM
Tiny
DRIAN_PANG
  • MEMBER
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My problem solved!

TB and MAF sensor cleaning does the job! After very much of running abt!

Thanks KHLow for all your help too
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Thursday, November 11th, 2010 AT 8:34 AM
Tiny
KHLOW2008
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Glad to know you have fixed the problem.

Have a nice day.
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Thursday, November 11th, 2010 AT 8:39 AM

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