emissions trouble

[Legendjet]

i have a 91 silverado and i rebuilt the motor( top end valve stem seals). i put a muffler on it because it didnt have a muffler. i take it through inspection and it fails emissions this time. it has alittle smoke on start up but it doesnt continue after it gets hot. my emissions are as follow: hydrocarbons : standard 220 ppm test showed 1,700 ppm my carbon monoxide; standard 1.20% test showed 1.72% i think that means i have a few cylinders that have no fire because of the hydrocarbons being so high gas is going in and going out unburned i think i started pulling plug wires which are new and #1 i got a huge spark #3 5 7 i got alittle spark. pluge wires, plugs, distributor cap and rotor are all new. im trying to figure this out before i have to spend a fortune getting it fixed. if any one can give me any advice please do so thank you

[MT-2500]

Originally Posted by Legendjet

i have a 91 silverado and i rebuilt the motor( top end valve stem seals). i put a muffler on it because it didnt have a muffler. i take it through inspection and it fails emissions this time. it has alittle smoke on start up but it doesnt continue after it gets hot. my emissions are as follow: hydrocarbons : standard 220 ppm test showed 1,700 ppm my carbon monoxide; standard 1.20% test showed 1.72% i think that means i have a few cylinders that have no fire because of the hydrocarbons being so high gas is going in and going out unburned i think i started pulling plug wires which are new and #1 i got a huge spark #3 5 7 i got alittle spark. pluge wires, plugs, distributor cap and rotor are all new. im trying to figure this out before i have to spend a fortune getting it fixed. if any one can give me any advice please do so thank you

Switch plug wires . try the one that has good spark where you have little spark.
If that does not help check the dist shaft for a worn out bushing.
Check for sideways play or crack striker plate in it.
And make sure cap /rotor are not bad.
MT

[FearlessFoe]

Check to see if the injectors are spraying good.. Check fuel pressure.. If there is too much, too much gas is getting in and it isnt getting burnt.. It's rare, but if too little gas is getting in and the concentration isnt enough to ignite, the gas will not ignite and it will just get thrown into the cat. So too much or too little gas is bad. Also, try replacing your oxygen sensor and see if that helps. If that's malfunctioning, the computer could be putting too much gas into the mixture. Also, is your oil level steady? Oil burns differently than gas and produces more HCs than regular gas. Make sure to gap the plugs too.. and make sure the connections on the boots are tight. If you have to, squeeze the boots a little with pliers to get them tighter so they make better contact with the plugs. Good luck!

[jj76ta]

Try having the ignition modual tested. This is in the distributor and controls fuel and spark,ect.. The molule can have a problem with out giving a service light. Most auto parts stores test them for free and a new one is only $30 bucks or so. It is a cheap free test and would be one more thing you could eliminate from the problem solving checklist. Also make sure the distributor cap is on correctly. The flat end should be seated in the grove and it is possible to put it on wrong and still have the motor run, but it will ruin the cap and driveablity. Good luck.