Bad missing pulling hills help!

[Trident]

Someone has had this problem with there 1998 airstream 30 LY motor home 7.5 liter please share your experience and if possible your solution. We are on the road and have changed distributor cap and rotor thinking we had a moisture issue. Put in three cans of heat in the gas thinking water in the gas. The plugs and wires and gas filter have maybe one year and 6000 miles on them but we bought a new gas filter tonight to put on tomorrow maybe.
Thanks
Trident

[bobmiller1]

A good place to suspect a problem with your concern is the pick-up coil inside the distributor housing. If it is the problem I would also replace the ignition control module. Don't cheap out and buy the non OEM parts from the big box stores and order Factory AC DELCO from Rock Auto.

[xrvr]

Spark plugs? Might have a bad one.

[PeterH-350LE]

Is it missing or could it be fuel starvation. Does you rig have the rear elec. fuel pump in addition to the mechanical motor pump?

[Waipio Rim]

x2 on the ignition coil, ours was bad when we bought the coach and got worse. Once the motor was warmed up it would miss under load.

[NavyCorpsman]

I would change the plug wires and spark plugs for sure. When the engine is under a load, there is an increase of cylinder pressure that increases with engine speed. This faster and more effective cylinder filling creates a need for a hot powerful spark, especially as the ignition timing advances and the manifold vacuum decreases.

You can idle all day and mutter at low speeds and it runs fine. The coil may be a problem, but they usually are a go-no go component.
A good way to check your plug wires is a night with the hood up in a very dark area. Watch for arcing along each wire.

[DaKarch]

Are you at high RPM when pulling the hills? I suspect you are.

Check the coil/coils for burn marks.

Something I do is get a spray bottle and find a dark spot. At idle mist around the cap, coil(s), and wires and look for small sparkles. (don't touch wet stuff with engine running high voltage is dangerous)

If you have a timing light check the timing. If its old school distributor with vacuum advance check for vac leak to distributor.

In fact check for vacuum leaks period. High rpm hill climbs draw more vacuum.

Older distributors have little governors in them that effect timing too, but that usually causes a sluggish throttle response.

What is the fuel delivery in this motor? Direct injection, the single port carb injection thingy or carberated?

I doubt it is a fuel problem, just from my own experiences. Spark, or vacuum leak

[Trident]

I changed that gas filter the next day and there was water in it, I could see it in the bottom of the bowl that I drained it in. I went to a Napa store to buy several cans of Heat he recommended instead 7100 Thermo-aid to remove water from tank. I don't know if there is any difference between Heat and 7100 but I think it ran better at the end of the day then at the beginning.

I did run the engine at night no visible sparks anywhere. The coil at jest the right angle emitted a little light no arks no trace marks. Considering the amps it is dealing with I would think there would be some sort of a surface charge am I wrong?
Thanks to all
Trident

[richinny]

an ignition leak can often be detected by listening for static on the radio. tune it to AM and pick a spot on the band that has no broadcasting at that point. listen for static that matches engine rpm.

[DaKarch]

That's interesting....How much water?

Water in fuel usually effects all rpm's.

If you were in total darkness and saw a light then you are leaking voltage. From my experience the voltage leaks tend to glow more than arc. I would not expect a surface charge because electricity follows path of least resistance.

[JCWDCW]

I would change spark plugs. Under pressure the spark can 'blow-out' when the plug is worn and has no sharp edges. An older motor may not have newer platinum plugs that do not erode as quickly
JCW

[NavyCorpsman]

Originally Posted by richinny

an ignition leak can often be detected by listening for static on the radio. tune it to AM and pick a spot on the band that has no broadcasting at that point. listen for static that matches engine rpm.

I have used an old pocket radio on the AM for the same thing

[L&C Woogie]

Timing, check your timing.

[Jabba]

I'd go with spark plugs. I replaced plugs on one of our cars, got Bosch platinum. It started developing a bad miss under load and in wet conditions. Turns out 3 out of the 8 plugs cracked with under 10k miles on them. Replaced with Ac Delco as my mechanic recommended and it solved the issue. Mechanic said Bosch and NGK are not what they used to be.
If that doesn't help, I'd try the coil. Had similar issues on a different vehicle. Replaced the coil, solved the problem and it started easier. Coils will start to break down over an extended time.

[Trident]

Originally Posted by Jabba

I'd go with spark plugs. I replaced plugs on one of our cars, got Bosch platinum. It started developing a bad miss under load and in wet conditions. Turns out 3 out of the 8 plugs cracked with under 10k miles on them. Replaced with Ac Delco as my mechanic recommended and it solved the issue. Mechanic said Bosch and NGK are not what they used to be.

If that doesn't help, I'd try the coil. Had similar issues on a different vehicle. Replaced the coil, solved the problem and it started easier. Coils will start to break down over an extended time.

Those of you that said spark plugs seem to be close but not all the way.
I replaced 4 plugs at a campground all on the drivers side. I turned the rubber insulator to the right then the left with a tool they would not break from the porcelain. I did manage to pry off those 4 with a great deal of effort and replaced with 4 platinum plugs (Ac Delco) .
The next day the missing was a memory😀. The next morning we filled up from about a quarter tank with three cans of Heat and about 40 gal. of Shell gas , the missing started at once and lasted all day 😁 the plugs I had the room and strength to get out were tracing down the side looks like it to me , I will try to include a picture.
Thanks all
Trident

[DaKarch]

From the looks of the plug you are burning lean...google spark plug images....then check timing and vac leaks

[DaKarch]

I looked at this on my phone at first....looking on PC its hard to tell anything from this picture.

But new plugs...run fine for a while then gets miss....most likely not the plugs

Just curious did you set/check the gap on the plugs?

Also that plug only has 6K miles on it right?

If its easy to get to the coil, change it... you said you saw a faint light at idle...bad juice at high rpm means bad burn

[Jabba]

I agree, coil would be my next thing to try.

[kscherzi]

If you have fuel injection I'm voting for a failing fuel pump.

[bkahler]

Even if it's a carburetor engine it could still be a fuel pump issue. There should be an electric booster pump close to the fuel tank. If this pump fails or is failing fuel delivery to the carburetor will be impacted causing low pressure to the carburetor.

Something to consider.