8.1L Vortec Loss of Power / Check Engine Light

[azstarr]

Guys,

Some day soon I hope to be full timer and be able to be as helpful to other folks on this site as they have been to me! In the meantime its back to the grindstone tomorrow and try to keep the ole RV running as best we can.

Any ways...any help / ideas on this problem would be much appreciated!

I was heading to Mexico the other day when the check engine light went on. Shortly after that I began to loose power to the point where I had to pull over and let traffic pass. If you've ever traveled Ajo highway west of Tucson you know pulling off the road is not an easy task!

About 30 minutes prior to this occuring I had topped off on fuel (I run 86 octane always). And I had confirmed the fuel cap was on tight.

After I pulled over I turned off the rig and let it sit for about 10 minutes. Re-started and was able to get turned around (another amazing feat of driving) and headed back to Tucson. Check engine light still on but she was running normally. Made it all the way back to Tucson with no problems and normal power levels: solid oil pressure and normal water temp range.

The guys at Tucson La Meas RV were slammed but they were able to get it in to check the codes (my next investment). Turned out to be an O2 sensor code, which they cleared. No time to work on my rig so I took a chance and drove it home (about 100 miles). No problems, ran solid and no check engine light. So the next day I decided to take her on a long run "just to make sure". Bang, about 20 minutes down the road check engine light comes on and loss of power (limp home mode?). Did the same thing as before, pulled over and let it sit for 10 minutes, started up and it drove fine for another hour.

Some back ground that might be related:

A few months ago I was stupid enought to drive through a rather deep "puddle"...more like a small stream a little too fast. Ended up cracking both exhaust manifolds. I replaced the drivers side manifold in Dec 2011 (that was fun) and have a couple of trips on it with no problems. I replaced the passenger side manifold just last month. It actually seemed fine originally, no exhaust leak or noise until on the way back from a recent trip. Evidently there was a hairline crack that finally totally failed.

And I also replaced the fuel filter and housing with the adapter from Oemy's in Dec 2011.

I've checked all exhaust manifold bolts and bolts from manifold to down pipes and checked the O2 conectors and wiring. Everything seems fine...no exhaust leaks.

I should also mentioned that when the "puddle" incident occured, the drivers manifold was cracked pretty good. Because I was in Mexico when this occured, I did have to drive it for several hours in this condition with the check engine light on the entire time but...it never lost power (never went into limp mode) and oil pressure and temp were solid.

I'm thinking the O2 sensors are fried?

BTW, if anyone needs any info on the Atwood electric level leg system, I am now master certified! Not technically certified but I've dealt with every component on that system and have literally rebuilt my system.

Thanks for the help!
Bob

[FloraBama]

Similiar issue: Started on trip this morning, got about 15 miles away and check engine light came on. Drove on thinking I needed fresh gas; started loosing power and added 19 gals. of fuel which made no change. At 40 miles I turned around and drove home.

Going to shop in the morning.

Coach Net didn't think it was gas; possibly fuel filter or many other things. Anyone have this situation? And what was the cause please? Thanks.

Still searching other posts.

[VanDiemen23]

you can get a cheapo code reader/clearer @ Wal-mart for under 60 bucks. Worth it's weight in greenbacks at least.

Somewhere in the manual there are instructions on how to but the engine monitor into a mode where it flashes the trouble codes. You need to start there.

Lots of vehicles have problems with the crankshaft position sensor, but that usually causes the truck to shut off completely. Bad O2 sensors will cause the truck to run rich and open loop - that's the fail safe mode - but unless you are using a lot of HP I'd think it would hardly be noticeable from a power standpoint (although I would expect poor gas mileage).

If it thinks it's running hot it might behave as you described - shutting fuel and spark off to cool the cylinders in limp mode.

[azstarr]

Making the OBDII scan tool investment tomorrow. At this point I can't stop thinking it may be be related to running with a cracked manifold....and possible subsequent damage to the O2 sensor(s).

[txdutt]

Originally Posted by FloraBama

Similiar issue: Started on trip this morning, got about 15 miles away and check engine light came on. Drove on thinking I needed fresh gas; started loosing power and added 19 gals. of fuel which made no change. At 40 miles I turned around and drove home.

Going to shop in the morning.

Coach Net didn't think it was gas; possibly fuel filter or many other things. Anyone have this situation? And what was the cause please? Thanks.

Still searching other posts.

do you get an extended crank when trying to start it? The loss of power on the road plus the hard starting were the two key symptoms on my rig when the fuel filter clogged up & the fuel pump to go bad

[FloraBama]

Not hard to start; cranks easily.

[Dadd]

In my 2001 Winnebago Brave with the 8.1L engine I have had multiple instances of a loss of power because of the heat shields around the spark plugs have gone bad and they apparently start arcing. In these instances I was getting a loss of power as well as kind of a jerking motion. There was also a bad fuel pump and a bad ignition switch as well as too many other problems not related to loss of power. Probably good Workhorse stopped making RV chassis.......IMHO.

