Limp Mode

[SparkleTooth]

Posting a New Thread for this:

So I had my first "limp mode" tonight. I came home from a drive with the girlfriend (mostly interstate). When we got home we were there about 10 minutes and then headed back out to a friends house to drop something off (only a couple miles away). When we left the friends house I was going up a hill and had no power, then as I kept driving I came up to another hill and it would not go above 25mph with my foot to the floor.
I pulled over and check the stats. 204 Water temp, 212 - 217 Oil Temp, and 204 Trans Temp.
Although warmish, I don't see a need for it to have gone into limp mode.

Anyway I took the girlfriend back home and shut it down to inspect some things. I ran a scan and found no errors of importance. I took it for another test ride for around 10 miles and found a big hill to take it up and had no issues. Now I am perplexed if this is a bigger issue or just another SOP for the ecodiesel.

Thoughts?

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[RicRecon]

I had a similar issue after taking a long drive from Elko NV to Craig CO last summer. It’s wasn’t overly hot but I had been running it hard through the mountains quite a bit before swinging into a small rest stop and immediate shutting it off. Less than 5 minutes later I started back up and as I pulled out into the 2 lane road, went into limp mode. Fortunately this was very rural and little to no traffic so I drive it slow for about 2 miles watching it cool down and then it regained speed. The PCM has a fail safe built in to derate. I knew better and should had let the Jeep idle while I was stopped for that short time after that long drive.

 

[SparkleTooth]

I had a similar issue after taking a long drive from Elko NV to Craig CO last summer. It’s wasn’t overly hot but I had been running it hard through the mountains quite a bit before swinging into a small rest stop and immediate shutting it off. Less than 5 minutes later I started back up and as I pulled out into the 2 lane road, went into limp mode. Fortunately this was very rural and little to no traffic so I drive it slow for about 2 miles watching it cool down and then it regained speed. The PCM has a fail safe built in to derate. I knew better and should had let the Jeep idle while I was stopped for that short time after that long drive.

I am hoping that is all it was, but I don't think the values I had would be considered out of normal range, but Im not exactly sure what the threshold is for throwing it into a Derate.

 

[RicRecon]

Yeah I was hitting high 230s into 240 but you never know. There are so many other conditions which could have an effect.

FYI, I spent the next two weeks traversing the Rocky Mtns, crossing at least 5-6 passes over 10k without any issues whatsoever. Oh and I was towing a 1,600lb overland trailer the entire way loaded down too.

I think it was two things: 1) that day I was going in and out of mountains through SLC and Northern UT/CO without stopping, and 2) I didn’t take the time to let it cool down for a few minutes before shutting it off.

 

[ChuckQue]

Your fluid temps are fine, could be heat soak causing something else or battery issues would be my first check. Those fluid temps are well within operating range.

 

[grimmjeeper]

Your fluid temps are fine, could be heat soak causing something else or battery issues would be my first check. Those fluid temps are well within operating range.

This.

After a drive at highway speed you get a lot of heat in the exhaust system and that will put you in limp mode if you start it up still heat soaked.

It happened to me once. I pulled off the highway at a gas station to make a quick pit stop. Jumped back in and I had no power getting back on the highway. I let it sit and idle for a bit and it was fine.

Now I have a gauge to show exhaust temps. Highway driving I can see EGT1 run 800°+ on a sustained drive at 75 MPH. When I stop now I idle until they drop down.

 

[ChuckQue]

This.

After a drive at highway speed you get a lot of heat in the exhaust system and that will put you in limp mode if you start it up still heat soaked.

It happened to me once. I pulled off the highway at a gas station to make a quick pit stop. Jumped back in and I had no power getting back on the highway. I let it sit and idle for a bit and it was fine.

Now I have a gauge to show exhaust temps. Highway driving I can see EGT1 run 800°+ on a sustained drive at 75 MPH. When I stop now I idle until they drop down.

Same here thanks to folks like you who posted about this stuff. I let the turbo cool down to about 450* before shutting down.

 

[SparkleTooth]

Well I did finally get my full belly skid plates and winch installed about a week or two ago so I am wondering if the skids are trapping more heat.

Looks like Ill be ordering a scan gauge today. Ive been putting it off because although I love to know the real time diagnostics of whats going on, I also find myself questioning or worrying about everything it tells me. For instance should this temp be this high, or should it be doing a regen now or etc etc.

 

[ALeeL]

This.

After a drive at highway speed you get a lot of heat in the exhaust system and that will put you in limp mode if you start it up still heat soaked.

It happened to me once. I pulled off the highway at a gas station to make a quick pit stop. Jumped back in and I had no power getting back on the highway. I let it sit and idle for a bit and it was fine.

Now I have a gauge to show exhaust temps. Highway driving I can see EGT1 run 800°+ on a sustained drive at 75 MPH. When I stop now I idle until they drop down.

