Thought you guys could help me out with something concerning the following truck

98 4.2L, manual tranny, 3.08 rear.

The truck has started to hesitate and buck under load. Actually, it hasn't just started, it has started it again. About a month ago I remedied the bucking situation by replacing the plugs and the wires. I found a wire that has arcing out under load. Up until about a week ago the truck has ran fine. But it has now started acting up again. Let me run down with you guys what has been done to the truck recently...

new wires
new plugs
new fuel filter
new air filter
recent oil change (has been done every 3k since the truck was new)
ran a couple cans of FI cleaner through, hoping the problem was dirty injectors or maybe water in the fuel.

Other than this annoying problem, the truck has been flawless. It has almost 70k on it, cranks off about 20 MPG consistently and has never let us down.

Any ideas? I was thinking maybe the coil pack, but I don't know if the 3.8L/4.2L ford engines have had this problem.

Now this problem only happens under load, that is either lugging the engine in too high of a gear, heavy acceleration, acceleration during passing (the most annoying) or at night with the A/C and lights on.

Any more ideas to try? I am beginning to get frustrated. The bucking feels exactly like a miss, which is what I think it is. For it to go away with new plugs and wires, and such an obvious arcing problem with the wires, to have it come back again is just plain frustrating!


Thanks for any advice you can give me..

Brian Skouby
98 F150
98 Ranger
94 Taurus

 

I had thre same thing happen on my 97 4.2 5-speed. It was a miss that happened under load. Ford replaced the plugs, wires, and reprogrammed the computer. It has been a few months and everything is good. If you want to fix your problem, I reccomend good aftermarket wires and plugs, reset your computer, and see what happens.

 

My 97 V6 W/5speed is doing the same thing as yours. Please keep us posted on the out come. Mine is a lease truck, so I'm not going to worrie about untill someone comes up with a fix.

 

Still haven't figured out the problem. It is more annoying than anything. So far the truck hasn't had any major problems, and it it coming up on the 70,000 mile mark. BUT I have noticed that it sounds even more like a diesel than normal. It almost sounds like valve train clatter or possibly the timing chain. I keep a very close eye on the timing chain cover as well as the coolant and oil levels, so far so good.

Still cranking out the same old MPG, just sounds terrible and likes to buck, sometimes.

 

bskouby - in many cases the deisel sound is the fuel injectors. They just seem to be noisy on these trucks.

Regarding the 'bucking', just about every engine with a manual transmission will do this if you are giving it too much throttle under a load at low rpm. IMO, your 3.08 gear ratio and the fact these V6's have pretty weak low rpm power is the likely cause.

A bigger engine with more torque would pull you through, but these little V6's want to be revved up. Downshift or put some 3.55's or 3.73's in there and the bucking will magically disappear!

 

I agree with dirt bike dave. However, you may want to get your MAF and IAT sensors checked out at your dealer - they can cause similar problems.

My 2 cents worth...

 

well i asked my mechanic(mike @ poorboys performance) what he thought . heres what he said " look on the pass. side of the truck close to the a/c box at the fire wall , this is where your harness goes into the truck , feel under the harness and make sure that the wires did not rub against the a/c system . this is a very common problem with the v-8 trucks . the harness usually get rubbed against and wears down the insulation and into the bare wires , for whatever reason it doesn't blow any fuses but it run like crap under a load ... " and i am not saying that is what it is but just a suggestion for you guys , hope it helps

 

1) Fuel Injectors: I hadn't thought about that one, I will check this out further.

2) Bucking: The bucking problem just started about a year ago. I had 55k on the truck before this started. I too thought about the fact that it happened under heavy load when the truck was being lugged. But it even happens when I am in 1, 2 or 3rd and really cranking out the RPM's. The most problems I ever had was pulling down into 4th and romping on it to pass someone, then it really misses and bucks.

I also can lugg the crap out of my little tiny, ity bity, 4 cylinder ranger and it never bucks or misses, just sounds terrible.

I truly believe that I have an actual problem since it used to not buck/miss under load, and now it does. And it seems to be related to RPM's. The more I am spinning, the worse the buck/miss is.

I will let you all know if I ever figure this one out. So far it hasn't been too bad as of the last couple of weeks, but it hasn't been as humid either. It seems like rain/humidity really causes the problem to become much worse, which leads me to believe that I have something shorting out somewhere. The plugs and wires are new (both motorcraft, not cheapy autozone ones) and the problem still exists. Oh well...

