Emissions on my '88 5th Ave

[MoparKidD-4]

Took my 5th Avenue in today to get it emissions tested; first test failed CO by a good amount so I talked to the mechanic who sold me the car and he said the problem is with the electronic enrichment solenoid in the carb; for some reason it tends to run rich once it's fully warmed up and in closed-loop mode (still the factory 1988 Electronic Spark Control system). He recommended pulling one of the vacuum lines that goes to ported vacuum to lean it out (air leak) which I did, I also put 4 oz. of Lucas Ethanol Treatment in my tank and filled it with 7 gallons of 91 Premium (I had it about 2/3 full with regular which is 85-octane up here at high altitude). I just took it back now and it failed again but only by 1.6xxx ppm mad:). It's so close to passing I'm thinking of just unhooking another vacuum line or maybe just a bigger line like the PCV but then I have to be careful to hide it because they do a quick underhood inspection at the e-test station... any thoughts?

I would also like to figure out what the base idle ignition timing is but I can't find any information on how to do that properly with this wacky computer BS lol

EDIT: I know the cats are old and probably need to be replaced but my plan is to cut out all the old exhaust and install headers with dual side-exit exhaust and a NEW aftermarket cat on each side which will take time, 2 years is more than enough time to get that stuff on by the time I need another E-test...

 

[BudW]

Before taking car back in, be sure to run at least one full tank full of 100% gasoline.
These cars do not do well with Ethanol and the fuel system cannot compensate its usage (You need 10% more Ethanol for car to run correctly, and carburetor can only compensate for about 5-7% difference).

You need to get a hold of a new solenoid – which are available.
I “might” have one from my old Holley 6280 carburetor (off of my '86 5th Ave). I need to first find my old carburetor and I would rather sell the whole thing than just a part off of it. It worked fine when removed (5 years ago) when I removed the Lean Burn system from the car.

My opinion, fix what you know is wrong and leave the other hoses be. Once car is running like it should, you can then drive car while gathering parts for any future changes.

My next question is: how does he know, that particular part is what is failed? (Yes, I am second guessing him).
BudW

 

[MoparKidD-4]

I hear where you're coming from but switching over to ethanol-free gas would raise my CO and richen up the mixture more... I got a tip from a guy on FABO (not just "some guy" he is credible) to add a couple gallons of methanol to the tank to raise the oxygen content even more and lean it out further.

The seller didn't specifically say the solenoid was broken, just that it is what causes it to run rich because when it's in open-loop mode the mixture is fine. So I guess that would mean that it is failed, because that defeats the whole purpose of having something like that on there in the first place?

I just want this thing to pass so I can get it registered then I will take care of all this stuff; gonna convert to 4-bbl and "conventional" ignition perhaps over the next month or so.

 

[MoparKidD-4]

Alright just read a thread on Dippy.org apparently my carb solenoid is bad. It says they can be fixed sometimes by cleaning them out I'll probably try that first. Any recommendations on that, and a way to test it out of the car?

 

[slant6billy]

So I run a dual H pipe (Catted) from a 99 stang. They are out there cheap and plentiful. So you failed on CO? What about Hydrocarbon numbers? What are your NOx2 numbers. When I first went through emissions in 2014 with the Edelbrock 750 performer carb and the MP ignition silver box, I failed for 1800 PPM. When I leaned the carb, I got it to 196. 200 was passing. You got more detective work to do. You have to look at each spark plug. Mind you, the No1 and No2 run the coolest, mid engine run hot (lean). Alcohol is a water grabber (Methanol/ Ethanol). Dry gas additive will help, but not perform miracles. If you have high ethanol gas or watery fuel, you will throw high CO emissions. The easy fix is a Edelbrock 600 and MP distributor and box. You have to convert the lean burn to the standard MP ingnition. Once you do that it will run like a top. I'm just offering a way forward and not the only way. Look at your EGR. Something may be not working there.

 

[MoparKidD-4]

So I topped off my tank of mostly Premium with 3 gallons of E-85... took it back to the test station this morning and all of the pollutants (CO, HC, NOx) were cut in HALF! Definitely going to keep that in mind for next time.

FWIW everything is working the way it should but regarding the rich mixture it's either that solenoid in the carb or a bad O2 sensor; regardless now that it's passed and I can get it registered next chance I get I'm pulling the factory exhaust and fabbing a set of duals with some new aftermarket cats. I'm betting the much lower backpressure will lean it out quite a bit. For the "ESC" computer I'm just going to run it the way it is for a while and gather up the small odds and ends I need to convert it over to 4-bbl and conventional ignition (probably one of the MSD boxes I have lying around).

Thinking about this issue more, this car was originally from Nevada so I don't think it had any factory tuning for high-altitude operation, and I live at 5000' above sea level here in Colorado... Even if the fuel computer is working right it might be outside of its adjustment range due to the thin air.

 

[BudW]

FYI,
In 1988, Chrysler (including Dodge, Plymouth and Dodge trucks), the only carburetors used was two versions of the Holley 6280 (2- bbl M-body), 2 versions of the Holley 6520 (2.2L Dakota’s, one is California and other is combined 49-state/High Altitude/Canada) and 6 versions of the Rochester QuadraJet (One for M-body and rest are 360 pickup/vans).

Of the two 6280 Holley’s used, my parts book does not differentiate what the difference is (one is model number is R40276 and other is R40354-A). I expect one is California and other is combined 49-state/High Altitude/Canada – but honestly, I don’t know and my parts data doesn’t say either.

The computer controlled carburetor’s can compensate for the altitude – but can’t compensate for the increased usage of E-90/E-85 (Ethanol) fuel (go figure).
BudW