I'm putting this post out there as a TSB for the Ranger community with the 2.3/2.5 Lima engines.

So many posts have these symptoms and most users fire the parts cannon at it and spend quiet a bit of money and never fix there issue. Threads become dead or the owner ends up getting rid of the truck with no resolution. I have strong feeling most of these trucks have the issue I'm going to explain.

Symptoms:

Rough idle at times (can be intermittent), smooths out when gas is pressed.
Sometimes stalls at red lights.
Will stall after full throttle on de-accel or when letting off to shift gears.
More prominent when engine is cold or when weather gets colder.
Doesn't stall nearly as bad when throttle is gradually let off.
Can throw any of the individual cylinder misfire codes or the random misfire code if idled long enough to trigger. May not show code at all.

If you have these symptoms follow along.

I started having these issues about 2 years ago on my 2000 2.5L. Here are my checks and maintenance.

Felt like it was missing so I fired up Forscan and watched the misfire total count. Sometimes it wouldn't start seeing misfires until the throttle was blipped. Sometimes the A/C had to be turned off to make the misfires more apparent. Got it high enough to get a pending P0301 or P0302 or a P0300, but the codes kept going back and forth after resets.

Fuel trims showed great. LT and ST were always like +-3. Once in a blue moon STFT would go up to 18-20% for a short period at idle and come back toward 0.

Mode $06 showed 1.28% misfire rate on cylinder 1 and 0.79% on cylinder 2. The rest were 0%




Vacuum gauge showed good vacuum with no fluttering. Smoke tested and no leaks except for the IAC valve vent (this is a metered leak so don't worry about it).

Check timing marks on timing belt and there were good.

EGR was working correctly along withe IAC. Also EVAP was working fine.

Pressure gauge on exhaust was good so no plugged cat.

Went ahead and bought a fuel pressure gauge and fuel injector pulser. Fuel pressure was correct and all injectors flow tested the same.

Compression check showed good.

Cyl 1: 185
Cyl 2: 180
Cyl 3: 180
Cyl 4: 170

Checking spark on all 8 plug towers was good. Over 1 inch of strong spark. Wires ohmed out ok. Plugs and wires were replaced anyways as it was 100k miles since last replacement.

Here is what put me on the correct path. I put a dollar bill/receipt flat against my hand and held it up against the tail pipe. Not the greatest test for newer engines (valve overlap at TDC) but this old SOHC engine is fine. WELL EVERY FEW SECONDS THE RECEIPT/DOLLAR BILL WOULD TRY TO SUCK BACK INTO THE TAILPIPE!

First thought was ok this is a sticking exhaust valve, so I got some Marvel Mystery oil and placed it into the crankcase before I had to do an oil change. I got 0 misfires after doing this. Ok I'm on to something. After I changed the oil, the issue came back. I'm thinking it was some weird placebo at this point.

This was a weird problem and I couldn't find a resolution. Recently I started thinking about possible recessed valve seats. After all this engine has 260k miles on it. On the Vulcan 3.0 a simple compression test picks these up, so how can a compression test not pick it up on a lima engine? Well it's because the lima has hydraulic lash adjusters.

Theory and root cause analysis:

Truck misfires or stalls due to loss of compression on 1 or more cylinders.
Why? Exhaust valves aren't seating all the way.
Why? Hydraulic lash adjusters have pumped up during high revs.
Why? Valve spring force is less allowing HLA to pump up higher than normal.
Why? Valve height is taller allowing for less valve spring force.
WHy? Valve seats are recessed causing taller valve height.
Why? Valve seat material has worn away from high millage.

I had a hypothese and I wanted to do one more check before pulling the head. I turned to IATN which is pretty much a forum/knowledge base for ASE certified mechanics. I was able to get access and check out all the stalls/misfire issues around this engine. 80-90% had the same symptoms had recessed valves. Issue confirmed.

Pulled the head off yesterday. Not bad. About 2 hours worth of work. Flip the head over and BOOM! Recessed valve seats!

I took a socket the same size as the valve diameter and zeroed out a caliper for the height. Then placed the socket on the valve and put the caliper on the side to measure the depth of the seat relative to the valve.

Cylinder 1: 0.030" recessed
Cylinder 2: 0.020" recessed
Cylinder 3: 0.000" recessed
Cylinder 4: 0.000" recessed

*******ABOVE IS WRONG*********Edited 10/18
After having to get a reman head due to original head having some cracks between valve seats, I've found that the valve heads are suppose to sit 0.050" proud of the seat height. Assuming the rebuilder set it correctly.

New measurements using this new information:
Cylinder 1: 0.080" recessed
Cylinder 2: 0.070" recessed
Cylinder 3: 0.050" recessed
Cylinder 4: 0.050" recessed
************************************************



This data goes perfectly with the mode $06 misfire rates. Also got to thinking about the Marvel Myster oil temp fix. MMO is thinner, so it thinned the oil, thus reducing the oil pressure so the HLAs couldn't pump up as tall. I believe this is why I didn't see any misfires when using it.







