99 528i Cold Start Rough, Runs Perfect After Restart

[bd92]

Hello all,

I am stumped with my brother's 99 528i running rough. Every morning the car turns on and it idles rough. You can feel it misfiring and vibrating. It does not stall and the gas pedal does not have to be held on for it to stay on. Once it warms up, you can drive it around and you can still feel the misfires as you drive it around town. Still has power and shifts fine, but you can feel the hiccups as the car revs up and shifts to the next gear. It will stay this way until you shut off the car and immediately restart it. Once you restart the car, it runs perfect. No hiccups as you drive it. No misfires. No stumbling idle. No weird noises from the engine bay. The Check Engine lights stays on even though it is running perfectly. EDIT: Forgot to add that Check Engine codes are only misfire codes for different cylinders.

If you restart the car as the engine temperature reaches the end of the "blue" coolant temperature, the car turns on and runs perfectly as if it were firing on all cylinders. It will stay this way all day until it gets cold and sits overnight.

Over the life of the vehicle, it has suffered several issues. It has been overheated about a year and a half ago and the head gasket blew. Used Blue Devil head gasket repair to give it some extra time before we decided what to do with the vehicle. It "cured" it and since then no oil changes have had the chocolate milk or the coolant be dark with mixture of oil. No white smoke from the tail pipe and it only smells a bit like fuel in the mornings due to the rough cold starts. Little to no oil consumption between oil changes and coolant level remains the same.

Repairs done to the vehicle:
- Vanos seals with Besian o rings
- 6 brand new OEM ignition coils
- 6 NGK spark plugs
- New Genuine BMW Crank position sensor
- Replaced CCV with Genuine BMW
- All vaccuum hoses replaced
- New knock sensor
- MAF has been cleaned
- ICV cleaned
- Valve cover gasket replaced
- Changed O2 sensors with Bosch

The car also used to suffer from throttle body codes. It would cause pentometer error codes and the car would barley move. I found a used unit with the same color sticker, same year, same model and same model number and when installed in the vehicle it would not move at all, only idle. I cleared adaptations with INPA and it still would not budge. Put in the old throttle body and it ran perfect with no more throttle body codes. The throttle body codes pop up once every 3 months now.

I apologize for the long read but the car other wise is in decent condition and I want to get more miles out of it, but driving it with misfires obviously is not helping the overall engine longevity. I saw only one post just like mine when I searched but it was 4 years ago and there was no solution posted. I feel like I may have a huge vacuum leak but i have inspected the hoses and I for the life of me cannot find any tears or unplugged hoses. Any ideas?

[effduration]

I have two 528i's ('99 and '00) with that engine. I have owned one of them since 2003 and do most of my own work.
I don't know exactly what's wrong with your car, but things I would look into - In no particular order

Would you post exact codes?

Not sure about that Blue Devil sealing product - How about a compression test to rule out any head gasket problems?

I have had 4 similar throttle body failures. I have replaced them with used units (resetting adaptations ea time) that haven't worked out. I have replaced the accelerator cable that was notchy. I am beginning to suspect a loose connection in the round connector that connects to the TB = Others have written about this. I have bought a used engine harness and will probably swap it at the next failure.

Pull the MAF sensor connector and see how it runs without it? (engine should revert to a known good fuel/air mix)

smoke test to make sure no vacuum leaks?

Due to the intermittent nature of all this, you might check and de-scale the major engine grounds in the engine compartment.

Please provide an update if things improve

[bluptgm3]

Spark plug coil extenders are also new and replaced with new coils?
Which spark plugs are you running?

Sent from my iPhone using Tapatalk

[danb1979]

Might be something you've replaced already but not mentioned, but what about the air intake boot from the MAF to TB, are there any splits to it at all? Drawing extra air in after the MAF will make it run lumpy, won't it?!

And as above, unplug the MAF and run the car, see how it reacts then

[StephenVA]

I would suggest that it is time to go to the basics and do a few tests with a code reader, compression tester, vacuum gauge and a voltmeter and then clear all the codes and go for a cold cycle to hot run 20 miles and re-pull the codes.

