Spark Gap Incorrect?

[Triton46]

Ford recommends a gap of .054 for the 91 Ford Explorer. I just put in new Bosch Platinums (not +4) which were originally gapped at .040.

I originally had Bosch non-Platinums installed for 20k in which I did not regap. I am guessing they were gapped to .040. With that being said...

My engine seems to stumble when starting out on a hill or pulling my jetski out of the water. The engine just wants to die. It runs fine on the highway but I think there is a slight ping. The car ran much better with the .040 gap and the only loss in mileage was 0.5 mpg.

Has anyone noticed this? Should I regap to .040?

 

[fastcougar]

Read This for my take on the spark gap: Dead Link Removed

 

[Triton46]

Interesting. What tool do you use to regap? The guy at AutoZone did mine when I bought them with the tool that looks like a $.50 piece. Thanks!

 

[fastcougar]

That's what I gap with, but with prolonged use, they wear down and before you know it, .050 is more like .045, which can make the problem just a bad, like what you are experiencing. There is a safe range, I would say within .010 where either side of that range will cause problems. I would NEVER gap above stock suggestion, .054 and no lower than .044 due to milage concerns and the possibility that the plug will aid in detonation.

I want to get this to make my gapping more accurate:

Dead Link Removed

Edit: Can be bought from Summit Racing for $39.99 + S&H. It's made by Jacobs Electronics (they know their stuff and have some of the best plug wires on the market). Summit Part number JAC-380700

Edit 2: a better picture

 

[JDraper]

Try resetting your computer. The vehicle "learns" the air/fuel ratio as you drive it, depending upon the way you drive and the readings it gets from the O2 sensor. A bigger gap will change what the 02 sensor sees, and the computer will have to compensate. It will over time, but it's quicker just to yank the battery cable, wait 20 minutes or so, and hook it back up.

 

[Triton46]

Thanks guys!

I'll try the computer first, as my knuckles have just healed from replacing the spark plugs.

 

[fastcougar]

If you just replaced the plugs, I will gaurentee that it's a plug gap issue. Tell you what, if it's not a plug gap issue, I will buy you beer

 

[JDraper]

I'd agree that it's a plug gap issue, but it might just be the computer not being happy with the new gap. The computer may be feeding it too lean a mixture for the gap, since the old plugs were gapped down to .040"

 

[Triton46]

fastcougar,

I will hold you to the beer if it works.

 

[Triton46]

The results are in. The plugs were gapped to .054 all around. I tried resetting the computer but still had major hesitation when taking off on any incline.

Being the lazy shadetree that I am. I took out 5 of the 6 spark plugs (anyone with a 91-94 knows which one I left in) and regapped all of them. Autozone says that the Bosch non-platinums out of the box are gapped at .040. Since I had good results with that last time, I regapped all 5 to .040.

Took the truck to the closest steepest incline and.....the hesitation is gone. I guess I owe someone a beer. Thanks again!

Why do you suppose my truck runs better on a smaller gap than factory recommendation?

 

[Triton46]

Well, it seems to have been a short lived victory.

My Explorer began making a pinging noise at highway speed. It started while I was in cruise control and got worse if I gave it more gas.

I figured it was due to the one spark plug I did not regap. On Friday I regapped it and took the car on a trip to Raleigh. I still have the hesitation while lauching from a steep incline or boat ramp (much worse from boat ramp), the pinging is only there under acceleration, but now there is a weird hesitation.

If I shift into 3rd at around 25mph and begin to accelerate. The car lurches/hesitates from 27 to 35mph. Its not bucking, but feels more like if you tried to leave in 1st and aren't giving it quite enough gas. You can't 'feel' the lurch/hesitation but you can hear it in the engine. I thought it had something to do with the transmission, but with all the problems I am having with the spark plugs it may be due to this. This same lurching/hesitation appears when shifting into 4th at 35mph.

Has anyone experienced this? I am using Bosch Platinum plugs (not the Plus4 or Plus2). I did not have this problem with regular plugs. The spark plug wires were changed out and are only 20k old. I'm going to try resetting the computer again today since regapping the last plug to see if that makes a difference. I'm also going to clean the MAF.

 

[Triton46]

After cleaning the MAF and resetting the computer things seem fo be fine. I commute 70 miles a day and the difference was like night and day from my trip to Raleigh on Saturday.

No pinging on cruise, no pinging when accelerating and I seem to have regained power when lauching from a stop.

I will hold off on commenting on the final part (lauching) until I take the ski to the lake this weekend. Thanks guys!

 

[Dan Whitaker]

The problem is you bought Bosch. I have had nothing but problems with them.

 

[Alec]

I have motorcraft double plats (one heat range cooler) gapped to .048.

 

[Triton46]

Well, the ride home went well. I agree about the Bosch Platinums. I have heard about all the problems.

After resetting and cleaning the MAF the car runs great now. I still have a problem pulling up steep inclines. The car sounds like all 6 cylinders are pinging at the same time. The car does not shut off, but feels like it is about too.

 

[Iggy flywheel]

Didnt mention that you changed the wires. The magnacores are great get them at cyberauto.com for good price. I have read threads where on inclines explores pickup a bumping type of miss in the engine. The wires corrected this. On the issue of the pinging I would check the voltage on the MAF. Haynes manual tells how to check may check while in driving on the inclines too. I would go with the larger MAF from ProM if your MAF is bad. May want to test the fuel pressure regulator and change fuel filter too.

 

[Triton46]

The spark plug wires were changed out and are only 20k old.

I used NAPA wires to replace the original wires. FPR was changed at 90k and new fuel filter at 100k.

I'm not sure if the plugs are to blame. On the old plugs the car would just shake (not enough gas leaving the incline) and die. Now it makes a horrible ratcheting sound but keeps pulling. It sounds exactly like all 6 cylinders are pinging.

 

[JDraper]

Another thing you might want to look at is your O2 sensors. They alter the fuel/air ratio to the motor which might cause the symptoms you are seeing. A vacuum leak might do it too.

 

[Triton46]

Hey Jeff, whats shakin (besides my truck).

O2 sensors were changed with the FPR. The truck is nothing short of awesome on the highway. Acceleration has vastly improved since regapping to .040 and forcing the new profile into the computer.

I took it up to 85mph on the way home yesterday and it was still pushing.

The original muffler, baffle and tail pipe were removed and replaced with a more free flowing muffler. No baffle this time and the exhaust now exits straight out the back like a 95+ Explorer. Would this cause a dramatic drop in low end torque? The car has never been a stump puller, but can you compare/contrast to your 92 (since yours was the same setup as mine)?

 

[JDraper]

Reducing the exhaust back pressure will drop your low end torque. How much?? Depends upon the exhaust system. I had the Flowmaster cat back system from Summit on that old '92, and I didn't notice much torque loss (remember I had the 5 speed), but I definitely gained power on the top end. It still pulled well off road at low rpms. If you have a low axle ratio, you would notice the loss of torque much more than with a high ratio. I think my Sport had 3.55's in it.

Glad to see your buggy is still running. Hope all the donor parts are working well. Tell ya what, I really miss my old Sport . I like my new truck a lot, but the old one had a LOT more character. Oh well, maybe I'll pick another one up here one of these days. We could use a 3rd vehicle for the winter since the Firebird doesn't exactly like snow.