Losing power when warm

[Wolfgang]

Howdy all. As the title suggests, my 09 H3T alpha has an issue with losing power at, from what I've read, the standard operating temperature of 220°F.
So, first off, is 215-225°F indeed the normal operating temp? And if so, any idea what could be causing this loss of power?

 

[alrock]

How you are defining losing power? Does it go into limp mode? How are you verifying the temp of 220? Is that low power just from taking off after sitting at a stoplight or does that include after driving fifteen minutes or so without stopping and just trying to accelerate past someone else?

If the engine is hot (say, high end of the range), it's hot outside and the fan clutch isn't working, your engine may seem sluggish. Or at least that's how mine will feel after sitting at a stoplight in 110 degree weather. After forcing air through the radiator by driving around, it operates more normally. I'm not sure if my fan clutch has failed but I'm going to replace it soon regardless.

 

[Wolfgang]

It's a general loss of power, about 30 to 40 percent loss if I had to guess, struggles to get going from a stop, and struggles to get up to speed.
It doesn't seem to be going into limp mode, it's certainly not telling me at least.
And I have a gauge that plugs into the OBD2 port that reads off of the computer to tell me my temps.
While it only really gets to that temp while sitting (probably due to my 160° thermostat),I believe I can hear the fan blowing harder once it gets up to 220, plus I recently replaced the fan clutch so I don't believe that's the problem, and 220 seems to be a tiny bit over the halfway mark on the factory gauge, so I dunno.

 

[jimmy p]

Can you check your intake air temperature from your obd2 gauge? See if the power loss correlates to hot air temps.

Sent from my SM-G960U using Tapatalk

 

[Jeepwalker]

Guys, are there two coolant temp sensors for this vehicle? ....I'm not sure. Often, vehicles will have one CTS for the cluster, and another for the PCM. The cluster can show normal, but the PCM temp 'could' be off (leading the vehicle to 'think' it's not warmed up). So i guess that would be one thing to find out. If there are two, ohm out the sensor when vehicle is cold, then again when warm. Or you can use your scan tool if it gives you that info. Generally issues turn out to be one or more a combination of basic maintenance items.

Items I would investigate:

1) MAF sensor reading (is it on the low end of the 'normal' spectrum, or right where it needs to be?). I had a worn out MAF on a vehicle (non H3) once which the mv read at the low end of normal spectrum. Vehicle ran poorly with dismal power. By all specs it should have been ok. I cleaned it several times, it made a marginal difference. Eventually I took a leap and spent the $60 on a new Bosch which immediately restored operation and normal power. So check you MAF readings, clean and check again. Aftermarket breathers that use oil can screw up a MAF.
2) Carbon depositing on the throttle body - This can have a much larger impact than guys often think. Make sure all surfaces are clean with carb cleaner and a plastic brush (don't use any metal brushes!).
3) Check spark plugs for wear or cracks in the porcelean. Not common, but happens. A crack (if present) can widen when warm and allow spark to leak. Same thing can happen with a coil too. Bad plugs can lead to premature coil failure.
4) Ohm out the coils cold and warm.
5) Install a vacuum gauge and observe readings. A rodent could have chewed a hole in a vacuum tube, or a plastic pipe (or gasket) could have cracked. A gasket could be faulty. Low vacuum will result in poor fuel evaporation ..and operation.
6) Quadruple-check batt connections and grounds - Sounds dumb but these vehicles (all modern vehicles) are sensitive to poor electrical connections
7) Inspect filter, air box, etc - In case a rodent happened to build a nest you didn't know about, plugging up the engine's airway once the vehicle reaches speed.
8) Fuel pressure.. Often fuel pumps show their weakness when they have warmed up.
9) O2 sensor readings - They don't last forever
10) Catalytic converter back-pressure
11) What is the operating temperature (actual)? Check close to the head with an IR temp gun or another instrument to get an *actual* operating temp reading. Could be as simple as a non-operating thermostat. And these T-stats aren't known to be forever-lasting lol. Buy a Delco if you have to replace.
12) Reset the PCM - Never hurts to unhook the battery cables and tie them together overnight (not hooked to the batt of course, but to each other), to drain and reset the PCM.

The list is random thoughts, not in any order. Start with the cheapest and easiest-to-check items on the list first. All factory service manual troubleshooting trees instruct the technicians to double-check the basics first as they are often the problem.

 

[Jeepwalker]

Couple things I would add to above list:

1) Check your alternator charging and battery (and again the grounds). The Grounds and battery connections are really important because all the switching and engagement for your engine's injectors, etc all happen through the 'grounds'.
2) Connectors for injectors (and sensors) for any corrosion that might lead to an intermittent signal when the engine warms up. Also check the injector o-rings. They can crack. Spray some ether or dispense some propane around the injectors to see if operation changes. I have a Jeep now that has a leaky injector 0-ring I need to replace.
3) I would perform a compression check cold, then warm (with all plugs out and do 4 rotations). Record the results. I doubt your issue is compression related, but you want to eliminate all possibilities. I happen to have one cylinder that's definitely enough lower (than the others) on compression. So it's definitely something that can can be a possibility.
4) PCV Valve. The little PVC valve can cause a lot of problems if they get gummed up and don't seal properly. Inspect and replace if you have doubts.
5) EGR - I don't know what EGR system (if any) your rig has. But if none of the other things on this list make a difference, it's definitely something to check.

Let us know if any new codes appear

 

[Gpcalero]

Howdy all. As the title suggests, my 09 H3T alpha has an issue with losing power at, from what I've read, the standard operating temperature of 220°F.
So, first off, is 215-225°F indeed the normal operating temp? And if so, any idea what could be causing this loss of power?

If your Alpha has an aftermarket thermostat, I am assuming you have it tuned as well? Even if it isn't, I would hook up a computer to the vehicle and use HPTuners or similar, to datalog all the PIDs and see exactly what the T is doing when it is losing power. That'll be the easiest way if you or a friend has the capability.

Guys, are there two coolant temp sensors for this vehicle? ....I'm not sure.

Just the one. It's on the driver's side valve head and very easy to replace if need be. There are other PIDs to pull temps from(ambient, oil, trans, etc.), but they are not coolant temps so just be aware.