1988 K1500 Emissions problem

I have a 1988 k1500 with a 4.3 v-6 and I moved to CA from ND and needed to get a smog check to register it.
It failed the test due to very high Hydrocarbons at idle.
The test results were as follows:

Idle: 621 RPM
%co2-11.82
%os-4.5
HC (ppm) -281
CO (%)- 0.01
Failed due to very high HC level
Now compare with 2500 RPM Test results below:

2500 RPM: 2537 RPM
%co2-13.40
%o2-2.1
HC (ppm)-37
CO (%)-0.16

This part of the test the truck passed but it was failed due to the very high Hydrocarbon levels at Idle.

The truck has what is almost like a miss at idle but when taken up past idle speeds it goes away.

Can anyone point me to some possible fixes as I need to get this fix and have it pass to get it registered.

It runs very clean at higher RPM's but is dirty as hell at idle and I am very confused.

Thanks for any help.

An idle miss on a TBI can be one of the following:

1) Bad pickup coil (inside the dist)
2) Bad ignition coil
3) Worn bushings in the dist
4) Worn timing chain
5) Worn dist gear

First thing to do is take off the cap and see if you can move the dist shaft side to side. If you can move it, the bushings are worn and the dist should be replaced (which will include pickup coil and dist gear).

If you have a timing light, watch the timing mark to see if it is moving around or if you can see the miss (i.e. the timing light does not flash every rotation).

Good luck.

//2000CAYukon

You can also look at the plugs, plug wires and distributor cap. If they're old I'd do the simple tune up and replace them. A carbon build up or a wire with a small break can cause a miss at lower RPMs and hurt emissions. As in the last post, put a timing light (you don't need to shine it on the timing marks, just see if the wire has good fire) on each wire and see if there is only one cylinder missing or if it's sporadic.

I have a new ignition coil and a new pickup coil that I will be installing.
When replacing the pickup coil do you have to remove the distributor or can it be replaced with the distributor still in the engine.

You have to pull the distributor, knock out the roll pin, remove the drive gear and then pull the shaft out of the distributor before you can get the pickup coil off/on. It's pretty straightforward to do, just use a new roll pin when you put the gear back on.