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kayble

450 CDI loss of power on open roads

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Dear all,Am typing this from a meeting that I've just driven to where I experienced a bit of a problem on the way. I was in the outside (fast) lane of the motorway (do you guys call it highway/freeway?) and experienced a noticeable loss of power. At one point I was pushing an indicated 75-80mph when I felt the engine's power output drop notably without me coming of the gas pedal any (pedal was pushed to the floor). The loss of power was notable to the point that I had to drop out of the outside lane as I was loosing speed. Whilst I was trying to figure the problem out by slowing down, changing gears etc, it did sound like the turbo wasn't spinning up as quickly as it usually does when on the open road at high speed.There was a little bit of stop start driving round town as I got to the office and the engine felt fine (was able to rev above 3k), was able to spool the turbo up fine and get around. There weren't any warning lights or smoke/ odd smells.When I get home, I'll take a look at the turbo, EGR, turbo hoses, turbo manifold etc...Is there anything else I should be looking for though?

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Just a quick update from the drive home:Quick bit of city driving before I hit the motorway - engine felt fine, turbo spools up and down nicely.When I get on to the motorway, all feels fine under heavy acceleration right up to about 75 in 5th gear, engine winding up nicely, turbo fully spooled up...then I feel the engine power fall away with engine speed slowing to settle around 3k in 5th gear. switching in to 6th gear means I have to leave the outside lane and a few minutes later I have to switch back to fifth to maintain motorway speed.Coming off the motorway back in to city roads, the engine still feels week until I leave the car for five minutes whilst I go to the shop. When I get back in, everything feels fine again.Almost feels like a limp mode, but there are no warning lights on the dash to indicate a problem..any ideas?I'm going to let the engine cool then I'll start poking round.TaJohn

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just round the back of the car at the moment.The wastegate actuator arm doesnt appear to be stuck. It feels sprung loaded and appears to move easily before snapping back in to place under the spring.Any other ideas anyone? Is the symptom in fact limp mode? I don't get any warning lights on the dash and would have thought limp mode would have been accompanied by a check engine light?

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If you had a ScanGauge you could tell if the engine load is limited to 85%, which, in the absence of a 3K rev limit, could mean that your clutch actuator is failing.

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I think I might well look at a scangauge/ xgauge - but first I need to replace the leaky intercooler.I very recently had the clutch adjusted (both mechanical and STAR electronic adjust) plus I serviced the actuator itself. The gear works nicely and the car pulls like a horse until the fault occurs at high speed on the motorway..

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Hmm... sounds to me like an overboost situation. Rights itself after 2-3 switch off/on cycles, right?

Under heavy load at high speed on the... highway... Yes, maybe the wastegate; lube it with high-temp lubricant. Check the little hose that goes from the turbo to the wastegate head; it may have a little leak that only opens under top boost :dunno:

+1 on getting yourself a ScangaugeII or X-Gauge to view codes, boost, intake air temperature, etc.

Let us know what you find in the end, eh?

Bil :sun:

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Posted (edited) · Report post

Well I've just taken the car for another test drive after checking the wastegate arm and checking for loose hoses etc and it was pulling really well indeed.There was lots of power, quick gear changes and pulling all the way to the redline. I took it to around 55mph and it felt perfectly fine. It's odd then that earlier in the day it developed a fault that felt like limp mode but only when getting up to around 75-80 mph on the motorway. With my foot on the floor all the way up to that speed it felt fine andf then abruptly I lost a fair amount of the engines power. Yet, after shutting off the engine for a few mins it felt fine again until pushing it on the motorway once again and tripping the fault.What's going on?!EDIT: I should mention that car isn't modified or remaped in any way - so I'm wondering if my car would trigger an overboost related fault code?

Edited by kayble

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It's so hard to know what to look at in the absence of empirical data.....with a ScanGauge, you can do real-time monitoring of parameters such as MAP, which would show an overboost, and also % engine load, which I found was a key indication of the limp mode my car was suffering back at 82,000-87,000 km. The failing clutch actuator was allowing too much clutch slip when shifting and once in 6th gear on the highway - mind you, at only 90 km/h or so, but under 99% load - the car would "pop" and the % load was then limited to 85%, which felt like a huge HP cut. This did not trigger a check engine light, as it is a non-OBDII error.

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It's so hard to know what to look at in the absence of empirical data.....

I agree. Trouble is, my car is a 2001 Fortwo cdi and from looking on the web at both Xgauge and Scangauge related posts, it would appear that my car is incompatible with both given it is pre 2004...what are my options?

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If anyone you know has a ScanGauge, could you borrow it to give it a try? If not you could order one and then maybe return it if it's not working.....

