I'm SO SICK of my Tacoma's rich problem

Seriously, nobody can figure this out, not even my mechanic. My '96 2.4L has been running rich and lacking power for months. I've done everything I can think of to it. I even just cut off the CAT to eliminate it as a possible cause. No change. I just put on a brand new MAF sensor as well. The tailpipe is still sooty as hell, and it still can't climb shallow hills worth a damn. The only other thing I can do it put the factory 14" tires on it. I have 15" on it now, and I don't see that making much of a difference, let alone making it run rich.

 

time for an upgrade!

 

I would love to upgrade to a newer 6cyl, but funds are not permitting that at the moment.

 

The bank has lots of money!!!

 

injector(s) stuck open
fuel pressure regulator allowing too high pressure
ECU dain-bramaged
O2 sensor(s) bad (or wiring to them)
cylinder blow-by
temp sensor not allowing closed-loop

just what i can think of now

 

I'm running a ScanGaugeII. Close loop good. Cylinder compression checked: good. New fuel pressure regulator: no change. Fuel pressure checked: good. O2 sensors: 3 months old- hesitation went away, but still rich and no power. Fuel filter changed: nothing. Air filter switched to K&N: nope. Plugs and wires changed: nada.

I haven't checked the fuel injectors. I also get a bad vibration when stopped in D or R, and I have read that a bad injector could cause that as well. I was thinking of pulling out the injectors one at a time to examine them. Before I do that, I need to get some new O-rings.

I don't know how I would check the ECU without replacing it.

I'm now getting less than 20mpg. This sucks!!

 

Not sure you'd be able to see if an injector is bad or not by just looking at it. My Haynes says to put an ohm-meter across the terminals and check resistance. How that would tell you the thing is stuck open I don't know.

Maybe you could pull them and bring them to a place that can do a professional cleaning. Has to be cheaper than replacing them. Even if it doesn't fix the root problem it can't hurt.

 

with all you have done already..................i say go ahead and pull the injectors out and have them cleaned thoroughly. especially if the ecu isnt throwing any codes. reason i say clean the injectors is because a new set aint gonna be cheap by any means. how does the truck idle??

 

The idle isn't that bad, except for the vibration. I'm going to pull the injectors sometime in the next few days. Would it even be worth it? The only way this could benefit me is if one of them is visually bad. Otherwise, I'd have to just take it to the shop so they can test them. There is a way to test them in the full service manual using a graduated cylinder, but I don't have the necessary kit to do it.

 

When you pulled the plugs were they consistently colored or some darker than others? If you have a leaky injector then one or two plugs will be darker than the rest. If they were all dark, you probably have some kind of engine management issue, I just don't see all four stuck/leaking. Pulling injectors only to look at them is a waste of time, either replace them or get them cleaned if you pull them. Are you getting full vacuum to the regulator at idle? 15 inch tires aren't gonna affect a thing, as far as engine management. Is your mechanic road testing it with a quality (snap on) scanner looking at sensor parameters? Does your scanguage ever have issues reading data? That could be a ecm issue. What were your compression readings? Check maf to throttle body tube for any holes/cracks/leaks however small they will affect it. Also try spraying some carb cleaner around your intake manifold, maf tube, and vacuum lines, any change in idle means a leak that needs to be taken care of.

 

The electrodes all look very clean. The rims below the threads are black on all 4. With as black and sooty as the tailpipe is, I was expecting at least one of them to be very black all over.

Not that I know of. I've never had issues with my readings.

I think they were up near 170 or 180.

That was done with no leaks detected.

 

Ok, so I took it up to a Toyota specialist. He did another compression check and came out with different readings:

Cylinder 1: 160
Cylinder 2: 155
Cylinder 3: 120
Cylinder 4: 125

He thinks that the piston rings may be stuck, so he added some chemical (MOA?) to the oil, idled it for an hour, and changed the oil. He said to drive it for a few days and see if there is any change. None so far. Could the rings need to be replaced? Or could the head gasket be leaking?

 

There doesn't appear to be any intermixing of the oil or coolant. The oil looks good when I change it; never totally black.

 

since cylinders 3 and 4 both are low and they are adjacent i'd look for a head gasket leak between the cylinders

 

Just remember the old way of checking for ring seal (or lack of). pull the plugs out of all the cylinders and take a compression reading . Squirt a bit of heavy oil (like differential fluid) in the cylinder you suspect has bad rings. Crank the engine for a few seconds to distribute the oil around the ring, then take a compression reading. If it's higher than before the oil, the rings are shot.

You can also manually turn the engine until the suspected cylinder is at TDC. Watch the compression tester, if it slowly bleeds down suspect leaking valves.

 

After a wet compression test (adding some oil), the compression went back up to 180. We also did a leak down test; the valves are not leaking. I guess my rings are shot. So...what now?

 

ring time i guess....

there's a few low miles engines on ebay too. make sure they offer a warranty.