DEQ: FAIL

[Grafiske]

So I've got a 1984 Datsun 720 pickup. Recently fixed head gasket so it's only been on the road for a week or so.

 

I failed the Hydrocarbons test by a LOT. supposed to be under 200. I was at 1100.. uh oh.

 

Anyone know any tricks of good DEQ specialists in Portland OR?

 

 

 

[Eagle_Adam]

i have a carb guy in sherwood that can make it pass and run good PM me 

[bonvo]

high hc means its running rich rebuild the carb then tune a little leaner if you were closer i could hook it up to the asilliscope and dial it in

[datzenmike]

Hydrocarbon =

 

choke stuck on or part on

float stuck, flooding

idle mixture screw needs adjusting.

idle too high

valve guide seals leaking oil

rings worn out

motor running cold, wrong or stuck/broken thermostat.

timing retarded

[HRH]

Yeah, assuming the motor is good, you definitely need to get that fixed.  Running rich washes out the oil, which then turns runny and doesn't stay on the rings or bearings like it should.

[Carwson]

Hydrocarbon is unburnt fuel. What does your CO look like? CO and O2 will tell you if its rich or lean. Is it at low or high RPMs? Most common Problems for high HC is misfire (Spark plugs, wires, cap rotor, points, condenser), vacuum leak (causing a very lean misfire), timing, lean idle mixture adjustment, pcv valve stuck open, CAT efficiency.  

[datzenmike]

The PCV is open any time the motor is running.

[MicroMachinery]

Hydrocarbon is unburnt fuel. What does your CO look like? CO and O2 will tell you if its rich or lean. Is it at low or high RPMs? Most common Problems for high HC is misfire (Spark plugs, wires, cap rotor, points, condenser), vacuum leak (causing a very lean misfire), timing, lean idle mixture adjustment, pcv valve stuck open, CAT efficiency.  

This is accurate. There is alot of raw, unburnt fuel in your exhaust for some reason.

[Trophy24]

I agree we need to know what the other 2 gas readings are to accurately help you.

Need more info

[arizonajones]

THREAD JACK! why make a new thread when I can jump into this one?

Looks like this conversation petered out so I'm gonna pick it up with my own situation...

 

I Live in Portland, OR - gotta pass DEQ, so I run a stock federal emissions rig in my 1980 w/ l20b

 

my recent test numbers (failed):

HC - 1620

CO - 0.0628

CO2 - 7.3

 

So Hydrocarbons need to be under 220 - which is a problem right now...

 

Backstory:

 

-New headgasket, intake gasket, re-timed, fresh plugs, cap, rotor, oil, oil filter, vacuum lines, recent valve lash, egr valve, oil pan gasket, coolant, & thermostat.

-Runs at the right temperature, doesn't blow blue smoke or steam. Doesn't leak oil, except for some blow-by that comes out of the dipstick tube 

-I think there is a slight exhaust leak at the manifold because I can hear that click/poof sound on acceleration

-It has been running a little more gutless than usual lately

- When I did that first emissions test, I had the carb really lean and right at 12deg btdc, so recently I richened it up and advanced it a bit and it runs a lot better, but I went for a second test and they told me right away they could smell it wouldn't pass

-I'm getting about 19.5 mpg, which is about 3-4 mpg lower than what I used to get in-town.

 

Right now I'm trying to set a to-do list that doesn't brake the bank because I have limited funds for tracking down the problem. The really frustrating this is, it may not be perfect but it's still running pretty damn well, but if I don't pass I can't drive it when March is over...

 

My to-do list right now:

-Compression check

-remove cat temporarily and see if it runs awesome

-seafoam/carb clean?

-new intake exhaust gasket

 

Let me know what you think.

Many thanks!

[DanielC]

High HC is unburnt fuel, a misfire.  Many times caused by being too lean.

if the engine is misfiring, you give it more gas to get is to go.  This causes the fuel consumption to go up.

 

So, being too lean can very easily make gas mileage go down.

[arizonajones]

So right now I have the carb mixture at about 3.25 turns out and last summer it was running great at about 2 turns out.

 

Now I'm wondering if I should start with the manifold gasket - maybe a tiny intake leak near the exhaust leak I'm hearing?

 

My big fear is that it would need rings or something requiring a total rebuild but it would be pretty smokey if that were the case, right?

[ggzilla]

So right now I have the carb mixture at about 3.25 turns out and last summer it was running great at about 2 turns out.

That suggests you have an air leak. Start with examining the many small vacuum hoses. If any has a split end, cut the end off and stick it back on.

 

The other common sources of air leaks are

* Weber adapter not tight

* carb bolts loose

* leaking vacuum diaphragm. A 720 has about six of these

 

Intake gasket leak is relatively uncommon.

[flatcat19]

So, so happy to live in an area with no emissions testing of any kind. 