Cylinder 1 (Bad)




Cylinder 4 (GOOD)

 

Thanks for all the details, photos, and descriptions in this post sheltonfilms...

I'm a carpenter by trade, so some of your scanner stuff went over my head, but I understand the overall gist of what you're saying. I do all the wrenching on my own vehicles, so I understand the grand scheme of things, but I rarely dig that deep into an engine.

Mine has similar symptoms but I don't get a misfire code at all. The only code that came up on mine was P0102, low voltage at MAF sensor (or something like that).

I'm curious to hear if getting the heads done is the solution. Any new details?

 

Well.......don’t know yet because I’ve ran into a little issue.

Sunday (10/20) I cleaned the top of the block, ran a tap through the holes, and blew all the debris off. Put new gasket down and put new bolts in to torque.

spec is 51 ft lbs (do two iterations) then turn an extra 90-100 degrees. I torqued to 25, then 51, 51 again, and then whipped out the torque angle gauge for improved accuracy. At about 80 degrees on the first bolt.......POP! Pulled the bolt out and it was ok.......uh oh. The threads in the block pulled out.

Ok no biggie. Got a Helicoil kit and put in an insert. Torqued fine as well as bolt 2-4. Number 5 on the other hand popped as well about 80 degrees. At this point I walked away.

3 things:
Did using a tap instead of a thread chaser cut out material and weaken threads?
Was there a bad heat treatment on the new bolts causing a higher than normal yield torque?
Is my torque wrench way out of calibration?

Well I’m going to fix this 2nd hole with another Helicoil and inspect all the other threads very carefully for issues. If issues are found the others will be fixed.

New bolts are almost a certainty at this point.

I’m going to go ahead and get a new digital torque wrench that also reads angles.

so there’s that. 😒

 

Oh mannnn.... sorry to hear that!

My first suspect would be the torque wrench itself... Sometimes they ain't true...

My second guess would be; "Were the bolts made out of Chineseum?"

I don't think a tap would hurt the threads, as long as you went easy with it... But I don't think I would've done anything with the threads at all (as long as the new bolts were easy to thread by hand).

Lubricating the threads will throw off the torque settings on the wrench (according to the directions on my Napa torque wrench).

I did the heads on an '88 2.9L once, and that was the deepest I ever went into an engine. I found step-by-step directions at The Ranger Station, and it worked like a charm. Very easy to read, "in plain english", and she fired up on the first try.

Sorry to hear about your troubles, I hope it works out in the end! Best of luck to ya!

 

Man i searched and searched the forums for the answer to my missfire and ended up nowhere! Pulled the head back in september and bingo, same issue! Must be common, my mazda 2.5 had 260k miles when the miss started and had just bought a ranger parts truck with 268k miles with the 2.5 as well and when i went to swap heads found that it had same issue. Got lucky it was friday and my bday so i had 3 day weekend, dismantled 3 2.5s and frankensteined my mazda back to life! I torqued mine to spec with a new torque wrench due to my buddy ******* his yota head up with a out of whack torque wrench! Hope yours goes back together rest of the way smoothly! Only issue iv had is 3 of the new plugs on the exhaust side habe cracked and sparked against the block, hoping its faulty parts like alot of the stuff i get from autozone but im leery. I also noticed my valves are orange, wondering if exhaust is burning hotter then usual or if its normal... its running great for now so im not gonna try and fix something thats not acting up lol

 

Lol! Cool pic racer, and I agree 100%!

 

Now that I read this again, I see that I missed that detail the first time..

When I did the heads on the 2.9, I was so tempted to just re-use the original bolts. They ain't cheap!

But then I found out why they have to be replaced, and it makes perfect sense... The bolts are torqued to near the point of breaking, and they actually stretch a little bit. So, since it's so much work in the first place, not to mention the cost of the gaskets and all, it's almost silly not to buy the new bolts too. In carpentry, we call that "save a dime, lose a dollar".

 

I think this issue is more prevalent than people think. Mostly because it is so hard to diagnose.

About these running hot, it's kinda a chicken or egg situation. Did high heat cause the valves to "sink" or does it get hot because valves are sealing? I know my temp gauge never showed hot.

I know my truck has had rusty coolant for years in it, so it possible the cooling efficiency has been diminished. Still in process of getting it back together (intake is about all I have left). I will be running a bottle of Thermocure through it to eliminate the rust in the block.

 

Yea mines never ran over 190, most of the time sits in the low 180s. On mine the intake valves are a little oily but not crazy and the exhaust valves are straight orange which when i installed the head they just had a little grey carbon. I also show egr and idle position overspeed codes but is all new parts, Wondering if my cats a bit clogged or if autozone gave me yet ANOTHER bad part. I installed a used header/cat while i had the top end apart along with egr, evap, and throttle sensors/parts. Going to send my old head off this upcoming week and see about adding a cam and possibly upgraded lifters.

 

Finally got it all buttoned up today. Made some awful noise until the lash adjusters got pumped up. After that it's purring like a kitten. Took it for a ride and no stall after revving and idles smooth at red lights. Even got some power back. So problem solved.