Cayenne Diesel Preheat Indicator Light and Check Engine Light
01-08-2014, 02:12 PM
#16
Rennlist Member
That's a loada crap, I've never seen diesel fuel gel until the temps got below 0F/-18C. Lower if you put in your own anti-gel additive. Sounds to me as if they didn't even read the fault codes. In my experience with the 958 diesel, the GP icon simply indicates that a minor fault code has just been recorded. They're usually self-clearing. The check engine icon indicates a more serious fault code has just been thrown, and it often has to be cleared via the OBD2 port. But in both cases, they're still in the fault code recent event history. The dealer should have been able to see EXACTLY what triggered each icon.
Regarding fuel additives, I use Power Service; silver jug spring/summer/fall, white jug winter. At normal strength, it's an fuel path cleaner - with emphasis on injector tips. At double strength it's a cetane booster; the higher the cetane rating, the more complete the burn. On our crappy US diesel fuel, that translates into more mpg. When I purchase fuel with a cetane rating of less than 46, I add 12oz of the silver jug to the tank. that supposedly bumps the cetane rating up five points. The white jug contains the anti-jell additive. 6 oz per tank is enough to minimize jelling, but I use 12 to get the cetane boost at the same time.
//greg//
Regarding fuel additives, I use Power Service; silver jug spring/summer/fall, white jug winter. At normal strength, it's an fuel path cleaner - with emphasis on injector tips. At double strength it's a cetane booster; the higher the cetane rating, the more complete the burn. On our crappy US diesel fuel, that translates into more mpg. When I purchase fuel with a cetane rating of less than 46, I add 12oz of the silver jug to the tank. that supposedly bumps the cetane rating up five points. The white jug contains the anti-jell additive. 6 oz per tank is enough to minimize jelling, but I use 12 to get the cetane boost at the same time.
//greg//
Dealers in any area that experiences - or may experience - cold weather puts anti-gel additive in their fuel starting in about November. You'll see a bump in prices and a drop in MPG which will indicate when you're burning winter blend oil. I can't tell you how low it's effective to, but I've fired my diesels up without issue to about -20F.
As for additives, they're a loadacrap, too, imo. Maybe they'll boost your cetane, but at what cost? Maybe you'll get more mpg out of a tank of gas, but what is your cost per gallon after adding 12 oz of fluid and does it pan out? Perhaps adding a cleaner once in a while might be beneficial, but in general, they're just something to suck money from your wallet... more than for the value you get back.
They will run a bit rough at first until they warm up which can let diesel fuel get down the sides of the pistons, so let them warm up a bit before romping on it (i.e. highway onramp).
I've been driving diesel vehicles for about 15 years now. I've had two Dodge Rams with Cummins diesels and an E320 Bluetec for the past 4 years, too. I've never experienced gelling, and I've lived in Maine, Washington and Colorado. I don't even plug in the big diesel unless it's going to be under ~10F. Nor have I ever added any fuel additives.
Yep, diesel fuel is filthy. Sometimes, you'll get a dirty load and plug the filter before 20K. When my truck starts running rough, the first thing I go to is the filter. It's rare, but it has happened. Fortunately, the filter housing in the truck is easy to reach and make the replacement. The Benz requires taking the intake air tubes out and is a PITA!
Some tips to avoid getting really dirty fuel:
1. Buy fuel from a high volume station. Lots of turnover usually means clean fuel.
2. Buy where truckers buy, if you can. Lots of turnover and if they're buying there, the rep is likely good. Word spreads fast when a station gets a bad load of fuel and refuses to make good on it. Rare, but it happens.
3. If you know the underground tank has just been refilled, DO NOT fill up! The fuel going into the tank will stir up any sediment that's settled to the bottom of the tank which will kill your filter pretty quickly. Give it some time to settle back down and it'll be fine.
