Low compression after engine rebuild,1987 2F.

[Output Shaft]

Definitely keep us posted on the smog test results. Very curious what the numbers will be with such a lean mixture (if it is indeed lean). Usually an over lean mixture will raise NOx (and eventually burn & warp exhaust valves)

Going for re-smog at 3 PM...

 

[Rainercar]

Either your wideband O2 meter is off or the engine is running too lean. It should -never- run above 15:1 except when decelerating. It should rarely even hit 14.7:1.

It should run below 14:1 while driving.

Maybe is related to the method I am using. I have

Either your wideband O2 meter is off or the engine is running too lean. It should -never- run above 15:1 except when decelerating. It should rarely even hit 14.7:1.

It should run below 14:1 while driving.

I agree. Had a similar experience with my 1967 Porsche 912, on which I used this fuel/air ratio meter. Had a hell of a time with getting the carbs adjusted right. I am using a AEM Power air/fuel ratio gage kit. O2 sensor slips into the tail pipe about 7 to 8 inches. Not the best set up.
As per my testing I run lean at idle, 16 : 1 at 1200 and 14.5 at 2200.
When under load while driving, it settles around 15 to 16:1. Goes to 18+ when coming off the throttle when shifting. Don't know, how to adjust it more toward rich, 14.5 or less.
After smog-ing I will know, if those readings are inline with the smog machine.

Checked the timing at varies RPM's:
Timing:
7 degrees @ 650 RPM
12 " @ 1200 "
18 " @ 1600 "
20 " @ 2000 "
31 " @ 2400 " or more

 

[gregnash]

Wouldn't you just turn the fuel screw out some to add more fuel to the mixture?

 

[Spike Strip]

I have an O2 Wideband on mine, stock everything and it runs a little rich at idle between 12.5 and 13 or so, which is kind of where you want it for power. Stoichiometric is just theoretical. 18 is too lean, if that's accurate. But I do try to get it up around 17 when I go in for smog ...

 

[gregnash]

Dear lord I SOOOOOOOO do not miss living in CA for that crap. We have smog here but nothing like CARB, plus we only have two counties that require smog.... and well I don't live in one of them!!

 

[LAMBCRUSHER]

blah blah blah...wanna get good, play a hard game

 

[LAMBCRUSHER]

yeah turn out the screw abit and see what that does...go fatter than you think you need and tune it down...I went out 6 turns once and backed it in about 2 and thought I was crazy at 4 turn out, but the truck said yes, please.

 

[LAMBCRUSHER]

by "the screw"..., I mean the idle mix screw, by the vacuum ports; not the idle speed screw, by the throttle linkage- just to be fully clear on my suggestion...

 

[Rainercar]

Wouldn't you just turn the fuel screw out some to add more fuel to the mixture?

I did that, but it made no difference. The reason is more underlying issues. See next post...

 

[LAMBCRUSHER]

where it is?

 

[LAMBCRUSHER]

if no response, then your idle plate is too far open and you're bypassing the mix screw....turn the speed screw out and try the mix screw again...

 

[LAMBCRUSHER]

turn the speed screw all the way out, turn the mix screw 4-6 turns out from gently seated, and start the truck. if you don't have any vacuum leaks, it'll run. it'll run slow and lumpy, but it'll run... turn the speed screw in till it idles about 600 and then trim the mix screw; then the speed screw, then the mix screw, and so on a few more times; check your timing at each cycle as well...

..if you're speed screw was out already to compensate for a lean mix, then you were already bypassing the idle circuit and your mix screw was out of the,...mix...

 

[Spike Strip]

make sure you don't have any vacuum leaks or loose hoses

 

[Rainercar]

Just returned from my smog test.

Passed all visual and functional checks, but failed the emission check (3).

1. High NO of 3X the max allowed - 3500 PPM instead of 1062 allowed.
Most likely caused by faulty EGR system (Per smog Tech)
2. High HC of 134 PPM . Max allowed 125.
Most likely caused by bad catalytic converter. (per Smog Tech)
From what I learned, after talking to the Smog Tech, catalytic converters go bad, for instance, when running the engine for extended period, after head gasket issues (coolant in exhaust), which the previous owner experienced and what I saw after seeing the condition of the head and piston rings and combustion chambers, after engine tear-down.

So, it looks like I will have to replace my cat and trouble shoot the EGR valve, to see what is bad. May just need to be cleaned. we'll see.
He said, that fixing the EGR issue may increase the HC. Looks like I won't get around replacing the cat.
I will do more research, to back-up the Smog Tech's opinion. I trust his judgement. (he should know...)