[DriVer]

Originally Posted by Dadd

In my 2001 Winnebago Brave with the 8.1L engine I have had multiple instances of a loss of power because of the heat shields around the spark plugs have gone bad and they apparently start arcing. In these instances I was getting a loss of power as well as kind of a jerking motion. There was also a bad fuel pump and a bad ignition switch as well as too many other problems not related to loss of power. Probably good Workhorse stopped making RV chassis.......IMHO.

Dadd,



Thanks for joining the Workhorse Owners Forum and please come back often.

I'm sorry to hear about the problems that you have been having with your 8.1L engine. Your issue is quite unique in all the thousands of posts we have here because none are oriented toward assigning blame on the spark plug shields. Grant it that the shield would provide a ready path to ground in the event a spark plug wire failed. You can also tell by examining the inside of the shield for color change. Orange is like new and black suggests that the cylinder has overheated.

At this time I run a Taylor extreme wires with no shields and I have found unequivocally that a bad wire will exhibit all the problems that you were speaking about and that I have experienced over the years.

A bad fuel pump can happen to anyone, including yours truly however I have not let that stop me. I have not had any problems with my ignition switch. Most of those faults were experienced by P series owners.

I have also had Throttle Control Module problem which gave me reduced power and issued a DTC. I've got over 95,000 miles on my Workhorse and so do several other owners and were doing just fine with our chassis and would most likely buy another if the opportunity presented itself.

[azstarr]

ok guys I got the OBDII reader today and I had four codes as follows:

P0131 (Freeze frame)
P0151
P0131 (Pending)
P0151 (Pending)


From my research P0131 is the bank 1, sensor 1 and P0151 is the bank 2, sensor 1. Possible causes are:

• Faulty o2 oxygen sensor
• Short to voltage on O2 signal circuit
• High resistance or open on O2 signal circuit

Given both exhaust manifolds were cracked, could this have resulted in damaging the O2 sensors or is it possible there's another fault triggering these codes?

Appreciate your thoughts.

[gauto5150]

Cracked manifolds can cause these codes but usually this is corrected once you repaired the manifolds.
Here's a list of possible causes:

• Check for air leaks in the exhaust manifold and in the exhaust pipes
• Engine misfire condition present (look for P0300 series codes)
• Fuel system too lean (possible low fuel pressure, water in fuel)
• HO2S connector is damaged (check pins for damage, and for moisture)
• HO2S signal circuit is shorted to ground
• HO2S has failed (e.g., cracked) or the air reference hole is clogged
• PCM has failed

[Arch Hoagland]

Had the exact same problem....check engine light and loss of power. Once stopped for a while everything ran fine.
I replaced the fuel filter as per advice on here. Still got check engine light but no loss of power.
Bought an Ultragauge and discovered pending P0131 codes. No other codes present. I haven't done anything just yet other than adding 5 cans of Seafoam to the gas and running it through, also ran the generator an hour with the Seafoam fuel. The next trip out over the same exact road and mountain where I had encountered problems was trouble free.
So....I'm not sure what's going on and plan to just monitor the situation. My UltraGauge is mounted and plugged in permanently now.
I had my exhaust manifolds and one head replaced during the warranty period 35,000 miles ago and several years. The manifolds had been a problem since new and worked on several times by the RV dealer where I bought it. Then I moved and the local Workhorse dealer fixed them right.
But it is interesting what gaut05150 suggests may be the problem. I may need to go for aftermarket exhaust headers if things go south again.

[azstarr]

Thanks, Guys....

I will probably replace the fuel filter (even though I just replaced it less than 1000 miles ago) and run seafoam through the system just to play it safe. As I noted in my original post I had just stopped for fuel less than 30 minutes prior to the check engine light coming on.

Good idea about running the generator...didn't think about doing that. I suppose if it doesn't run very well then that could be another indicator of fuel issues.

Will be back at it tonight and post results of latest efforts.

[azstarr]

Update: Rather than start with replacing the O2 sensors I figured I'd begin troubleshooting with the lease expensive courses of action. Cleared out the OBDII codes yesterday after dumping a couple of 16oz bottles of Seafoam in half a tank of fuel. Drove rig about 40 miles; no check engine light. Used OBDII scanner to check for pending codes; no pending codes. Plan is to drive on interstate this weekend and get operating temp up.

Did a sound check for exhaust leaks and heard nothing...tight as a drum. Although I did read something where a procedure to check for leaks is to put a few drops of seafoam into a vacuum line, which will result in creating smoke in the exhaust, which in turn will show if there are any exhaust leaks. Anyone ever try this?

[DriVer]

Originally Posted by azstarr

Did a sound check for exhaust leaks and heard nothing...tight as a drum. Although I did read something where a procedure to check for leaks is to put a few drops of seafoam into a vacuum line, which will result in creating smoke in the exhaust, which in turn will show if there are any exhaust leaks. Anyone ever try this?

I have not seen this diagnostic method detailed in the maintenance manuals. Exhaust leaks are best determined by direct observation and inspection.