01-08-2014, 05:12 PM
#17
Can't speak for Ram diesels or E320 BlueTecs, my 2006 E320 was of the previous generation. But the EPA estimated mpg on the Porsche that replaced it is 19 city/29 highway/23 combined. I use a diesel tuning box and Power Service regularly, and have recorded 30.2 mpg combined since Dec '12. I've seen up to 36.2 mpg highway as well, so don't try to tell me that cetane additives don't help. It's a scientific fact that the higher the cetane rating, the more complete the burn. What that means in plain language is - less unburned fuel goes out your tailpipe.
And any of the new generation of common rail/direct injection clean diesels that "...run rough a bit at first" has something wrong with it.
//greg/
And any of the new generation of common rail/direct injection clean diesels that "...run rough a bit at first" has something wrong with it.
//greg/
01-08-2014, 05:24 PM
#18
Burning Brakes
I've had three diesels (not Porsche) and found it best to buy diesel at high volume stations where there's a lot of product turn-over. Crud grows in diesel left in storage tanks for extended periods.
01-08-2014, 06:10 PM
#19
Yes, diesel bugs can propagate in wet diesel tanks - on the vehicle as well as underground. But back to the matter of cetane. American refined diesel sucks; with few exceptions, it's hard to find any with above a cetane rating of 46. And those exceptions are usually brought in from Europe by tanker. In the rest of the developed world however, cetane is more typically rated between 50 and 60. Porsche actually had to remap the ECM to accommodate the lesser quality North American diesel fuel. Nevertheless, running rough when cold - while not normal in this new breed diesel - should not automatically be blamed upon the fuel.
//greg//
//greg//
01-08-2014, 08:31 PM
#20
Rennlist Member
Maybe "rough" is the wrong word, but used for lack of a better word. In the coldest weather, while the engine is cold, even with CRDs, they will sound different as they come up to temp.
Agreed that US diesel has lower cetane ratings than European fuel. I find it hard to find the cetane rating at the vast majority of stations.
I've heard of at least one CD recording 29.something over the past year and, as far as I know, that's without additives. Everything I'm hearing about these engines is phenomenal! I mean, an SUV, with AWD, getting damn close to the mpg that the E320 sedan is getting? Amazing!
I'm trying to convince the wife to make the jump now, but she wants to wait. The E320 is hers... and paid for.
Agreed that US diesel has lower cetane ratings than European fuel. I find it hard to find the cetane rating at the vast majority of stations.
I've heard of at least one CD recording 29.something over the past year and, as far as I know, that's without additives. Everything I'm hearing about these engines is phenomenal! I mean, an SUV, with AWD, getting damn close to the mpg that the E320 sedan is getting? Amazing!
I'm trying to convince the wife to make the jump now, but she wants to wait. The E320 is hers... and paid for.
01-09-2014, 03:28 PM
#21
Best my E320 returned was 39.6 mpg highway (275 miles stretch). Gonna be hard for my Cayenne to beat that. Best I've squeezed outa the Porsche since new has been 36.2 highway (350 miles stretch). That said, onroad diesel engine mpg generally increases between 0 and 35k miles, at which point it levels out.
//greg//
//greg//
01-10-2014, 01:32 PM
#22
Rennlist Member
How's this:
OK, OK, this was going downhill from 9000' to 6500'. But according to the computer - which I find 1-2 mpg optimistic, I've seen 41 on the highway, so ~39 would be about right.
If an SUV, with more room and AWD can get to 36ish, that's damn good!
OK, OK, this was going downhill from 9000' to 6500'. But according to the computer - which I find 1-2 mpg optimistic, I've seen 41 on the highway, so ~39 would be about right.
If an SUV, with more room and AWD can get to 36ish, that's damn good!
01-10-2014, 04:38 PM
#23
Shortly after I added my BSP I did a late night trip into the city and back with some driving around and getting caught at lights over an 80 mile round trip. If I remember correctly the MFD reported 36.7 (which really means in the 34 range from what I've observed). Like your trip it was ideal in that I didn't have traffic to contend with, but I didn't have gravity working for me in that case 
Just after I picked it up we did a run to FL and back from the DC area with a 16 cubic foot roof box and still managed 26 something (high 28 on the MFD) and that was before I installed the BSP. If the MPG drop matches the feel of the extra drag from the box, an actual 30MPG might have been possible.
