My timing is at 10 degrees and these were what the sniffer said I was emmitting.


max avaerage mine
HC
idle 300 99 519
2500 350 95 133

CO
idle 3.00 1.10 2.32
2500 3.50 .90 .21

I have did a complete tune up; plugs, wires, air filer, pcv, cap, rotor, because it failed a pretest.

it is only failing @ idle, what do I have to do to correct this.

1978 bronco, 351M, it has a EGR. nothing else that I can see.

 

Sounds like your carb may be running rich at Idle. Might want to look idle mixture settings?

 

jopey,

Wow, that idle HC is outrageous! Something is causing it to run way too rich at idle, either too much fuel or not enough air.

Since you changed the air filter, check your choke to make sure it isn't sticking partially closed. If the linkage is jamming, you can temporarily wire it wide open to pass the e-test, then go back and fix it later. Also check the rest of your upstream airflow path. Make sure the snorkel heater flap door isn't closed, and make sure you don't have some other obstruction in the snorkel or intake hose.

Next thing to check after the choke is idle mixture (like aco suggested). If you have the stock Motorcraft 2150 2V carb, the idle mixture screws are located on the front bottom of the carb. Try turning the screws all the way in and counting the turns to see where they were to start with. Make a note of the original position. (Both screws should be set the same, BTW.)

To tune the idle mixture, open the screws gradually until the engine idles smoothly and at the proper speed, then try leaning back in smaller increments to get the optimum idle mixture. In my experience, just slightly richer than optimum actually provides the best e-test results. You want to avoid lean misfires, which will cause worse emissions than just slightly rich.

On the 2150 2V, start by setting both mixture screws to 2 turns out from all the way in. If your engine idles roughly or slow, try turning them both out in 0.5 turn increments until it smooths out. You should be able to go all they way out to 3.0-3.5 turns out without excess emissions, unless your carb has another problem. If you get good idle quality with less than 2 turns out, you have an internal problem with excess fuel, probably float level too high or fuel bowl valve not closing.

I some cases, a ruptured power valve can cause fuel leakage that throws off the idle mixture, but there are usually driveability problems associated with a bad power valve.

If you suspect fuel bowl problems, check the float level first. If the float level looks good, check the needle valve. The neoprene tip should be smooth with no grooves in its surface. Also look for any debris or contamination on both the needle tip and the valve seat.

If all these things check out good and you still can't pass the e-test, you may need to disassemble and rebuild the carb to clean out the internal air bleed passages.

Good luck.

BubbaF250

1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.

 

I should have mentioned that just off idle say 1k rpm's it runs real smooth.

there are no drivability problems.

Runs real strong, doesn't burn oil. there is no snorkle after the air filter.

I do know it is a motorcraft carb, 2 barrell. I have seen those screws on the carb, I will have to adjust them.


Couple more questions, can a EGR valve also cause this problem?
And if the vechile was higher in elevations could that cause this pictular problem as well?

 

[font size="1" color="#FF0000"]LAST EDITED ON 08-Aug-01 AT 05:43 PM (EST)[/font][p]jopey,

The answer to both your questions is "yes, somewhat," but I don't think high altitude or EGR problems could account for the severity of your high HCs at idle. With no cat and a decent tune, you shouldn't be showing more than 100-200 ppm HC at idle, and 200 is really on the high side.

If an EGR problem was significant enough to have an impact on idle emissions, it would make your idle quality so horrible you'd barely be able to keep the engine running.

BubbaF250

1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.

 

Thanks. I will go thru the timing and idle mistures, and have a pretest done it next. Hopefully it will pass then. If not I will probably just replace the EGR, and possibly the coil to give the spark more of a jolt.

Thanks for the help. I will report back what happens.

 

tried setting the idle mixtures.

I used a vacume guage off the intake manafold and the highest I got was 18.5hg but it was constantly jumping around upto 1hg.

I looked thru my haynes manyal and it said I could have a ignition problem. The engine seems to have a minor missfire which you can hear @ the exhaust pipe tip.

