So I just got my hands on a 92 F350 cab and chassis. It has a PTO and dump bed on it (reason I bought it) it’s low miles, drives great, but I’m having some engine issues.

Its been sitting 3 years. It ran rough so I added Lucas injector cleaner and topped the tank off with super. So it has half bad gas half good in it. Seems to run better and better as I try to burn it all. Oils been changed and air filter.

So it idles at like 1500 or so If the IDle air control is plugged in. Unplug it and it idles a little lower than good but ok. So I cleaned it and it didn’t work, installed a new one and it hunts around some, but is still way high. Do I need to program it? Is there something that controls it I need to look into? Where do I go from here?

The truck is kinda a dog in general. I assume that’s just the little engine in a big truck. I’m used to diesels. It does run 75 (eventually) on the highway. Gets around good in 1-2-3 gear and becomes a dog in 4th and 5th.
it is a dually, but currently has “super singles” 33x12.5 mid grips. I’ll be putting duals back on the rear. Probably some 265’s.

 

Check and change 5he plugs if you haven’t, and while doing that do a compression test. Plugs will tell you if it’s running lean or rich if you’re getting oil in the cylinder (for some reason people think it’s a good idea to dump a quart of oil into the intake if they’re going to let the truck sit), once compression and plugs are checked/replaced if everything is good burn off the old fuel by using marvel mystery oil and not some snake oil (I guess Lucas is ok lol) in the tank with current fuel, and once you add new fuel see if it finds different.

Keep in in mind when these trucks sit for a long time it can take quite a bit of miles/time to burn off the spot that’s accumulated from sitting. Keep an eye on the engine and tranny temps (laser thermometer would be good for this as the sensors may be gummed up), and if everything is within specs let it burn off whatever old fuel it has while idling, replace with new preferably high octane 91-93 fuel and see how she does.

Btw gasoline goes bad in a year or so so that’s probably your issue, hopefully. But seriously run a high quality cleaner like sea foam or marvel, can do so in engine oil as well.

 

Correction - burn off old gas AFTER pumping out what you can from gas tank so it’s as empty as possible, pumping it out will also tell you how much corrosion is in the tank and if you need to just buy a new tank (hopefully not), once you’ve pumped it out and if it looks fine then throw in a gallon or two of new gas, run it until it’s almost out of gas and refill tank with new gas.

 

gasoline doesn't keep nearly as well as diesel. 3 year-old gasoline is about 2 1/2 years past it's "best before" date. it makes a good cleaning solvent though.

 

check for codes, and all vacuum lines
EEC-IV Codes | Throttle (5.1K views)
(16) How to read a check engine light code on a Ford 1983-1995 EEC 4 system - YouTube

 

Wow that’s cool how you check codes.
Vac lines look like hell so I bet I need those. I almost got the gas burned out today hauling firewood. I think the fuel filter is plugged so I grabbed one. Can’t find my fuel line tool for now.

Theres some crap on the motor that is disconnected. It’s some sort of emissions junk. Electrical plugged in but I don’t think it’s hooked up to function.

I run across the scale at the coop earlier weighing 10500, the thing was a dog. I had trouble getting up to 55. I’m hoping I get it livened up. I’m assuming I should be able to get around descent weiging maybe 15000 total with a trailer OK.

 

those should be your TAB and TAD(emissions) keep them electrically plugged in(no CEL) and PITA to check but do you know if the piping is still there or removed, if removed check that its plugged off that pipe goes down to catalytic converter, can cause issues.
here is a wordy(vacuum line install)
Replace Plastic Vacuum Hoses with Rubber - Ford Bronco Forum

 

Also check that someone hasn't jacked with the physical throttle plate adjustment.

Someone may have messed with it to correct an IAC problem and now the IAC does not have full control of the idle because the plates are not closing fully.

 

Ok so I’ve been messing with this more and using it. I got the old gas all gone. Fresh tank of super, new fuel filter.
It’s running better but still has fast idle if I plug in the IAC. I have checked for vac leaks and can’t find any.
So I checked the codes and found,
tPS code, oxygen sensor code, and the pcm code

153 , 328, egr assuming this doesn’t matter. 512. I think the tps was 121 I’d have to look back at my video.

It smells like it’s pig rich so that makes sense. I ordered an O2 sensor, and TPS.
It has dual exhaust pipes that go into 1 muffler. A single 02 sensor. No cats.

 

On the lack of power: I've had really good results on several engines by pulling the injectors and bench cleaning them. You activate the injector with a 9 volt battery and spray brake cleaner or carb cleaner through each injector forward and backward. Use a rag around the end you're spraying into to direct the spray. I can't believe the crud I've seen come out of injectors. Doing this also checks that each injector is working - they click if they're good and do nothing if they're dead. You must take the upper plenum off to do this, but it's a good excuse to change leaky valve cover gaskets. You don't have to disconnect the rail from the feed and return lines.

Another thing common to these engines is being off time. You'll want to time it correctly - 10BTDC IIRC. And adding 2 - 4 degrees more advance is a power hack. There's a plug you have to undo next to the ignition control module to set the timing.

The dual pipes that go into one "muffler", if stock, should be the catalytic converter. The converter has a rectangular flange on one end that bolts to the two pipes, then exits from one regular pipe on the other end. On regular cab trucks there is no pipe extension between the muffler and cat - they clamp together. Extended cab and crew cab trucks have a short run of pipe between the cat and muffler. But if you've only found one "muffler" it's probably the cat. They can clog, but all my F trucks (seven OBS over the years) have had cats and I've never had a problem with them. If you pull the cat the best way is to take an angle grinder to the four bolts and then knock the leftover stubs out of the flange. This way you can get new bolts at the hardware store and bolt it back on to a straight flange and the gasket won't leak. If you do pull the cat you can check it by looking through it.- if it's clogged you cannot see light through the honeycomb. If you buy a new cat the small block and big block cats have the same bolt-on flange, but the big block converter has a 3 inch outlet and their prices are similarly expensive.

The vacuum lines have been covered, so I won't rehash that. But, bad attempts at desmogging can introduce lots of bugs. When you get things fixed the IAC will still hunt around for a few hundred miles. I guess it's a computer learning thing, but a quirk I've noticed in several of these trucks nonetheless.

 

This is definelty a muffler. It says dynomax or something On it and it’s way in the back right in front of the axle. The exhaust has been pretty butchered all around. It doesn’t leak though. Looks like at one point it had dual exhaust , then merged into the quiet muffler later. Lots of cut and add going on, not leaking, but the muffler itself must be rotten inside because it sounds horrible, muffled in a bad way. Pipe zig zags everywhere and kinda comes out in an odd spot. Regardless, I’ll probably add some glasspacks at some point and turn them out the sides right behind the cab.

Good to know about the IAC Valve. I haven’t been able to put any miles on it after replacing because it has to idle for me to run the PTO so I haven’t been using it. But it’s a pain because if the PtO experiences high load it stalls the motor since the IAC can’t help me maintain rpm.

 

So the TPS fixed my high idle. I cleaned the throttle body while it was off too.

Ive not changed the O2 sensor yet. Maybe tomorrow.
So now truck idles and runs smooth.
HP is pretty weak feeling though, check engine light comes on momentarily under heavy accel in 3rd gear and up.

 

That isn't normal and suggests a potential bad PCM, did you clear codes after changing the TPS? Also check base timing to see where it is set, should be 10deg BTDC with the spout plug removed to disable computer advance.

 

How do you clear the codes?

 

remove battery cables for about 10-15 minutes