And on top of that, it's still a blast to drive
Just after I picked it up we did a run to FL and back from the DC area with a 16 cubic foot roof box and still managed 26 something (high 28 on the MFD) and that was before I installed the BSP. If the MPG drop matches the feel of the extra drag from the box, an actual 30MPG might have been possible.
And on top of that, it's still a blast to drive
01-11-2014, 09:49 AM
#24
I want to thank everyone for the feedback on my original post. I also want to give some additional follow experience I have had related to my preheating indicator light.
Everything worked fine until approximately 2 weeks ago. One morning, I noted the preheating indicator light flashing after I started the vehicle and began driving. The light continued flashing for about 4-5 minutes, until I pulled over on the side of the road and turned off the engine. After restarting the engine, there was no flashing preheating indicator light and no check engine light. Everything has worked fine since, so I decided not take it back to the dealership. The temperature that morning was in the 40-50 degree F range and the vehicle had been sitting outside in a light rain overnight.
This all happened about two weeks ago, and I have had no problems since that episode.
I went back and looked in the Porsche manual and found the following:
"If a fault occurs in the engine control system while driving, the indicator light starts flashing or lights up continuously. Have the engine checked immediately at your authorized Porsche dealer"
The manual goes on to state:
"If the indicator light comes on when the ignition is switched on, this indicates that the glow plugs are preheating. The engine should be started as soon as the indicator light goes out"
So I can't help but think my second episode of a flashing preheating indicator light was somehow related to the first episode, whatever that problem may be? But the second episode was not associated with a "check engine light" as was the first episode. I still have not gotten around to using any additives and I am still using mostly Chevron and Shell diesel fuel. By the way, no problems at all starting up each morning during our 8 degree mornings of the Arctic Vortex.
After reading the manual again, I realize I should maybe simply turn on the ignition key and wait for the preheating indicator light to go off before starting the engine. I have never done this before, but the manual seems to imply doing it that way. This is my first diesel vehicle and I am not very knowledgeable about the mechanics of my vehicle.
I am wondering if I should take it back to the dealer for a check up even though I'm not having any problems. The manual seems to imply it would be necessary. But since the dealer seemed to be scratching their heads the first time, I can't imagine they would be able to figure it out now. During the second preheating indicator light flashing episode, the engine ran smoothly the entire time, never hesitating, skipping, etc....
Any thoughts?
Everything worked fine until approximately 2 weeks ago. One morning, I noted the preheating indicator light flashing after I started the vehicle and began driving. The light continued flashing for about 4-5 minutes, until I pulled over on the side of the road and turned off the engine. After restarting the engine, there was no flashing preheating indicator light and no check engine light. Everything has worked fine since, so I decided not take it back to the dealership. The temperature that morning was in the 40-50 degree F range and the vehicle had been sitting outside in a light rain overnight.
This all happened about two weeks ago, and I have had no problems since that episode.
I went back and looked in the Porsche manual and found the following:
"If a fault occurs in the engine control system while driving, the indicator light starts flashing or lights up continuously. Have the engine checked immediately at your authorized Porsche dealer"
The manual goes on to state:
"If the indicator light comes on when the ignition is switched on, this indicates that the glow plugs are preheating. The engine should be started as soon as the indicator light goes out"
So I can't help but think my second episode of a flashing preheating indicator light was somehow related to the first episode, whatever that problem may be? But the second episode was not associated with a "check engine light" as was the first episode. I still have not gotten around to using any additives and I am still using mostly Chevron and Shell diesel fuel. By the way, no problems at all starting up each morning during our 8 degree mornings of the Arctic Vortex.
After reading the manual again, I realize I should maybe simply turn on the ignition key and wait for the preheating indicator light to go off before starting the engine. I have never done this before, but the manual seems to imply doing it that way. This is my first diesel vehicle and I am not very knowledgeable about the mechanics of my vehicle.
