TBI's running too rich

[chevyaddict]

Here is a question. I went to get the '84 through emissions and it failed at an idle only; too rich - too much CO. The car has been idling a little lower than usual - but there are no trouble codes and of course, this type of carb is not easily adjustable. So, how do I fix this? Is the IAC the culprit? Any suggestions??
:confused

 

[vigman]

A trick

The LAST time I had smog done (in my 84)... the dealer had PULLED a small vac cap off one of the throttle bodies to induce a vac leak..

This leaned out the car JUST enough to pass smog..

Worth a shot....

The other thing... Air filter,new plugs,wires, 02 sensor and a full tank of GOOD GAS.. a few high speed runs on the freeway will drop you about 7% in emissions if your that close to the wire.


Vig!

 

[chevyaddict]

Actually, the car just had a complete tune-up not even 4000 miles ago - and I mean complete - oxygen sensor, EGR valve plus all the usuals. It is idling too low - not low enough to stall just lower than it always has. I was never enough of an issue to worry about..........until now.

Some of our old cars would pass with some denatured alcohol in the gas but because of the ECM I don't want to throw things too out of wack - this is a daily driver after all.

So - if I create a small vaccuum leak that might do the trick? But, if it is idling low already, won't that make it want to stall - the vacuum leak I mean??

 

[c4c5specialist]

HI there,
Actually, a vacuum leak will cause the idle to go higher than what you have now.
Just remember, that if you were running really rich, you would have high HC, or hydrocarbons, that are not being burned.
Double check your timing, as if it is slightly off, this could also cause your condition of higher emissions.
IAC will really NOT have any bearing on the actual HC or CO in your engine.
Please keep us posted, c4c5

 

[vigman]

And

moving the timing UP to 7 degrees BTDC will be close enough to pass smog and might make the burn a TAD hotter@idle.

Make SURE you disconnect the jumper by the brake booster when you setting timing.


Vig!

 

[geekinavette]

If it hasn't been done in quite a while, try replacing the evap canister. I was just reading how this thing operates in the shop manual...if I understand correctly a saturated canister will cause a rich idle, since it is only purged into the intake at idle. Or you might try just blocking the hose between the canister and the intake and see if that helps the rich idle condition.

I've never messed with this system myself...just throwing some thoughts out there.

Bill

 

[geekinavette]

Just an afterthought...

How many miles does the CAT have on it?

High CO reading...low idle...could be clogged converter?

Again just kinda thinking out loud here.

Bill

 

[MoeJr]

How low an idle we talking? My 84 idles 600 inn drive. I would definitely check the cat.

 

[geekinavette]

600 RPM

That's about where mine idles in D also. (at least it did when it was running)

Bill

 

[chevyaddict]

You know - I am such a nincompoop. Actually it failed both HC and CO at an idle only - under load readings it was good. Just changed EVERYTHING about 4,000 miles ago. At an idle in drive it is idling at 500 but is smooth. So now - I don't think it is necessarily a fuel problem - it should be some kind of timing problem but the timing is controlled by the ECM. Car runs great right now so really don't want to mess with anything.

AAAAGGGGHHHH! Emissions - I hate 'em..

You guys are mentioning the cat - the car has 159000 miles on it - the cat has never been changed. But, don't you get a weird smell with the cat begins to fail??? BTW - replaced canister about 10,000 miles ago.

 

[geekinavette]

If that is the original CAT with 159K miles...

REPLACE IT!

A clogged CAT won't necessarily cause any strange odors. Now a new one will stink something terrible for a little while.

Timing IS ECM controlled but the base timing setting is very critical, worth checking out. Factory setting is 6deg BTDC...you could probably go a couple more if you run high-octane gas, and as was already mentioned - don't forget to disconnect the EST bypass (single wire connector near the brake booster).

Good luck

Bill

 

[vigman]

Here Kitty

The CAT should be NO MORE than $400.00
installed with a GOOD after market one.

@ 160K

Do it!


Vig!

 

[kmcewan]

Inspection.....

I replaced my CAT with one from NAPA for around $170.00 and did the labor myself.

Replacing the cat, doing a tuneup, adjusting timing, creating a vacuume leak and adding RXP to the gas helped my 84 pass North Carolina State inspection.


Ken

 

[Twin_Turbo]

If that is the original CAT with 159K miles...

REPLACE IT!

A clogged CAT won't necessarily cause any strange odors. Now a new one will stink something terrible for a little while.

Timing IS ECM controlled but the base timing setting is very critical, worth checking out. Factory setting is 6deg BTDC...you could probably go a couple more if you run high-octane gas, and as was already mentioned - don't forget to disconnect the EST bypass (single wire connector near the brake booster).

Good luck

Bill

Hey geekybill

 

[geekinavette]

WHASSSSUP Marck!

 

[Twin_Turbo]

Howdy