Need advice and guidance please.
Working on my sons 93 Honda Accord and trying to get it back on the road. Sorry this is long but I did not want to leave anything out.

Check engine light only comes on when driven, not on when just idling in the driveway. I am using the Honda service manual to troubleshoot the problem. Jumped the service connector and got a Code 12. Followed the ECM reset procedures as listed and then drove the car as instructed. Check engine light return and it was a Code 12 again.
Followed the flow chart in chapter 11-106 with the following results'

-Disconnect #16 hose from EGR valve and connect vacuum pump/gauge to the hose. No Vacuum.
-Moved vacuum pump/gage to the EGR valve. With engine running apply 8 in HG of vacuum. Engine runs rough and EGR valve holds vaccum.
-Turn engine off.
-Disconnected the 4 pin connector from the control box. Turn ignition on and measured voltage between BLK/YEL (+) on the terminal main wire harness and body ground. Got 13.4 volts.
- Reconnected the vacuum pump/gauge to the #16 hose and started engine and allowed to idle.
-Connected battery power to the A terminal on the 4 pin connector and grounded the B terminal while watching the vacuum gauge. Had vacuum with 1 second.
-Turned off the ignition and reconnected the 4P connector.
-Turned the iginition switch on.
-Disconnectd the 3P connector from the EGR valve lift sensor and measure voltage between YEL/WHT (+) terminal and GRN/WHT (-) terminal. Got 4.99 volts.

And here is were I can't go any further. The following steps call for the Test Harness to be connected between the ECM and connectors to read out items with a multi meter. Seeing that this is a 1993 not to many repair shops have a test harness for Honda that old.
But reading through the rest of the steps the problem is either the ECM or the EGR Valve. Leaning towards the ECM due to once the car is warmed up and is being driven it wants to stall when you come to a stop. And during my reading the ECM also controls this as well.
All so of note, the car failed emissions as well and this was before the check engine light came on two months ago.
Just don't want to start throwing expensive parts at the problem and hoping to get luck.
So please if anyone has seen this kind of problem or has more guidance it would be greatly appreciated. Dad is getting tried of driving his son to work.

 

Suggest checking the EGR lift sensor signal out wire (wht/blk) for varying signal when you manually apply vacuum. This is described in manual. Idle output should be ~1.2 V and 8" hg vacuum should produce ~4V. You will need to backprobe the wires to measure voltage.

If this checks OK, it's either wiring fault or ECM. You can disconnect wires to ECM (EGR solenoid valve and EGR lift valve) and check them from under hood to ECM connector. Use wire jumpers to ground to check each wire. If wires check OK, then ECM fault is indicated.

You can mimic all the "harness tests" by using backprobe pins at ECM connector.

good luck

 

TexasHonda,

Thanks once again for the help and guidance. I will give that a try in the next day or so and post the results. It is just to hot here in Houston to do it in the afternoon, we have to do it in the am.

Thanks,
Mike

 

Yes, it is brutal weather. I stay inside all day!

good luck

 

TexasHonda

Just completed the first part of what you suggested, and here are the results:

-Back probed the white/black wire at the EGR valve lift sensor connector.
-I have a constant 4.3 volts. Applied vacuum to valve and no change in voltage.
-EGR valve does hold a vacuum.
-Started the car and let it warm up to see if their was any difference in voltage. Still have a constant 4.3 volts, with no vacuum and with vacuum applied.
-Also with the engine running and vacuum applied to the EGR valve the engine does not stall or run rough as it did before when this check was performed earlier.
-ERG valve will hold a vacuum.

In the shop manual, it ask the question if the engine stalls or run rough and does the EGR valve hold a vacuum, when you apply vacuum to the EGR valve. If no it says replace the EGR valve.

So I am assuming that the EGR valve lift sensor controls the amount of voltage that goes through the signal out wire (wht/blk) and with it being a constant 4.3V the and that the engine does not stall or run rough with vacuum applied to the EGR valve that the EGR valve is the issue.

So what do you think?

Thanks,
Mike

 

If you can't manually lift the valve w/ applied suction, replace the EGR valve. From your description, it's frozen.


If you can manually lift valve w/ suction and voltage out does not change, then valve lift position sensor is faulty.


good luck

 

Thanks once again. Ordered the EGR valve Sunday and due in today. Keeping my fingers crossed. Will post results after installation, test drive and hopefully pass state inspection.

 

TexasHonda,

Changed out the EGR valve and cleared the codes from the ECM. Test drove for 30 minutes with no problems or check engine light.
Just returned from having the car inspected and she passed. Thank you so much for all the help and guidance.

Mike