Have you checked the codes?  You should also check the fuel pressure.

 

Yeah nothing for the codes. 37 is the only one, but if I recall its not importantn as I don't have a lockup torque converter. I might check the fuel pressure yet, seems good to me though like no issues starting or idling or anything. I pulled the drip line off the fuel pressure reg and no fuel leaks out so I guess that is still good aswell. Notably when I removed the fuel line from the TBI to rebuild it, I got a short of gas to my face , I guess that means there is adequate pressure though. BTW, I've changed the plugs, wires, dist. cap and rotor, fuel filter.

 

Notably when I removed the fuel line from the TBI to rebuild it, I got a short of gas to my face , I guess that means there is adequate pressure though.

The issue is that you might have *too much* pressure.

 

what he said, if everything if functioning properly, you could have (the easy ones here)

a bad o2 sensor, causing it to regularly read a lean condition

stuck open injector (cracked, failed, bad o ring, bad spray pattern etc)

too much pressure (causing an injector to drip or inject too much fuel per cycle of operation)

another thing to look out for, some models had an o2 sensor in the cat, did yours?

 

Hi all. First post although I am a regular reader.  Noticed this post as I was troubleshooting the same problem today. Thought I might put my two cents in.  My 90 is running pretty rich as well, and after checking the vacuum lines, I noticed that the evap vacuum line goes to ported and manifold vacuum sources below the air cleaner.  There is a check valve and restricting orifice between them, then they go to the evap canister (white/black right in front of tb).  The check valve was bad.  That allowed the manifold vacuum to bleed over to the ported side, and act like a vacuum leak!! plugged both until I can find a replacement but it is a night and day difference.  Hope this helps!!

 

alright well i drove the truck today with this in mind. When i gently bring up the rpm's there is no black smoke, however when i blip the throttle really quickly there is a puff of black smoke with the exhaust. Almost as if it dumps too much fuel in and doesn't have enough time to compensate the mixture. Anyways it still runs overall rich, it smells much like a 2 stroke quad.

Im getting new injectors from ebay on monday, so i guess ill compare with those installed. Curious though as too much fuel pressure seems like it could be my problem. What could cause too much? the wrong fuel pump installed?

On the O2 sensor thing, basically the O2 sensor looks to be in the driver manifold. When i got the truck there was a cat with a single hole in it...the shop that did the duals claimed it was not for the 02 sensor but for a drain plug that someone lost. Besides, if there was an o2 sensor in the cat that someone potentially unplugged it would throw a code.

 

Exactly the same problem here....tap the throttle pretty fast and it will bog more an more until the gas is cleared out with wot...not alot of power from a stop either...the vacuum valve brought a good bit of it back...but let us know if you find anything else...mine gets better as it warms up...btw the hole in the cat may have been for the air pump line

 

Interesting. Im trying to find this check valve though. I was looking at vacume line going from the tbi which goes to the left (if you are facing the front of the truck). There is a small piece of white plastic that the line from the tbi connects to which connects to another line (through this white plastic connector/valve. Is this the one youre talking about?

 

Too much fuel pressure is caused by either a bad regulator, plugged or kinked return line. Your fuel pump will put out maybe 50 pounds or more of pressure and the pressure regulator steps it down to 15 pounds. The only way to tell if you have good fuel pressure is with a gauge.  They can be purchased for cheap or used on the loaner program from many parts stores. The unit you need is the pressure /vacuum gauge that goes above 20 pounds not the regular high pressure fuel injection tester.

  You can also use that gauge to check the vacuum of your engine.
You should also check your timing. A timing light is also available as a loaner tool. Unplug the temperature sender when setting the timing.
  The timing light can also be used as a strobe to see the pattern of the fuel coming from the injectors. If you. have a fine mist and not drips your injectors are probably good.

 

Yep that's the one...on the larger diameter hose from the vacuum plate on the bottom of the tb...

 

Can somebody define what "smells too rich" smells like?

I've noticed my exhaust has an strangely sweet almost pungent perfumy smell, especially started stone cold in cold weather. I've got no smoke, getting 14.7 mpg, and it flat out flies, effortlessly passing, especially from 50 to 80+ even w/ AC on.

 

Perfect i will take a look and update accordingly. My new injectors are coming today so i will see, also i will do the O2 sensor this weekend probably as its a PITA to get too.
....And what smells rich to me is unburned fuel, have you ever had a whiff of a 2 stroke quad, thats pretty much how it smells rich. 14.7MPG for a 360? I get like 10MPG

 

One more thing, let me know when you find out which valve this is because i can get it a napa if i knew what it was called.

 

round here, a pungent smell, almost like bad eggs would be normal at wot, running rich will have actual fuel vapors coming out the exhaust, almost like pouring some fuel on the ground and lighting it with a match, you can tell it is gasoline burning, and that not all of it is on fire.

 

Can somebody define what "smells too rich" smells like?

I've noticed my exhaust has an strangely sweet almost pungent perfumy smell, especially started stone cold in cold weather. I've got no smoke, getting 14.7 mpg, and it flat out flies, effortlessly passing, especially from 50 to 80+ even w/ AC on.

sweet, perfume-like could easily be coolant from a leaky heater core.

 

so I cleaned the valves with carb cleaner you mentioned. Looks like the tube goes all the way back to the vacuum cylinder. It all connects to the PCV valve through a bunch of t's and what not. like I said I cleaned the t's but there is a small line going back to the cylinder. At any rate I will probably clean out the little line. So after this and replacing injectors, the truck runs better (more power). I still think the O2 is bad though so I bought one for $60, but I cant find out how to get the old one out.

WTF the O2 is recessed in the manifold, I cant use an open wrench and I cant use a socket because of the wires coming off it. Anyone know how to take this off?? A special tool perhaps?

 

A special tool perhaps?

Appropriately named an Oxygen Sensor Wrench/socket lol.

 

Ahh lol yeah I just googled it. K well im back to square one I just took it for a drive and it is stalling and bogs down and backfiring through the throttle body when I give it more gas. It does this from time to time (prob should have mentioned that along with running rich), but today was BAD (30C today though), barely could drive it. If I get the RPM's up in first gear with the shifter it runs fine. Almost feels like a clogged fuel filter but I changed that last year, however I've been running a lot of injector cleaner through the tank. Could this make the filter bad?

Or perhaps it is a fuel pump? no way to test it because it rev's fine in neutral but when you get on it that's when it boggs down. So unless I can plug something in while im driving im at a loss. Should I unplug the vacuum line from the EGR? And block it off?

 

Not coolant/leaking heater smell--know that one too well, like bad pancake syrup.

This is at the tail pipe, the exhaust has a faintly "sweet" smell more akin to incense burning.  Not the smell of gas, burned or raw.

 

that smell is normally coolant burning. may be a leak into the exhaust or whatever, but keep an eye out for your coolant level, doesn't take much of a leak to cause the smell.

 

Where could coolant seep into the exhaust from?

 

Where could coolant seep into the exhaust from?

leaky head gasket, cracked head or block, leaky intake gasket.

 

That all sounds seriously bad

 

should pressure test your coolant system, leak down style, one way is to install the pressure testing equipment then run the engine a little bit, (till you smell it again) then shut it down and check the testing equipment.

 

watch your coolant level.  if you aren't losing any, the smell isn't coolant.