Failing emissions... :(

[doc65]

Trying to get the SX4 to pass emissions without too much expense as the engine will get replaced with a 4.6 injected engine in the next couple months, just be nice to drive it around & deal with the other issues like T-case & axles in the interim.  I rejetted it, readjusted the timing tuned the mixture for best vac etc, and now the highspeed(2500 rpm) test easilly passes, but the idle numbers actually got worse, though in fairness the rpm is a better 650 vs the original test which was about 815 I think I have a vac leak, and am pretty sure it has to be at the intake manifold to head surface as all the vac lines are plugged/gone except the vac adv(it is DEFINITELY on a ported source) and PCV.  I swear I hear a vac leak, but with hearing loss(at some frequencies) in one ear it's tough to tell WHERE.  It is currently way high on both CO & HC at idle, but both are really good at the 2500rpm.

I'm thinking that the idle mixture is too rich in order to compensate for the vac leak, I can also hear an occasional mis at idle, lean mis-fire??

The config is MC 2150(1.08 with 45 jets, though those aren't really in play at idle), 82 SX/4 with later duraspark module, so no computer control of spark, Bosch platinum plugs, all gaps checked & re-checked, MSD Blaster II coil, 7.5mm premium NAPA wires, TFI Cap/Adapter/rotor setup, timing set at 12 BTDC which should be about right for
 4500 MSL altitude

Thoughts?   

[GRONK]

What are your failing #'s at idle?

Will the testers allow you to test tune while on the machine?

[BenM]

Do you have your cat hooked up still? If you do, connect a vacuum valve to the downstream valve. The extra oxygen will allow the cat to burn off the extra CO and HC at idle. If the numbers are close that could make all the difference. The ECM had the downstream open on warm idle.

[doc65]

Gronk,

Tuning while testing sadly not possible, the machine is paid for by the operators, but controlled by the county, it doesn't show numbers while the test is run, only once the veh either pass or fail, then you can get the numbers out of it.  I was the one in the car running the throttle while it was running, got to go up to 2500 & hold for 30 seconds, then back to idle and it tests for 30 more, then gives a pass/fail.  Numbers are:

high speed(good)
HC standard 220 me 70
CO standard 1.20% me .07%

Idle(BAD)
HC standard 220 me 319
CO standard 1.20% me 7.92%

Ben,

The exhaust is completely new 2.5"(little big, but I had a new unused CAT in that size on hand) so yes there is a CAT installed, but it sounds like what you are referring to is the Extra air fitting on the side of the CAT, that is not installed, never was.  This car initially had an airpump, but that is gone, and for what it's worth, my wagon originally had Pulse Air  injection setup, but it's gone as well, so it is very similar config except that the exhaust in it is OLD & original, it passed VERY easily.

[GRONK]

The failed CO could be from the larger exhaust.  When you open the exhaust it puts less pressure through the cat (less heat) that's why at open throttle you are good.

re you running the lowest octane fuel possible?

Find what your MAX idle speed is and increas your idle speed within 50rpm of the limit, that should help.

I might also suggest a hotter T-Stat for the HC.  You need to creat more heat w/ the open exhaust.

[eaglefreek]

I had a similar situation when I lived in CO. I needed to pass emissions with the Carter before my tag expired and wanted to install the 2150 but didn't have the funds at the time. I put about a 50/50 ratio of  E85/E10 and it passed with flying colors. Can't say that it will work for you though.

[doc65]

I had actually thought of the t-stat, as the temp guage does read low, I'm wondering if a PO put a 160 in it, guess I'll pull the housing & check.  I forgot to mention that it does have a gallon of "alternate fuel", ie denatured alch, mixed in with a full tank of regular 85 octane fuel that "...may contain up to 10% ethanol..." The EGR isn't connected to vac right now, so it's not opening, but while testing it with a vac pump I don't think it moves anyway, would fixing it help at idle?

[GRONK]

I would say NO on the EGR.  I never run them and never failed the E-Test when we had it. 

[doc65]

I don't really WANT to buy an egr if it's not going to be a magic bullet as it would be wasted money once teh stroker motor goes in... but I do want to get it going till them.

[thereverendbill]

does utah still have the 300 dollar exempt rule?

[Draekon]

Check to make sure the intake manifold bolts are tight.  If they are loose, it could cause a vacuum leak.

[ammachine390]

EGR is inactive at idle, it won't help you to replace it. The only thing it would affect is NOx emissions, not HC nor Co.

Loose Intake manifold would cause a vacuum leak, that would make the engine run leaner. Lean engine conditions cause higher NOx levels, and LOWER Co and HC.

High HC and Co are a result of incomplete combustion, usually caused by too rich of a air/fuel mixture. What I would do is make sure the intake manifold bolts are snug and you have no vacuum leaks, then try to lean the idle mixture. Adjust until you have the highest manifold vacuum. If this doesn't work, you could just lean the idle mixture for the test, then bring them back to where the highest vacuum reading is.

[doc65]

Bill,

Never heard of $300 rule?!?

AMC, my thinking exactly on the mani bolts, already done though.  I did notice on an extra intake that I have that the EGR was loose, and when looking at the gasket it looked like it might have a vac leak at that point on that manifold, so I went & looked at the one on the car, it was barely snug, and the gasket came off in pieces, so new gasket(already had it) Now I don't seem to hear as much of what sounded like a vac leak.  I also pulled out the trusty vac guage & had lower vac than when I last adjusted the idle mixture(like 2 in Hg) so I started readjusting and probably screwed in each mixture screw like 3/4 turn.  I have a new manifold gasket on hand if it gets to that, but I'd rather not, it's a bit of a pain...  I'm also a little worried that if I were to start down that road the EGR interconnect tube might be damaged and that's an order it item

I'll probably adjust it just a LITTLE on the lean side, though going far enough to cause lean mis-fireing would be counter productive as I'd then be pumping the whole fuel air charge for that missed firing out the exhaust...

[ammachine390]

I'll probably adjust it just a LITTLE on the lean side, though going far enough to cause lean mis-fireing would be counter productive as I'd then be pumping the whole fuel air charge for that missed firing out the exhaust...

Correct, ideally, you want to be at the stoichiometric ratio (perfect air/fuel of 14.7/1) where there would be VERY little CO, and VERY little HC, however, this is a carburetor, not fuel injection, so the perfect ration will be impossible to get too. When the engine is producing the most intake manifold vacuum, that should be near the stoichiometric rate. If thats not enough, then you may have to lean it out more to take car of the HC and CO. But as you said, too lean, and you get a misfire, then you just shoot your HC levels through the roof as you just pumped a whole gas charge right into the exhaust.

[carnuck]

Do they show the NOx readings? That's a good way of testing timing. High readings = too much advance and misfire at idle can happen.