Community Forums

NASAGuy · 11-08-2006, 11:19 AM

After 31,000 miles my faithful Winnebago Adventurer suddenly developed a slight miss under load. My local RV repair shop confirmed this was probably the infamous Workhorse bad spark plug wire situation. The spark plug wires and spark plugs were replaced and that fixed the problem. The wires were not burned and were very flexible. I saved the old wires thinking it would be nice to have some spare wires if this occurred again when we we hundreds of miles away from a Workhorse repair shop.
I have two questions that maybe someone could help me with:
1. Is there any way to determine which cylinder or cylinders are missing if the engine starts running rough again? This is assuming the wires have no obvious visual flaws.
2. How can I test my old wires to determine which are still usable?

thanks

NASAGuy

NASAGuy · 11-08-2006, 11:19 AM

After 31,000 miles my faithful Winnebago Adventurer suddenly developed a slight miss under load. My local RV repair shop confirmed this was probably the infamous Workhorse bad spark plug wire situation. The spark plug wires and spark plugs were replaced and that fixed the problem. The wires were not burned and were very flexible. I saved the old wires thinking it would be nice to have some spare wires if this occurred again when we we hundreds of miles away from a Workhorse repair shop.
I have two questions that maybe someone could help me with:
1. Is there any way to determine which cylinder or cylinders are missing if the engine starts running rough again? This is assuming the wires have no obvious visual flaws.
2. How can I test my old wires to determine which are still usable?

thanks

NASAGuy

Ultra RV Products · 11-08-2006, 12:00 PM

NASAguy,

From what we have seen it is usually number 5 that burn's out first.

commander 11 · 11-08-2006, 04:46 PM

One way to check which cylinder is missing is to pull off(loosen them all first so it is easy to get them off)each wire one at a time with the engine running. If the engine runs rougher you know that plug/wire/cylinder is working. If nothing changes you have the culprit

Toby · 11-08-2006, 04:52 PM

Our Spark wires went bad at about 12,000 miles. They replace them and it runs fine. I was thinking about puting a marine engine blower under there some place and see it it keeps it cooler. I wonder it would be best to blow away from the engine or towards it? s/Toby

Cat · 11-08-2006, 05:10 PM

Watch your spark plug wires at night. You can should be able to see it arcing around the spark plug connections or at supports. Where ever you see the arc that is your bad wire. Make sure you keep your hands away from the wires. It will give you one heck of a shock 50,000-70,000 volts.

Oemtech · 11-08-2006, 06:13 PM

You can install some Taylor 409's or TV50's from and that should take care of the problem. You can also get some Nomex style covers to add a bit more protection. Is this a 100% fix... no. Im some cases the air flow is so poor that you will need aux cooling.

ron55 · 11-09-2006, 03:28 AM

If you get the ECM reprogramed it will lower your heat problem. I did and it is unbeliveable how much cooler it is around my engine. Before reprogramming I could not touch the frame anywhere close to the engine. Now i can lay my hand on the frame anywhere and it's just warm.

NeilV · 11-09-2006, 07:19 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by NASAGuy:
After 31,000 miles my faithful Winnebago Adventurer suddenly developed a slight miss under load. My local RV repair shop confirmed this was probably the infamous Workhorse bad spark plug wire situation. The spark plug wires and spark plugs were replaced and that fixed the problem. The wires were not burned and were very flexible. I saved the old wires thinking it would be nice to have some spare wires if this occurred again when we we hundreds of miles away from a Workhorse repair shop.
I have two questions that maybe someone could help me with:
1. Is there any way to determine which cylinder or cylinders are missing if the engine starts running rough again? This is assuming the wires have no obvious visual flaws.
2. How can I test my old wires to determine which are still usable?

thanks

NASAGuy </div></BLOCKQUOTE>

#1 - You could pick up an inexpensive code reader such as this one from Harbor Freight:

http://www.harborfreight.com/cpi/cta...emnumber=46030

#2 - Use the results from #1, visual inspection for cracking or burning or loose connectors and when in doubt they are obviously all bad.

NASAGuy · 11-09-2006, 08:20 AM

After reading all the excellent suggestions and thinking about it some more, I realize the smart thing to do-in my case at least-is to purchase a spare set of quality spark plug wires. Hopefully, it will be another 31,000 miles before I have the problem again. But you never know.
The engine ran smoothly at idle and only misfired while under load so I suspect there is no practical way to pinpoint which cylinder was missing. I did not get an error code of any kind.
I also suspect there is no easy way to test my old plug wires to determine which had failed.
Thanks again to everyone who responded.

NASAGuy

Horsepowerfan · 11-10-2006, 01:26 AM

Hi NASAGuy,

If your engine starts mifiring under load again you could try misting the plug wires with a spray bottle of water. This tends to cause any arcing out to occur under much less load. You then may be able to hear or see which wire is defective.

The only other way I know to determine which cylinder is misfiring is to watch the ECM's misfire graphic on a GM Tech-2 scan tool. So, to answer your question, yes there is a way to see which cylinder is misfiring, but I don't know if it is an option for you. Typically, even if a code sets in the Engine Control Module it is a P0300 code indicating a misfire, but doesn't differentiate which cylinder is misfiring. Some vehicles will set a cylinder specific code like P0307 which indicates a misfire on cylinder #7. You might be able to enlist the help of a friendly auto technician with a scan tool capable of monitoring the ECM's mifire counters to pick out your culprit.

As far as testing your old wires, use a digital ohm meter to measure the resistance of each wire. The specification for the wires on the 8.1L V-8 is 1,000 ohms per foot.

Hope this helps.

DriVer · 11-10-2006, 05:36 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Horsepowerfan:
</div></BLOCKQUOTE>

Thanks Jim!

NASAGuy · 11-10-2006, 11:04 AM

Hi Horsepowerfan
I followed your suggestion about measuring the resistance of each plug wire and the values were almost exactly what you had predicted. Only problem was each of the original Packard wires measured 1200 ohms. I wonder if a wire could have continuity and still have a loss of high voltage insulating properties?
I would never have thought of misting a plug wire. I will certainly try that the next time we are in the middle of nowhere and the engine starts running rough again.
Thanks for your excellent input.

NASAGuy

Full-Timers · 11-10-2006, 05:57 PM

All 3 times my wire burnt it was the #5 wire. The first one was hard to spot the failure. I finally looked it over under a microscope at work and found a pin hole in the boot. The others were obvious. I carry an inexpensive set of Autolite wires I got from Pep Boys for $40. Didn't cost me a fortune and will get me back on the road. Since I installed the Workhorse vent kit I haven't had another failure.