Cold start rough idle and surging E39 1998 540iA

[I Love Curves!]

hi all

'nother question.

My car doesn't like to idle very well on cold starts, it'll rough idle until it's warm, if you drive off without letting it warm up it will be very sluggish. It will loose power as you press the gas petal down until all the sudden it takes off like a bat out of hell! Also the transmission acts like it's in sport mode until the engine warms up too, meaning at normal acceleration it will hang on to the gears up to about 3k RPM before shifting.

The car has not died on me yet though.

After it's all warmed up the transmission shifts fine and the car idles just about like normal. The only issue after that is at part throttle, cruising down the road the car will cut out for just a moment like it's misfired. I had the codes pulled and it's registering a misfire on all 8 cyl and a random misfire code. I thought maybe it just needed a tune up. I've changed the plugs and it still dones it. I noticed that the coils are mismatched while doing the plugs, 5 have model xxx60 and 3 are xxx59. I have new coils and wires coming to see if that helps. I also orderd a crank angle sensor. The only other thing that i can think of that might thow a misfire code would be a crank angle sensor that i haven't ordered yet.

I seen someone with a 528i post something similar and others suggested a possible Cat being plugged up. I don't know if that's my problem for sure since I was under the car the other day and seen that the cats for this car have been replaced at some point.

Anyone else have this issue?

[I Love Curves!]

I should probably add that the car does not seem to have any mis when under hard acceleration.

Oh, and I just won a '93 525i on ebay, picking it up next Friday. Yay, a car for me!

[thejlevie]

A rough cold idle and associated misfires could easily be as a result of an intake leak and/or contaminated MAF. With no other known problems, that's where I'd start looking.

[I Love Curves!]

Ok, that helps. I've never had to work on, or replace a MAF. If a MAF is contaminated is it discarded for a new one?

[John 540i6]

how are the sparkplugs?

[I Love Curves!]

The plugs were pretty normal, maybe just a tad blackend on the electrodes.

[I Love Curves!]

Still waiting on parts from comment 1.

How does one know if a MAF is bad or test it?

[ataie]

ok,

- replaced all the spark plugs (they were bad)
- cleaned the ICV (which was dirty, sticky and not bouncing back/forth)

not ever 10% improvement on my problem - when started cold first thing in the morning, the car idles rough. after about 5 minutes of driving it's all perfect.

codes I'm getting:

BMW scanner:
- 16: Pre car O2
- 23: Fuel Trim QL additive cylinder 5-8

OBDII scanner:
- 0170: Fuel trim malfunction (bank 1)
- 0173: Fuel trim malfunction (bank 2)

the car has a little over 100k on it and it looks and runs awesome.

So what's the next step - please advise carefully, since replacing MAF or O2 are costly and I just don't want to change things for the hell of it. I do however want to solve this problem.

thanks

[C.Thurman]

Could be a bad oil separater on the back of the intake manifold!

[ataie]

I don't think so - I've changed several of them and you can usually tell if the car smokes first thing in the morning. there is no smoke on this one.

[I Love Curves!]

I know what it is on my car now. Front and Rear Intake Manifold cover gaskets are bad. The easiest way to tell is to spray a little starter fluid around the intake manifold and if the engine idle levels out or surges, then you've got a vacuum leak. It's also possible that your lower intake gaskets are the ones leaking or even an injector o-ring is responsible. Check out this thread:

http://forums.bimmerforums.com/forum/showthread.php?t=622905&highlight=intake+manifold

My local BMW shop quoted me $1060 to replace the intake manifold gaskets and valve cover gaskets... I bought all the parts to do it myself and the cost was less than $300.

[Hotswimmer]

+1. I had the same problem. Intake manifold gaskets. http://forums.bimmerforums.com/forum/showthread.php?t=566175

[Hotswimmer]

ok,

- replaced all the spark plugs (they were bad)
- cleaned the ICV (which was dirty, sticky and not bouncing back/forth)

not ever 10% improvement on my problem - when started cold first thing in the morning, the car idles rough. after about 5 minutes of driving it's all perfect.

codes I'm getting:

BMW scanner:
- 16: Pre car O2
- 23: Fuel Trim QL additive cylinder 5-8

OBDII scanner:
- 0170: Fuel trim malfunction (bank 1)
- 0173: Fuel trim malfunction (bank 2)

the car has a little over 100k on it and it looks and runs awesome.

