hello im new to the forums and i have a 1998 ford ranger 2.5l automatic and im currently having some issues with a rough idle and when accelarating it seems very bogged down. also around 50mph it seems to really be working overtime. Im not very educated about cars and working on them but very willing to learn. ive replaced the sparkplugs, Egr
i purchased a fuel pump because i thought that was the issue but i had a friend take a look at it said he doesnt think thats what it is. i thought maybe crankshaft sensor or cmp sensor and synchronizer.
i checked the firing order and that was ok and i also checked the fuel injectors and they were good aswell. not really sure what direction i should go and also theres no check engine light

 

Welcome to the forum

You have a dual spark plug setup, so first thing to check is if all 8 spark plugs are working, its easy

Each coil pack has a 3 wire connector
Unplug one of them and pull back connector far enough so it can't arc to coil
Start engine
Should idle OK, no steady misfire, if it has a steady misfire then a plug or wire is bad

Now do the same with other coil pack
If it runs the same with either coil pack unplugged then this takes spark off the table as the reason behind rough idle and low power

The 2.3l/2.5l Lima engines ran just fine from 1974 thru 1988 with just the 4 spark plugs
Dual spark was added for a bit more power, no other reason, so both spark plugs fire at the same time regardless of what you might have read

Down side of dual spark plugs is you can't tell when 1 spark plug is not working, because other spark plug prevents misfire, lol
So you should do the above test once a year
And you can drive it this way, 1 coil pack and 4 spark plugs, just has slightly less power


As for the low power when was timing belt last changed?
Needs to be done every 80k miles, if timing belt gets old it stretches and that lowers compression which lowers power
You can test compression, expected is 160-170 PSI

Crank sensor no, engine wouldn't start
Cam sensor maybe but there would be a code set and CEL(check engine light) would be on
Synchronizer is on V6 or V8 engines

Computer monitors sensors so sets codes if they fail or are out of range
Low fuel pressure will set Lean Code

MAF sensor can get dirty and not set a code, easy to clean these


Clogged exhaust system limits power, and doesn't set codes
Can use a vacuum gauge to test for that

 

i checked the coils and they are all good and the sparkplugs were recently replaced, timing belt was replaced about 30,000 miles ago, im gonna check the MAF and i have check engine light now but no code for cam

 

Whats the exact code or codes?

Did you check the coils and spark plugs as described above, if not then they were not tested, just FYI

 

My 98 2.5 liter has a lope at idle and runs real poor like I’m bogging down, but every once and awhile it’ll run like a champion. I’ve replaced everything on air intake side and spark wise. It has a new fuel filter. I’m just tired of replacing stuff and it not being fixed. Any suggestions will be appreciated.

 

You will need to do some tests or you will just keep throwing money/parts at it

Get a $15 Bluetooth OBD2 reader(elm327 is fine), works on ANY vehicle 1996 or later, not a Ford thing, ANY vehicle, it was required by Law in 1996, still required in 2022
You can see Live data while driving or idling,YOU SEE what the computer sees from all the sensors and controls
Also reads and clears codes of course
APPs are FREE, torque lite is a good one, once you get used to using it the torque pro for $5

While you are waiting, do a compression test, all 4 cylinders
Pull out 1 spark plug from each cylinder before the test
Then test 1 at a time and write it down
Expected average on a 2.5l is 165-170psi
Under 140psi means timing belt may be stretched, needs to be replaced every 80-100k miles

EVERYTHING comes down to compression, which is why its good to start there, its mechanical, so good or bad, no maybe's about it, like fuel or spark
If compression is bad then its a waste of time and money to look at other fixes
If compression is good you can move on to fuel and spark(computer stuff) which is what the Bluetooth reader is for

You do have Dual spark plugs for better power, but this 4cyl Lima engine can run just fine with 4 spark plugs
So as a test, once a year, starting now, unplug the 3 wire connector on either coil pack, so disable the 4 spark plugs on that pack
Start engine, CEL(check engine light) should come on, thats OK
Engine should not be misfiring, you can drive it to make sure
If there is a steady misfire then one of the spark plugs, or more, on the working coil pack is bad, or miswired

Now swap it around and test the other coil pack and its 4 spark plugs
Dual plugs are great but....................you can never tell when just one spark plug is bad, BOTH spark plugs in one cylinder need to fail to notice it
So do the test once a year

This 4 cylinder Lima engine was used with just 4 spark plugs and distributor from 1974 thru 1988, so it runs just fine on 4 working spark plugs, but better power with 8

After engine is warmed up and idling, unplug the 2 wire connector on IAC Valve
Engine RPMs should drop to 500rpms, barely running or engine may stall, either is GOOD, it means no vacuum leaks
IAC Valve needs to be Motorcraft or Hitachi brand, 3rd party won't work well on Fords, so just a heads up if you have changed it
Better to get a 30 year OLD Motorcraft IAC Valve from wrecking yard than a brand new 3rd party Valve

 

++++++++++++++++++++++++++++++++
Hey Ron,

I've been battling an odd issue and would appreciate your input:

Driving my 1998 2.5L Ranger to work and about 1mile after filling my tank it started misfiring very badly. (no CEL)... was barely able to get it back home.
(note: i had installed new coils, plugs, wires, and fuel filter 4 months prior to this happening)

- I pulled engine codes. there were no active faults but P0303 & P0304 were pending (cyl 3&4 misfires)
- Replaced all fuel injectors as truck has 350k miles and these have never been replaced. Old ones tested ok electrically but spray patterns were vary bad and cleaning did not help. This allowed the engine to run a bit better for trouble shooting below.
- Checked compression on cylinders: all were 140psi range. These readings are likely a bit low cuz i was not able to get a wrench on the gage fitting and it was barely finger tight. I can retake these when i get a wrench but I think compression is OK
- Checked ignition i found coil 2 (exhaust side) signals from PCM were not working. one was 100% high and one was 100% low. I found the transistors firing these signals in the PCM were bad. Got replacement PCM and resolved this issue. Verified all coil signals working properly
- Further ignition checks: with engine running i would remove signal cable from one coil at a time, engine ran same with either coil plugged in.
*** With only one coil plugged in, I removed spark plug wires one at a time. Did this for each coil. In both cases, all wires were sparking well. However removing #3 and #4 from either coil had no impact to the engine performance. Jives with original engine codes 3&4 misfire.

