Why running rich?

Sub74 · #1 11-21-2012, 03:16 PM

My 2.9 is only getting 10-12 mpg

You can smell that it is running way to rich, what controls the air-fuel mix?

Yes it has stock gears and 33" tires but still I should be doing better on gas and you can smell the unburnt fuel

reconjb · #2 11-21-2012, 03:24 PM

What year?

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Sub74 · #3 11-21-2012, 07:32 PM

Sorry it is an 88

CAPTIAN KODSKI · #4 11-21-2012, 07:41 PM

My 87 stx is doing the same thing, I get like 15 miles if I'm lucky and I can smell he unburnt gas..

reconjb · #5 11-21-2012, 07:42 PM

are they carburated?

CAPTIAN KODSKI · #6 11-21-2012, 07:45 PM

Nope. Injected. It also burns oil and it misses.. Changed the cap roter plugs and wires.

reconjb · #7 11-21-2012, 07:51 PM

Quote:

Originally Posted by CAPTIAN KODSKI

Nope. Injected. It also burns oil and it misses.. Changed the cap roter plugs and wires.

what did the plugs look like?

Sub74 · #8 11-21-2012, 11:14 PM

They were a little fouled (black) but not horrible

By the way mine is a STX too

Due to other problems it is almost all new...
Injectors
Computer
Both fuel pumps
TFI
Cap
Plugs
Rotor
Fuel press reg.
IAC
Inlet air temp sensor
Crank turned 20 under with correct bearings
New timing chain
New oil pump
After market oil pressure gauge
Headers
Port matched the intakes to each other and to the heads

Ran really rich before all this was done and the oil press was about 10psi when it was warm, 40-50 psi when it is first started cold

Now it runs much better but it still runs rich and the oil pressure still sucks at 15 psi when it is warm

I obviously really like this truck but it is frustrating me to death

I'm looking for a cheap 302 I can rebuild

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Oh couple more things

All the cylinders test at 130 psi except #4 which tests at 100 psi

It burns oil too, did before u did all the work and still does. (I suspect #4 is the reason for that)

It has 40 psi fuel pressure

Does not throw any codes to the tester either KOEO or KOER

I have messed with this thing so much over the past two years I can quote the Chiltons & Hanes manuals both

I have done it so many times I can pull the motor in about 2-3 hours & put it back in 3-4 hours

reconjb · #9 11-22-2012, 06:45 AM

I would guess head gasket or rings for the oil but I don't think I have ever heard of them causing a vehicle to run rich but possible I guess

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dangerranger42 · #10 11-22-2012, 07:23 AM

I have the same problem with my 88 ranger stx I thought it would be the o2 sender. But I haven't found out yet can't even keep the rear window open..

Sub74 · #11 11-22-2012, 09:17 AM

I was going to replace the O2 sender because it made sense that it could cause the problem

But then we come back to the no codes

Replacing it is a pure guess

dangerranger42 · #12 11-22-2012, 09:19 AM

Yeah that's what I'm thinking bc I'm not getting any codes either but its worth a shot.

CAPTIAN KODSKI · #13 11-22-2012, 10:00 AM

Sub74; did you have to put a lift on your 88 to fit those 33s? I have 30s with 2inch spacers and I couldn't fit 31s.

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And how does your truck do with the 33s? I've been very hesitant to do it cuz I think imma lose a lot of power and over work my tranny. I have 294xxx on the engine and tranny.

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Eh the plugs where bad. All the guts stuck to the spark plug.

And I'm also having trouble with some electrical, my tack is 1000rpms off.. So when it's idling its a 1000rpm under 100.. So in other case when idling it doesn't even reach 100 Rpms.

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So when I'm at a 1000rpms on my tack I'm really at 2000rpms

Sub74 · #14 11-22-2012, 10:51 AM

I have a 4" long travel super lift soft ride suspension with new springs

It is a great set-up but it was so soft I had to fab a sway bar on the front. (taken from an exploder)

I also replaced the axles a 8.8 in the back and a Dana 35 in the front

I used stock wheels with 33x10.5x33 BFG tires, works great. If the tires where 12.5's then it probably wouldn't work as well.

I attached a picture so you could see what it looked like

As far as your tach problem I would look at replacing the TFI on the distributor, I'm pretty sure that is where the tach gets its signal

Sub74 · #15 11-22-2012, 11:52 AM

By the way mine has 243,xxx miles on it.

The 33's are not horrible but yes it has to work harder because of them, the axles have 3.73 gears in them

I installed a 4.0 clutch and flywheel on the 2.9 because I knew I would be working it hard, the clutch works great

I cannot use 5th gear because at 70 in 5th it has about 1600 rpm, in 4th at 70 it is a constant 2500 rpm but still lugs down on even small hills

Someday (after I win the lottery

I plan on installing 4.56 gears