So what's the next step - please advise carefully, since replacing MAF or O2 are costly and I just don't want to change things for the hell of it. I do however want to solve this problem.

thanks

By the way, you're making the same code interpretation error that most people make on the "16" BMW scanner code. If you read the manual and go back and look at it again, you'll see that it's actually code "1b" which is "Fuel Trim QL additive cylinder 1-4", which corresponds to the P0170 code from the OBDII scanner. Your manual for the Peake Code Reader will explain how to differentiate between "6" and "b".

[ataie]

thanks for the '16' and '1b'. info. my bad, now it makes sense - thanks

but now the questions is what the heck is fuel trim malfunction? I don't want to just change both of my pre cat O2 sensors, since there is a seperate code if the O2 was bad. I have no smoke at the start up so it's not the CCV neither. on all the BMWs I've changed the CCV, I had start up smoke. this car just runs / idle poor for the first 5 minutes, then when the temp is in the middle it runs just excellent. new spark plugs and also cleaned the sticky ICV - no change.

[Hotswimmer]

http://forums.bimmerforums.com/forum/showpost.php?p=7983552&postcount=3 And a fuel trim malfunction means that the air/fuel mixture going into the cylinders is incorrect, usually due to a vacuum leak, malfunctioning MAF, bad O2 sensors, bad CCV, etc.

[Big Chaze]

http://forums.bimmerforums.com/forum/showpost.php?p=7983552&postcount=3 And a fuel trim malfunction means that the air/fuel mixture going into the cylinders is incorrect, usually due to a vacuum leak, malfunctioning MAF, bad O2 sensors, bad CCV, etc.


What the heck is a bad ccv??

[Hotswimmer]

The CCV (or CVV) is the Crankcase Ventilation Valve - the equivalent of the PCV (positive crankcase ventilation) valve in the old days. On a BMW V-8, it's a large plate that seals off the rear of the intake manifold. On an I-6 car, it's this bell-shaped device that's nestled under the intake manifold. Do a search on CCV and CVV - there's been so much written about it on here, it's not worth repeating.

[razahyde]

haha you beat me to the thread randy. ive been in timeout for like 3 weeks lol

[jcdavis]

I have the exact same symptoms in my 540i, but I don't have any codes. Did anyone ever find out what the problem was? :help

[I Love Curves!]

Mine turned out to be the front and rear intake manifold cover gaskets (CCV is the rear cover).

I changed all of the gaskets though just to be safe. See this thread: http://forums.bimmerforums.com/forum/showthread.php?t=708385

[DJMarco]

Hello to all- I'm a newby here!

I have a 540i on a '98 plate (Multipoint LPG coversion) with a similar but not precisely the same issue. My car starts fine, seems to run ok for the first 10 seconds then seems to overfuel to the point where it bairly runs at all.. It spits and coughs and is basically undriveable until it warms up and then once at nearly optimum temp, she runs completely fine- in fact once she's warmed up properly the motor really couldn't sound smoother.

I've replaced the airmass and a temp sensor thus far to no avail (the sensor was on the housing that takes the water flow from the top of the rad to the head).

Any ideas??

Many thanks.

[alxvry]

Check CCV

[BM Fanatic]

Reading your symtoms of rough start up, sounds like my E39 540i. I will have to bite the bullet and replace my intake gasket and CCV valve at same time. I would like add another observation. Mine has a Schnitzer exhaust (Alpina model), so you hear every thing. Mine has developed a surge on uphill inclines, not steep enough to change down gears, so is between 1200 revs and 1800 revs, and only when the car is up to full operating temperature. The surge sounds like a change in timing and power and sounds like a cycling sequence of about 1.5 secs. To fix at the moment, I flick into sports mode and it goes down a gear and then OK. I saw on U tube someone has bought out a 80 degree therostate mod to stop pre ignition or knock in these cars, where the knock sensor probably retards the spark. That made sense to me as the problem sounds like a 318i with a faulty knock sensor causing surging under load. The diagnostic read out didn't list any faulty knock sensors only that it was reaching limit of controlling lean mixture. I don't want to modify thermostate as yet but will try intake gaskets fist and hopefully fix both problems. I will let you know results

[slammed540]

I have a 1998 bmw 540i that idles horrible when cold then smoothes out when warm any help.?

[gmak]

Did you read the thread? - likely gaskets where there are metal parts that expand when hot. You have a vacuum leak.

[theWalkinator]

Replaced intake manifold gaskets, CCV and CCV gasket, throttle body mounting plate gasket and throttle body gasket just in time before the cold weather, no rough idle in the cold morning anymore, car does not shaking after started in cold morning anymore. Past few days are brutal frigid but car starts fine, idlling smoothly and no white smoke coming out from exhaust.