Appreciate your thoughts on next step. Points to fuel issue but seems unlikely given new injectors and new PCM unless #3 and #4 injectors have harness issues?

Really appreciate your insight.

 

You should have started your own thread, its free, lol

Poor running after adding gasoline to the tank can mean you got some bad gas(gasoline with extra water in it)
Water is heavier than gasoline so sinks to bottom of gas tank where fuel pump sucks it in
When this happens you can add a can of HEET or Octane boost which is mostly ethanol, ethanol can bond with water in a fuel system allowing it to pass thru the engine without causing misfires

Good test on running engine on each coil pack separately, these engines ran on just 4 spark plugs and distributor from 1974 thru 1988 just fine
The extra spark plugs are there for added power, 1989-2001

You have a Waste Spark system so pulling one spark plug wire may not disable that spark plug, just FYI, not really a good test on this type of system
Each coil pack has only 2 coils, the Spark plugs are in Matched Pairs, 1/4 and 2/3, each pair is on one coil, both spark plugs in that pair fire at the same time
One sparks center to tip(normal) the other sparks tip to center(reverse), so they are wired in Series
So if you pull one spark plug wire on the pair you would disable BOTH spark plugs, or neither spark plug, depending on Series wiring

Misfire codes are not generated by spark, the Cam sensor is used to time power added when a cylinder fires, or no power added when it misfires

Misfire is caused by spark, fuel or compression
If compression is equal across all 4 cylinders and engine runs then its not a compression issue, but Equal is the bigger deal than high number, if 3 and 4 were slightly less than 1 and 2 then that would be an indicator that you need to investigate more on compression

I have found an old timing light to be good for spark testing, inductance type with clamp on for spark plug wire, find them at garage sales for $1 to $5, lol
Test each wire for steady strobe flashing at varying RPMs, its very obvious if its not steady, missing a beat or two now and then

Fuel is harder because its not an on off thing, like spark or compression
There is the mix ratio and the fuel "quality" and the pressure which effects ratio, and in the case of injectors the spray or drip factor
But if you eliminate compression and spark as the cause of a misfire then fuel would be the issue

Couple of other things can effect engine operation
Vacuum, get a vacuum gauge, under $15 usually
Warmed up engine
Steady needle at 18-21" at idle is what you should see, lower could mean vacuum leak, PCV Valve or brake booster
Blip the throttle, i.e. open it wide then release it, let it snap closed
Should see drop to under 2" then a jump up to above 25"
If its slow to come back up then clogged exhaust
Or if it doesn't drop quickly to under 2" then clogged air intake

Google: engine vacuum testing
Loads of tests and diagnostics can be done

 

Thanks for the reply Ron.

To be clear on my ignition test: I was running one coil only, pulling both #3 and #4 plug wires simultaneously did not change the performance. This was same behavior on both coils.
I did add heet to the fuel and let it idle for 30min. But Ill drain some fuel put and physically examine it for water to be thorough. The performance degradation is very consistent so it did not seem like water in fuel type of issue.

Thanks,
Mark

 

And running one coil pack only did not seem to be having a misfire?
You can drive it that way to see if it misfires under load

 

It is consistently mis-firing through all of these tests.
Replacing the fuel injectors and PCM improved the roughness but the main issue is persisting.

I very much appreciate your feedback. Once I investigate your suggestions I'll provide more info.

Thanks,
Mark

 

I miss that part, I read it ran fine with either coil pack

If same cylinders misfire on either coil pack its not spark related unless coils are mis-wired
As said 2 coils in a coil pack and each fires 2 spark plugs
They are 1 and 4 on one coil and 2 and 3 on the other
These coil pack are divided in half at the 3 wire connector
1.......2
4.......3
..../\
Connector

seen here: https://www.route66hotrodhigh.com/im.../CoilPack2.jpg

As seen in picture 1 and 4 can be swapped, doesn't matter since both spark at the same time, as can 2 and 3 their position doesn't matter
Only that both are on the right coil in the coil pack
With 3 wire connector at the bottom
1 and 4 on the left
2 and 3 on the right

 

OK. Sorry it took me so long to get an update posted but I had not been able to work on the truck until this past weekend. Great news I got my Ranger running great and back on the road.


I purchased a vacuum tester and found my vacuum to be about 25% too low. Embarrassingly I immediately found that the issue to be the PCV valve was completely out of the engine!
I do not see how this could have been my original issue as I see no feasible way this could have come out while driving.
I think I inadvertently pulled it out when I was replacing the injectors. I think I fixed the original problem when I replaced the PCM. I know my old PCM was not firing the exhaust side coil. It likely had another issue that I did not root cause. I think the injectors needed to be replaced as they were original but doubtful they were the primary issue.
This is why it ran better after replacing the injectors and PCM but still rough leading me to believe I had not fixed the original issue.

Lesson learned next time I have the intake manifold off.

Ron thanks for your feedback. My red Ranger is 25yrs old this yr and I plan on driving it at least a couple more yrs!