My readings at 25 mph..... Rpm= 1868 CO2%=13.7 O2%=1.6 HC(PPM)=18 CO(%)=0.01 NO(PPM)=1406....... I need to know how to raise my CO(%) and maybeHelp!!!!! I have a 86 jeep Comanche I just bought and I have failed 4 smog test. Please help me?
The Jeep is failing for NOx. NOx problems are the most difficult to diagnose. NOx can be present as a unique problem, or it can be the result of a secondary failure.
By raising the CO the NOx will come down.
Two things come to mind, what is the:
1. fuel pressure and
2. fuel volume (there are specs for both but rule of thumb is 1 liter of fuel in 30
seconds). Low fuel pressure will cause low CO and high NOx.
The other big thing is, where is the timing set to? Retarding the timing (if it is adjustable and I think it is) will bring down the NOx.
I had so, so many problems with after-market EGRs that I simply wouldn't use them. And, is the EGR system actually functioning? This is should be a vacuum actuated EGR valve and there is probably a computer controlled vacuum solenoid. Is it working? My guess is that it is, otherwise the NOx would be much higher.
Carbon build-up on the pistons, could also be causing an increase in NOx. The carbon starts glowing and causes preignition resulting in increased NOX. Although if that was the case the HC would be elevated too. There are top end engine cleaners available which might make a difference.
And finally, the CAT might be the problem. There is a large volume of oxygen in the exhaust in the presence of CO and HC. If the CAT is really working well, it will use all available O2 and
burn any and all CO and HC.
Good luck,
MarcHelp!!!!! I have a 86 jeep Comanche I just bought and I have failed 4 smog test. Please help me?
your failure is due to elevated NOX. do me a favor adn do a compression test on all the cylinders and get back to me, ill bet that you will find elevated readings in most if not all cylinders. i had a similar issue the last 2 times i went in for smog. took a teachers advice and resolved the issue in about 45 minutes.Help!!!!! I have a 86 jeep Comanche I just bought and I have failed 4 smog test. Please help me?
I would guess that the easiest fix would be a different, or maybe just an additional, catalytic converter.
An 86 is bound to have some oil blowby, so switch to Castrol 20w-50.
Add a very long hose to the crankcase breather, which goes to a cold metal condenser someplace low, and then back up to the air cleaner, would help.
But you could try leaving the air filter element out completely for the test.
You could also try opening up a small intake manifold leak. You would not want to do that for long, but for the test it might help.
With the high NOx, you have too good of an explosion, so it needs to be poisoned. That is what the EGR is supposed to do, so make sure its ports are not clogged. Add a length of hose to the control input, and suck on it to simulate actual perations. If the EGR works then at idle the engine will almost quit running. Then check the hose that is supposed to be on the EGR, and make sure it gets vacuum at 1500 and above, rpm, until up to around 3000. If that is good, then the EGR is not the problem, but you might be better off with premium gas or some alcohol additive.
If you get really desperate, register the truck at a rural post office box in an area that does not require DEQ testing, because they don't have a station.
People do this often at vacation cottages, so is perfectly legal.
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