1989 Honda Prelude Rough idle and running rish

Tiny
JPC1952
  • MEMBER
  • 1989 HONDA PRELUDE
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 185,000 MILES
I replaced some coolant hoses under the intake manifold and when I put everything back together, it ran rough and would almost stall when I gave it gas while in gear. I rechecked everything and checked timing. Everything looked good but I got codes 2, 5, 12. The oxygen sensor code was already there. 5 is for the MAP sensor and the 12 is for the EGR. The Map sensor checked out as good. The voltage for it called for 3 volts and read out at 2.75 volts. I got a different ECU to see if that is the issue. The ECU I have may be for a stick rather than an automatic. The number is 37700-PKI-661. The engine runs so rich it is fouling my plugs. Runs smoother warm but still too rich and blowing dark smoke out the exhaust.
Saturday, October 17th, 2009 AT 7:26 PM

7 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Running on the rich side could be one of the following below

Could be a bad O2 sensor, excessive fuel pressure (bad fuel pressure regulator or plugged return line), leaky fuel injectors, dirty air filter or restricted air inlet, or a defective coolant sensor that prevents the engine management system from going into closed loop mode.
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Sunday, October 18th, 2009 AT 2:01 AM
Tiny
JPC1952
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  • 5 POSTS
The coolant sensor was checked out and is working properly. If the O2 sensor is faulty and keeping it running rich, why was it not running rich before replacing the coolant hoses. I am looking for a cause and effect. How did replacing coolant hose evolve into running rich?
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Monday, November 23rd, 2009 AT 10:55 AM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the O2 sensor again-the coolant hose has nothing to do for it to be running rich-check the rest I've mentioned.
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Monday, November 23rd, 2009 AT 12:00 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Check the MAP sensor vacumn hose installation and presence of vacumn.
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Tuesday, November 24th, 2009 AT 7:59 AM
Tiny
JPC1952
  • MEMBER
  • 5 POSTS
The MAP Sensor hose and voltage were checked out and was 2.75 volts. I put a used ECU on the car to see if that was the problem. I am attempting to put two new O2 sensors in but I don't think that is going to help me start the car.
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Tuesday, November 24th, 2009 AT 12:51 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
I am attempting to put two new O2 sensors in but I don't think that is going to help me start the car. Its not gonna help, the O2 sensors does not prevent the engine from starting.
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Tuesday, November 24th, 2009 AT 4:14 PM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Sorry if I did not make myself clerar. What I meant was the hose installaion. Quite often the wrong vacumn port is used causing the MAP to read an error.

During the replacement of the coolant hoses, were the IAC and Fast Idle Thermo Valve coolant ports and hoses checked for clogging?

Before the replacement of the coolant hoses, adjustment could have been made to compensate for the clogging of coolant hoses and when the clogging was cleared, the engine is running under a different temperature range which is affecting the idling, IAC and FITV.

Check the TPS calibration and coolant level. Any air trapped in cooling system can cause erratic running.

Rasmataz is correct about the O2 sensor. They would solve the O2 sensor problem, helps in the rich running condition and would have a bearing on the EGR code.
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Tuesday, November 24th, 2009 AT 4:27 PM

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