Air/fuel mixture?

[Speedwagon]

Seems like the warmer it gets, the worse the truck runs. Starts to really lack power when the engine fully warms up. Feels like it's missing a bit when cruising down the highway.

Also, if I go full throttle on acceleration, it will give off a bit of an explosion when I shift. It occurs as soon as I open the throttle plate back up after shifting gears. There is a bit of a hole in the exhaust before the muffler, so the explosion is a very audible bang in the exhaust.

Seems to me that this is likely an air/fuel mixture issue. If so, coolant temp sensor, TPS, O2 sensor? Something along those lines?

[84broncoII]

I could think of a situation like that if You were running too rich ,due maby because your carborator floats are set too high .Im not a mechanic so ... Do You have acces to a code reader? what year is Your truck I have a code reader somewhere for Mine but you live way far away ...

[84broncoII]

Funny thing about carborators is that You can fix one little thing and then it wont run like re setting the float but in reality Your main jet is cloged and now that the float is fixed it doesnt get gass at all LOL .If You suspect the carb and dont know when the last time it was rebuilt then either replace it or rebuild it .If your fuel injected forget everything I just typed and have a good day I dont know a thing about injection systems .

[PaleBlue90]

i agree, check your carbs float levels and if your running rich. it sounds like your running rich

[Speedwagon]

It's an EFI truck. So that likely means I have a sensor that's borked somewhere. I just drove the truck to Chicago(where I am right now), and got 13mpg on the trip. So it's definetaly running rich. Want to replace the O2 sensor, and see where that gets me.

[Digger]

Is this your 2.3L?

I would start by checking out your fuel pressure regulator. If the diaphram has ruptured, fuel will start dumping into the intake manifold and it will start running rich, and possibly miss or backfire. It is easy to check. With the truck running, pull the vacuum line off the regulator and see if there is gas coming out of it. It would be safest to do this on a cold engine in case fuel spills. I would have a rag and a fire extingisher handy.

If not, I would start checking ignition components.

[shawns 64 F100]

didnt you just put a timing belt on this engine? I may be mistaken but thought you did, as well, when you do a tune up, did you remove your spout plug before checking timing?

[Speedwagon]

Is this your 2.3L?

I would start by checking out your fuel pressure regulator. If the diaphram has ruptured, fuel will start dumping into the intake manifold and it will start running rich, and possibly miss or backfire. It is easy to check. With the truck running, pull the vacuum line off the regulator and see if there is gas coming out of it. It would be safest to do this on a cold engine in case fuel spills. I would have a rag and a fire extingisher handy.

If not, I would start checking ignition components.

I'll have to look into that. On a recent trip to Chicago and back, I averaged 10-13mpg on the drive to/from. While in Chicago, I replaced the TPS(truck started acting like the TPS wasn't working), which did seem to fix it to a certain extent. I got a consistent 17mpg around Chicago, until about 200 miles on the way back, it went down to 12ish again. Seems to act ok when the truck has had an hour or so to cool down, and on short trips it doesn't seem to act up as much.


didnt you just put a timing belt on this engine? I may be mistaken but thought you did, as well, when you do a tune up, did you remove your spout plug before checking timing?

Yes I did, on both counts. Truck is set at spec, with the spout disconnected. And the computer is advancing timing when I reconnect the spout.

Some other things I noticed on my 2,000 mile trip: frequently when I shift gears, it will pop, and I'll see a black cloud come out of the tailpipe. So it is obviously running too rich(not that the 10mpg didn't tell me that). And I get spurts of power on occasion, and spurts of absolutely no power on occasion. With a middle ground of low power, but enough to make the truck actually drive ok(not good, but ok).

Did find out that my cat has fallen apart, and was likely hiding out in the muffler, so the muffler got replaced, and cat is currently empty.

[Speedwagon]

Update: Replaced the fuel pressure regulator, didn't solve the problem.

Replaced the coolant temp sensor, didn't solve the problem.

Pulled the plugs again to take a look, and they indicate a lean condition(very white), with ash(I think) deposits. According to the Haynes, ash indicates oil consumption, but I already know it burns oil on startup(valve stem seals).

Replaced the fuel filter this morning, and there was a LOT of rust colored gas on the inlet side. I'm sure that wasn't helping things.

Just did a vacuum check again, and it was reading 14-15. Spec is 17 to 22 at sea level, with -1 for every 1,000ft about 2,000ft. So 14 should be the same as 17-18. It varies from steady, to slight(within 1-2) fluctuation, and the haynes tells me that indicates a possible ignition system problem.

If I hold the engine steady at around 2-3k(I think, no tach), the engine varies from steady to fluctuating rpms. I have noticed this while driving around at times too. I haven't driven much since changing the fuel filter, so I don't know if the big under powered on load mid throttle problem is still there, but I will find out later tonight. But it still does do afterfires when I shift gears at full throttle.

As for the ignition: Coil, plugs, cap, rotor are all new. The only thing I haven't replaced this year are the wires.

[bronc_17113]

try setting your timing to vacuum set it as high as advanced as you can till it pngs then back it off till it stops pinging

[Speedwagon]

It's electronic advance. I don't think it's timing now though. Last night while it was acting up, I disconnected the spout connector, and put the timing light on it. Timing was solidly on target.

[Speedwagon]

I may have located part of(or maybe all) my problem. Apparently it is a bad idea to have large rocks hit your gas tank directly under the fuel pump, thereby pushing the bottom of the tank into the pump and bending things. There was a rusty mark where the fuel screen has been rubbing on the tank. It was also the highest area of the tank(directly under the pump). I'll know tomorrow after I pickup some new parts and get it back together.