First I have a '95 4Runner with the 3vze 6 CYL engine. Just short of 267,000 miles. The engine has had the head gasket replaced in the last 2 years, at the same time valve job was done. The compression is good, the injectors have been cleaned I've run Seafoam through a couple of times.

But the MPG's have been pretty sorry like everyone else. So I pulled the plugs and replaced them. The old plugs were moderately worn and dark brown to black dry and sooty, the exhaust pipe is dry and sooty with occasional black smoke blowing out at start up. And intermittently hard to start.

I'm thinking it is running rich based on the above symptoms. So I have turned the wheel/gear in the VAFM clock wise a couple of clicks as per the Downey website in order to lean it out.

Am I heading in the right direction or do I need to re think this?

Thanks.

 

well has the adjustment helped at all?

 

Can't tell about the MPG yet just did the adjustment Saturday. Seemed to have a little more pep. But who knows. I can wash the thing and I think it runs better.

I did set off the check engine light. I'm not sure if that was because of the VAFM adjustment or pouring the Seafoam down its gullet or the plugs or what. I've looked to see if anything was left disconnected and thats not the case, I don' think. So I reset the computer and waiting to see the result.

I really just wanted to know if my assessment of it running lean was correct and if my solution was the correct one.

 

For what it is worth, your symptoms are similiar to mine as the exhaust valves in #3 and #4 slowly went south. When the head gasket was done, did you do any work on the heads, by chance?

Oops, I see you did work on the heads, my bad.

 

The check engine light probably went off because your 02 sensor is dirty because your truck is running rich. What is your compression? Did you do a leak down test? My 3.0 has 330,000 on it but it needs a valve job. It runs on 5 cylinders and tons of soot. Maybe you are starting to lose compression and the fuel/ air ratio is off now? did the problem start after the head job or was it a problem before?

 

Not sure if you are asking question of JREB or me. Had a valve job done and compression rechecked about 6 months ago. All of the cylendars were over 170 PSI. So don't think my problem is related to low compression. The O2 sensor was replaced at the time of the valve job and the injectors were removed and cleaned at the same time.

 

If your MPG are sore, it may not really be the engine, what size tires do you have? what PSI are they at?

 

I think your going in the wrong direction. If for years and years/miles and miles it was running fine now something is off I doubt that its a AFM issue.
Of course a search of this site would help more than my sudjestions but here goes:

Tires and gears(mentioned above)
oil weight (maybe you to light)
Are you sniffing your trucks ass pipe when its cold (open loop)
have you pulled trouble code
have you check you cat converter (they don't last forever/with one in place your calibrated sniffer may be getting a false result)
Do is your vehicle leaking fuel anywhere else and making you think its coming from the exhuast
There other things too just can't think of them now

bear with me haven't had coffee yet.

 

Tires are 31's not sure of the gears. 31in tires are what came on it when it was new. I'm also running tire pressure at 45psi, thats nearly max. I used to get 18/19 MPG. I have smelled gas once in a while but not often. I guess the cat could be bad but don't understand why a bad catilytic converter would cause the plugs to be sooty.

 

[QUOTE=muddpigg;50885940]

oil weight (maybe you to light)
QUOTE]

I'm using 10w-40 wt. How would "light" oil increase fuel consumsion? I can see heavier wt oil doing that. So I don't understand the oil being too light.

 

[QUOTE=vj95;50886018]
Lighter oil more oil burning, more oil burning more soot, more soot clogged cat, clogged cat exhaust constriction, exhuast constriction poor fuel. Of course this process doesn't occur over night.

Also increasing wear due insuficient(sp?) lube poor fuel consumption.

 

Don't think I'm burning oil. Not adding oil between changes at every 3000 miles. No blue smoke. Always used specified wt oil.

 

I think the problem is obvious, its the calculator your doing the math with.

Did you check the solar batteries?

 

I think you're running rich. I'm a tad conservative in my approach, so I don't advocate messing with adjustments like that. I'd advance timing a hair before messing with the AFM....for a temporary solution. Speaking of which, have you tested the AFM? I'd check that, the cold start injector switch, and the coolant temp sensor.