five7kid

iTrader: (14)

The trouble codes are stored in the computer memory for something like 50 starts after the light came on the last time for a particular code.

RocketyMan

So even tho the light came on and went off during operation, it will still store the codes? I would figure it would still be on because something made it trip in the first place. And if it made it trip, then it should still continue to make it trip.

naf

iTrader: (7)

Yes it will light the SES if, after a period of time and conditions, it continues to sense a rich or lean mixture.

Yes, as long as the ECM is not powered down it will store the code for later.

RocketyMan

Wow. Ok-good! Maybe this can help me further asses what else I might need to do with my carburetor.

RocketyMan

So I checked my computer for what codes it flashed at me.

After the third flash of code 1-2, it flashed code 1-3. Next it flashed code 2-3.

Haynes repair manual:
"CODE 13: Circuit or system: Oxygen sensor circuit; Probable cause: Sticking TPS; poor electrical connection, open or short in circuit; defective oxygen sensor; defective ECM"

"CODE 23: Circuit or system: Mixture Control Solenoid; Probable cause: Open circuit or short to ground in the mixture solenoid circuit; defective mixture control solenoid; defective ECM - If the mixture control solenoid is shorted to ground, the ECM may have been damaged."


Ok...well this is great. I basically don't understand how my mixture control solenoid can be messed up if I hear it ticking. So maybe code 23 is referring to something else? And if the ECM has a chance of being defective in code 23 then it's highly probable???

Code 13...I'm guessing my oxygen sensor could be defective as well...but in code 13 there is a chance the ECM may also be defective as well?!?!?!


Is my ECM screwed?!?!!? Aww...sh!eat!

naf

iTrader: (7)

It's highly unlikely the ECM is bad. Re-set the ECM by unplugging it and see if the codes show back up. Both are likely due to a bad connection at the O2 and the MCS (or the plugs being temporarily disconnected while the engine is running or in 'run'-maybe while you were working on it?). Examine the connectors and wiring, repair/replace if necessary.

RocketyMan

You're right. That's what I ended up doing. I unplugged and plugged the ECM power and let it run for like 10 minutes and the code didn't reappear. I'm thinking that's what it was (O2 was unplugged for one start up along with the MCS when I tried running it and forgot about it).

But now its something different. My timing advanced isn't working right. It started acting up when I was letting it idle. It was doing fine at 550 rpms, then all of a sudden it started bogging and idling at like 450-475 and basically trying to die. When I looked under the hood this electrical piece right next to the distributor was making this HIDEOUS noise. And so I unplugged and tried plugging my vacuum advanced and it acted like it did nothing (I would plug the vacuum leak on the back of the carb to ensure no excess air).

I really don't know what that piece is called, but it's right next to the distributor right above piston #8 intake runner. I'll have to get a picture of it and show you because I have no idea what it even is. I'm just guessing it has something to do with the timing advanced.

naf

iTrader: (7)

EGR solenoid. Should have vacuum line in from carb and vac line out to EGR valve (metal mushroom attached to intake manifold). Sure it was the timing making it idle poorly? A failing EGR could cause poor idle.

Test your EGR, with the engine running use your fingers to pull up the diaphragm underneath the valve. This should open it and cause the motor to run worse. If there's no change and it's already running poorly, your valve could be stuck open.

RocketyMan

Naf...just for confirmation. that thing is the EGR???

That thing would make really WEIRD noises after the car warms up and what not. It like vibrates or something. But anyways, I'm gonna see if I can pull that thing off and take a closer look.

RocketyMan

Here's a pic of it off.

Looks like some sort of vacuum line thingy... no idea.

RocketyMan

Anyways, I took the egr off and cleaned the heck outa it. I still don't know what that other piece is. Maybe some solenoid to the egr?

Anyways, she's running good again. So I'm happy about that.

naf

iTrader: (7)

Yes the solenoid is controlled by the ECM and opens to allow vacuum to the EGR. One of the tests for the EGR is to compare the effort to open it to the effort to open a new one. But clean the crap out of it and hopefully you'll be good for a while. They're relatively expensive (though not as much as a "digitial" one for later models).

RocketyMan

Well..anyways. After cleaning the EGR, I thought I would check my dwell and really dial in my carb.

Now my problem is that my dwell is fixed at 25ish degrees.

I did everything I could think of. I checked the O2 sensor and got around 700-800 mV. So I think I'm running a little lean. Then I checked my TPS and it seemed to ohm out ok and vary STEADY with throttle. Next I check my coolant temp sensor and grounded the leads.

When I grounded my leads, I then got 30ish degrees dwell instead when I have 25ish degrees dwell.

I have no idea what could make my dwell fixed and not vary regardless to choking the mixture or leaning.

naf

iTrader: (7)

From a few pages earlier:

If the dwell reading is steady and unresponsive then the O2 readings are likely out of the narrow range that the sensor can work with (assuming the motor is warmed up and everything else is working correctly). If your readings are steady try shorting out the leads to the Coolant Temp Sensor (CTS). This will trick the ECM into thinking the engine is fully warm and rule out a bad CTS.

Next try setting your idle mixture screws at 2-1/2 turns out each. Run your IAB screw from 2 turns out to 7 turns out, pausing for about a minute each half turn to see if the dwell responds. If nothing go another 1/2 turn on each of the idle mixture screws and repeat. Don't go past 7 turns out on either. The goal is to be near 3-4 turns out on each with dwell near 50% and properly reacting to changes in O2 readings (like choking the air horn).

