2.5L ('98-'01) Truck runs like it's cammed intermittently

[bigscrimpin47]

My truck intermittently runs like crap and I have no clue what's going on but I do have a video catching it. I am currently in the process of replacing the valve cover gasket since its leaking oil. I'm also replacing the 2 manifold gaskets, the throttle body gasket, and the IAC gasket, as they all came in the kit. While I have such easy access to the plugs on the driver's side, I am doing all plugs as well since I'm hoping a tune up will fix this. Any input is welcome, I will gladly try any suggestions when I pick back up tomorrow.

 

[RonD]

Welcome to TRS

You have a 2.5l SOHC Lima engine, its a stroked version of the 2.3l Lima first used in 1974 Pinto, and used in Rangers from 1983 thru 1997
2.5l was only used 1998 to mid 2001
Good reliable engine, your 2001 was the last year

It runs Dual spark plugs for extra power, both fire at the same time or there would be no point in using dual spark plugs
So spark misfires would mean BOTH spark plugs in 1 cylinder would have to misfire at the same time on BOTH coil packs
But it can happen if one spark plug fails and you don't notice it.......until the other spark plug also starts to fail, lol

But what you can do, once a year, is to unplug the 3 wire connector on 1 coil pack
Start engine and make sure it idles steady, no steady miss indicating a spark issue, and you can drive it that way, this engine ran fine on 4 spark plugs from 1974 thru 1988(got dual spark plugs in 1989), just had less power

Then switch to other coil pack to make sure other 4 spark plugs are working

That will tell you if there is a spark issue
CEL(check engine light) should come on with one coil pack unplugged, that's OK, it will go off and reset when both are plugged back in again

Yes, vacuum leak can cause high idle and loss of power
Replace PCV Valve as well, should be replaced every 3 to 4 oil changes
Also fuel filter should be changed every 5-7 years

It has a Timing Belt that needs to be changed every 80-100k miles, but no engine damage will occur if it should slip or break, just won't run, lol

 

[bigscrimpin47]

Welcome to TRS

You have a 2.5l SOHC Lima engine, its a stroked version of the 2.3l Lima first used in 1974 Pinto, and used in Rangers from 1983 thru 1997
2.5l was only used 1998 to mid 2001
Good reliable engine, your 2001 was the last year

It runs Dual spark plugs for extra power, both fire at the same time or there would be no point in using dual spark plugs
So spark misfires would mean BOTH spark plugs in 1 cylinder would have to misfire at the same time on BOTH coil packs
But it can happen if one spark plug fails and you don't notice it.......until the other spark plug also starts to fail, lol

But what you can do, once a year, is to unplug the 3 wire connector on 1 coil pack
Start engine and make sure it idles steady, no steady miss indicating a spark issue, and you can drive it that way, this engine ran fine on 4 spark plugs from 1974 thru 1988(got dual spark plugs in 1989), just had less power

Then switch to other coil pack to make sure other 4 spark plugs are working

That will tell you if there is a spark issue
CEL(check engine light) should come on with one coil pack unplugged, that's OK, it will go off and reset when both are plugged back in again

Yes, vacuum leak can cause high idle and loss of power
Replace PCV Valve as well, should be replaced every 3 to 4 oil changes
Also fuel filter should be changed every 5-7 years

It has a Timing Belt that needs to be changed every 80-100k miles, but no engine damage will occur if it should slip or break, just won't run, lol

Thank you for the welcome! I will try this once my plug wires get in tomorrow and I can put everything back together. The PCV valve is good according to my dad "if it rattles when you shake it, its fine" so I left that. As far as the fuel filter, I'm not sure it has ever been replaced in the lifetime of the truck, so I'll shoot one of those in there. I have already had the timing belt go a while ago, so I hope I don't need to worry about that for a while lol. I will make sure to report back when my plug wires get in and everything is up and running.

