I recently purchased a 1991 Ranger with a 3.0 in it, that had been owned by a kid and not surprisingly, has been driven hard and put away wet too many times. It has taken me two months so far to get the bugs ironed out and I had it running pretty good until today when a new set of double plat sparkplugs were installed to replace the "Autolite" ones that have probably been in since day one.
I have been replacing whatever needs replacing, 1 item at a time with the idea that I would be better able to undo something if the trucks drivability takes a sudden dive after being worked on.
I have never had a problem with this trucks acceleration ability in pretty much any gear ( ok so it doesn't like pulling a hill in 5th, I can live with shifting down a gear...) I have always been able to step on the gas or let off the gas without any hesitations or bucking and hiccupping like it wanted to flood out of choke off. The ONLY thing that was done was changing out the plugs! I disconnected the battery for a short while and then took it for a drive after hooking it up again. The darned thing can hardly push itself from a standstill now and I can only get it to run if the accelerator is mashed full throttle to the floorboards. It takes forever to get it to come up to 1/2 highway speed but it will idle smoothly and it starts as it normally has, without much hassle.
I will check for codes in the morning as the check engine light actually came on during the test run. Is it possible the computer resetting caused the problem? All the plug wires are on snug and I've checked and rechecked everything else that might be loose or disconnected, don't see anything obvious.
Prior to the new plugs I had NO problems with the trucks performance, the new plugs were put in simply because none have been installed for at least a decade. Oil was changed w/ new filter recently, a new MAF was put on and new TBS was also installed. Every little item has given the little Banana boat a little more energy and this fix has me at a loss. Does anyone have any suggestions I can try to restore my lost power?
I'm up too late writing this and I'm sure I should be offering more details about my set-up, but they are eluding me at the moment. If you need to know something specific, just ask and I will respond as quick as possible... This is my daily driver that I am stuck depending on to get me to my job until my Bronco rebuild is complete... I need advice from the experts I refuse to let a Stealership have a look at it, I am not feeling I need to finance their kids college tuition over this truck.
Thanks a bunch!

 

Check for a vacuum leak. sometimes at idle it will act fine. But drive it and its sucking way too much air.

 

Welcome to FTE. You've been busy on this one!!!!

Seeing as how you now have a CEL lit, scan the computer for trouble codes & post All code Numbers, as they can provide good trouble shooting clues.

Seeing as how you didn't have the problem Before the spark plug replacement, revisit that area to see if maybe you have a couple of plug wires crossed, or maybe accidently disconnected a vacuum line, as has been suggested.

Using a torque wrench, did you tighten/torque the plugs in to spec????
Our engines are kinda persnickety about spark plugs, so what brand plugs were installed & did you check/set the proper spark gap with a wire gauge & without dirtying/marking up, or cracking the internal & external insulators?????

 

You really need the DTC codes since you have the check engine light to narrow your problem down. I would suspect if the wires were not replaced and they are old they might have suffered damage pulling them for sparkplug replacement or a wire crossed as PAWPAW stated.

 

First of all, thank you folks for taking the time to try and help me with my `91 Ranger, I will refer to her as the Banana. It's more interesting to give these enigmas some sort of personality and my Ranger is very banana-ish in pretty much every way.
Merace, I can't help but feel like there has to be some sort of vacuum leak happening but it isn't consistant and nothing seems to be amiss that I have found so far. I hate to just start throwing new parts at a problem hoping to eventually nail it down. It can start getting costly in a hurry! Is it a possibility that the MAF can be a dud? I replaced the old one about 30 days ago and the Bananas idle did come down nicely.
PawPaw, I was hoping to treat the Banana to some new sparkplugs and try to squeeze a little more energy out of her. Off the line it almost feels like I should stick a foot out of the door and help get her rolling but once I manage to get up to highway speed the Banana cruises along in 5th real nice. The slightest incline will start bogging down and dropping a gear, naturally is all I need to do.
I did NOT replace the plug wires or cap & rotor this last time. I like to be able to back things up if the repairs suddenly go south like they have with new plugs. I replaced the old Autolite 104 plugs with Autolite AP 105 plugs after a Napa parts person deemed them to be the next best thing to sex for the Banana's get up and go. So far ... I'm pretty sure the Banana doesn't agree, maybe the Napa guy should have sent flowers first... hmmms
Yes, yes and absolutely to your questions re: torque, setting and checking gap and gently cozying the plugs into place. I try not to she-ra replacement parts when I am trying to get things to run. It's just counter productive to have to replace the replacement parts because of sheer stupidity. I can say I know this from "personal experiences" that were epic failures along the way... (Has anyone else had to head BACK to Napa for a 3rd front main seal? I swear the Napa guy sabatoged me...)
I ran a quick koeo test just to see if any code happened to be lurking and it gave me a 67... WTH? Ran again and still 67... Now I am totally head scratching as the Banana doesn't even have A/C Monday must stop into someplace who will run a proper test and see what codes they can pull...

 

OK, good feedback, so messed up plugs from gapping, or over torque, isn't likely, so lets think about this some more. A number of things can cause a loss of power.

Weak spark, low fuel pressure, or low flow fuel volume over time from a clogged fuel filter, weak fuel pump, or acting out fuel rail mounted fuel pressure regulator, or crimped fuel line, or return line, messed up MAF sensor, worn out O2 sensors, clogged air filter, messed up AIT or engine coolant temp sensors, acting out TPS, so without some trouble codes for clues, you have to go on the clues you have, or begin a systematic trouble shooting check of a number of things, which can be time consuming without the aid of a scantool, which can read sensor PIDs & trouble codes in real time as the engine is running, or while the vehicle is being driven.

