I keep feeling like there is a misfire. 94 ranger 4.0 ohv.
from the tailpipe I can feel an extra puff every few seconds. Like pata pata pata PUFF. Autozone guy said it sounds like a bad catalytic converter. Ran a bottle of cataclean through it. And checked vacuum for back pressure. Holding throttle at 2k RPM the vacuum stayed high. Like 30s
sometimes I feel like it hesitates starting to accelerate from 1st gear when it's cold.
I replaced plugs and wires. It's a distributorless coil. Checked resistance on the harness plug that fell within spec. Not sure how to check fuel injectors without pulling them out. I checked the fuel pressure and pulled vac hose out of fuel pressure regulator. That was within spec. Replaced fuel filter.
fixed all the issues running the eec-iv diagnostics. With koeo and koer. Cant do a cylinder balance test on this truck as it's not a California emissions model. has no EGR and no sequential fuel injection. Only 2 different ground wires to power the injectors. So 3 fire at once and then the other 3 fire. Anyone have any ideas what to check next? Dont want to start throwing parts at it if you know what I mean. I'm thinking either replacing the distributor pack or pulling the fuel injectors. But dont really want to. Lol.

 

Also one time I got a coolant temp sensor out of range code. But just once and never again. So I figured I didn't have the engine fully warmed up during that test. And it has an aftermarket cold air intake on it. So it isn't making use of the factory air temperature control in the air box. Could that be a factor?

 

Any other codes besides the one temp sensor? Cat could be the problem and cat cleaner may not solve anything if it's broken inside. If spark plugs were recently changed then that shouldn't be the issue. Mass airflow sensor could also cause the hesitation but that should throw a code. Just some guesses as I'm not a professional mechanic.... not sure.

 

first code I got was for the Manuel lever position sensor. It was preventing me from running the engine running diagnostics. Found the sensor on top of the tranny. With one wire broken off where it goes into the sensor. So I just shorted those wires out so the truck thinks its always in neutral. Then I could run the test. Came up with a rich code for bank 1 and bank 2. Took off the air filter and that fixed that code. Got a 1-1-1 all clear code now.
but this year doesn't have many codes/sensors. I can pull a spark plug wire off and drive it and it won't trigger a check engine light. So a lot can fly under the radar.

 

Did a compression check all cylinders within 5psi.
cyl 6 =165psi
Cyl 5 = 168psi
cyl 4 = 170psi
cyl 3 = 170psi
Cyl 2 = 169psi
cyl 1 = 170psi

 

I would soak the exhaust bolts in in pb blaster and pull off the catalytic converter, look inside and see what you find. It should reveal if it's stopped up and needs a new one, just 5 rusty nuts and bots holding it.

 

ok just got back from work. Sprayed a lil wd40 on those bolts. Gonna wait for the cat to cool down before removing it. It's a double cat kinda shaped like a long hourglass. What am I looking for inside there?
also are the gaskets reusable? Should I wait to get new gaskets I am using this as a daily driver.

 

Link to video here seems a little long just to give description of a bad cat but basically you're looking for the inside to be in pieces and look like it's clogged. If the insides rattle when you take it off and shake it then it needs to be replaced. You should be able to see straight through the tiny comb holes inside, which heats up and burns off excess fuel when the motor is running. If it's the original catalytic converter then my best guess is it's flogged and causing power loss. https://youtu.be/JMEzfykJMEzfykhz0

 

Yes, not a bad idea to replace the gaskets, especially if you need a new converter.

 

whelp. I broke the catalytic converter gasket. Cat looks perfect inside. Really easy to remove like you said it's just 5 bolts came out in 5 mins. Hardest part are those darned rubber exhaust hangers for the life of me I could not get the muffler out of the way its held on with those rubber hangers that would not come off. So as I tried to force the cat off the gasket got caught on one of the bolts and snapped in half. Guess I'll see if the parts store has one of those. now to see if I can get that muffler to drop down so I can put the cat back without breaking the new gasket.
any tips or tricks to remove exhaust hangers?