 

[bigscrimpin47]

Hey I'm back. Just got everything all cleaned up and I am in for the night (8:18 pm). My plug wires took longer than expected to get here (6 pm) but I got everything put back together with no bolts to spare! The truck sounds great after the fuel filter, cleaning the throttle body and intake manifold, and the new plugs and wires. That is, when it isn't doing its weird stumble still. I am also noticing a new sound in my exhaust that I think has been there since before all the work. The sound is some sort of quiet pops but doesn't trigger a CEL. I did take a video of the exhaust but its kind of hard to hear it over my dad and I talking haha. Any ideas of things to check/test are appreciated
Edit: I forgot to mention, I didn't try unplugging one of the coils, but I will try that tomorrow.

 

[RonD]

Check the coil pack firing orders, easy to mis-wire that

diagram here: https://www.justanswer.com/uploads/crzydrvr00/2008-06-08_020732_92714683.gif

 

[bigscrimpin47]

Check the coil pack firing orders, easy to mis-wire that

diagram here: https://www.justanswer.com/uploads/crzydrvr00/2008-06-08_020732_92714683.gif

I used that exact one! I am about 99.99% I got it all wired up right, but I will double check that in the morning.

 

[RonD]

Firing order is the one thing all gasoline engine mechanics have in common
All have messed it up and all would swear it was fine, BEFORE they found it wasn't fine

 

[bobbywalter]

Almost sounds like canister purge line is open pulling air.... or egr

 

[bigscrimpin47]

Firing order is the one thing all gasoline engine mechanics have in common
All have messed it up and all would swear it was fine, BEFORE they found it wasn't fine

Double checked the firing order, all is well. I let it idle for a bit to re learn the computer, and its running fantastically. I does however still have its intermittent weird chop. I tried the coil pack test you suggested and it persisted through that on both coils (caught a long one) but cleared and theoretically runs fine like you suggested, leading me to not suspect the coils or anything spark.

Almost sounds like canister purge line is open pulling air.... or egr

How could I test these? pulling off the vacuum lines and plugging them?

 

[bigscrimpin47]

Update: I visited my dad's mechanic (friendly visit) and asked him about it, he thinks it's the valve seats or something and that my engine runs fantastically for 22 years old with 160k miles. So basically, id have to rebuild my engine if I actually want to get this fixed. Before anyone sees this and says "he just wants to charge you for that" he's done doing repair work. He started doing only custom suspension stuff because that's more sustainable for him, so its not that.

 

[RonD]

You don't have to rebuild the engine at 160k miles, the lower end should last to 300k+, my 1994 4.0l is at 400k
The head can be removed and rebuilt without removing the engine

You can get a rebuilt head and do the swap on a weekend, then return the old head for core charge
Or pull your head and take it to a local machine shop for a valve job, expect two week turn around but less cost

A compression test can confirm leaking valves or failing rings, for sure
Failing rings would require a full engine rebuild but not at all common on engines built after 1985 or so, almost unheard of under 300K miles

Burnt exhaust valves are not common but expected on any engine with valves, lol
That's why most people have heard of a "Valve Job", there many reasons for valves to fail, and it can happen at anytime not specifically related to miles

 

[bigscrimpin47]

You don't have to rebuild the engine at 160k miles, the lower end should last to 300k+, my 1994 4.0l is at 400k
The head can be removed and rebuilt without removing the engine

You can get a rebuilt head and do the swap on a weekend, then return the old head for core charge
Or pull your head and take it to a local machine shop for a valve job, expect two week turn around but less cost

A compression test can confirm leaking valves or failing rings, for sure
Failing rings would require a full engine rebuild but not at all common on engines built after 1985 or so, almost unheard of under 300K miles

Burnt exhaust valves are not common but expected on any engine with valves, lol
That's why most people have heard of a "Valve Job", there many reasons for valves to fail, and it can happen at anytime not specifically related to miles

I would hope to not need to rebuild the whole thing, I will try to find my next longer weekend and talk to my sister to figure out some carpool situation for the downtime. The way he made it sound i was thinking it would be a "while you're in there" thing. I'll definitely call around and try to find a machine shop that would work on it.