Workhorse Chevy Loses Power After Warming Up

[rvgeorge]

well this morning I took it back to my friends shop, I drove it for about an hour did about 75 to 80 KM and nothing, ran fine. Only difference today is it was kind of cool this morning so I'm puzzled, outside heat causing it not engine heat? After the fuel pump instal I went about 50KM on a hot day and it started to act up, one hot day I barely went 10KM and it started acting up. When I spoke to my mechanic friend he did say when he had hooked up last time I think he said the fuel pressure was off but it was mostly the left side. Hope he figures this out soon, love to go away with no worries for a couple of days. Oh and I bought one of those OBD things and got the Torque app, hooked it up to my Pickup truck first and it worked gave me readings no codes then I put it on the RV, it found it, knew it was a Workhorse but when I asked for the diagnostics it kept saying error try again, did that a dozen times, nothing.

 

[DonTom]

well this morning I took it back to my friends shop, I drove it for about an hour did about 75 to 80 KM and nothing, ran fine. Only difference today is it was kind of cool this morning so I'm puzzled, outside heat causing it not engine heat? After the fuel pump instal I went about 50KM on a hot day and it started to act up, one hot day I barely went 10KM and it started acting up. When I spoke to my mechanic friend he did say when he had hooked up last time I think he said the fuel pressure was off but it was mostly the left side. Hope he figures this out soon, love to go away with no worries for a couple of days. Oh and I bought one of those OBD things and got the Torque app, hooked it up to my Pickup truck first and it worked gave me readings no codes then I put it on the RV, it found it, knew it was a Workhorse but when I asked for the diagnostics it kept saying error try again, did that a dozen times, nothing.

Something I just now remembered from that . . .

This is somewhat of a longshot, but have you tried the highest grade gasoline? We once had a car that lost power going up hill because of pinging which we could not hear. Gasoline needs higher octane when the engine is hot. A higher grade gasoline than recommended in the owner's manual was the fix.

In that case, it was a Buick V6 that lost power when going up Waldo Grade (just north of the Golden Gate Bridge) back in the late 1970's and was a lot worse on warmer days.

-Don- Richfield, CA

 

[rvgeorge]

Maybe but I have used regular gas since I took delivery in 2008 and never had an issue, even when I was in Florida 100 degree plus weather.

 

[DonTom]

Maybe but I have used regular gas since I took delivery in 2008 and never had an issue, even when I was in Florida 100 degree plus weather.

There was a time we could say the same for that Buick. What happens in time is carbon builds up in the cylinders and increases the compression so then a higher grade gas is required to prevent pinging, which cannot always be heard.

But we never had an issue with that car where it was pancake flat, such as would be the case in Florida.

Anyway, intermittent issues usually require some guesswork and often what is not expected will be the simple fix. So try the various simple things first.

-Don- Richfield, UT

 

[rvgeorge]

thanks, I'll keep that in mind and try it when I get it back if he cant figure it out.

 

[Mark_K5LXP]

Quite improbable this issue is octane, but if you want to prove it you can watch timing advance in Torque. For the engine to lose that much power I would expect the timing to go to zero advance. Now, if that ends up being an actual result I wouldn't suspect octane but I might suspect the knock sensor(s) which are actually high on the suspect list for this engine. Generally the problem with the vortec is the opposite, despite a lean condition causing knocking the ECM was programmed to ignore knock literally to the point of destruction. Which is why it's important to monitor long term fuel trims because that's the first clue it can be running lean. Another cause for reduced power can be engine temperature sensors. There's more than one and while the dash gauge may be reading normal, the ECM may be seeing something else. Torque will show what operating parameters it's seeing.

Mark B.
Albuquerque, NM

 

[Ex-Calif]

I had a very, identical problem on my 93 jeep Cherokee. Distributor capacitor on old style points ignition had a hot short. Also an ignition coil itself can have hot condition open or short failures.

I replaced capacitor and no fix. Troubleshot all over and replaced new capacitor again. Yup. Failed new out of box.

 

[rvgeorge]

might be fixed, I think the problem started with an exhaust leak before the 02 sensor, that may have caused my original problem where I could drive for a while then it would act up , shut it down for a bit then go again but that may have caused one or two injectors to fail and that's why it started happening more often and complete shut downs. I knew I had an exhaust leak, wasn't that bad so I didn't really worry about it but I was told a leak before the sensor is a bad thing. Anyway I had all injectors changed and fixed the leak. I drove about 70 to 80 KM towing my MKX with the AC on to make sure and sure enough it ran well. Only concern is it was warm day and not a hot day and every time before it was always a very hot day. Fingers crossed but its almost Sept so no more real hot days to test it up here in the great white north. May have to wait until next summer to know for sure.

 

[DonTom]

, I think the problem started with an exhaust leak before the 02 sensor

I have run a couple of cars as well as one old motorhome with the O2 sensor disconnected. No noticeable difference in performance, just a check engine light. So I have my doubts that the 02 sensor had anything to do with it.