RocketyMan

Naf.....youda BEST!

Duh! That makes sense. Mk well I'll try that next and see where that leads me there.

RocketyMan

Ok...I just really don't get this.

I reset my idle mixture screws back to 2 and 1/2 turns out and idle air bleed 4 turns out.

I'm still getting the same steady dwell reading REGARDLESS of any sort of adjustment!

I don't understand! Maybe it's my O2 sensor. I'm not sure...I have no idea.

naf

iTrader: (7)

Did you make adjustments to the IAB with the mixture screws at different settings?

Pages 13 and 14 may provide some insight:

https://www.thirdgen.org/forums/carb...e-rebuild.html

RocketyMan

I adjusted the idle mixture screws from 2 and 1/2 turns to 3 while keeping the IAB constant at 4 turns out.


I checked my O2 sensor again and I am getting voltage...but its kinda all over the place. I'm wondering if my O2 sensor really isn't working right. But I have no idea how to check it if my SES light isn't coming on telling me its bad or if the ECM isn't adjusting dwell based on O2 readings.

Basically, the dwell meter is only varying like 1 degree. And it stays the same even when I try to choke the carb.

On the sticky, it did say the adjustments are very sensitive and the IAB should be adjusted 1/8th turn increments. So maybe it's a very finite tweak?

naf

iTrader: (7)

Set your idle mixture screws at 2 1/2 turns out. Then start with the IAB at 2 turns out and turn it in 1/8 turn increments, waiting about 30 seconds each time for the dwell to respond. If you get to 7 turns out on the IAB, turn the idle mixture screws another 1/2 turn out and repeat the process. Keep repeating until the dwell begins to vary or you've exceeded 7 turns out on the idle mixture screws.

Make sure the engine is fully warmed up.

RocketyMan

Mk. I guess that would be the most thorough way to do it.

I'll have to try that tomorrow.

RocketyMan

Sooo...I tried everything from 2-1/2 turns and 2 turns IAB up to 3 turns and 7 turns IAB.

The dwell didn't change one bit.

I then notice when i went to turn my car off, it popped out a code 13.

Sticky TPS or defective O2 sensor.

So I'm really thinking its my O2 sensor now.

naf

iTrader: (7)

Check your TPS voltage at idle first. Make sure it's around 0.40 volts, not above 1 volt. If that's good replace your O2.

RocketyMan

It was the O2 sensor.

I took it out (and I'm so happy the sensor came out with a little PB blaster), and it looked pretty carbon fouled when I pulled it out.

So I tried cleaning it by scorching the O2 sensor and spraying DeepCreep on it and then squelching it in a water bath when I got it as hot as I can. It helped quite a bit because it broke off a lot of the fouled carbon.

Out of curiosity I then took a voltmeter and actually got some voltage when I got it hot enough!!

Anyways, I put it back in and drove it for a while and then checked my dwell.

Now my problem is, is that the dwell goes up and down all the time and never really settles down. Which I guess might be good. But it's kinda hard to get it to settle down. And then it acts completely different when I put the air cleaner on. The dwell would be at 35ish ( really hard to get to 30 degrees) and then jump to around 40 degrees when I put the air cleaner on. Any ideas? Whatchu think naf?

P.s. my idle mixture is at 2-1/2 and IAB is 4 - 1/2 ish turns.

naf

iTrader: (7)

Try 3 turns out on the mixture screws and see if the IAB can be losered a little, but it's normal for the dwell to range. It will constantly be varying as much as 10 degrees or so each way once it's receiving feedback info from the O2.

Installing the air cleaner can cause the dwell to increase. The increase is a response to a rich condition. Just shows how restrictive the factory air cleaner is.

RocketyMan

Ok...so I tried checking my dwell again...but it never went into closed loop. (the dwell needle pretty much stayed in the same spot the entire time)

I tried it at 3 turn out on idle mixture again...but nothing. So I then went to turn it off and saw the check engine light on.... code 13.... :/ ughhh...

Code 13
Defective oxygen sensor


I don't know why the oxygen sensor would decide not to work again for sitting a few days. Maybe I need to clean it better by torching the sensor instead of just a little grill.

I'll have to see if it'll help it again.

naf

iTrader: (7)

Everyone else I know just buys a new O2 sensor when the old one is bad. Do you also re-tread your own tires?

RocketyMan

Hey! Some truckers retread their tires! It's alot cheaper I guess than buying new ones.

But so far to get this car running has been under $200. Sooo....yeah.

But if it still won't work after I mess with it more, I'll probably go to the junk yard and pull one off.

Hey! It'll work, right?

jmd

iTrader: (4)

You don't?

Great thread, guys. I've got NOx readings at the smog station just a tiny bit above the 2.50 limit (2.52 to 2.58) so you've inspired me a bit to dust off the dwell meter and get 'er passed.

('88 LG4, 86 SS Q-jet; retarded timing seems to be key.)

RocketyMan

Anything for the lil 305!

L695speed

Rockety, worse comes to worse, an O2 sensor is a $20 part.

RocketyMan

Yeah...true...it's $20 bucks. I guess I should get a new one.