Recently bought a 96 4 cylinder 5speed 2wd ranger. 200xxx miles on it and its former owner had a young guy change spark plugs . Truck ran fine before ,but after is when the rough running showed up.
A quick check of the plug wires and there locations looked correct and also tested the wires for spark with a timing light attached to them, checked shows all are firing.
Seems to smooth out a bit when rpm's are raised up, but still acts like not running smooth.
I swapped out plugs. Looks like they haven't been changed in a looong time .Some of the straps are burnt and are shorter than they should be, but still runs rough, very little improvement .
Check vacuum lines for leaks/breaks and all looked good. removed line off brake booster and plugged, didn't matter.
It doesnt throw and check engine lights. It does smooth out some as the rpm's rise, but still not smooth .

Anybody run across something like this???



Thanks

 

You've been busy on your trouble shoot.

I'm not clear on your post about the plugs. You say a young guy changed plugs & afterward it began to run rough, you've swapped out plugs & they look like they haven't been changed in a long time???? So, how long ago did the young guy replace the plugs, what brand was used & did you replace All of the plugs, or just a few???

Our engines are kinda persnickety about plug design, so, did you set the spark gap to spec & replace All of the plugs with the Specified design & heat range, preferably Motorcraft, or Autolite plugs, torqued to spec & if you don't know if the plug wires have ever been changed, did you replace them with Motorcraft or the like & route them as the factory did, using All of the wire looms & stand-offs, as with the 200K+ miles on them, they've lived two lifetimes & with the voltage they carry, we need to pay attention to the wire quality & routing. So at this point, plugs & wires still belong on your suspect list.

 

seller claimed had changed them recently and ran poorly after that and then didn't drive it after that.
Found Champion RS14 YC plugs in it. Of the 8 only 2 looked to be newer.
Replaced them with motorcraft AGSF32 FM plugs.
Stopped today and picked up some wires from NAPA and fuel and air filters too.
Thanks for the reply!!!

 

If you don't have an idea where the vehicle is on all past & present due scheduled maintenance, probably a good idea to begin with the plugs, wires, filters, fluids, O2 sensors & you seem to have a good start by using the Motorcraft plugs & wires. Our waste spark ignition needs the double platinum, or finewire iridium enhanced center electrode with platinum pad side wire plug design, to slow plug gap erosion, & plug wires that can tolerate the double work load the waste spark ignition puts on them. I enjoy faster year round starts with the fine wire plugs.

Use a wire gauge to slowly sneak up on the specified plug gap & don't pull/force it through too tight a gap, so as not to damage the fine wire center electrode or platinum pad on the side wire. I set mine to the low side of gap spec, as its always opening up, so spark gap stays in spec longer & it'll help with cold starts & will have the effect of a slight spark advance.

Apply a little nickel anti-seize compound on the plug threads & torque them to the low side of spec, to allow for the anti-seize lube effect & not over tighten & mess with plug gap, or damage the head threads.

Consider applying a thin film of good quality di-electric grease to the plugs external ceramic insulator & inside the plug wire boots on both ends, to prevent flashover on dewy morning starts, or wet rainy days. Also makes it easier to remove the plug wires later. Be sure to run the plug wires one at a time so you don't get them mixed up, exactly as the factory had them, using All of the wire looms & stand-offs.

Have the computer scanned for trouble codes, especially if the CEL is lit, as they can offer up good trouble shooting clues.

More thoughts for consideration, keep us posted on your trouble shoot.

 

changed the plugs and wires as suggested, also used the di-electric grease .seems to run better ,but not normal.
Now has code P1506 which was idle air solenoid, which just replaced it, but didn't seem to change anything.

Seems to be running overly rich. Does run out and drive decent, which is a good thing being this is it first drive for us.

Thanks for your help

 

After replacing the IAC, did you disconnect the battery B- cable for say 15 min, to wipe the KAM & then perform the cold & warm idle relearn strategy routine????
If not, have a read here on how to do it & let us know how it goes. https://www.ford-trucks.com/forums/s...9&postcount=12

 

On it seeming to be running rich, have the O2 sensors ever been replaced???? If not, they've live two lifetimes too & their switching speed & range slows with age. If you have access to a scan tool, monitor their switching speed & range & the short & long term fuel trim numbers. If you have O2 sensor, or mixture trouble codes, they belong on your trouble shooting suspect/maintenance list.

