Running like crap

[ray krick]

My 78 J10 360 has failed emissions 4 times. I can't get it to pass. I have installed new plugs/wires & rebuilt the carb. I get a strong exhaust smell in the cab. The first 2 passes it failed CO (that's when I rebuilt the carb)and fixed the ignition. The second time it passed the sniff test at high rpm but fails at idle, first the CO then HCO the second time. The engine does not hold a carb adjustment. I'm thinking either the carb has internal leaks or the cat is toast. I've seen several methods to test the cat, measuring temp pre then post cat and the rattle test seem most popular but how good are they? How much air should the smog pump put out, maybe there is not enough to assist the cat burn the unburned fuel?

[Floodsie]

Hey Ray... sorry to hear you're having trouble there.. I can sympathize since I had to replace the entire AIR system (pump, valves and tubes), the EGR and the cat was missing completely... i have a '79 Chero so i don't know how different your '78 J might be... also, Cal. might differ from Az but here goes.... I didn't have it tested prior to fixing everything but once it was it read a zero on CO... I can't recall the HCO reading but I passed with a wide margin... my thoughts on your situation are this.. 1. AIR system - if you have a functioning pump (ie. not siezed) then it's likely doing it's job... you can check by pulling off one of the hoses, start it up and see if air is coming out... the injection pipes can also be clogged (which was the case with mine)... I had to replace mine along with the check valves that are attached... if the system is working properly, it has a profound effect on idle CO 2.CAT - cat's don't often go bad but after 20 years it's possible... a replacement that you can splice into your system is around 40 bucks and might be worthwile... this will help with your CO across the board... 3.EGR - some of your problems with idle and tuning may be due to a bad EGR diaphragm... this creates a monstrous vacuum leak... if the valve is original, it's most likely compromised... the EGR helps with the HCO by recirculating some exhaust back into the intake to cool cylinder temps (curbs combustion)... anyway, the archives are rich with smog stuff and you should do some searches ('smog' 'air system' 'egr')... good luck and don't give up!! If you need a line on any of the parts, I can direct you to some places to go AND stay away from!!! Take it easy!!! Floodsie

[reddog]

SOnds like a bad EGR is certainly possible but without your readings kinda hard to speculate. I had the same problem and replacing the EGR fixed it enough to pass. One thing to check is the tube that feed air to the convertor. I found that mine had been rubbing where it crosses the exhaust pipe and has worn a hole it the tube. Here is a good site on SMOG EQUIPMENT (http://smogsite.com/ecdevices.html)

Kerry

[joe]

[ I've seen several methods to test the cat, measuring temp pre then post cat and the rattle test seem most popular but how good are they? [/QB][/QUOTE]

Ray, if your cat is questionable I'd just dump it. You must have a truck that was originally a CA rig cause all 49 states "except CA" didn't require a catalitic converter in 78 on FSJ's nor did they come with one from the factory.