E38 735i 1997 Engine Stalls when cold. Bad idle when cold

[MrChrysler]

Hello everyone,

I have problems with my BMW e38 735.

Just before I explain my problem on forum, please watch whole video with annotations.

https://www.youtube.com/watch?v=KFjQW92uty4

Most of the problem is described in the video.
The biggest problem is when engine is really cold, it stalls every time when I engage a gear, or when I brake to stand still.

What could cause this problem?
I replaced MAF - nothing
New o2 sensors- nothing
New idle control valve - nothing
New spark plugs - nothing
Fuel pressure - constant 3 bar
No air leaks
Fuels injectors have been tested - they are in good condition

[kulgan]

How did you test for vacume leaks? and where did you test for vacume leaks?

Does the car start to run better after its warmed up?

I'd be willing to bet that you have a vacume leak somewhere around your inlet manifolds or your throttle body gasket has cracked?

[MrChrysler]

I tested it for vacuum leaks - there are none - That is how I tested the system - I took maf out, placed plastic bag on it and then I installed it back on - like that the air was unable to escape from system - then I connected my air compressor to one of the smaller pipes that is connected just after MAF and before throtle...I Created 1 bar of pressure in the vacuum system, absolutely nothing happened, I couldnt hear air escaping!

[Keymaster1234]

Air filter maybe? Does it really "bite" when you put it in to gear, it could be the trans messing around, stalling the engine. I also noticed that you dash seemed to be varying in brightness when you rev'ed it, is your battery good? these cars are very sensitive to voltages, bad battery's cause all sorts of problems.

[kulgan]

Does it run better when the engine has warmed up?

[MrChrysler]

It's not possible to stall i when it runs for like 10 min.

I tested it on 3 different batteries, all of which were good.

[kulgan]

I still think you have a vacuum leak. Get a can of engine start and spray all your intake manifold gaskets and throttle body gasket. If the engine revs higher when you spray you've found a leak.

https://www.youtube.com/watch?v=s1fTSP8VHvA

[MrChrysler]

I dont think so, but I will check it and let you know...

[MrChrysler]

P0443* (pending) Evaporative Emission System purge control valve circuit - could this cause a problem?

[MrChrysler]

Any idea?

[kulgan]

Have you done the vacuum test with the can of engine start yet? I'm curious to know what you found?

[Keymaster1234]

CCV maybe, checked the air and fuel filter, checked the spark plugs?

[MrChrysler]

I think that i found a problem. o2 sensors... for people how are going to read this!
If your o2 sensors are dead, they will make your engine to look like, you have an air leak + also like your MAF is gone!

There are so many posts where people write about rough engine idle, lack of power, bad consumption, engine stalling - my advice check o2 sensor before doing anything else in first step.

[Sobek]

I thought o2 sensors weren't factored into anything until the exits its cold start program? Hmm, not entirely certain.

[Nyc Dito]

how about the jet pump?..i wonder if this would affect what youre seeing happen in your car...

[MrChrysler]

Lambda Sensor tell the engine to adjust a mixture of fuel to air... when lambdas are gone, engine thinks that the mixture is too lean and it tries to enrich a mixture... Too much fuel causes rough working since there is not enough air to burn it completely... Engine has no power and therefore it stalls when load is applied.


Now the car works fine, apart from when the engine is warm!? When I start the car in morning, it is fine. I can engage gear as many times as I want to.... However when it warms up to mid-temp... the car stalls everytime when I engage a gear. Why? Also when is hot, the car is working fine.

[Chalkynz]

Hello everyone,

I have problems with my BMW e38 735.

Just before I explain my problem on forum, please watch whole video with annotations.

https://www.youtube.com/watch?v=KFjQW92uty4

Most of the problem is described in the video.
The biggest problem is when engine is really cold, it stalls every time when I engage a gear, or when I brake to stand still.

What could cause this problem?
I replaced MAF - nothing
New o2 sensors- nothing
New idle control valve - nothing
New spark plugs - nothing
Fuel pressure - constant 3 bar
No air leaks
Fuels injectors have been tested - they are in good condition

I have very similar symptoms with my automatic 1997 E38 740i. Car stalls when put into drive or reverse. NEVER happens after warmed up. Possibly worse in bad weather. Computer show P0340 - Camshaft Position Sensor. I am yet to replace it, I'm going to get oscilloscope screen grabs first. I did try a replacement sensor from Ebay, but it was a cheap knock-off job, the car wouldn't actually start with that installed. Does make me wonder if mine is fine, maybe issue is just dodgy wiring. We shall see.

[MrChrysler]

Are lambda sensors the same on 1996-1998 and from 1998-2001?

[MrChrysler]

I had 0258 003 802 on left cat, and 0258 003 453 on right cat...

Can someone tell me which lambda is for 1996-1998 735? I have only 2 lambda in the car, not 4.