[Poolman]

Well how about this,,double temp sensor, not giving accurate reading for cold weather, which in turn leaves the engine fuel mixture , not rich enough at idle when cold

[BimmrMeUpSnotty]

So many of these same threads going on this winter.

My post from the other thread, someone had suggested some gas treatment for the possibility of h2o in the gas.

It’s not h2o in the gas. I have the same exact issue on my 528 wagon, just as a lot of others have too on their i6’s since the fall. It always comes up as a misfire code on my #4 coil, it doesnt change if i move the coil to another plug. My 528 does it every winter, once the car is warm, and you restart, it runs perfect. I have done everything but ccv and vanos, but am not ruling out a peepsqeak vacuum leak somewhere. The colder it is, the rougher the car runs at start up. It does stall sometimes, up until the temp gets past the blue area in the guage. Once it gets past the blue, restart the car and all is perfect. In the fall, gas milaege dropped down to 19/22, city/highway, I did the rebuild on the DISA valve, changed the plugs, car is now back to 24/28 mpg, but yet the goofy start up exists. If it was the maf sensor needing cleaning or replacement, wouldn’t that throw another code? I have not seen it, but if it’s the maf sensor, then the car would run like crap the whole time. So I don’t want to accidentally ruin the maf sensor if I don’t have to. Anyone have any luck using CRC maf sensor spray cleaner?

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Well how about this,,double temp sensor, not giving accurate reading for cold weather, which in turn leaves the engine fuel mixture , not rich enough at idle when cold

all my temp sensors are new, well, less than a year old, but for the external temp sensor under the front bumper. But it reads right, just a few degrees off from what the weather channel says it is on my phone.
Sorry for the hijack/piggyback, op.

[bd92]

Thanks for all of the replies all. I will definitely attempt to do a compression test once i can source one from an auto parts shop and see what the results are.

As for the codes, i will try to get those tomorrow when i get home early enough to connect INPA to the car.

The new coils were also installed with new coil extenders. Spark plugs are NGK OEM. They have been replaced several times, never any discoloration or signs of issue with the used plugs. New intake boot from MAF to throttle body as well.

I was thinking of the temperature sensor since i have never replaced that. I may order it and see if it helps any. I was thinking possibly vanos solenoid for the intake? If i recall correctly, my brother told me that he got a code for that many months ago, i personally never saw it on INPA though. Theres a chance i could have remembered wrong. Any symptoms of a DISA valve failing? What does it do exactly?

I was thinking maybe our Secondary Air Pump could be a cause? It doesnt make any weird noises but it seems its not rare for it to fail. Possibly it causes issue when car is cold and attempting to do its thing. Then when we restart the car, the DME realizes the car is not cold and decides to not turn it on, so the car runs perfectly. Again, just throwing ideas out there hoping to find a solution for a problem i didnt realize alot of us have been experiencing. I dont mind anybody chiming in if they are experiencing the same issues. The more information we gather, the better we can find a solution.

[geargrinder]

Yes indeed tons of 'cold start problems' cropping up these days!

For a normal rough idle misfire situation I'd like most of the suggestions above (vac leaks, temp sensor, etc.) but almost none of them explain the 'runs fine after the restart' angle.

That symptom points to something that gets triggered or jammed at a cold start, but then 'releases' when there's a warm start.

Something like the SAP, although the SAP typically won't cause a misfire like that since it just blows into the exhaust... so unless its related to the SAI vacuum solenoid getting jammed and causing a vacuum leak (that'd be 2 failures - sticky solenoid + vac leak on the downstream hose...) so not sure I'd put money on that specifically.

Here's an E46 thread suggesting lifters with leaky bores can cause the cold-misfire-goes-away-on-restart issue, however that seems like an extreme replacement job for such a minor symptom on an aging car.

https://www.bimmerforums.com/forum/s...olved-(finally!)

