Redneck_Yota7

I have two issues with my Toyota truck. It's a '91 Toyota pickup DLX with 4X4 and the 3.0L V6 3VZ-E engine with the 5 speed manual transmission. It's running very rich, I had my emissions inspection done a month ago and the HydroCarbons are supposed to be below 220 ppm and for my high speed test they were 1900 ppm and on the idle test they were at 2600 ppm. I did a full tune up on it and changed my oil just before this emissions inspection. I was wondering if anyone has any suggestions on where I should go from here? I also ran a full tank of gas with fuel injector cleaner in my truck and put new gas and heated it up really warm before I had the test. My second issue is I changed my PCV valve and to get to it I had to take the top half of the intake manifold off. I replaced my upper intake manifold gasket and got everything hooked back up right and tight and now there is a horrible knock around the 2nd cylinder head, any suggestions for this issue? I know there are a lot of options at this point and am just trying to narrow down the possibilities. Thanks for your time

skybox

I don't know if it applies to the v6 but i do remember reading about 4 cylinder engines that rattled or knocked pretty bad when the valve cover was to tight. Did you tighten your manifold down to the right torques or just tighten down by feel? does the manifold share any bolts with anything else? I'm new to toyotas so i don't actually know this engine to well yet, but I bet it would be quick and easy to check this and rule it out. I imagine you know your way around that manifold pretty well by now.

tried4x2signN

I'm thinking something I don't want to say yet...

Why don't you check the compression and put my mind at ease...

Redneck_Yota7

i was actually wondering about the compression myself, it was on the low side unfortunately, but i got told that with the altitude i'm at that the compression would naturally be lower than recomended psi. i only had a chance to check my drivers sides cylinders. the second cylinder was 120 psi, the fourth was 120 psi, and the sixth was 90 psi. my house is at about 4200 ft and my haynes manual i have say that my cylinders should be no lower than 142 psi.

yayfortrees

Even at 4200 ft, you should have way more than 90 PSI. Squirt a little bit of oil down that cylinder and recheck. If it helps it, you have some ring problems. If it doesn't, it's likely valve related.

About the emissions: What do the plugs look like? A very lean condition can also cause high HC. Question: Did it always run like this, or did it start up suddenly? Did you replace the PCV valve before or after the emissions check?

Redneck_Yota7

the plugs looked good. my gas mileage has gone down which leads me to believe it's running rich. is it possible it's my mass air flow sensor that's causing this issue? i checked it with an ohm meter and between two of the prongs it had more resistance than was allowed. i changed the pcv valve after the emissions check.

jskijoe

When I had my 3.0 (pre 3.4) mine was running super rich and I ended up having to change the O2 sensor and do an adjustment to the mass air sensor (don't know what the adjustment was). So, something that was done could have pushed the O2 sensor over the edge if it was close to going anyway. I've heard that some cleaners and treatments aren't always so sensor-friendly. Don't know about the knock though...

4Reigner

Running rich can be related to an exhaust leak also, telling your o2 sensors lies...
How's your pipes looking? I had same problem, plugged the hole and passed emissions.

Redneck_Yota7

my pipes look good as far as i can see. i actually fixed the knock and idle problem. the knock was caused because i took my distributor out to check the air gap and when i put it in i missed it by a tooth, so i reset my timing and put it back to where it should be. the idle problem was caused because of a misadjusted tps. i will have to take another look at my exhaust. i just changed the muffler, but the O2 sensor is before the cat and muffler so i don't think that would cause the O2 sensor to go nuts, unless it is bad, is there a way to check it?