TinMan

Ok all I am about at wits end trying to figure out why this little motor is running so rich nd throwing code 5 for O2 sensor circuit.

Here is the stats on the motor, complete rebuild with about 3 hour run time. All EB lower end parts, .020 over, an gaskets. Stock head casing, with EB 268 cam, LCE adjustable cam gear, over size stainless valves, new stock ratio valve springs, EGR blocked off, PAIR removed, fuel pressure VSV removed. All new vacuum hoses. Injectors sent off to witch hunter for rework.

Compression - 180/185/190/190 respectively for 1-4

This is what is going on, when the motor reaches operating temp, CEL 5, O2 sensor circuit is tripped. It runs so rich that it will carbon foul the plugs in about 10 min.

I was not confident that the O2 sensor was bad, so I started trouble shooting things that would also trip the O2 sensor. Burped the air out of the coolant system.

Checked the thermo switch, it give resistance within specs hot and cold.

Checked the cold start injector time switch, it reads resistance within specs.

Checked and reset the throttle position sensor. It checked out fine, and is set well. Also giving proper voltage at the ECU.

Checked the AFM, it gave good resistance readings.

Checked the cold start injector to make sure it is not leaking. It did not drip more than 1 drip the entire time I watched it. And it sprays really good.

Just to make sure the cold start injector ws not continuing to spray while in closed loop, I un hooked the injector wires. Still no change.

Continuity check from the O2 sensor to the ECU, good.

Continuity check from just about all the sensors to the ECU. Good

Installed a new DENSO O2 sensor, no change.

Tried to get a read on the O2 sensor voltage swings, but I don't have a analog multimeter. My digital does show more than 8 voltage movements in 10 seconds, but they are very, very small swings.

Checked for vacuum leaks with carb cleaner. Nothing to note.

Checked nd double checked the vacuum line routing. Seems fine.

Timing set at 5* before jumpered. Idle at 750 rpm. As good as I can get it with the rich condition.

Cam set 2* advance.

I can clean the plugs, and clear the ECU and it will start up and run just Beautiful, until the it is supposed to go into closed loop mode. Then it goes down hill do to the rich condition.

Tonight I am going to check all the voltages at the ECU, and record the numbers. I'll post up what I get.

I'll also pick up another set of plugs as these may be fouled by now.

Also the rich condition is the same across all the plugs.

I am about at the point of trying a new ECU. but I am just not confident that the ECU is the problem. Wish I had a spare to swap in and try it.

Thanks in advance for any help. Because I am really frustrated.

Later

snobdds

It looks like you have coverd all your bases. The only other thing I would check is the AFM. Make sure it's not stuck and open and closes freely.

Let us know...

Buck87

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waskillywabbit

iTrader: (-1)

That makes MY head hurt Todd.

Interested to see what it turns out to be.

Whenever I get frustrated, I go work on something else and pick it back up later.

:wabbit2:

TinMan

I hear ya Brian. My head deffinately hurts. I guess I could take a brake and hang Christmas lights. But then I would just have to take those down later, which would take more yota time away. I took a trip out to the pick and pull at lunch, picked up two ECU's for an 84/85 efi. Maybe one of them is good. But I am just not convinced the ECU is bad. Tonight I am going to start all over.starting with the O2 sensor. Circuit and record the numbers for everyone. When we figure this thing out may help someone else. I can't picture the blocked off EGR causing this but maybe. Well see. Later

CajunKenny

Does timing change as you install and remove the jumper?

TinMan

And the winner is snobdds!!!!!

Came home and decided the vain door on the AFM was the one thing I had not checked. Pulled the air pipe and sure enough the AFM was stuck wide open. I could not even move it with my finger. A little brake clean and then some PB blaster and it is running like a dream. No CEL anymore.

Basically with the AFM door wide open the ECU was giving wide open throttle fuel at idle. I would say that will make it run a little rich.

Now I have two extra ECU's, anyone need one.

Thanks guys it is nice to at least be able to come on here and vent.

snobdds

Good job...There really was not much else to check.

Plus if the cold start injector is working then the AFM is about the only thing left to check.

TriForced

Yeah, I'm happy I found this site out. Seems like everyone is well informed with their information. Also wit the ECU, I might be curious. I'll drop you a PM soon.

Buck87

Congratulations! I love a happy ending.