Mod Tech or OEM? Stroker fails CA smog check

Not sure if this should be Mod or OEM.. but it involves a modified engine, so here it is

'87 XJ 4.0L stroked & bored to 4.6, AW4 auto.

I miserably failed my smog test today. Readings were:

HC PPM@15mph: Max 133, GP 321, Meas. 143
HC PPM@25mph: Max 104, GP 271, Meas. 139

CO %@15mph: Max 0.89, GP 2.19, Meas. 2.51
CO %@25mph: Max 1.12, GP 2.42, Meas. 2.78

NO PPM@15mph: Max 1090, GP 2057, Meas. 710
NO PPM@25mph: Max 1130, GP 2114, Meas. 689

So I failed HC, and exceeded GP (gross polluter) for CO. NO is not too bad.

I put on a brand new cat yesterday, so that's not the problem. I'm installing a new O2 sensor this weekend as well. Cap, rotor, plugs & wires are less than a year old, and this is not a DD, so they have maybe 8-10k miles on them. I drove around for 45 minutes, mixed city & freeway driving to warm everything up right before the test.

A big question mark for me is: I currently have 26 lb/hr injectors installed (got a great price on them). Should I install 24 lb/hr injectors (or even 20 lb/hr)? Of course I can't find my stock 19 lb/hr injectors, or I'd try retesting with them installed :rattle: It appears to be running very rich, but I don't know how much to scale back on the fuel injectors.

Last problem: they failed me on the visual portion of the test since I don't have a 'thermostatic air cleaner', which I removed when I installed the stroker with the Mopar performance header (with EO sticker, so that's legal). Anyone know where to get a universal-fit TAC, or how to fab one up?

thanks as always-
chuck

Most strokers are happy with the 23# injectors, but you may need to build a MAP adjuster to "dial them in." The 23# units are close, but I'm wanting to think the trypical stroker likes just a touch less fuel.

Since it's HC and CO that are failing you, I'm inclined to think it's a fuel mix problem - which is why I'm thinking your injectors are too big, and you may need the adjuster. It's a fairly simple voltage divider - but you'll have to Google it, since I don't have links handy. Try a search here for "MAP Adjuster" and see what you get as well - that will likely turn up a link.

The "thermostatic air cleaner" (what rot!) is little more than the "choke stove" - the sheetmetal around the exhuast with the air tube going into the box. Are you RENIX (1987-1990?) It's possible to fail the smog if you don't have that air tube installed - but they don't seem to look to see if it's connected at the other end up here. Hell, I've gotten smogged without even having the airtube - and all my reports say "not present." I keep one with me when I go to get smogged again - just to show 'em. So far, they've done that every time.

Running with your stocker injectors - 19-20#/hour - is likely to decrease your HC and CO, but increase the NOx emissions - due to a lean fuel mix and the resultant elevated combustion chamber temperatures. Probably not much help.

You'll eventually want a MAP adjuster anyhow (keeping the right AFR also helps to cut fuel consumption,) so you might as well build it now.

5-90

Make sure the smog tech runs your xj in 1st and 2nd gear on the dyno, NOT in Drive. I don't have a stroker, but a failure turned into a passer with flying colors. Oh yeah, good idea on the injectors too.

The 26lb injectors are definitely too big and that's why your engine's running rich but rather than swap in smaller injectors (Ford 24lb'ers are the most common on '87-'95 based strokers), you can build a MAP adjuster and turn down the input voltage below the stock 5.0v to shorten their duty cycle. This will correct the richness and the MAP adjuster will only cost you ~$10 in Radio Shack parts. If you're handy with a soldering iron, making one is easy. Here's my MAP adjuster write-up:

http://www.angelfire.com/my/fan/MAP_adjuster.html

I also have a 4.6 stroker but it's a HO version and my XJ is a '92. I'm using Ford 24lb injectors, stock fuel pressure regulator, and MAP adjuster set at 5.15v. I pass emissions with flying colors.
My guess is that you'll need to set your MAP adjuster at ~4.5v (a 10% enleanment from stock). This should get you very close.

Follow up for reference sake:

I installed Ford 24 lb/hr injectors, did a tune-up (new plugs, air filter & oil change), replaced the O2 sensor (which tested bad- no continuity in the heating element), repaired a couple of cracked vacuum lines (which fixed my wandering idle), tested various other sensors, and installed a heat stove/"thermostatic air cleaner".... and passed! Readings were a bit above average, but well below the maximum limits.

New readings are:

HC PPM@15mph: Max 133, Avg 43, Meas. 95
HC PPM@25mph: Max 104, Avg 32, Meas. 60

CO %@15mph: Max 0.89, Avg 0.16, Meas. 0.66
CO %@25mph: Max 1.12, Avg 0.15, Meas. 0.70

NO PPM@15mph: Max 1090, Avg 406, Meas. 112
NO PPM@25mph: Max 1130, Avg 349, Meas. 54

Still a bit higher than average on HC and CO, and well below average on NO. I've had the parts to make an adjustable MAP sensor in my garage for a while, so I may (finally) do that and lean it out just a bit more (higher NO, but lower HC and CO, right?)

Thanks guys... now I'm just waiting for my sticker