 

bskouby;
I have had exactly the same problem as you are describing. It started almost imperceptably and gradually worsened until I was having the symptoms whenever I accelerated or hauled a heavy load. I took the truck to Ford who did not find anything but suggested that I clean the fuel injectors. I then took the truck to a private garage who spent some time on the problem. They changed the spark plugs and the problem was worse. They then changed the wires and the problem was cured. They told me that that disturbing the wires when they changed the plugs had made the problem worse. Apparently the Ford wires are prone to core failure and it shows up as the bucking that we experienced. You stated that you changed the wires and the problem went away. That should also indicate that you were on the right track. Did you use Ford wires or an aftermarket brand? Aftermarket wires may not be able to handle the electrical load. If I were you I would tackle the wires again. If it is the cause again, you could probably get your money back for the others that you bought. Good luck, GlennMc.

 

I changed the plugs first, the problem did not go away. Then I changed with wires (two months, and about 5000 miles ago) and the problem went away for a bit over a month. Then it just came back with a vengence. The first time I had the bucking problem, I was able to find a plug wire that was arcing under load (hood open at night with the engine loaded down). So I thought that I had cured the problem 100%. But now it is back (with the new wires) and I cannot locate a wire that is arcing against another wire or grounding out somewhere.

The new wires are motorcraft wires, and the new plugs are motorcraft plugs. I also have changed the fuel filter, air filter, had the MAF cleaned (by my mechanic and myself). Was thinking about having the injectors cleaned, but I just don't feel that they are the problem. I just don't understand why the problem gets worse when the humidity is high or it rains. It is almost like something is actually shorting out.

Thanks for all of the ideas, I will keep looking and keep all of you informed if I find the problem.

I am used to constantly working on my Taurus trying to keep it together, working on the truck is getting somewhat frustrating.

 

I know it sounds simple, but did you put a shot of the silicon that comes with the wires in the boots ? You said it gets worse in rain and humidity so for something cheap and easy you might try it. You never know it might work! Good Luck.

 

Yup, I sure did. The silicon is almost a must because of how tight the boots fit onto the plugs.

 

As I posted earlier, my 98 4.2L was suffering from hesistation and bucking. I replaced the plugs and wires earlier, but was never really able to get rid of the problem. Last night, on my way home, I was stuck behind a slow moving vehicle and got in the situation where I either had to run in fourth gear and run the RPM's up a bit, or lug the engine a bit in fifth. Either way, higher RPM's or lugging is what causes the engine to buck.

At this point the hesistation and bucking started again, and then it progressed all the way to a dead miss in the engine (never done this before). when I got home, I popped the hood with the engine limping along and was greeted with a light and sound show. 1 of the plugs was arcing out on the block (hence the dead miss) and 3 more plugs actually had blue glows right above the base of the plug.

Come to find out, the plug that was arcing was cracked and the other three plugs had grooves burnt into the porcelin of the plug running from the tip of the plug to the base where it was glowing blue.

I have NEVER seen this happen before. I replaced the plugs in the truck about 30,000 miles ago, and the plug wires about 15,000 miles ago. As far as I can tell, either the plug wires went bad first and starting arcing out and grooved out the plugs porcelin, or something was wrong with the plugs, and ended up destroying the wires.

When I pulled these plugs today, I noticed also that the porcelin had also started flaking off. Almost like they all had gotten extremely hot (even though the engine has never been ran hot). At first I thought it was the old silicone boot grease drying out, but after cleaning off the old plugs you can see where the glass had begun to flake off. Really strange.

Anyhow, I decided to stay away from these plugs again (Bosch Plats) and ended up going back to the old faithful plugs, Autolite Plats. I also noticed when I put the autolites in, they fit in the boots of the plug wires much tighter than the Bosch plugs ever did. The Bosch plugs were the correct plug for the truck, I checked again today to make sure.

The truck runs great now. I have put slightly over 100 miles on it today trying to make it hesistate and buck. I have ran the engine up high and lugged it down to the point of almost stalling it and cannot get any bucking out of it.

maybe this did it. I guess I should have replaced the plugs and wires together (even though the plugs only had 15k on them at the time). Another thing I noticed, the Bosch plats had actually lost their gaps in 30,000 miles. And I know that the gap was correct when I installed them cause I indexed the SOB's.

Oh well...hopefully this fix will stay fixed for a while. 80,000 miles and counting. Too bad this didn't fix my door cracks as well!

 

I have a 99 and it did the same thing.
I replaced the plug cables and put in the +4 plugs in and a new MAF sensor and it worked.

 

I cant belive this crap happens to other people besides me.I thought it was just my truck.i have had this problem for awhile.the first time i had this problem was right after i changed the plugs.i put in bosh platnums,then two days later it did it for the first time.it did it so bad the check engine lite came on.so i bought a code reader from auto zone.the reader said it was a misfire in the #2 cylinder.so i swaped plugs with another cylinder and it still said #2 cylinder,then i swapped wires with another cylinder and thats what it was. so i bought another one from ford.someone in here said it came back with a vengences.that is so damn true.its like its pissed now and there is no stoping it.this time there is no engine light on,but after blindly checking everything and spending my last dime on fuel and motor additives i bet money its the plugs again.so i wonder what after market wires are best.if any knows???