[ggzilla]

Didn't bother me none. I always keep my cars running good. Few times I failed simply fixing/tuning always made them pass. From a 1971 celica to a 2006 Subaru they've always passed.

 

If you have a misfire, fix it! Even if you aren't required to pass emissions test, it will save fuel money if you fix it.

[arizonajones]

thanks for the input.

 

I'm reassessing the to-do list:

 

-test bpt valve - I've never done this and its the original - EGR is new but maybe not effective if BPT is toast?

-thermal vacuum valve? - I don't totally know how this works, but it did crack and I epoxied back together - maybe now's the time to replace

-charcoal canister - I hear hissing around the purge line and the cap to the control line - I know its supposed to be sucking air in but maybe not from there?

 

These are three things that I've been thinking about, but putting on the backburner in case it was something more obvious, but may one of these could be the culprit?

[ggzilla]

may one of these could be the culprit?

Perhaps. But I would start with the most common cause -- inspect the condition of all the many small vacuum hoses. If you find one is split, or a hole burned in it, or is disconnected, then you won't have to test the other more complicated stuff.

 

Was the FAIL on the idle test, or on the cruising test?

[arizonajones]

it was a fail at idle - the exhaust does get a bit stinky when it idles for a while - for what it's worth... 

 

i'll double check all hoses and go from there. 

 

another point of interest is that the egr passages were completely blocked up with crud before I redid all the gaskets. So maybe something was leaky before but didn't show itself till I cleaned it all out

[arizonajones]

Ok! Update! Here's the order of events:

 

 

 

-I checked the quality and routing of all hoses.

-Found a crack in my TVV valve - replaced

-Replaced my BPT Valve with a newer one

-Found a leaky valve in the purge line of the cannister - replaced

 

--Pics:

TVV

 

BPT

 

 

Cannister

 

 

So after that, it ran smoother - less gutless. I kept the carb a bit rich because it still didn't run very smooth at 2 turns out.

I also did a pass of the Seafoam spray that you squirt into the intake (not the fuel additive) and burned off a bunch of gunk - also made it run tiny bit smoother.

 

Did another test, and here are the results:

 

HC - 674

HC after a rev - 745

CO - 0.03 both times

 

So a fail, but progress.

 

I did Seafoam one more time, and leaned out the signal a bit, and then:

 

HC - 630

HC after rev - 1316

CO - .25

CO after rev - .072

 

Figured I'd give it one more shot while I was there. I richened the carb back up and advanced the timing a bit:

 

HC - 891

HC after rev - 894

CO - 4

CO after rev - 3.6

 

double-fail that time!

 

So... starting to wonder if it's a bad cat or a clapped-out carb.

 

I took off the cat from the exhaust line and drove around - soooo loud! Sounded like a loping Harley! Anyway, I wanted to see if there was less smoke, smell, and more consistent power. It was inconclusive. There was still a bit of herky jerky idling but it did seam less stinky (but that's pretty hard to judge for me.)

 

I put it back together and today I plan on taking the carb off and giving it a thorough clean - I rebuilt it about a year ago, so it shouldn't be too bad off, but who knows. if the carb clean doesn't make a big difference, I guess my next move is buying a new cat. 

 

What do you guys think?

[ggzilla]

Congrats on fixing the leaks and making it run better.

 

 

:l

 

... I kept the carb a bit rich because it still didn't run very smooth at 2 turns out.

 

... I richened the carb back up and advanced the timing a bit:

 

What do you guys think?

You'll never pass with an idle that is not adjusted, especially one that is rich. To pass DEQ it must be adjusted per the factory "best lean idle".

[arizonajones]

Well, I just got it all back together after taking the carb off to clean it.

 

I made a great discovery! the bottom 1/3 of the carb was loose! I don't know if those gaskets dry & shrink over time, or if I just under-torked the screws when I did the rebuild kit, but it is now cleaned and tightly re-torked back together. I still need to do a proper test drive and put it through its paces, but I'm feeling pretty good.

 

I love finding actual problems. I hate trying to guess what, if anything, I'm doing is actually fixing something!

 

Soonest I can get through the DEQ now is Tuesday, so hopefully it will be a '5th times a charm' kinda week.

[datzenmike]

I hate taking something apart, finding nothing, put it together and it works. I like the results but don't have the satisfaction

[arizonajones]

So, just finish the conversation, it passed!

 

I retarded the timing (probably 11 degrees BTDC), set the mixture to exactly 2 turns out, and raised the idle speed to 900 RPMs (max for the test in OR) and my HCs were 206 (with a 220 max). Blammo!

 

So I have her on the road for 2 more years now. I'll probably need to do a rebuilt before the next test, but hey, not yet!

[505plus5]

Good stuff. Congrats!!!

Btw:

 

Anyone know of a Gooooood, inexpensive, trustworthy Datsun mechanic in the SoCal., Pasadena, C.A. area, for my 510 & 280Z? I'm having similar problems with the 510.

 

Thanks everyone.