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Changed spark plugs and now runnings really rough

Dragonslayer1

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Year, Model & Trim Level
1993 ford exploder
I have a 1993 ford explorer. I have always stayed up on my maintenance. Recently it as been running progressively rough. I thought it was about time to change the spark plugs. It has been about 70K miles since I last changed them. I changed them with a napa autolite brand. The same brand that I have been running for the last ten years. After starting up it putting it into gear it chug's like either is not getting gas or miss firing. I took all the plugs out to check to make sure none were cracked and all gaped correctly. I double and triple checked to make sure all of the wiring was correct and had a good connection. Any thought?

Thanks,
 



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Usually it's the wiring, since the firing order isn't sequential, and the coil pack has a different arrangment than the engine cylinders. It's easy to get the wires mixed up and think it's right even when it's wrong, unless you either mark them beforehand or somehow keep them where they are supposed to go.

Other than that, the plugs could be bad, just because they're new doesn't mean they are good. It'll be an unpleasant job to redo, but you could put the old plugs back in and see if that fixes it, which would let you know it's the plugs. Personally I'd always suggest running Motorcraft plugs. They are better than Autolites, there IS a difference and the 4.0L OHV seems to run better and idle smoother with the OEM Motorcraft plugs.

Other than that, it might be that you damaged a plug wire when removing/moving them, or the coil pack might have been on it's way out and the tuneup or firing the new plugs damaged it.

If it's not any of those I'd guess that you forgot to reoconnect some hose or wiring plug, or accidentally bumped something during the process that just need to be put back like it was.
 






From experience after a plug/wire change problems after are user related. But maybe the coil pack is bad. It happens. My mom Mustang's was fine until I unscrewed it to replace the wires...It just died. Bought a new one it it was fine.
 






If your wires are old, it could be the culprit since you disturbed them.

Remove the hood light bulb, if it has one. Crank the truck outside in the dark...the darker the better, so you'll need to remove the hood light bulb beforehand, if it has one. The wires need to be changed if you see any arcing from the wires. Or, you might could just reroute one if it's touching something, but I'd still replace it or all of them if it's arcing.
 






Did you drop any of the new spark plugs, or could an employee have dropped the box? The porcelain insulators can be damaged and have hairline cracks, which will cause a misfire. Sometimes it goes away once the engine gets hot enough. Check the porcelain both on the outside and around the small tip for hairline cracks. To find the bad plug more quickly, isolate the misfiring cylinder(s) by removing spark plug wires one at a time while it is running, and see which one makes no difference to the idle of the motor. That is the cylinder that's not contributing.

Check the spark plug wires for resistance or at least continuity. One could have separated internally. The spark may jump the gap but still misfire at low RPM.

One more thing to check. One one of my 4.0s, I noticed for some reason almost all the spark plugs were not seated all the way in. Perhaps at some point in its life, too short spark plugs were installed, so the innermost threads were carboned up and the plug would only thread in halfway before it "felt" like it was all the way in. I used a spark plug thread chaser to clean the threads several times and the random misfires went away.
 






I concur on the wires being in the wrong location. Happen to me almost every time when I take them all off. Remember that the passenger side is 123, for 123: coil to cylinder respectively, but the driver-side is 564 to 456 coil to cylinder. Very easy to mix up.

Also, you might check vacuum lines from the tree on the intake. It is easy to pull one out when messing with plug wires. Another thing to check is that the plug wires are firmly seated on the coil pack and the plugs.

As for arching, I have used heater hose cut length wise in 6 inch sections and installed them over the plug wires and ground straps as they crossed other wires to help cure misses from crossfire or interference. It works quite well with my large diameter wires that don't fit in the stock wire looms on the intake.
 






Problem not fixed

So I my explorer is still having the same issues. It chug's when I put it in gear like its not getting fuel. I switch the new wire with the old ones, no change. I got some better (or more expensive) spark plugs and still no change. I check the wiring and I am sure all the wire is correct. I switch the two on the right bank that are prone to mixing up, for testing purposes and it really started to pop. So i'm sure it all connected correctly. I swapped out the spark plug distributor(can't remember what is is called since it is actually distributor less) and still no change.

