Causes Of Running Lean? (Bronco 302)

[Robb]

Hey Guys

-'95 Bronco 302 (EEC-IV with distibutor)

To start with, we (my and I) are just assuming a lean condition by the fact that the exhaust is years old and very clean at the tip, actually a bit white. Only have had the truck about a month or so, and has had noticably less power than a '91 302 we had a few years back.

Only code thrown was a TPS code, it has been replaced. Along with: plugs (showing lean condition also), wires, cap and rotor, fuel filter, O2 sensor, and cleaned MAS. Fuel pressure is well within specs. Timing has been set. K&N has been added. Had the pressure drop accross the CAT checked by trusted muffler guy and found to be fine.

With these fixes, performance has improved.......but still not great yet. Simply not as quick as the '91 was with the same gearing. My dad's main concern is that he wants to start towing his 21' SeaRay with it soon, and is scared of it running lean while towing.

What else should we look into? Nothing else seems to be bad enough to throw any codes.

Thanks for any suggestions!!

 

[Muskrat]

400M

 

[Glacier991]

Lean.... hmmm... off the top vacuum leak looms large. Intake manifold area is a possible area to check. Bad o2 sensor could falsely show rich commanding a change to ean (unlikely without a MIL(CEL), but ya know... sometimes they don't set em...). Injectors can cause lean... anyway I'd try and eliminate any chance of a vacuum leak. I'd be curious to know how your 02 sensor or sensors (front, not post cat) are acting voltage wise too.

Happy Exploring

Chris

ps. If you have access to an untrasonic "sniffer" it's dandy for finding the smallest vacuum leak.

 

[james t]

im thinking a minor vacuum leak.

you know those little $10 propane torches? they make a GREAT vacuum leak tester. let the engine idle, turn the bottle all the way up but do not light it. poke around all the lines/fittings. if the idle rises, you've found your leak.

what do the plugs look like? are they whitish? brown? black?

 

[TravisC]

Originally posted by james t
im thinking a minor vacuum leak.

you know those little $10 propane torches? they make a GREAT vacuum leak tester. let the engine idle, turn the bottle all the way up but do not light it. poke around all the lines/fittings. if the idle rises, you've found your leak.

what do the plugs look like? are they whitish? brown? black?

Off the subject because I have no clue what it would be but I think that would be scary as hell doing that. Is they any saftey risk in doing something this that? Just curious because that sounds risky.

 

[james t]

nah. if something were to ignite it, it will just ignite the torch as if you were lighting it for useage. ive done it/seen it done a million times without incident. if it were possible to blow the bottle up, you could blow it up by just lighting it with a match.

EDIT- im not talking about an actual propane grill tank, im talking about the little bottle torch.

 

[TravisC]

Yeah I know what kind of bottle you were talking about I was just curious about it. Alright, back to the lean....

 

[Robb]

Thanks Guys!

Hopefully, I can come up with some time today to look into a vacuum leak. Funny how I forget the basics sometimes. With all these damn sensors and junk, I sometimes can't see the forest through the trees.

 

[james t]

Originally posted by TravisC
Yeah I know what kind of bottle you were talking about I was just curious about it. Alright, back to the lean....

i was certain YOU knew what i was refering to, but this is the interwebnet. i didnt want some lurker to read my post, hook up a 10 foot hose to their gas grill, and then start spraying their idling engine down; thus igniting the hose only to have the flame run back into the tank and make things chared and smelly.

 

[TravisC]

Originally posted by james t
i was certain YOU knew what i was refering to, but this is the interwebnet. i didnt want some lurker to read my post, hook up a 10 foot hose to their gas grill, and then start spraying their idling engine down; thus igniting the hose only to have the flame run back into the tank and make things chared and smelly.

Haha, good point. That wouldn't be very pretty, well the big fire ball might.