2.5L ('98-'01) 2.5 Lima mystery miss. Calling all Lima wizards

[The Ranger That Could]

Hello, I have a 5spd 1998 Ford Ranger xlt, 4x2 2.5 lima. I am getting this mystery miss when the truck is at low idle, Especially after idling down from high idle. The truck has 176k and just started to act weirdly randomly on a warm day. I have owned the truck for the last few months and haven't had any issues aside from replacing the consumables. It doesn't do it all the time but seems to do it no matter if it is warm or cold. I have attached videos showing what it is doing exactly. here is a list of what I have done since owning the truck:

replaced both upstream and downstream o2 sensors (i felt they needed to be replaced as the pigtail wiring started to dry rot)
replaced lifters and valve cover gasket (lifters were a bit noisy)
Replaced Maf (after cleaning the old one and having surging issues)
replaced all intake manifold gaskets (fog tested system afterwards with no leaks visible)
replaced all 8 spark plugs, wires, and both coils (old plugs didn't show any extreme color)
compression tested all cylinders and all tested within 10% of each other with no visible leakdown
replaced differential sensor and egr (truck through a code for egr flowing excessively and they were still the oem units, also blew through egr tube and replaced dps rubber hoses)
replaced battery and alternator
cleaned throttle body cleaned what grounds i could easily see.
tested fuel pressure at 64psi when truck was running.
ohmed out the 1st and 4th injector (couldn't reach the injectors under intake) and both tested at 14.4 ohms
measured the header temps coming off the head at each cylinder and the temps were all within 20-40 degrees of each other

i feel the issue is rpm speed related and clears up when i rev the truck up, would this lead me to believe it is a timing issue (cam or crank pos. sensor) and causing this miss?

 

[Sloryd66]

Do you have a good OBDII reader? Be interesting to see some of your live MAF, Spark, O2 and fuel trim data.

 

[The Ranger That Could]

Do you have a good OBDII reader? Be interesting to see some of your live MAF, Spark, O2 and fuel trim data.

I do and can get a pic of the data later, when i viewed it, the new maf had less voltage and less air reading which seemed more accurate over the previous. the o2 sensors oscillated what seemed normal between high and low voltage. the fuel trim correction wasnt too far out of alignment, cant remember exactly what it was but didnt concern me at the time. cant remember my spark advance but will try to get the data captured later

 

[Sloryd66]

Your MAF should read around 2.5 g/s at idle.....i just had an issue where mine was reading too high and adding too much fuel and missed the rule of thumb regarding MAF readings when troubleshooting. It's grams/sec align with the displacement of the engine in liters...so for example a 4.0L should pull around 4 g/s give or take.

 

[ben_2_go]

I'm not telling you this to scare you. I'm telling you this to prepare you for the worst possibility. I had a very similar issue that I could never solve. I used a scan tool and threw many sensors and what not at my truck. I took it into several shops and they did the same thing. I finally found an obscure video on youtube and an obscure post on scannerdanner website that talked about a common problem that is consistently misdiagnosed. After talking to my machine shop, it's a common problem that they see, but goes unreported and misdiagnosed on forums. That problem is receded valves. If you look for a reman head, you won't find one easily. Most chain stores can't get them. Many of the online suppliers rebuild heads but don't understand the receded valve issue and cut the non-receded valve deeper into the head to match. I have run into this problem with one very popular online reman company. I won't call them out here. I've returned a head to them because of this and they refuse to correct it. I know of other people that have had the same issue with rebuilders. The only way to make it right is buy a new head casting and have a machine shop build the head completely new. Don't use any of the old parts. I am currently looking to do this and the cost will be right around $1300 just for the head build.

This is scannerdanners post. Mine got worse than the case he worked on, but it started at a mysterious miss at idle after driving on the highway.

2000 Ford Ranger 2.5L Rough idle, misfires at idle, stalls

2000 Ford Ranger 2.5L Rough idle, misfires at idle, stalls

www.scannerdanner.com

Here is the video that lead me down the path of discovery

 

[Shran]

I'm not telling you this to scare you. I'm telling you this to prepare you for the worst possibility. I had a very similar issue that I could never solve. I used a scan tool and threw many sensors and what not at my truck. I took it into several shops and they did the same thing. I finally found an obscure video on youtube and an obscure post on scannerdanner website that talked about a common problem that is consistently misdiagnosed. After talking to my machine shop, it's a common problem that they see, but goes unreported and misdiagnosed on forums. That problem is receded valves. If you look for a reman head, you won't find one easily. Most chain stores can't get them. Many of the online suppliers rebuild heads but don't understand the receded valve issue and cut the non-receded valve deeper into the head to match. I have run into this problem with one very popular online reman company. I won't call them out here. I've returned a head to them because of this and they refuse to correct it. I know of other people that have had the same issue with rebuilders. The only way to make it right is buy a new head casting and have a machine shop build the head completely new. Don't use any of the old parts. I am currently looking to do this and the cost will be right around $1300 just for the head build.