 

Broken gasket

Muffler side

Engine side looks the same

Muffler hanger from hell

Headers still do that pata pata PUFF just slot louder. So I'm pretty sure it's not the cat.

 

I've used wd40 on the rubber part that connects to hanger and that seemed to help some getting it off.

 

tried that. Maybe I'll try to shove a big screwdriver in there and pry it. Kinda wish the bolted that bracket up there. Instead of using some kinda rivet.

 

Any ideas what I could check next?
idle does seem to fluctuate a lil. With a vacuum guage on there its easier to see. Vacuum Bob's up and down maybe 2-4 Hg at idle

 

sorry, I'm running out of ideas...maybe someone more advanced than me can chime in. Obviously me and autozone were wrong about the cat needing replacement. Does this motor have a distributor or the camshaft position sensor on it? And did you check that?

 

Got a gasket and put the old cat back on. Finaly got that muffler hanger down. Just had to really yank the crap out of it.

 

It's a distributorless coil. Not sure on CPS. Might try to clean the MAF like someone else suggested. Or check the paper test at the tailpipe to see if it's a sticking valve

 

Another thing not sure if its related as i have no more coolent temp code but the truck never reallly heats up, not according to the guage. It was 92⁰ out today and im sitting in traffic and this is as warm as the engine gets. Just barely reaches the cold/normal line. Never gets warm enough to activate the fan clutch. Either its got one of those oversized Nascar radiators in it or something aint right?

 

You're thermostat is stuck open or coolant temp sensor is bad, I suspect the thermostat. If you pull the cam position sensor to check it then make sure you put it back in the same place, cam, crank shaft, sensor wise. After years of service they do get loose and can cause problems, not sure if it would cause a misfire. The thermostat stuck open can cause it to run at higher idle than normal and burn more gas, from my understanding. Thermostat is an easy fix but should *not cause a misfire. Does your radiator have plenty of coolant or does it run low? My rebuild motor project all started due to cracked heads and a botched mechanic head job.

 

right now just running water in the radiator. Guy I bought it from had water in it, rusty water. But it was full. No apparent leaks. Might drain and fill it a few more times then put actual coolant in there along with a thermostat. Add it to the list, lol.
I'll research that CPS thing. See if I have one and where it is located.

 

Also, I think the maf sensor should throw a code if it's causing the misfire, from my experience but not that hard to remove and clean and make sure air is flowing past it. During my rebuild (1.5 years...) dirt daubers clogged the maf where air flowed past. I was getting hesitation and stalls at initial acceleration and throwing maf sensor code. Once I found that and cleaned it, no more issues.

 

You have a csp if you have the coil pack. It replaced the distributor on these motors

Cam position sensor on back side of motor next to fire wall. The lower intake is off in this picture so it's easy to see here.

 

Oh that looks like it's real easy to get to, with the intake removed. Lol.
I do have a coil pack. So its probably tucked up in there.

 

The 91-99 4l ohv are basically the same motor with a few minor differences. I highly recommend a Chiltons or Haynes manual. If you end up having to mess with the csp you'll definitely need a manual and may need to pull both intake manifolds, which if you get that far into it, the heads are just right there... It could be as a simple as another post I read where the vacuum hoses weren't connected properly.

 

yes. If I'm gonna pull the intake manifold I might as well rebuild the top end. Push rods have an oiling problem with this engine I've seen. That could be what's causing this anyway. Sooner or later I'll probably need to buy the gaskets and a set of pushrods, maybe some lifters etc.. then check the CSP sensor while I'm in there. I believe the heads are fine as coolant levels where good, oil just looked like really old oil. And it passed a compression test. So I'm thinking my problem area is gonna be in the intake, lifter, fuel injector area. Might make that a week long project when work slows down a lil.
how much of a job is doing the top end like this? I'm sure you've gone over this with your motor rebuild