So I made a post awhile back about my Stick Shift 97 Ranger and got little help on because they kept pointing me in a direction that I already knew was not the culprit.

Anyways here's my problem(s).... I have been trying to track down my misfire codes since I got the truck but the computer has misfire codes for cylinders 1, 4, and 6. I've done some tests and I tried the dollar bill trick on the exhaust and it hardly ever gets sucked into the pipe but it's obvious some misfires but they're subtle misses not like a dead miss. The idle is also rough on top of that and the idle controller is compensating for something in the motor because it loves to idle at 1300rpm and slowly go down to normal warm idle when I come to a stop light or a stop. Power seems lacking for boasting 180bhp in a 3400lbs truck it's not as quick as one would expect. Ignition system is brand knew from coil and up so it's not ignition from coil and up and yes all my wires are correct and I know this for a fact. There is some back fire in the intake manifold if I hit rev limit both with and without clutch pushed in neutral (fun fact: redline is only 5 grand compared to 5600rpm when clutch is pressed) I've done a compression test and from what I remember every cylinder was 130psi plus but I don't think compression was above 160psi on any of the cylinders but they were all withing 5 psi of each other so I've ruled out compression being the soul culprit of the misfires. I'm 90% it is not fuel related because I've checked all the injectors and none are leaking or clogged. This is leaving the last option needed for combustion left which air and my father swears on it that my timing chain is going bad and I'm really hoping it's not because I'm not about to go a couple days without mode of transportation.... I have not tested the play of the chain using the distributor way because it doesn't have a distributor and I can't pull off the valve covers without taking half the engine off first.

I know this is alot of info but it's my last ditch effort to see if its anything else besides the timing chain...

Payton

 

1995 and up Rangers, and most other vehicles, will hold RPMs above 1,000 until speedometer is under 5MPH, it an emissions thing, 1,300rpm sounds high for fully warmed up engine, but not cold engine it should idle at 1,000-1,300 in Choke Mode
It should also hold idle high when shifting in a manual trans Ranger

What were the misfire codes?
Are they all P030X
Or any P1XXX?

1997 4.0l OHV is rated as 160HP and is a strong engine, with good torque
Best power/torque is at 2.400rpm
Highest horse power at 4,200rpm

130psi compression is too low, 4.0l OHV runs 9.0:1 ratio so new it would be 160-165psi, higher miles 150-155psi, my 1994 4.0l is still 155psi at 300k
But could just be compression gauge isn't reading correctly, the important thing on a compression test is that all were close in PSI

Never heard of timing chain issue with a 4.0l OHV but they do run a tensioner which I guess could start to fail

A Vacuum gauge test would be good to do, that can tell you if compression is low and when most misfires are occurring
Also tells you of valve issues partially blocked exhaust and a host of other internal issues
Any piston engine is just a self power air pump, and best was to test any pump is with a pressure gauge, in this case a negative pressure gauge


Misfires are detected by the Crank position sensor and the Cam Position Sensor, each cylinder will add spin/power to the crank shaft, and the cam shaft, when it fires correctly
So the computer times each cylinders "power adding" ability
If a single cylinder produces less spin or no added spin, repeatedly, computer will set a P030X code for that cylinder

There are only 3 coils in the coil pack, each coil fires 2 spark plugs
3/4
2/6
1/5
front

Those are the match sets of spark plugs that fire at the same time, the 5 6 4 side can get mixed up, on the coil pack or at the cylinders, triple check those
4.0l OHV eats spark plugs
And needs a big gap. 0.054
Motorcraft lasts the longest, then Autolite, have had OK luck with NGK, if first 2 aren't available

Only use regular copper or Double Platinum spark plugs, Single platinum are a waste of money as 3 spark plugs will wear out the same as regular copper, because of the dual spark setup

The coil packs seem to last on these engines, my 1994 is original, but I did change spark plug wire after 18 years and it did clean up my idle misfires, lol
Since all 3 coils would have to be effected for the 1 4 6 misfires I wouldn't think coil pack issue



MAF sensor causes bogging and hesitation in the 4.0l OHV, so misfires, clean it once a year

After engine is fully warmed up and idling unplug the IAC Valve's 2 wire connector
RPMs should drop to 500 or engine may even stall, either is GOOD, it means no vacuum leaks

If idle doesn't drop then there are some leaks

If its fuel related you would usually get pinging/knocking during acceleration, a lean mix, which you don't mention
Back firing is the unburned fuel from a misfire being ignited in the HOT exhaust manifold, since there is usually a crossover when exhaust valve and intake valve are both slightly open you can see this in the intake some times

 

All the misfire codes are P030X. I'll have to check the plugs tmrw and I go to a trade school for Auto tech so since I don't personally have a vacuum Gage my school will most likely have one I can use so I'll get back to u on that one. I don't know much about vacuum readings but I'll report back in a reply tmrw or if not tmrw sometime latter this week if I can't get my truck into lab. I did do the unplugging the IAC and rpm does drop and stalls the engine. If anything it's not running lean it would be running rich because it used to run very rich but I replaced the DPFE and that solved that problem. I didn't know it would hold that idle rpm during shifts so thank u on that part. When the motor is cold it does seem to have more power but it could be my butt Dyno just isn't that accurate. I think I addressed everything u have said so I will get back to u with the vacuum readings and such

 

I like this article on using a vacuum gauge on gasoline engines: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine

Its how I learned it 50 years ago, lol, and its still exactly the same now, they can add all the electronics they want to the outside, but its still just a self power air pump
Still one of the best diagnostic tools you can get for any price, but they are only $20

 

Okay so a couple days have passed and I replaced the plugs and erased the codes, well the check engine light came back on and no longer had the other misfires besides cylinder 1 which I have had since I bought the truck but it gave me a P0133 code saying slow response on the O2 sensor for bank 1 and it ran worse than it did before and I thought maybe it's something with the memory or something and I erased it again and now I have a P0107 code for bank 2 too lean and I just replaced my bank 2 sensor. I havnt ran a vacuum test, I'm bringing it into my shop on Friday to perform that test

 

Just a heads up
I do this all the time with the 4.0l and 3.0l, coil pack spark plug firing order GOOF

3 4
2 6
1 5
front

The 5 6 4 side gets me quite often, either at the spark plugs or on the coil pack
I would bet money that I did it right "this time" ..........................and I would lose that money, lol