 

set timing to 7 degrees and engine sounds like it is pinging @ idle.

upped it to 8 degrees and pinging went away.

it really seems no matter what I do I stil have a little mis once and a while. it is idleing aroun 750rpms right now. it runs with no bogs, or lag.

the left idle screw seems to have more effect than the right one. if the right is more than 2 turns out it does nothing. the left how ever will work past 3 turns out. currently they both are around 2.25 turns out. I have no idea if this is too much or not enough. I did set them by getting the highest vacume I could. the vacume also jumps arouns 1 hg @ the best I can get. some times it is as much as 2 hg.

I did how ever crank up the base timing to around 30 degrees and let me tell you the thing ran very smooth. Think some dumby screwed up the cam timing when the engine was rebuilt?

Here is a picture from inside the distributor. this is the best of 8 I took. if you want a better one let me know.

 

I had the same problems, my HC at idle was around 1500, and I tuned the carb as best I could, got it around 20HG, so I thought I was good. I could hear and feel a slight miss out of the exhaust, but I had replaced the whole ignition system, so there wasn't really anything else I could do. I went to a smog referee(I'm guessing you're in CA), you can call them at 18006227733 to make an appointment. It turned out that they were cheaper than anywhere else, and they spent over 5 hours at no labor cost, using a scope, exhaust analyzer, and all those other nifty expensive equipment that I can't afford. Long story short, I paid $38.25 for 3 visits, over 5 hours of labor, to find out that after all that I had done, that last thing I had overlooked is I had three bad spark plug wires, even though they were brand spankin new. I recommend a smog ref and use of a scope, that will solve your miss problems. Also, if its a '79, I have all the possible documentation and resources you could need. Let me know if I can help at all.

 

Yes I live in CA

It is a 78.

I am gonna do some other things to it this week. replace the thermistat because the hoses are in dire need of replacing. I am also going to pull the EGR and replace that as well.

It passed and I had to do some work to get the EGR to get vacume. When I did that it passed functionality but failed emmissions. This is where I stand now.

Maybe I will call a ref and see what he has to say. I am just wondeing if the timing can affect it that much or possibility of a leaking EGR @ idle. I will let ya all know what happens

 

Oh yeah, about timing too. Sorry about the long posts. Check your timing at about 2500rpm. For that high side, if your idle goes past about 25-30, or over whats marked on the balancer, then I'd check your vacuum advance. there are single and dual advance units, I had a dual on mine and it advanced it way too much, pushing the hc's up. on the idle side, my carb screws never did too much either, at one point I had one all the way in and the other all the way out, I'd check the ignition, and see if you can;t get the smog shop to tune your carb while 'sniffing' the exhaust, thats the best way to do it. Hope I could be of some help

 

I couldn't really understand that last post. Did you say it passed altogether, or just passed the visual/functional test? Still running bad throught the sniffer. Oh yeah, if you're near San Luis Obispo, I can give you the phone number of the smog ref, I may even be able to come help you out. Let me know.

 

Had a pretest and it failed. That dude said all I needed was a tune up.

plugs, wires, cap, rotor, pcv, air filter. I did all of that and I took it to a different shop, because where I bought it from and where I live is over 50 miles away.

any ways. it passed smog emmissions, but the tester failed it because there was a vacume hose mis routed and the EGR was not getting vacume.

I fixed both and he offered free 2nd testing. well it passed functionality meaning everything was hooked up right aand working. but it failed emmissions @ idle.

I have since set the timing to 8 degrees, and turned the idle up about 75-100 rpms to idle @ 800rpm. but the ;eft mixtrue screw seems to work more so than the right.

The left will change the mixtures past 3 full turns out. the right seems to die around 2 turns out.

if I turn them in too far it will run real rough, and want to stall.


thanks for all of the info. Did the ref actually pass yours? and what was causing the problems?

 

Sometimes it helps to set the idle speed up to about 950rpm and make sure you are well warmed up. Dirty oil can send some bad thing through the PVC into the intake.


1977 Ford F-100
400m/c6/4:11/Gear Vender O.D.
Crane hydralic roller, forged, ported polished,Deamon,Edlebrock, yada, yada, yada
280,000 miles
Stock on the outside
modified/rebuilt everything

 

The oil is pretty clean.

I did set the idle up higher but it desiled when shutting it off. So I backed it down some. If you know some way to stop the deseiling I am all ears.

Can a weak coil cause a weak spark @ idle?