To be continued...

 

[LAMBCRUSHER]

again, if your idle mix screw adjustment doesn't return a response, you're throttle plate is open too far...

 

[Rainercar]

turn the speed screw all the way out, turn the mix screw 4-6 turns out from gently seated, and start the truck. if you don't have any vacuum leaks, it'll run. it'll run slow and lumpy, but it'll run... turn the speed screw in till it idles about 600 and then trim the mix screw; then the speed screw, then the mix screw, and so on a few more times; check your timing at each cycle as well...

..if you're speed screw was out already to compensate for a lean mix, then you were already bypassing the idle circuit and your mix screw was out of the,...mix...

I know exactly what you are talking about. I went thru that on my Porsche. if the throttle plate was just a small amount open, and we are talking no more than .010", the RPM would jump and go to the secondary circuit and I would be back to square one. On top of that, I had 2 carbs to deal with, made it that much more complicated. On my Land Cruiser, it didn't go to the secondary circuit, the RPM's would stay low.

I did do the basic method:

1. Set idle screw to 650
2. Unscrew mixture screw, to highest RPM, say 675 to 700
3. Adjust idle screw out to lower RPM to 650
4. Unscrew mixture screw again to highest RPM.
5. Repeat until the RPM will not go up anymore when turning the mixture screw out. (In my case that was around 680 or so)
6. When that happens, turn mixture screw in to set RPM to 650

That's what I did, but since I had other issues, I may have to do that again, when I am done with those. I will try your method, if it does not work..

 

[Rainercar]

Checked my EGR system as per Emission Control Manual and found everything working properly, EGR modulator and EGR valve checked out fine. I did find a cut vacuum hose cut, the piece that connects between the top of the modulator and the top of the EGR valve. Replaced with a new one.
Waiting for a used, checked-out OEM catalytic converter from Cruiser Parts. I paid 487.00 incl. shipping, instead of going with an new, aftermarket cat. I feel more comfortable with the used OEM unit, although it was more expensive.
When I receive the unit and have it installed, I will have it re-smog-ed. But I will re-check my mixture screw setting to get it to run less lean.
I want to get it below 14.7 : 1 on my air/fuel ratio gage... I am curious, if those readings are any better, once I have installed the replacement cat, and before adjusting the mixture screw.
In the meantime, I will check the EGR system again, to be sure and also check the AI system, per manual. I did buy and installed a rebuild air pump (OEM not Caldone non OEM style)...

 

[Output Shaft]

If the smog tech didn't actually shoot a timing light on the flywheel to check the timing, (most don't) retard the timing one or two degrees. That will lower the peak combustion temperature which will lower your NOx.

But replacing that leaking vac hose to the EGR valve will probably lower the NOx a ton. The EGR wasn't operational with the leaking hose.

 

[gregnash]

Checked my EGR system as per Emission Control Manual and found everything working properly, EGR modulator and EGR valve checked out fine. I did find a cut vacuum hose cut, the piece that connects between the top of the modulator and the top of the EGR valve. Replaced with a new one.
Waiting for a used, checked-out OEM catalytic converter from Cruiser Parts. I paid 487.00 incl. shipping, instead of going with an new, aftermarket cat. I feel more comfortable with the used OEM unit, although it was more expensive.
When I receive the unit and have it installed, I will have it re-smog-ed. But I will re-check my mixture screw setting to get it to run less lean.
I want to get it below 14.7 : 1 on my air/fuel ratio gage... I am curious, if those readings are any better, once I have installed the replacement cat, and before adjusting the mixture screw.
In the meantime, I will check the EGR system again, to be sure and also check the AI system, per manual. I did buy and installed a rebuild air pump (OEM not Caldone non OEM style)...

Probably a good call on the used OEM cat, and really not that much more expensive than the CARB compliant aftermarket CATs I have seen. Normally they run like $400ish maybe slightly lower.

 

[Spike Strip]

Dude, am I reading that right that you bought a USED OE CAT instead of a new Magnaflow? The old CAT is VERY restrictive and if you paid almost $500 that's 250 more than what a more efficient and better NEW C.A.R.B compliant bolt-in Magnaflow.

How did Cruiser parts test the CAT? Hold one end up to the light and say, 'yup, looks good to me'...

Axe for a refund and buy a Magnaflow or go to a muffler shop and have one installed.