-Don- Baker, NV

 

[TheBar]

I have run a couple of cars as well as one old motorhome with the O2 sensor disconnected. No noticeable difference in performance, just a check engine light. So I have my doubts that the 02 sensor had anything to do with it.

-Don- Baker, NV

I had problems with my RV O2 sensor causing intermittent check lights by running too lean. Which was a known problem on a Ford forum. I installed an O2 extender spacer so it reacts slower than being directly in the exhaust stream. I did not delete the catalytic convertor. The light went away and I never saw a decrease in gas mileage.

 

[rvgeorge]

took it out today since it is much warmer, MKX attached and AC on did well for about 70KM but sure enough it started acting up, from a stop push the pedal down it starts very slow after a second or 2 she starts go but its not full power. At least its wasnt making me do a complete shutdown now. I bought some electronic cooling spray on AI advice to cool down the computer when it got hot, didnt work.

 

[woof-n]

I would check your chassis grounds for the ECM. Clean, wiggle test and reassemble with Dielectric grease. Low cost, noninvasive, your mechanic should be able to do this for you in an hour. He can also show you where to lift the wire on the ECM temp sensor. This will keep the motor in closed loop mode. If the camper goes in limp mode lift the wire to see if runs better. I would try to divide and concur. Is it in the ECM circuits or not.

Good luck

 

[rvgeorge]

I would check your chassis grounds for the ECM. Clean, wiggle test and reassemble with Dielectric grease. Low cost, noninvasive, your mechanic should be able to do this for you in an hour. He can also show you where to lift the wire on the ECM temp sensor. This will keep the motor in closed loop mode. If the camper goes in limp mode lift the wire to see if runs better. I would try to divide and concur. Is it in the ECM circuits or not.

Good luck

Thanks I need it, I'll ask him to look at the connections when he gets back from vacation. I also ordered a cheap scanner so I can see what is happening when it starts cutting power. I tried the Torque Pro but all it did was tell me it was connected, if I wanted anything else it wanted me to buy a subscription, gave me no info whatsoever. Wish I could get a mechanic to drive for an hour or so but all they do is take around the block and tell you its running good now. Then I'm back the next day telling him no its not.

 

[woof-n]

Thanks I need it, I'll ask him to look at the connections when he gets back from vacation. I also ordered a cheap scanner so I can see what is happening when it starts cutting power. I tried the Torque Pro but all it did was tell me it was connected, if I wanted anything else it wanted me to buy a subscription, gave me no info whatsoever. Wish I could get a mechanic to drive for an hour or so but all they do is take around the block and tell you its running good now. Then I'm back the next day telling him no its not.

You could also fill up the tank. Tell him you will pay him to drive it with his scanner plugged in on a hot day. An hour of diagnostic labor is less than guessing which part to change next.

 

[rvgeorge]

You could also fill up the tank. Tell him you will pay him to drive it with his scanner plugged in on a hot day. An hour of diagnostic labor is less than guessing which part to change next.

I was thinking that already, I'll ask when he gets back.

 

[Mark_K5LXP]

I tried the Torque Pro but all it did was tell me it was connected, if I wanted anything else it wanted me to buy a subscription,

Free Torque will give you all the basic emission gauges. You have to place the gauges on the screen and select what they measure. Torque Pro offers a greater number of engine parameters, along with some transmission and brake codes if your ECM is supported. Free torque will show MAF, MAP, TPS, Load%, timing, short and long term fuel trim. Plenty to start with.

Mark B.
Albuquerque, NM

 

[Jackiemac]

Can you (or preferably a friend) take video or photos when it happens. That might help...

 

[rvgeorge]

Free Torque will give you all the basic emission gauges. You have to place the gauges on the screen and select what they measure. Torque Pro offers a greater number of engine parameters, along with some transmission and brake codes if your ECM is supported. Free torque will show MAF, MAP, TPS, Load%, timing, short and long term fuel trim. Plenty to start with.

Mark B.
Albuquerque, NM

wouldn't give me anything, it connected, it came up as a workhorse but nothing else, everytime I selected anything to look at it took me to a subscription page.

 

[Mark_K5LXP]

It looks like the pay for free version is an apple thing. Only two ways I know to fix that.

Mark B.
Albuquerque, NM

 

[Henry J Fate]

Do not know if this has been mentioned or not

The air intake to the engine (intake manifold) is regulated by throttle (gas peddle). Sensors (I think 2) determine how much fuel to inject into the cylinders.

The air intake control has an actuator that opens and closes a butterfy like design on the intake manifold based on your gas pedal position.

Since all cylinders (I assume all) have a no response to the request for more power, I would be suspecting either the actuator for the air intake or possibly any of the sensors calling for fuel into the cylinders however, I would suspect that the air intake butterfly is malfunctioning unknowingly to the computer which is not providing a fault code.

Hope you get to the bittom of this. The 8.1 Vortex is a great engine and should be providing great reliability.