Wonder if a nice light visco oil might have 'solved' the lifter pump up problem temporarily for that guy... (what visco oil is in your brother's car?) The 'only in cold weather & works on restart' would possibly be explained in that case from the warm oil being thinner and flowing in better at startup vs. at cold temps when the rapid movement of the lifters cavitates air before the thicker oil gets a chance to fill the cavities quickly enough.

[effduration]

I was thinking maybe our Secondary Air Pump could be a cause? It doesnt make any weird noises but it seems its not rare for it to fail. Possibly it causes issue when car is cold and attempting to do its thing. Then when we restart the car, the DME realizes the car is not cold and decides to not turn it on, so the car runs perfectly. Again, just throwing ideas out there hoping to find a solution for a problem i didnt realize alot of us have been experiencing. I dont mind anybody chiming in if they are experiencing the same issues. The more information we gather, the better we can find a solution.

My first cold start problem occurred yesterday am when it was near 0 degrees F. I started the '00 528i and took off without much of a warm up. I threw an SES (Check engine ) light immediately. Once I realized I was not in limp mode, I continued on for 15 mins. Drove home at end of day with same SES light. When I got home I scanned it and got Secondary Air Pump insufficient flow codes (Peake table 15 codes F6 & F5) on banks 1-3 and 4-6. I reset codes and car re-started last night and this am (not as cold..maybe 9 degrees) without throwing the SES light. I chalk it up to very cold temps and not warming up. since all was fine today, i am guessing secondary air pump is fine. The secondary air valve mounted to head could probably use a replacement. Vac lines were recently replaced.

At least my secondary air pump system doesn't like the cold weather.

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[bd92]

I apologize for the late reply to this thread i had started.

I ended up spending an afternoon rechecking all of my vaccuum hoses and looking for loose wires. The top vaccuum hose that runs on top of the intake manifold ending up being bad. A simple tug and it broke right off. Definitely was a vaccuum leak there. Fixed it and put everything back together. Hoping for the best and when i started the car, it still sounded like an old school v8 engine struggling to idle.

I noticed i had an "!" warning light on the dash that comes whenever the throttle body is throwing a code. Throttle body always seems to throw a code whenever you look at it wrong. What fixed the warning light is by pushing the wires on the throttle body connector inwards on the connector. I figure there may be a bad connection there. It explains why some people have had luck replacing the engine wire harness when they were getting throttle body codes and it making the codes go away. Since i have done that, i have only received the throttle body codes 1 other time.

When i was taking apart the car to look for another possible issue, i noticed the Cam position sensor infront of the vanos had some oil inside the connection. Everything in the area was dry and clean, so i assumed maybe the sensor broke internally somehow and it was allowing oil to get through. I ended up replacing the two cam position sensor and it was night and day! Car still started like a v8 but definitely a huge improvement. No misfires codes initially but you can feel the slight rumbles of misfires while it idled cold. Runs amazing warmed up! It didnt throw codes for the CPS but it was definitly bad. Or possibly the engine wire harness could be bad and just moving stuff around with a new sensor helped fix something? Not sure, but putting a new CPS regardless was a great decision.

I got a code that comes every now and then and it is for the VANOS intake solenoid. I think this may be the last possible issue to fix the rough cold start. Is it possible to clean the solenoid or is just buying a new one the best thing? Used? Could it be a sign of something else being wrong? Either way i plan on putting the vanos intake solenoid of my other 528 that is working perfectly and see if that solves my cold start idle issue.

Thats it for now. Just wanted to give an update for people still looking for a fix. Hope it helps! Atleast with the warmer climate (atleast in Socal) the issue isnt as prevalent. I will update once i get a working vanos solenoid switched in.

[geargrinder]

AFAIK there's nothing you can do to 'service' a VANOS solenoid except clean/check the electrical connector... Since you have another to swap I'd do that first and see where you get. I dunno how $$ the M52 solenoids are but the V8 ones aren't cheap - I'd be tempted to try to find a cleaner / low miles junkyard one.

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(that said I did buy 2 new ones for my car years back when I discovered that somebody had tried to hack the ones in the car for some bizarre reason -probably thought he could do some performance mod or something with them...)