85 PGM FI Problem!!!!

On my 85 Prelude SI, initial startup is fine. However, if you turn the car off and try to restart it hot, the idle is very low, there is no power, it stalls, and the PGM FI light comes on. If I remove the key and restart several times it will eventually find itself. The LED on the computer is flashing three times. Any troubleshooting solutions would be most welcomed.


Mike

what i have from the 92-96 pgm-fi manual is that it could be either of 3 things

A) other fuel supply (doubtful eh)
B) Exhaust Gas Recirculation (i doubt your car has that ?, but what do i know)
C) The idle Air Control Valve. (IAC valve)

I took that from a troubleshooting chart reffering to "frequent stalling - AFTER WARMING UP"

and the a,b,c are listed in the order from most likely cause to least likely.
I know it's from a different time span but perhaps it still helps and can give you a place to look?

reading on...

you can test the IAC, by

with the engine running and the accelerator pedal released, disconnect the the 2P connector from the IAC connector

is their a reduction in engine rpm?

if NOT, substitute a known good IAC valve and retest.

Thanks Ludeguy, bit it's not stalling when warm just when I turn it off for a few minutes, (like pumping gas) I read that the ecu on these controls the fuel mixture, Timing ect. through the variouse sensors. Apparently there are some number of pre-sets programmed into the ECU's memory as different settings in a sequence. I don't think these primative ECU's can make sophisticated real time changes. I need to isolate the sensor thats causing the PGM FI to start at a setting other than the one it should be based on temp,throttle position, manifold pressure, Oxygen ect.... Also I have the single LED ECU and the code thats it is flashing is 3. MAP sensor, Could a faulty MAP sensor cause tyhese symtoms

ttt

hmm, code 3 is for an electrical failure of the map sensor, not mechanical...

from the guide it says to check the voltage of the 3 terminals of the map sensor plug ...|wht/blu| |blu/wht| and |red/wht|

turn the ignition switch ON

measure the red/wht (+) voltage and ground = 5v
between red/wht (+)and blu/wht (-) = also 5v
between wht/blu and blu/wht = also be 5v.

if you get that on all three, then you are supposed to measure the pins on the ecm/ecu (with a test harness, because the ignition has to be on)if you get 3v from the ecm pins - it says to replace the map sensor.

I think it could play a role in your problems ? but perhaps it's not the end all... the map sensor does as you say reads the absolute pressure in the intake manifold and feeds that information back to the computer.

when your car is turned off the absolute pressure should read atmospheric and usually be around 29.92" (of mecury) on a standard atmospheric day (ie: based on sea level altitute and 15 degrees celcius)... when your car is running the pressure would be lower than that (sometimes half of what ambient pressure was) and increase as throttle is increased, on a normally aspirated engine it would never exceed ambient pressure, on a turbocharged engine it could - but i assume you're not turbocharged.

anyways it's an interesting problem, and when you get it solved I hope you report back, keep in mind the wire colors i gave you are from 92-96 and may not coincide

cheers...

Thanks Ludeguy,

I think I have the correct wire colors for the 85 in a haynes manual, I will check it out, I suspect you are right that thie Map sensor may not be the end all but its definatly sparking the code 3. I am leaning towards the temp sensor. They are cheap enough to just replace and hope.

I'll let you know

Mike

ttt

ttt

ttt

The map sensor does read the vaccuum in the intake manifold, so u can also check for leaks around the intake manifold gaskets, and the vaccuum lines going to and from it. I have an 84 prelude carbed, and have a hell of a time with the vaccuum lines, etc. I would think though that if u had a temp sensor problem that the code would read that or maybe the 02 sensor as the problem. Do you have a vaccuum tester etc. Let me know and I'll look up your car in my book when I get time. GL.

-Bob-

Thanks Ohio. I grew up in Dayton before moving up here in new york. I don't have a vacuum tester nor would I know how to use it. I will have to have my mechanic check it. However I was poking around under the hood looking for bad wires Vacuum lines ect. I unplugged the connector from the vacuum house ( where the MAP sensor is) Thhe car continued to idle fine. Started it up a dozen or so times no problem. Then I get in it to back it out of the garage and as soon as I closed the door the car died and the original problem was back. I'm confused...... On the 85 the ecm is located behingd the drivers side rear sail panel. subject to vibration from the door closing.

this is weird.