Hey everyone...

I am new to posting here, so please excuse my ignorance.

I still have my 1990 CRX Si, with 315,000+ miles on it (bought new 10/90), and am having a "random" but recurring issue with my idle. Can someone offer some ideas and/or thoughts?

* 1990 CRX Si
* "newer" 1991-1992 Civic engine put in about 2 years ago
* my car is still OBD-0
* "newer" engine w/solid cross-hatching in cylinders is OBD-1
* MPG 30-32 ( with the E091 no ethanol fuel )
* I have replaced ( recently )

• distributor
• plugs
• wires
• fuel filter
• IAC valve
• Air Temperature sensor

* Still original to the car:

• ECU ( OBD-0 )
• Throttle body
• Throttle body "dashpot"
• EGR
• Fuel injector rack
• Fuel injectors
• MAP sensor
• Fast idle solenoid
• Fuel pump / level sender board

* Symptoms:

• During startup - fast idle works perfectly
• Within the first 1-2 miles of driving, if I approach a stop and go into neutral:
  • idle will drop down to 500 or so
• As soon as car is fully warmed up
  • car idles smoothly @ 750 +/- 50
• Fewer problems when outside air temp is "cold" in the 30s or lower

* I run E091 ( no ethanol blended ) fuel
* Water level is always "spot on" full ( in recovery & radiator )

* The issue is just very "hit & miss" / "random"

• Some times it will really act up
• Other times it just runs very well ( but with a low idle )

I would really appreciate some help as this is my daily commuter and I don't have the extra $$$ to go buy a "newer" car ( I actually really like my CRX ).


Thanks!
-Scott

 

Do you have any check engine lights?

The only other thing you actually haven't changed is the TPS aka Throttle Position Sensor.

Since you have changed out the Throttle Body though, I would assume the the TPS changed with it.

I don't believe you actually have an EGR...

When you are in neutral, is your foot on the clutch or no?

Are you headlights on/AC on when it does this?

 

bleed your coolant
Check your grounds

check the plug for the rad fan

 

Thanks for the replies! I forgot to share a couple of additional items:

* I still have my ORIGINAL MAP sensor
* I replaced my clutch cable (last summer) - it had "stretched"
* I still have the ORIGINAL wiring harness in the engine compartment.
* I still have my ORIGINAL TPS
* I did "pull/replace" the hazard fuse to reset my ECU about 2 weeks ago.

To answer the replies:

*Caoboy:

Do you have any check engine lights?
No.

The only other thing you actually haven't changed is the TPS aka Throttle Position Sensor.
Correct.

Since you have changed out the Throttle Body though, I would assume the the TPS changed with it.
No. Still original Throttle Body - but was "dipped/soaked" clean.

I don't believe you actually have an EGR...
Correct. Only the California DX Hatchbacks, did. Mine is not a CA model.

When you are in neutral, is your foot on the clutch or no?
Yes, most of the time. If at a long light/line of cars, no.


Are you headlights on/AC on when it does this?
Headlights, Yes.
A/C, Off.
Idle seems to hold "steady", if, after the first 2 miles of cold driving.

===============================

*Acmoc:


bleed your coolant
Done w/full flush before winter ( in early November ).

Check your grounds
Which ones?

check the plug for the rad fan
Fans work as expected (come on when coolant is hot enough).
Temperature Gauge rises to just below the "middle" and stays there.

I appreciate your feedback and look forward to additional idea(s).

 

The ground on the thermostat and the head to valve cover