I have never changed the DPFE sensor, not sure if that could be the problem.

So now I'm wondering if I am having a fuel pressure issue. My fuel pump was replace about 3 years ago. I'm not sure if they replaced the filters or not. How of often do they go out.

Any suggestions would be helpful, Thanks
 






At night with the hood light off and car running and as little lights around you, watch the areas where the spark plugs and wires are, if you see little lightning bolts anywhere, then you might need all new wires.

So I my explorer is still having the same issues. It chug's when I put it in gear like its not getting fuel. I switch the new wire with the old ones, no change. I got some better (or more expensive) spark plugs and still no change. I check the wiring and I am sure all the wire is correct. I switch the two on the right bank that are prone to mixing up, for testing purposes and it really started to pop. So i'm sure it all connected correctly. I swapped out the spark plug distributor(can't remember what is is called since it is actually distributor less) and still no change.

I have never changed the DPFE sensor, not sure if that could be the problem.

So now I'm wondering if I am having a fuel pressure issue. My fuel pump was replace about 3 years ago. I'm not sure if they replaced the filters or not. How of often do they go out.

Any suggestions would be helpful, Thanks
 






At night with the hood light off and car running and as little lights around you, watch the areas where the spark plugs and wires are, if you see little lightning bolts anywhere, then you might need all new wires.

I can try that again. I tried one by just looking when it very very dark. And then I tried at night using a spray bottle. I didn't see arcing either times. I did replace all my wire's.
 






Update

Ok. So have have cleaned the MAF, Idle control valve, cleaned throttle body, tested for arcing from the new wires, changes fuel filter, put in better or more expensive spark plugs, new air filter, added some injector cleaner to the fuel.

After completing the above. I clear the codes and then took it for a drive. It still chugs and seem's loaded up when I push on the gas. Every once in a while when I'm accelerating I feel it start to clear out and then its back to old the way it was. When ideling I can hear a ticking, from my exhaust almost sounding like and exhaust leak. I looked under the vehcle and could not feel any leaks but it felt like it was coming from either the CAT.

No CE lights during the drive. The only code that ran was the 111 - all systems go code.

The exhaust did smell funny. A hint of rotten egg smell.

Could that be a bad CAT?

I was also going to check the water pressure, trying to decide if I have a bad head gasket.
 






Yes, maybe cats, but have u checked the ignition coil? I'd go get a spark tester for your type of ignition...it'll tell u if current is even making it to ur spark plugs.
 


















Has the fuel filter been replaced lately? I think i'mhaving similar problem. Mine needs it though i know for sure.
 






Has the fuel filter been replaced lately? I think i'mhaving similar problem. Mine needs it though i know for sure.

I did replace the fuel filter a few days ago. I started it again this evening and it ran very poorly. A few codes came across, saying the right side was running lean; 538, 536, 172, 136. I am in the process of purchasing a fuel pressure tester and spark wire tester.

However, I think it may be my head gasket. Water has been disappearing for some time. I have changed the water pump, radiator, and thermostat due all wearing out last year.
 






Time to cut the cord?

Checked out the radiator this evening while it was running. Took the cap off and topped off the coolant. After letting it run a while, I noticed air bubbles coming up out of the radiator and coolant did not go down.

Correct me if I'm wrong but this indicates that I have a head gasket problem.

My rig has 210,000 on it. And from what I've read at this point I would basically need new heads. Costing around 700$.

I am considering cutting my losses and not dumping any more money into. I've had the car for 11 years, so it might be time.
 






Is the engine oil a "milky" white color indicating it's mixed with water or coolant? Compression checked?
 












Code 538 and 536 are from improper KOER procedure.

KOER requires throttle and brake inputs at the right time. So ignore those.

Code 136 and 172 together however means you definitely have a bad O2 sensor.
 



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