SO, lets continue with what you know. The single platinum plug you used is the proper design & heat range for your engine.
But, seeing as how the problem didn't come about until After the plugs were installed, you could still have a defective plug internally, if Murphys Law is messing with you????!!!! lol

Agree the 67 trouble code doesn't seem to apply in your case, Unless you mis read the flash code by one, which would give you a 66 code & thats for the MAF sensor, which would fit your lack of power symptom, as the MAF sensor is measuring air flow into the engine for the computer, so if its PID to the computer is corrupt, it'll cause the computer to mess up the fuel trim/air/fuel ratio & that sure can affect engine power.
So maybe revisit pulling the code a third time to make absolutely sure its a 67, which doesn't fit your non AC equipped vehicle.

If the code turns out to be a 66/MAF sensor code, back probe the MAF connector to make sure its getting the proper operating Ref voltage to it from the computer.
Was this replaced MAF sensor a new one, or a remanufactured one & why was the old one replaced?????

As bratman2 has suggested, since the plug wires haven't been replaced & you think maybe like the plugs, for at least 10 years, by all means add them to your suspect list, as one or more may have given up the ghost by being flexed on removal or re-installation.

SO, to check them, maybe disconnect the plug wires one at a time & measure their end to end resistance with your multimeter & while flexing both plug wire connectors, the reading should be steady. End to end resistance should be about 1000 ohms/inch of wire length, 30,000 ohms max, no matter the length.

If you come to suspect the plug wires, or just want to replace them because of service life, Autolite has a rebate/special on theirs & you can come by an online discount code from Advance Auto that can knock off 20-40% of the cost, depending on how much your buying in parts. If your going to do the plug wires, I'd also consider replacing the distributor cap & rotor too, if they haven't been replaced lately, or are showing corrosion or wear signs, as excessive gap there will weaken the spark.

A bunch more thoughts for consideration, keep us posted on your trouble shoot.

 

I replaced the MAF because the previous owner had the wrong one istalled for some reason and the Banana had a nearly runaway sounding idle speed. The kid had been using the poor Banana for boonie bouncing with friends, you know... the High school party barge. He was aspiring to graduate into a 4x4 to better destroy the local fauna with and he offered the Banana to me for a mere $250.00. How could I walk away from a deal like that? I was planning a rebuild of my B2 and was going to need a donor vehicle soon anyway.
Once I got the Banana home I started going over her with a microscope (not literally of course) and began fixing the more obvious issues as they cropped up. The high idle was a priority so a new MAF slapped in place and bingo, she ran like a contented kitten.
Smogman said new Oxy sensors were a good idea and a couple of bottles of engine detergant, an oil change (+filter) new plugs, wires, cap and rotor and mechanically she should be good to go. The Banana has 110,000 original miles and the old plugs were burning in the "ideal" range. Not what I expected I would see when they came out considering they seemed to be welded in place. It took annointing the block with knuckle hide and blood a few times to get the old plugs to let go and situate new ones in their place. Yes, the computer was reset in the usual manner. From the initial start-up the Banana has been cranky about the plugs, or whatever is causing the problem. The first day the Banana hiccupped and bucked and couldn't be coaxed out of 4th gear. Day 2, yesterday, the Banana wants to run-away again... Can't get the idle to come down for anything, until the MAF is disconnected... then the idle levels out and power seems to have joined the party. Like I mentioned, the only code I am getting with koeo is a 67. I am 100% sure it is a 67. I'm wondering if the Banana HAD A/C at an earlier point in her life and the compressor has just been taken off... I'm not finding much to support the possibility under the hood but the dash does have an A/C option on the temperature selector.
Anyway, I digress, PawPaw... I very much appreciate all Your suggestions and I am going to head out and give them all a try. I'm a little bit of an obsessive when it comes to my chariot, I want to be able to rely on getting to my destination AND home again without a fuss. Creeping home on the side of the highway with flashers going is too much drama to be tolerated more than once a month.
Oh another fix that I neglected to mention was flushing the cooling system totally. The 3.0 was full of rust and scale and it took a few flush outs and rodding the radiator to finally get the water back to flourescent green instead of tomato soup. I never noticed an overheating tendency, but that was pretty much one of the first things that was rectified once the Banana came home. Now she seems to run on the low end of the temp guage and the heater works correctly for my needs. I'm not sure that is important for diagnosis but I'm confessing anyway.

 

OK, more good feedback.

Good idea & feedback on disconnecting the MAF sensor & having the high idle speed come back down. That suggests something isn't right with the MAF sensor, or its circuitry has been messed with. I've heard of folks using a resistor to fool the computer & that would mess up the replacement MAF sensors PID to the computer.
So have a cose look at the MAF sensors wiring & electrical connector, to make sure it hasn't been messed with, or damaged, or has a connector pin/socket problem, like spread sockets, bent pins, or corrosion on them.

Was this a reman MAF sensor????

 

Yes it was a reman MAF ... you get what you pay for I guess... upon closer inspection, the MAF sensor wires (the filaments) have what looks like corrosion on one of them. Off to the store for MAF cleaner and commence with cleaning ... Reinstalled and so far it's behaving nicely. Going to go take the Banana for a drive and see what we have now...

 

OK, good to hear you think its fixed & your on the road again!!!!