I am lost guys....need your help.

Just to get you all up to date, I have a 1997 F150 4.6 4x4.

Last year, around Feburary, I started to notice a loss in power around 130K miles....I dare say that the truck has lost 40% of its power. As of todays date, I have replaced the plugs, the PCV valve, and the fuel filter. No change.....at this time the "Check Engine" light came on.....the code advised to replace the 02 sensor. I did....check engine light went out after I cleared the codes, however the power loss is still there.

Compression test came back fine, all cylinders ok. Air Intake (K & N) is fine, but just in case I took out and reoiled. Still a power loss......dumped a few bottles of few injector cleaner in (Lucas) over the next few tanks of gas.....still nothing.

Took the truck to the transmission shop, tranny is fine. Took it to the exhuast shop, they hooked it to a machine that claimed the cats/muffler are ok.

Checked all the brakes to make sure no brakes are frozen or dragging...nothing.

Opened up the left side fender to make sure no bird nest or trash could have blocked the intake....nothing.

I am lost guys.......any ideas or help would help. This truck has been looked at by me and my father, both of us are decent wrenchers......then the truck has gone to 4 different mechanics and 1 dealership. They all agree a power loss is there, but no one can figure out why or how to fix it.

I am taking it this wek to a different exhuast shop.....they claim that they can hook it to a machine as well to see if the cats are blocked. Are they machines dependable?

Anyone have any answers or idea for me?

 

clean your MAF. it could have oil on it from your filter. also check all your vacuum lines, plugs, wires. could also be a problem with the injectors.

 

Had this happen once and I'm drawing a blank for the name of the unit but, back by the firewall on the drivers side is a round disc like unit that has a diaphragm in it. On one side of the diaphragm is exhaust gas and the other side is vaccume. We had the same problem with loss of power and found that the diaphragm was bad (dry and cracked) and the exhaust gas was overcoming the vaccume, not to mention the loss of oxygen in the exhaust gases. Dealerships could not find it and it passed the tests at the muffler shops... Still cant think of the things name but hope this helps..

 

I am heading up the road to grab some electrical contact cleaner to clean the MAF...see if that works.

Will check the exhuast diaphram thing also.......got to get this thing fixed. The truck but a half of a tank of gas yesterday....in 90 miles. 11 gallons gone just like that.

 

I think this is the EGR valve (exhaust gas recirculation valve)

 

Just got back from cleaning the MAF....that seemed to bring some of the power back. From a holeshot a full throttle, it almost chirped the tires. Think we are starting to get there.

Gonna look into the ERG valve next.....

 

I would clean the Throttle body next . Make sure your running Motorcraft, Denso or NGK plugs in their or it won't ever run right without righting that first.

Test your EGR valve this way -

Start your vehicle, while @ idle disconnect the green vac line from the EGR valve. Find a piece of hose about 3' long that you can plug into the EGR valve in place of the green line. While your Vehicle is still at idle , suck on the hose like you were drinking a milkshake. Does your idle change? does it want to stall? If so , then the EGR valve is good . If there is no deflection or change in idle speed your EGR valve needs to be replaced..

You might want to replace your forward O2 sensors if your mileage is real bad.

Keep in mind - just because you went thru gas pretty quick from the half tank mark , doesn't mean you went thru 11 gallons that fast . That's NOT how it works. All these trucks drop fast from the half tank mark. Half tank actually = closer 7-9 gallons of petrol or maybe even less.


Good Luck

 

Today I replaced the 3 remaining 02 sensors......replace downstream Bank 2 last month.....plus I cleaned the throttle body. Semmed to bring alot of power back. Thanks for the help!