Emissions help - any ideas?

[boomer1]

Hey everyone - thanks for looking

I've got a 1988 - 4.0 MJ that I've restoring.
Picked it up in 2009 with 291734 miles on it. According to the seller, his dad had rebuilt the motor at one time, but he didn't know how long ago, or how many miles ago. I can say that it runs like a scared rabbit, smooth, no leaks.

In 2009 when I ran it through emissions these were the numbers:
HC limit 3.0 reading 1.0
CO Limit 25.0 reading 9.35
CO2 reading 298.179
NOx limit 5.0 reading 1.9
Passed with no problems

In 2010 when I ran it through emissions 297186 miles on it:
HC limit 3.0 reading 1.35
CO limit 25.0 reading 24.97
CO2 reading 394.422
NOx limit 5.0 reading 1.27

As you can see it barely passed with the high CO limit. No changes to the engine between the years, but it does seem to idle a little high when it's cold, I guess it might be the TPS, but don't know.

I'm thinking that maybe the cat and O2 sensor might need to be replaced. Would that be a reason for the CO readings being so high?

I don't if I want to see if it passes, or suck it up and replace the exhaust system. The exhaust pipes and the muffler are pretty rusted it out, so it would probably be a good idea to replace the entire thing from the exhaust manifold back.

In your expert opinion, what do you think?

Thanks in advance for any suggestions

 

[Hypoid]

Is the air filter clean?
Is there a crack in the exhaust manifold above the O2 sensor?
How old is the O2 sensor?

My only other thought, is to cheese old_man into hooking his scanner to it, get some real-time data.

 

[old_man]

Well first off, not even necessarily for emissions, I would start with running a can of BG44K through it. It cleans out the carbon and injectors. It really tends to put things back to efficiency and restore gas mileage. I would like to see the spark plugs before and after. I'm old school, sparkplugs can tell you more about an engine than about just about anything.

Other than that, a fresh O2 sensor or new cat might be in order.

 

[5-90]

High CO is usually a side effect of running rich, and you're catching it early (or you'd have high HC to go with it.)

Me? I'd start with testing/replacing PRN the MAP and IAT, since those are the primary inputs for baseline fuel metering (the TPS helps to establish engine loading data, the HEGO is a feedback loop. Generally, when the HEGO goes, HC and CO spike while NOx drops right through the deck, because the ECU "fails over" into a rich running mode, with an AFR somewhere around 13.0:1.)

The MAP and IAT are easier to access, probably both cheaper than a new cat, and are a bit more likely anyhow (methinks.)

Most times I see a cat fail, HC, CO, and NOx are all elevated.

 

[boomer1]

Okay, I'll start at the top:

1.
Air filter - new
no crack in the exhaust manifold
O2 sensor - not sure hold old - I haven't replaced it

2.
I'll pull the plugs nad take a picture this weekend
Run a can of BG44K and check them again

3.
Holy Crap!
PRN - MAP - IAT with the TPS and HEGO and ECU and AFR around 13.0:1

5-90
Obviously you know what your talking about, but it's way over my head lol


I guess I start with the BG44K and see if that helps. Might go ahead and change out the O2 sensor, since I don't know when or if it was ever changed.

I post pictures of the plugs and an update as soon as I can. I've got this month to iron it out - thanks for all the replies.

 

[Hypoid]

Me? I'd start with testing/replacing PRN the MAP and IAT, since those are the primary inputs for baseline fuel metering
The MAP and IAT are easier to access, probably both cheaper than a new cat, and are a bit more likely anyhow (methinks.)

Most times I see a cat fail, HC, CO, and NOx are all elevated.

I'm not finding PRN in my RENIX manual???

Boomer, if you don't have a copy of the RENIX manual, I'll loan you mine. You need to email me at hypoids.haus at yahoo, so we don't violate policy here.

 

[Digger87xj]

swap that O2... bets are it will run better than ever

 

[5-90]

I'm not finding PRN in my RENIX manual???

Boomer, if you don't have a copy of the RENIX manual, I'll loan you mine. You need to email me at hypoids.haus at yahoo, so we don't violate policy here.

Sorry. "PRN" = "as required." It's medical shorthand. I don't recall the original Latin.

(My notations are derived from a large number of disciplines. Most of the foreshortenings are standard - just from a broad range of fields. I've been that way since high school - I didn't have any trouble loaning out my notebooks to people, because I knew they couldn't read them! Writing was somewhere in between Greek and Arabic, and good luck figuring out what I'm talking about, with notes in three languages and symbology from about fifteen different fields...)

 

[fallacist]

Well first off, not even necessarily for emissions, I would start with running a can of BG44K through it. It cleans out the carbon and injectors. It really tends to put things back to efficiency and restore gas mileage. I would like to see the spark plugs before and after. I'm old school, sparkplugs can tell you more about an engine than about just about anything.

Other than that, a fresh O2 sensor or new cat might be in order.

Interesting your mention BG44K. the old timers at carquest just sold me on a can the other day. Is it really that wonderful for $25ish/can?

 

[Digger87xj]

BG 44K .. Good stuff for sure. STP EFI cleaner a very close second.