I have a 1997 540i/6 with 140300 miles. Every once in a blue moon (about once ever 1k miles on average), my engine will cut out for a split second, or at least that's what it feels like. It's almost as if someone quickly jabbed the brakes, but it's not the brakes, just the motor cutting out. I scanned for codes when it did it in the past and nothing came up besides "Catalyst Converter below efficiency threshold" on both banks. That's a separate issue. I have not replaced the cam or crankshaft position sensors which is my first guess. I don't really want to go on a spree of replacing parts until I know what's wrong and I know if I fixed the problem. Right now the problem is more annoying than anything else - it leaves doubts in my mind about the car's reliability though it's never stalled or been hard to start and the problem is mostly embarrassing as it invariably happens when I have a chick in the car What all could cause this? Cam/Crank position sensors, MAF, TPS, anything else? Oh, the car has always been warmed up and driving for a solid hour before the problem occurs.
:edit: Actually, here's what it reminds me of. If any of you have spent some time behind a muscle car, it feels like when the timing is off and you're coasting down a hill. The car hickups - it's like what my car does, only mine is a bit more violent. I should also mention that every time this has occurred, I was at a very light throttle maintaining speed.
Last edited by Cyrix2k; 12-09-2008 at 01:48 PM.
Cyrix2k,
The first thing that comes to mind is the DSC. Does the loss of power feel anything like when the DSC cuts in to prevent the wheels from spinning in icy, slippery conditions?
hmm... that's a possibility. Again, it feels more violent then when ASC kicks in, but it does feel very similar to when ASC kicks in during hard acceleration in dry conditions. Hmm... maybe I'll disconnect the ASC throttle body cable for now and see if it happens again. I'm pretty sure sensors would throw codes so the ASC system would be a possibility.
BTW, I should mention I have almost new coil packs, spark plugs, and a full complement of gaskets. The throttle body boot needs to be replaced at some point, but is leak free at the moment. The normally runs great... no missing, smooth idle, plenty of power, and great mileage. I'll be sure to check on ASC system. I don't mind driving with it disabled for now.
My 2002 is doing something very similar. In fact, I just posted on this forum last night about it. In my case, it is a "shudder" that is very similar to the rev limiter kicking in. The engine shudders, coughs, etc., much like you describe, but in my case, it actually stalled a few times as well. As you mention, it is a fairly violent shudder that feels a lot like the ABS kicking it.
But I had the dealership pull the codes when I bought it in June and got it here to Alaska and they did not see anything at all. It only started this current violent shudder last night. Before that, once in a while when I was pulling out, the car would shudder almost like the ABS kicked in. A few times that caused it to stall, which is why I had the dealer pull the codes to see if there was a problem with the ABS system.
Wonder if the colder temp has anything to do with it as this car has led a California life until now. Could it be affecting the MAF or Dinan engine settings? I don't on't know.
Sounds like our cars' symptoms are very similar. Please see my thread "engine rmp limited and shutoff -- a little help please" from last night. It is on page three of this forum now and has not had any replies. If someone could "bump" my post for me, I would appreciate it.
Last edited by AKFine39; 12-09-2008 at 06:23 PM.
I'd tell you to check the IAC, but you don't have one... I just had another theory pop into my head. It almost feels like my dad's '69 when the gas tank vent was blocked. I have the wrong gas cap on my car which has been there pretty much since I bought the car. I borrowed a different cap from the 3er for about a week before I left it on the trunk and drove off Could this just be vapor lock or something?
Here's a time table for each hiccup:
1) 135000 miles, hiccuped at light throttle after a 90 minute drive. Rainy weather.
2) 136500 miles, hiccuped after ~90 minutes, but was turned off at 60 minutes. Dry / warm weather.
3 & 4) 137900 miles, hiccuped after driving about 200 miles. Turned off after 130 miles and again 50 miles later. Got gas, drove for ~10 miles, it hiccuped. Did it again 30 miles later. Drove home another 200 miles without event. Dry / warm weather.
5) 139000 miles, hiccuped after ~50 minutes. Rainy weather.
6) 140300 miles, hiccuped after ~70 minutes. Cold, dry weather.
The only common element is the long drive time. On the shorter drives, I had usually driven a significant amount immediately prior. Also, at least 5 of the six happend after getting gas. I can't recall if I had a fresh tank with #5.
:edit: I should also mention #3&4 was the most I ever drove the car in one go.
Last edited by Cyrix2k; 12-09-2008 at 06:26 PM.
