1986 Bronco II Smog Problems (Urgent! Help!)

[edselman]

Hello All,

Having more problems with the 1986 bronco II. I have replaced the oxygen sensor, the throttle position sensor, the Idle Air Control Valve, and the TFI Module on the truck. It keeps failing smog!

Here are the results:

HC PPM

220 Limit, 375 Reading (Fail)

CO% Limit 1.20 Reading 4.70 (Fail)

C02 16.60

02% 0.4

RPM 838

I can't figure out what else needs to be done to make this work! It's a 2.9 V6, with the automatic transmission.

Any help is appreciated!

Thanks!

Dane

 

[410Fortune]

is the Check engine light on?

 

[edselman]

no, the check engine light is not on. it needs to be smogged by the 16th or the dmv starts fining us until we get the vehicle smogged

 

[Stic-o]

When was the last time you replased the cat? That will make it fail. I use to have a '85 long ago that would not pass and it ended up being the cat and a cracked intake. New cat and some RTV sealent and it passed. Then I sold it as quickly as possable

 

[410Fortune]

Well I can only suggest new plugs, distributor cap and rotor, check for vacuum leaks. then get the sucker HOT before you go for the test, Catalyst works better when its red hot, also you should put in a can of "sure pass' or whatever with just a 1/4 tank of gas and try again.

 

[edselman]

I do believe the catalytic converter is original to the truck, and if I remember correctly still has some ford tags welded to it (which makes me think it is original) The truck still does have a weird idle, (going from 800 into the 1100 rpm range if I remember correctly, even sitting at a stop light it does that) Is it safe to assume the catalytic converter is plugged up? What's a good way to tell?

Dane

 

[410Fortune]

an exhaust shop can do a few tests to determine if your cat is shot, it likely is.
the weird idle can be vacuum or fuel related, have you done a fuel pressure test? KOEO and KOER

Also run a check on the timing........

When I installed a MAS 4.0L in place of my speed density 2.9L, the emissions numbers out the pipe were literally 1/4 of the 2.9L, Colorado never questioned what engine was under my hood, it blew 1/4 the numbers allowed for a 2.9L, goes to show you how more efficient a MAS and DIS engine is...

 

[Stic-o]

Change the cat.

If it's original it's toast for sure.

That should solve 99% of your problems

 

[edselman]

Forgot this in my first post. The smog check guy was talking about Hydro Carbons and that the gas is not burning off according to the test machine. What does this mean?

Dane

 

[410Fortune]

running rich or your cat is not burning up what it should
Since you have no CEL and the 02 is functioning I would say it is not running rich. Maybe leaky injectors or just a BAD CAT

 

[n16ht5]

mine was 2 clogged cats ?(straight piped one and rammed a rod through the other one) also my timing was off. runs awseome now.