I am wondering if I should take it back to the dealer for a check up even though I'm not having any problems. The manual seems to imply it would be necessary. But since the dealer seemed to be scratching their heads the first time, I can't imagine they would be able to figure it out now. During the second preheating indicator light flashing episode, the engine ran smoothly the entire time, never hesitating, skipping, etc....
Any thoughts?
01-11-2014, 10:16 AM
#25
You're misinterpreting the manual slightly.
1. You're starting the engine correctly, the glow plugs are on a temperature sensing timer. Older diesels required that you wait until the GP light went out before turning the key to start, but not these new clean diesels. When you turn the keyfob to START, it energizes the sensor and the timer. When starting parameters are met, the sensor engages the starter motor and turns off the GP light. As part of the clean diesel technology, the GPs don't actually turn completely off after the engine is running. This is called "after-glow", and helps promote more a more complete burn under cold engine/cold fuel conditions. I haven't seen it on my own, but there's a chance that 2nd flashing GP light was related to after-glow.
2. After starting, the GP light should never come on - unless/until the ECM throws a minor fault code. Minor codes stay in memory, but the GP light extinguishes with an engine restart. Any OBD2 diagnostic device will tell you what code(s) is(are) stored in memory. Most can also clear them from the memory. It's not necessary to take the car to a dealer for minor faults, unless they are chronic. Yours is clearly not (yet).
3. The check engine light comes on when the ECM throws a major fault. It too can be read with any OBD2 diagnostic device, but will not clear with an engine restart. Some of these faults are significant enough to put the engine/transmission into "limp mode". If/when you get a major fault, it should be checked out at first opportunity. If you get a major fault AND go into limp mode, go to the dealer immediately.
Most consumer OBD2 diagnostics are PC based, and connect to the car with a USB to OBD2 adapter cable. You should be able to find a selection with your internet search engine. I don't have a laptop or netbook, only an iPhone and an iPad. So I use a wireless device called iOBD2 ($65). It's a small WiFi device that plugs into your OBD2 port. The iOBD2 app is free, for both Apple and Android devices. The upside is that I can find out almost immediately - in plain language - which code was thrown and why. It also gives me the capability to clear codes from memory. The downside is that it cannot clear my "change oil now" warning.
//greg//
1. You're starting the engine correctly, the glow plugs are on a temperature sensing timer. Older diesels required that you wait until the GP light went out before turning the key to start, but not these new clean diesels. When you turn the keyfob to START, it energizes the sensor and the timer. When starting parameters are met, the sensor engages the starter motor and turns off the GP light. As part of the clean diesel technology, the GPs don't actually turn completely off after the engine is running. This is called "after-glow", and helps promote more a more complete burn under cold engine/cold fuel conditions. I haven't seen it on my own, but there's a chance that 2nd flashing GP light was related to after-glow.
2. After starting, the GP light should never come on - unless/until the ECM throws a minor fault code. Minor codes stay in memory, but the GP light extinguishes with an engine restart. Any OBD2 diagnostic device will tell you what code(s) is(are) stored in memory. Most can also clear them from the memory. It's not necessary to take the car to a dealer for minor faults, unless they are chronic. Yours is clearly not (yet).
3. The check engine light comes on when the ECM throws a major fault. It too can be read with any OBD2 diagnostic device, but will not clear with an engine restart. Some of these faults are significant enough to put the engine/transmission into "limp mode". If/when you get a major fault, it should be checked out at first opportunity. If you get a major fault AND go into limp mode, go to the dealer immediately.
Most consumer OBD2 diagnostics are PC based, and connect to the car with a USB to OBD2 adapter cable. You should be able to find a selection with your internet search engine. I don't have a laptop or netbook, only an iPhone and an iPad. So I use a wireless device called iOBD2 ($65). It's a small WiFi device that plugs into your OBD2 port. The iOBD2 app is free, for both Apple and Android devices. The upside is that I can find out almost immediately - in plain language - which code was thrown and why. It also gives me the capability to clear codes from memory. The downside is that it cannot clear my "change oil now" warning.
//greg//
