Workhorse Chevy Loses Power After Warming Up

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Original Member Title: engine derating
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A member with a 2008 Adventurer on a Workhorse Chevy chassis reported that it runs normally for about 30 minutes, then loses power or enters a limp-like condition after warming up. It may rev higher before shifting, sometimes has almost no power in gear, and usually runs normally again after being shut off for a few minutes. No check engine light or stored codes have been found, despite prior work including catalytic converters, tune-up, fuel filter, fuel pump relay, O2 sensor, and a planned...
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rvgeorge

Advanced Member
Joined
Nov 22, 2014
Posts
51
Hello again, my 2008 Adventurer on a Workhorse with a Chev engine keeps derating after it gets hot. Runs great for about 30 minutes then I lose power, sometimes it seems to cut back to half power it shifts gears ok but revs much higher before shifting. Other times it pretty much makes me pull over, no power, floor it nothing. When stopped I can rev it sounds fine put it back in gear and nothing.
Usually if I shut it off for 5 minutes or so it fires back up and runs normally again for a little while then acts up again.
This started last year, it did it once on a hundred mile trip but then ran fine for the next 150 miles or so. We dont use it much anymore but this year it is doing it all the time. Took a trip about 80 miles and it shut down on me about 10 times.
No codes no check engine light so when you hook up to it there is no codes.
First thing I was told was change the Catalytic converters, I did that and they were really bad, all broken up inside but that didnt solve the problem. Had a complete tune up done last year as well. Changed fuel filter, changed the fuel pump relay.
Anyone had this issue? Thanks.
 
Does the engine lose power or feels like the tranny is slipping?

Do you have a tranny cooler or a tranny temp gauge?

Do you have oil, water and tranny temp readings?

I don't know how sophisticated the computer is but first guess is it's some kind of protection mode, although usually that limits to a limp mode and you can still go.

What does the tranny fluid look like? Bright red is good. Dirty red to black is bad and very bad.

I'm guessing tranny due to you saying a period of half power.
 
tranny not slipping, just changed the tranny fluid and filter, looked fine. No the only temp gauge I have is water temp. At times it is limp mode and I can keep going but eventually it makes pull over and do a reset. Other times it completely shuts me down right a way and I have to let it sit and cool down. When it fires back up it runs great.
 
rvgeorge said:
tranny not slipping, just changed the tranny fluid and filter, looked fine. No the only temp gauge I have is water temp. At times it is limp mode and I can keep going but eventually it makes pull over and do a reset. Other times it completely shuts me down right a way and I have to let it sit and cool down. When it fires back up it runs great.
Click to expand...
Surprising it gies into limp mode with no stored codes.

Have you dumped the memory?
 
Not the 8.1 but I had a Manufold Absolute Pressure sensor disconnect caused poor performance.

You need a code scanner the connector is to the left (Usually) of the steering column. You can buy a scanner or a simple BT adapter like I use.

Some electronics will malfunction if too hot.. or too cold (like -40 cold)
Had both happen the latter on a car.
 
John From Detroit said:
Not the 8.1 but I had a Manufold Absolute Pressure sensor disconnect caused poor performance.

You need a code scanner the connector is to the left (Usually) of the steering column. You can buy a scanner or a simple BT adapter like I use.

Some electronics will malfunction if too hot.. or too cold (like -40 cold)
Had both happen the latter on a car.
Click to expand...
been hooked up to a scanner, no codes.
 
I am understanding you to say, the RV runs fine when cold or when you first start out then loses power. The engine control module, (ECM) has two modes, open loop and closed loop. Open loop uses predetermined values from the OEM to control the engine until it reaches an optimum operating temperature. It then goes into closed loop mode where all of the engine sensors provide the input to optimize the engine performance. My first test. I would disconnect the ECM temperature sensor at the engine to keep the RV in open loop mode. Test drive to see if the if the problem goes away. If it does not, it leads me to believe the problem something other than what ECM controls. Such as the catalytic converter, fuel delivery, ignition etc. If the problem goes away, this is NOT the resolution, it is just a test. My gut feeling is that one or more of your engine sensors to the (ECM) has a bad ground connection. The ECM is thrown into limp mode because it does not know what to do. Typically, the ECM grounds, are found on the frame in the engine bay. (Note!!!!!) do not test grounds with a digital multimeter. They do not produce enough load to adequately test the connections. Use something that creates load such as a light bulb. Good luck Please let us know what you find.
 
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