1990 Honda Civic check engine light on. Engine RPM fluctuat

SEBASTIANJE

MEMBER
1990 HONDA CIVIC
4 CYL
2WD
AUTOMATIC
125,000 MILES

Hi,
My car nowadays has a problem during colder weather where the check engine light suddenly come on and then within second the rpms start to fluctuate and the car stalls. Sometimes when I restart the problem disappears as in the check light also disappears. Today the problem was constant. The check engine light stayed on and the care refused to start. Is there any idea on what the problem could be. The computer gave out the codes 4 and 8.
Any hints from experience would be much appreciated. Thank you so much for taking the trouble.
regards,
Sebastian

3 Replies

KHLOW2008

MECHANIC
41,814 POSTS

Hi Sebastian,

Thank you for the donation.

Code 4 and 8 shows a problem with the distributor where 2 of the sensors or their circuits are malfunctioning and if the check lights are coming on intermittently, it could be caused by any of the following :
1. Faulty distributor
2. Wiring circuit
3. Faulty ECM.

Engine unable to start and CEL not going off can be due to :
1. Faulty PGM-FI main relay. Remove the relay and check for cold solders on the circuit boar, if any found, resolder them to rectify.
2. Faulty ECM. Remove ECM and check for leaking capacitors, if any found and the circuit board is not badly corroded, DIY rebuild by replacing the affected capacitors, it might work, no guarantees. ;)

The engine idling rpm surging and stalling sould be related to the above malfunctions.

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Tuesday, February 3rd, 2009 AT 3:07 PM

SEBASTIANJE

MEMBER
1 POST

Hi KHLow2008,
I had replaced a distributor a month back. We just checked the resistances at the distributor and its seems within the range.
1)We have still decided to reorder and check by puttin in another one as the new one was still under warranty.
2) "Faulty PGM-FI main relay" This I did not know about so I will ask the shop about this.
3) If the above two dont work the shop suggested
replacing the ECU. Any ideas where a direct consumer should be looking to buy one of these (new)?
Let me know your thoughts regarding this chain of thought.
Thanks a bunch
sebastian

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Tuesday, February 3rd, 2009 AT 3:30 PM

KHLOW2008

MECHANIC
41,814 POSTS

Hi Sebastian,

A new ECU is going to cost alot of money and you can try the scrapyard which would have it at a much lower price. There are shops which does rebuilds as well.

Here is a location of the PGM-FI main relay.