Is that post or pre turbo, or with a constant grade? If the is pre turbo, then that is fairly hot for just cruising at 75 mph. My diesel BMW and 6.7L Cummins are at around 600F flat land driving at 75mph. Of course, both are deleted and I cannot remember what it was before they were deleted since it has been so long.

OP, I would wager that you were putting such a load on your Jeep that it caused to the DPF to get hot enough to go into a passive regen. Either that our you were close to your maximum soot level in your DPF and was close to an active regen. Both instances will cause EGT's t climb quickly and cause the engine to de-rate or cut fuel until these EGT's get back to safe levels.

It is also worth noting any restriction in your intake system or exhaust system along with any boost leaks will cause higher than normal EGT's so if your DPF is close to being clogged and air cannot escape quick enough, then it gets trapped before the DPF causing high EGT's. We don't really call this "limp mode" on the manufacturers level since that is reserved for when there is actually something wrong that needs to be fixed. We generally just call it de-rate or cutting fuel which happens more often than you think with various level of cutting power/fuel. At least that is what we called it at Cummins.

 

[grimmjeeper]

Is that post or pre turbo, or with a constant grade? If the is pre turbo, then that is fairly hot for just cruising at 75 mph. My diesel BMW and 6.7L Cummins are at around 600F flat land driving at 75mph. Of course, both are deleted and I cannot remember what it was before they were deleted since it has been so long.

OP, I would wager that you were putting such a load on your Jeep that it caused to the DPF to get hot enough to go into a passive regen. Either that our you were close to your maximum soot level in your DPF and was close to an active regen. Both instances will cause EGT's t climb quickly and cause the engine to de-rate or cut fuel until these EGT's get back to safe levels.

It is also worth noting any restriction in your intake system or exhaust system along with any boost leaks will cause higher than normal EGT's so if your DPF is close to being clogged and air cannot escape quick enough, then it gets trapped before the DPF causing high EGT's. We don't really call this "limp mode" on the manufacturers level since that is reserved for when there is actually something wrong that needs to be fixed. We generally just call it de-rate or cutting fuel which happens more often than you think at various level of cutting power/fuel. At least that is what we called it at Cummins.

That's the post turbo EGT. Some of that is we have a few grades here in Colorado. Sustained grades I'll see it up over 12000. But even relatively flat ground at altitude and speed I'll see some high temps.

 

[SparkleTooth]

Is that post or pre turbo, or with a constant grade? If the is pre turbo, then that is fairly hot for just cruising at 75 mph. My diesel BMW and 6.7L Cummins are at around 600F flat land driving at 75mph. Of course, both are deleted and I cannot remember what it was before they were deleted since it has been so long.

OP, I would wager that you were putting such a load on your Jeep that it caused to the DPF to get hot enough to go into a passive regen. Either that our you were close to your maximum soot level in your DPF and was close to an active regen. Both instances will cause EGT's t climb quickly and cause the engine to de-rate or cut fuel until these EGT's get back to safe levels.

It is also worth noting any restriction in your intake system or exhaust system along with any boost leaks will cause higher than normal EGT's so if your DPF is close to being clogged and air cannot escape quick enough, then it gets trapped before the DPF causing high EGT's. We don't really call this "limp mode" on the manufacturers level since that is reserved for when there is actually something wrong that needs to be fixed. We generally just call it de-rate or cutting fuel which happens more often than you think with various level of cutting power/fuel. At least that is what we called it at Cummins.

Good information thanks! It certainly caught me off guard because I had a car behind me and had to do an "Emergency" pull off onto a sidewalk because I lost all power basically and couldn't get above 25 mph and was declining. It was fine after sitting a minute or two.
I just purchased the Scan Gauge 3, so now I'll have 100 different new metrics to fill my head with.

 

[ALeeL]

That's the post turbo EGT. Some of that is we have a few grades here in Colorado. Sustained grades I'll see it up over 12000. But even relatively flat ground at altitude and speed I'll see some high temps.

Sorry, I meant to say if that was post turbo then it is fairly hot. Post turbo is generally 200F-400F cooler than pre-turbo. If that is an average with grades at altitude then that is about right.

On my Cummins, I have it set to alert me at 1,200F pre turbo. With the stock turbo, stock intake and a 5 inch turbo back exhaust, it would get their fairly often if I was just giving it the beans to get on the highway. Changing to a new intake helped a little, but upgrading the turbo to a fixed geometry really helped to the point I don't even get alerts anymore unless I am pulling a long grade while towing heavy. The BMW hardly hits 1,200F since it has been deleted.

 

[jrice454]

Good information thanks! It certainly caught me off guard because I had a car behind me and had to do an "Emergency" pull off onto a sidewalk because I lost all power basically and couldn't get above 25 mph and was declining. It was fine after sitting a minute or two.
I just purchased the Scan Gauge 3, so now I'll have 100 different new metrics to fill my head with.

Lol...was just thinking the same thing, would love the information but my engineer brain would go down the OCD hole.

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