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Yeah, a scangauge (if it even works on the earlier diesels) would be the ideal way to check what fault code might be stored against this problem.I did take a look at the wastegate actuator arm yesterday evening. I gave it a good lub with some silicone based spray lube and worked it in to the joint on the manifold and as the arm enters the actuator itself. I then greased up the joint on the manifold with some copper based grease. I took the car for test drive and the fault did not reveal itself.Now that isn't conclusive as when I got to the arm, it didn't seem to be rough in its movement or overly rusted up on the manifold joint - so I'm thinking that the underlying issue is still present.That said, I still need to replace the intercooler and will be doing that before buying any scangauge!

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This is after you re-sealed the old intercooler? Or was that someone else?

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Ah yes, forgot to mention - the intercooler repair failed...again!It never rains but it pours... and I also got a glow plug warning light on the dash today. GRR

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Intercooler replaced for new part.EGR valve thoroughly cleaned.The fault is still there.....As it happens, I'm due a fuel filter change. I've ordered the filter and it will be in tomorrow so I shall change it out and see if the fault persists. If it does, I don't think I have any other choice than to have my fault codes read out at Mercedes :(

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Ah yes, forgot to mention - the intercooler repair failed...again!It never rains but it pours... and I also got a glow plug warning light on the dash today. GRR

Again!? What failed - your sealing job let go, or...?Bil :sun:

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Again!? What failed - your sealing job let go, or...?Bil :sun:

Yes, the silicone seal gave out so I had to source a replacement part from Mercedes.I'm getting to the point of fixing one fault, only to have another occur in a few days. I know the intercooler seal would probably fail - but to go from replacing the intercooler to getting a limp/safe mode fault all the time is getting real tiresome.

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I've been sniffing around for new intercoolers in Germany and it seems that some are out there for under 100 Euros new....so I will see if I can get one to replace my leaky one (which, for all I know, may be leaking through a wear hole).Kayble, have you managed to get any codes on the car read yet? I had a limp mode in my car some time ago that did not throw a CEL code but there was a proprietary M-B/smart code stored that indicated the gearchanges were slippy, clutchwise, which was traced correctly by my dealer to the clutch actuator. It's probably something simple like that.

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I've been sniffing around for new intercoolers in Germany and it seems that some are out there for under 100 Euros new....so I will see if I can get one to replace my leaky one (which, for all I know, may be leaking through a wear hole).Kayble, have you managed to get any codes on the car read yet? I had a limp mode in my car some time ago that did not throw a CEL code but there was a proprietary M-B/smart code stored that indicated the gearchanges were slippy, clutchwise, which was traced correctly by my dealer to the clutch actuator. It's probably something simple like that.

Mike, I'm going to bite the bullet and have the codes read next week. Do you have the code written down that your car stored?

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Kayble, the fault code in mine was P1704 (RPM difference between engine and transmission when clutch engages - slippage).

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mine pulls nicely up to 115km not sure what that is in mph . i have up graded to brabus by the dealership when they first came out. plus have added k&n and s mann air vent for more air and brabus heat shield in the back and other goodies from the dealership. MB cdn upgraded to a two smaller turbo unit which i find is smoother. after my first service back in 2006 the killed my engine and replaced it with a better unit the whole engine ever part .first turbo unit starts up at 30kph and second around 55kph and sounds great up to 4500rpm then up shift and the fun starts again . it pulls really strong catching many cars off guard at the lights once i get to speed settle back and listen to the turbo sing and the engine go . ah yes brabus power . :D:rolleyes::smile_anim::speak_cool:

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Kayble, the fault code in mine was P1704 (RPM difference between engine and transmission when clutch engages - slippage).

Thanks - there's a chap on the UK Smartmaniacs site saying that his CDI came down with this particular issue. He didn't mention the particular code, but mentioned RPM difference etc. He replaced the clutch as opposed to the actuator in his case owing to transmission oil leaking past the input shaft seal.I don't see any oil mist on the bellhousing on my car - but I have had to service my actuator more often than not. After about a year of owning the car, the actuator became noisy so I serviced it with lube and had the actuator adjusted by MB.Since then, I've stuck to servicing then adjusting the actuator at B service intervals. I wonder if it is now giving up the ghost?Before I have the car diagnostics check done, I still have a problem with blaming the clutch because the car shifts really nicely round town and I don't feel any slip at all. In fact, the only time I feel a problem with the car is when it throws limp mode. Right up until then it feels perfectly fine.In fact, there's another question - which might be a little hard to phrase:Since the car only feels like it has a problem when it throws limp mode, do I need to get it to throw limp mode before I go to Merc to have the codes read, or will it have stored a code associated with the last time it threw limp mode?

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MB cdn upgraded to a two smaller turbo unit which i find is smoother.

I would love to see some pictures of how they did that.

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MB cdn upgraded to a two smaller turbo unit which i find is smoother. after my first service back in 2006 the killed my engine and replaced it with a better unit the whole engine ever part .first turbo unit starts up at 30kph and second around 55kph and sounds great up to 4500rpm then up shift and the fun starts again .

I would love to see photos of this alleged Mercedes-Benz sanctioned twin turbo engine :huh:

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