My car has only 70K and it happens when I'm accelerating aggressively on the highway -- reving past 4500rpm yesterday. Last night in fact, after it shuddered/coughed/burped, etc. the tac then seemed to "freeze" at about 2500rpm and the car ran fine as long as I did not accelerate hard or take my foot off the throttle completely slowing for lights. If I accelerated hard, it shuddered again and kicked the revs down. If I slowed for a stop, that's when it stalled out. Running steady, it was fine.
The first major studder occurred when I was accelerating hard and going downhill.
I haven't filled it up recently and the gas cap is the same as when I bought the car this spring. But I did have the coolant system redone recently and the water pump replaced.
Not trying to jack your thread -- but thought your "hiccup" and "power loss" sounded very similar to what mine is doing. You describe it in terms very similar, although my problem produces a shudder more violent than you suggest -- all though it feels as you describe, like the ABS kicking in. Does not feel like DSC though. I'm familiar with that from our X5 and 325xi in past years. That kind of violent shake/stall is much worse and only happened when the car was breaking loose. This seems engine related for sure and affecting the tac/revs. Suppose it could be the MAF settings, fuel line or CAI. The engine didn't overheat, just wouldn't run close to normal.
Last edited by AKFine39; 12-09-2008 at 06:39 PM.
I'm not entirely convinced your problem is the same as mine. Your car is much newer so it has the M62TU instead of the M62 like mine, yours is DBW, and yours has DSC. I'd also recommend checking your fuel filter and cats. My issue has never been at high rpms and runs great to the redline. My shudder / hiccup is pretty violent though.
The CPS in an M60 did the same thing at high RPM, about 5500.
-Denton
I'm having a similar problem as the other poster with a TU. My car car won't rev above 4,500 sometimes I have no idea what it could be. It feels like there's more power down low than normal, but it won't rev past 4500 ?
have you guys replaced your vanos seals? before replacing mine during highway speads or past 3rd gear the car would hiccup as mentioned around the 3500rpm to 5500rpm range and it would feel like an intermintent loss of power. After replacing the vanos seals the problem went away. It has something to dow ith low pressure in the vanos due to the failed seals so the cars switching back and forth between camshafts... idk just another possibility
Yup. My car would occasionally shake violently before the cam sensor finally tripped a code. It would shake so bad at times the tranny would slap on the floor, but still no code. I threw in a sensor from Autozone. the AZ unit had "Germany" written all over it. So far, so good. BTW, mine died at 77k or so. Any other "stumbles" would most likely be your intake gasket(s).
I looked it up on EAC as well... was $12x. I wish it would throw a code so I could confirm the sensor is the problem. I'd prefer not to throw money at it to *hopefully* fix it. Oddly enough, Autozone does have the best price so far. I wonder if their sensors are okay to use?
I'm pretty sure your catalyst inefficiency issue is what is causing your cutout. I used to get that same somewhat violent cutout on the highway and in stop and go and when I replaced the busted cat and the 02 sensors in the car it all went away.
If the 02 sensors on the car haven't been replaced then they definitely need to be at this point. If you don't replace the cats then you'll probably still have issues with the car and will burn out the new O2 sensors pretty quickly.
I think the catalyst inefficiency is only due to the use of craptastic aftermarket cats. I'm fairly certain they're not blocked... my 318iC was in a similar situation. After running a hollow cat for a year and a half, the O2 sensor was still good in the rear... or at least good enough not to throw codes. My understanding is the front O2s are the only ones that affect fuel trims. I'll certainly check it out, but I really think it is something else such as the CPS, especially considering it only happens once every 1000 miles or so.
Yeah, I ended up shelling out for the OEM cat and 02 sensors. The local dealer gave me a parts discount to $1350 or so for the one cat I needed. Still astronomical, but now I have no codes and the cutout problem went away.
I think my cutout happened a bit more frequently than yours, but basically everytime it happened on mine the Check Engine light would either flash or go on and then I was getting 02 sensor codes and catalyst inefficiency codes.
OEM cats are insanely expensive. I guess that's why they were replaced with aftermarket units on both my cars. I paid $60 for a new aftermarket cat on the 318 and it was enough to get it through emissions. Another thing to keep in mind is that cats typically only fail if something else is wrong... such as the engine running too rich. That's probably where your O2 codes came from. I've never thrown an O2 code or any code BUT the cat efficiency code as a matter of fact. I bought an OBD II reader - best $99 ever. I'm looking into trying to get Carsoft to work now
I did some research on the aftermarket cat issue and there are really no aftermarket solutions that work as well as the OEM cats (not that the OEM ones are terrific either). All the aftermarket ones throw codes and/or burn out quickly. I've heard from vendors that used to sell replacements that no longer sell them because they would just burn out too quickly.
Bust the guts out of the cats . I think that may cost less than OE replacements.
Bookmarks