pepsi2451

Hi, I have a 1991 3vze pickup. When I bought it, it had a blown head gasket and a broken rod. When I got it all back together, it had a miss and a ruff idle. I tried to get it smoged and it failed horribly but I don't remember the levels.

After replacing the distributor it seemed to be running a lot better. I took it to get it smoged again but this time I decided to put some alcohol in to help make sure I pass. I added 1 gallon denatured alcohol to about 1/4 take of gas. I think that was too much because by the time I got there it seemed like it wasn't running very good. My HC was EXTREMELY high. It was 1756 at idle and the limit was 120. At 2341 RPMs it was 3254 and the limit was 180. Its hard to read the copy the guy gave me but it looks like all the other levels were OK.

The guy that did the smog test said if he had to guess without doing any tests it looked to him like a bad cylinder. I did a compression test and I have about 160 in all cylinders though.

Also since California won't give out temp registrations anymore, I haven't been able to drive it much at all to run it in. I have read that a recently rebuilt engine can fail a smog test before its run in.

My question is, do you guys think my extremely high HC could be caused by too much alcohol? Or maybe the combination of too much alcohol and the piston rings not being fully seated yet? Or do you think I probably have another problem?

mmcpeck

High HC is unburned fuel, which means you are either running really rich or have a cylinder or two with bad ignition. Compression is only one part of combustion, are you sure you have proper ignition on all cylinders?

pepsi2451

I think the ignition is good. I was having problems with it missing, I would pull a spark plug wire off with the engine running and nothing would change. The miss seemed to move around, it would be on #1, #3, or #5 or some combination of 2 of them but always on that side. After I replaced the distributor it seemed to pretty much fix the problem. I have now replaced the distributor, cap, rotor, wires and plugs.

scope103

Use a timing light to a) make sure the timing is set correctly (if that's off you'll fail right away, no matter what the HC is doing) and b) to check that each plug wire is firing. The pull-off-the-wire test is worth something, but with HC that high you are either running really, really rich (as in almost black smoke), or you've got one or two cylinders missing.

Another easy test is to put a voltmeter on Vf (in the diagnostic plug) with TE1 jumpered to E1. That's the amplified O2 sensor, and should flip between about 0.5 and 4.5 volts 8 times in 10 seconds. With HC that high it's probably pinned on the high side, but it's an easy test to do.