This is scannerdanners post. Mine got worse than the case he worked on, but it started at a mysterious miss at idle after driving on the highway.

2000 Ford Ranger 2.5L Rough idle, misfires at idle, stalls

2000 Ford Ranger 2.5L Rough idle, misfires at idle, stalls

www.scannerdanner.com

Here is the video that lead me down the path of discovery

I suspect that this is a very common issue on all of the Lima heads. My '88 does it, my old '96 did it, my '94 did it... etc. Never had the heads off any of them but I have ruled out just about everything else.

Where are you finding new head castings at?

 

[ben_2_go]

I suspect that this is a very common issue on all of the Lima heads. My '88 does it, my old '96 did it, my '94 did it... etc. Never had the heads off any of them but I have ruled out just about everything else.

Where are you finding new head castings at?

It is common and commonly misdiagnosed. It happens to most D port heads from 93 on. They have the biggest valves with heaviest valve springs. I haven't heard of it before then but it's roughly the same head machined differently.

They have come down from nearly $600 to less than $400 since I started looking at them earlier this year, when I started suspecting head damage with my truck.

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[Shran]

It is common and commonly misdiagnosed. It happens to most D port heads from 93 on. They have the biggest valves with heaviest valve springs. I haven't heard of it before then but it's roughly the same head machined differently.

They have come down from nearly $600 to less than $400 since I started looking at them earlier this year, when I started suspecting head damage with my truck.

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That's not bad for a new head.

I don't suppose you have seen any new 4 plug heads? That's what I am after, I believe there was some reason why the later heads won't easily replace a 4 plug head aside from the extra four spark plugs.

I had my head gone through at a machine shop about 8 years ago and they said it was fine but I'm skeptical that it actually is. They built me an engine that knocked immediately so I suspect that their attention to things like recessed valves is lacking.

 

[ben_2_go]

That's not bad for a new head.

I don't suppose you have seen any new 4 plug heads? That's what I am after, I believe there was some reason why the later heads won't easily replace a 4 plug head aside from the extra four spark plugs.

I had my head gone through at a machine shop about 8 years ago and they said it was fine but I'm skeptical that it actually is. They built me an engine that knocked immediately so I suspect that their attention to things like recessed valves is lacking.

Yeah, I'd say that shop isn't knowledgeable about these engines. The only 4 valve head that I know that can be made to work is the Volvo head. Modifying it to work is pretty simple. Making the FI and ignition work is a pain. A lot of the 2.3 turbo guys use the Volvo head. I don't think it will make much difference to a non forced induction engine. From my understanding, the later 2.3/2.5 head flows more than enough for a stock engine. If I was building an engine I'd get with Esslinger racing.

 

[Shran]

I just want a stock head. At this point, though, I have been dealing with it running weird for over 8 years, and it's not getting any worse but the truck is falling apart from rust. I'd probably still consider fixing it...even if it cost me a few hundred dollars... chances are pretty good that I could round up another good body or use the engine in something else eventually so not a wasted expense.

 

[scotts90ranger]

For the 8 plug head it's the intake manifolds that mount to them that's the problem, they don't clear a distributor...

 

[ben_2_go]

For the 8 plug head it's the intake manifolds that mount to them that's the problem, they don't clear a distributor...

I've read and watched videos where people change over to distributorless ignition system with Ford EDIS4 using a megajolt ignition controller.

 

[scotts90ranger]

As long as the engine has a computer, adding a '89-94 style crank sensor, DIS module and one or two coil packs (can be ran on 4 plugs no problems...) is a non issue, I'm running a '86 turbo block drilled for the crank sensor, stock Ranger harness repinned for the turbo ECM, DIS module mounted on an aluminum plate that's between the two intake halves running on just the passenger side coil pack... I have the wiring pinout saved somewhere to add it to a TFI engine...

 

[scotts90ranger]

A little more on topic, the Lima heads do like to crack between the valves leaking coolant into the exhaust port, I tried to take a head to a machine shop to get hardened seats put in (didn't like how deep the valves were) but it was cracked if I remember right, I just had my spare head ground I think... I've forgotten a lot of details on the '90 over the years... I'm pretty sure I'm still running my ported head so maybe it wasn't cracked? then what's the head standing in my shed? I'll figure it out one of these days...

my '97 does run a bit rough at times but it seems to have some valvetrain rattle for a couple minutes after startup, I have a feeling the lash adjusters are on their way out... at 180k it might be about time to look into it, I've put almost 40k miles on it in the last couple years...

 

[The Ranger That Could]

sorry for going dark, but finally got back in town and had time to mess with the truck. i unplugged the intake side distributor and the truck misfired like i described before. plugged the distributor back and unplugged the exhaust side and the truck seemingly cleared it self up. thought this was interesting. maybe I have some interference between plugs wires and the distributor with a miss is interfering with the one that isn't. maybe a ground problem? are both distributors timed off the same sensor (crank or cam sensor?)