Got it running! Now, error codes?

[FirstRanger86]

I had a long thread, and a lot of help, but after tuning up my auction 86 Ranger, I changed the TFI and the fuel pump relay, along with the high pressure pump, to find it was the low pressure pump that had died.

I was finally able to run the KOER test, with my Craftsman scanner. I'll admit, I didn't set the timing first, which I will do, but it kicked out some codes that I was hoping you all could identify, or point me to a link that lists them.

Code 42 (02 sensor, explains all the black smoke)
Code 25 (knock sensor -- ok)
Code 31 - EGR, got this code on the KOEO test too, working on getting another valve and sensor
Code 77 - unknown
Code 75 - unknown

Thanks!

Tom

 

[RonD]

Here are the OBD I codes:
http://www.therangerstation.com/tech_library/2digitcodes.html

After doing any adjustments you need to reset the computer, either with the scanner or by leaving the negative battery cable disconnected for 5 minutes.

Computers don't retest systems unless reset, so even if you fix a problem CEL would stay on until reset and fix was recognized.

 

[FirstRanger86]

Thanks, Ron.

Gonna change the 02 sensor and the EGR sensor. 86 had no CEL, so at least I won't be annoyed by that! It runs rough when cold and smokes quite a bit, so I'm hoping that correcting these two codes will improve running.

 

[FirstRanger86]

Hey Pete,
Thanks for weighing in again.
I'm a carburetor guy learning that the 02 codes don't necessarily mean a bad sensor, but I bought one when I bought all the tune up parts from rockauto, figured it was ancient, and possibly no good.

I did check the regulator when I was trying to get her going, and I would pull off the vacuum and 30psi of fuel pressure would jump to 40psi. I'll see what codes I get, and if the rich condition is corrected. It sure is blowing some nasty smoke.

If the sensor doesn't fix it, what path of elimination do you like to go to, in figuring out why the a/f ratio is off? Having a similar problem in my 88 325i! Hoping it's just the old sensor in this case.

 

[RonD]

This is a great site for understanding sensors, what they do and how they interact:
http://oldfuelinjection.com/?p=10

You can test injectors using a small hose as a stethoscope, with engine idling listen to each one, should have a steady "tick, tick, tick", you may have one stuck open.

You can also test injectors with an OHM meter, they should test at about 14ohms, 11-18 is the "allowed" range, but this would usually be done if you had a miss not a rich condition.

The ECT(engine coolant temp) sensor is the "choke" for fuel injected engines, it is a 2 wire sensor that tells the computer the coolant temperature, it is only used by the computer, there is a 1 wire sender that looks similar, it is for the dash board temp gauge.
The ECT sensor is a simple resistance sensor so can be tested with an OHM meter.
If ECT tells computer engine is cold the computer runs engine rich, raises the idle(IAC) and advances the timing, just like the "choke plate" did on a carb, this is called "Open Loop" for the computer, it runs preset fuel/air mix and doesn't use the O2 sensors.

As the ECT sensor warms up the computer leans out the mix, lowers the idle and reduces the advance on the timing, just like the "choke spring" did, this is called "Closed Loop" for the computer, it now uses all the sensors to determine best fuel/air mix.

A faulty ECT is rare, but not unheard of, it's symptoms would either be poor cold starts and running until warmed up, or good cold start and running but rich condition after warm up, so one or the other but not both.

 

[FirstRanger86]

That is a good site, thank you. As an update, I popped in the new O2 sensor, and I'm still smoking pretty good. Given that it's been sitting so long, could be some crudded up injectors, or just about anything!
It's not blue smoke, and it doesn't start smoking until it's been running for 2 minutes or so, but it gets pretty nasty, floating across the yard. When I get the exhaust buttoned back up, and the bed tightened down, I'm going to drive a tank of gas through her, with some Techron, and see if I can't drive it fixed a bit! If that doesn't do it, I'll need to start making my way through the checklist of why it's running rich.

 

[RonD]

Also once engine is warmed up, unplug the electrical connector on the MAP sensor.
Engine should start running poorly, this means MAP is working, maybe not working well but working.
Also check the vacuum line on the MAP sensor carefully.

MAP sensor should be located on the passenger side firewall, follow the vacuum line to it.