Community Forums

bill06447 · 10-26-2016, 07:17 PM

Similar symptoms with my 91 454, no codes but ended up being a faulty EGR valve. I changed the valve and the solenoid and the problem never came back.

harleyjt · 10-26-2016, 10:49 PM

Quote:

Originally Posted by RMFUN

Couldn't find the correct filter here locally, so I will order it and install later.

Just curious if anyone checked codes with this issue? A local shop loaned
me his Matco scanner and it showed no codes at all ?? How can that be ?

Russ

It just means that whatever is causing your problem probably isn't a monitored function or device.
jt

MoCoTom · 10-27-2016, 08:32 AM

I would be sure to follow Ultra RV recommendation of .045 plug gap. The facory .060 gap may be fine for a pick-up truck, but at the engine load required to pull these rvs it can lead to misfires at some throttle settings.

Sehc · 10-27-2016, 10:14 AM

I'm surprised that a modern electronic ignition engine would falter because of plugs. I can see a plug wire becoming problematic, leading to distributor cap arc, also.
Sure does sound like fuel, being intermittent. Do the filter, maybe get the injectors checked.

Mudfrog · 10-27-2016, 12:52 PM

Quote:

Originally Posted by RMFUN

Couldn't find the correct filter here locally, so I will order it and install later.

Just curious if anyone checked codes with this issue? A local shop loaned
me his Matco scanner and it showed no codes at all ?? How can that be ?

Russ

In our case, no codes on either occasion. A bad spark plug was the culprit the first time. This last time, not positive, but i believe it was a wire since one of them left its crimp on the #5 plug when i went to remove it. The 8.1 is running good now with new AC plugs and Magnum wires.

**JohnRR** · 10-27-2016, 01:00 PM

Quote:

Originally Posted by JohnRR

Bought from a iRV2 vendor so as to be able to use a normal GM fuel filter instead of the one of a kind Workhorse filter.

Workhorse uses four tie down clamps for the filter, one can not be seen on the line running out of the right hand side of the filter.

Just to give you an idea.

MoCoTom · 10-28-2016, 06:00 AM

Quote:

Originally Posted by Sehc

I'm surprised that a modern electronic ignition engine would falter because of plugs. I can see a plug wire becoming problematic, leading to distributor cap arc, also.
Sure does sound like fuel, being intermittent. Do the filter, maybe get the injectors checked.

The 8.1 does not have a distributor, it uses individual coils and a designated plug wire with the firing order being controled by the ECM. The wider the plug gap is set the more demand it will place on the coil and it's given plug wire. Considering the work load placed on the engine while pulling these beasts down the road, anything that helps fire that fuel mixture is a plus

harleyjt · 10-28-2016, 08:26 AM

Quote:

Originally Posted by MoCoTom

The 8.1 does not have a distributor, it uses individual coils and a designated plug wire with the firing order being controled by the ECM. The wider the plug gap is set the more demand it will place on the coil and it's given plug wire. Considering the work load placed on the engine while pulling these beasts down the road, anything that helps fire that fuel mixture is a plus

I'm not sure I understand the wisdom behind the 0.045" gap vs the 0.060" factory gap. The wider the gap, more voltage is required to jump that gap resulting in a hotter spark and presumably better burn. By reducing the gap, it is easier for the coil to fire across the plug, but it will be a bit weaker spark. If your plug wires are marginal, then the reduced gap might make sense to me as they aren't taxed as much. Same with a marginal coil. But if the system is in good condition, the wider gap should provide better ignition, better power, and reduced emissions. I know there is a lot of talk about reducing the gap, I just don't understand it.
jt

RMFUN · 10-28-2016, 09:33 AM

When I bought the spark plugs ( a/c 44-101) at Car quest, their computer
showed to gap them to .045. It showed the factory plugs were .060.

When I looked into this, posters on the LS forums also reported GM changing the recommended gap from .060 to .045 to stop high rpm miss.

Russ

TexasTom · 10-28-2016, 09:37 AM

I have had spark plug/wire issues and they were not intermittent. The issues may have been a little different at different engine speeds and loads, but they didn't go away until new wires were installed. I have had similar problems to the OP on a truck, and at that time it was a fuel filter. So that gets my uneducated guess.

harleyjt · 10-28-2016, 11:31 AM

Quote:

Originally Posted by RMFUN

When I bought the spark plugs ( a/c 44-101) at Car quest, their computer
showed to gap them to .045. It showed the factory plugs were .060.

When I looked into this, posters on the LS forums also reported GM changing the recommended gap from .060 to .045 to stop high rpm miss.

Russ

Well that may make sense. GM may have found the system just isn't robust enough over the service life of the plugs, wires and coils to handle the 0.060" gap. Perhaps they needed bigger wires or more coil capacity.
jt

vettenuts · 10-28-2016, 11:58 AM

Some of the LA guys have replaced the original coils with the LS truck coils that provide better spark. However, GM did issue a TSB on the spark plug gap reduction to 0.045.

harleyjt · 10-28-2016, 12:39 PM

Wonder if it's worth pulling plugs and regapping? I'm only at 12000 mi and no problems other than a bad miss in heavy rain I think due to old plug wires. I changed them over to a set of Taylor's. If they don't hold up I'll probably go back to AC Delco.

vettenuts · 10-29-2016, 06:52 AM

Quote:

Originally Posted by harleyjt

Wonder if it's worth pulling plugs and regapping? I'm only at 12000 mi and no problems other than a bad miss in heavy rain I think due to old plug wires. I changed them over to a set of Taylor's. If they don't hold up I'll probably go back to AC Delco.

That sounds a lot like water intrusion. I had the same issue as did the previous owner. He fixed it but unfortunately the seal he put around the hood had deteriorated and I didn't notice. Found out the hard way. Last fall I sealed the air box and bought some ribbed foam tape from Home Depot. That took care of it along with a new air filter and cleaning the MAF while I was in there.