Post All trouble code Numbers you have. If you don't have a code reader, or scan tool, most auto parts stores will scan the computer for trouble codes at no cost, if the CEL is lit, some will do it if your having problems & the CEL isn't lit, as you could have "pending" codes stored that haven't happened often enough to have the computer turn the CEL on.

 

pawpaw,
ThankYou for your advice with us on this journey.

Son changed out the o2 sensor (1 on the head pipe off the exh. manifold) today & didn't seem to change much . We checked the timing and it was off it's marks and is now corrected.
Runs alittle smoother, but at times the idle searches around and when does go steady it's alittle high, doesn't have a tach but would est. it at 1200 rpm. Could the idle/air solenoid still be learning? Has been driven maybe 300' since beening changed.
Put the timing light on it and came in at 23*.
It got a cel now & don't have a scan tool, but will stop back @ the parts store for another scan.

Feel like we made headway today.
Many thanks again!!!!

 

Did you disconnect the battery to wipe the KAM, after replacing the O2 & IAC???? If so, the engine needs to be run until it fully warms up, with no electrical or mechanical loads on it, so the computer can relearn its cold & warm idle. The idle relearn link I posted above is for an auto tranny & I just noticed you have the 5spd manual tranny, so with a manual you don't need to shift, just let the engine idle without any electrical or mechanical loads, like turning the steering wheel which has the power steering pump load the engine, or turning any lights or other heavy electrical loads on, so it can relearn its cold & warm idle without any engine loading.

Disconnecting the battery also wipes the fuel trim tables, so after doing the idle relearn, it'll need to be driven on the road & in town some as you normally would, while the computer rebuilds the fuel trim tables.

Another thing that can affect idle is a vacuum leak & with the mileage on this puppy, the PCV valve & its rubber elbow belong on the maintenance/suspect list, as they're way past due for replacement & a leaking PCV elbow, which is common, or sticking open PCV valve, will cause an unmetered vacuum leak & that can mess with fuel trim & idle quality & speed & if its a bad enough leak, the computer might not be able to use the IAC to compensate idle for the unmetered vacuum leak.

Of course rubber vacuum lines & their connections, or intake manifold gaskets belong on your maintenance/inspection list, as they can corrupt idle quality.

With the mileage on this ride & not knowing the past maintenance history, it was probably a good scheduled maintenance idea to replace the O2 sensor.

 

We had the battery cable off and did a restart and then let it run until came up to operating temps w/o any accessories running.

I replaced the pcv valve and inspected its vacuum line and seal.
Added some Berryman injection cleaner to a 1/4 tank of fuel and headed out on the road.
It had set the cel light again ,so first stop was the parts store for a scan.
Had a P1506 code again.
trucks runs decent once out of the idle range. Seems to pull up through the rpm range decent and has ok power. At 65 on the road in 5th gear with the go pedal to the wood it's still seems to pull its self with speed climbing up.

Came back home and removed air/idle valve and check passages in the t.b. and seemed clean and clear, also sprayed carb. cleaner in them while its apart.
Checked vacuum lines again and plugged several, hoping idle quality would improve.
On thing noticed on the drive is that with the vent on (non a/c truck) that when you go the full throttle that the upper vents would switch to just the defrost vent and would return after getting out of wide open.

Used a mini vacuum pump to check it from under the hood- would hold for awhile then go to 0.
Ran vacuum check from the intake line that goes to the egr valve and over to a solenoid/valve on the passenger side near the #2 cyllinder. It didn't hold vacuum long at all with the 3 ports plugged off.

I guess what i was trying to do is plug all the vacuum lines to see if have a leak in them.

Tried fuel pressure gauge while at the parts store, but the schader valve adapter was messed up and won't work.

Try another this week to check it also

Sorry for the long post