528i hesitation and juddering when hot

[gav2612]

Just posting to see if anyone can help with a problem I have on my 1997 528i runabout.
The car runs fine when cold usually for ten miles or so. After that it hesitates and judders when accelerating and occasionally stalls at idle.
temp gauge sits bang on and doesnt budge.

Following previous postings I have:
Replaced the spark plugs
Swapped all of the coilpacks with ones from my other halfs X5, made a small improvement, but not major and X5 still runs great on the ones from the 5 series.
Cleaned the MAF
Cleaned the ICV
Replaced the fuel filter
Checked for vacuum leaks(seems to be a small leak round the inlet manifold, but that would surely affect the car at all times not just when hot)
Have cleared all fault codes and re read after a couple of days driving. No fault codes now showing where I presume a vacuum leak would throw lean misfire codes?
Any further ideas of what to check now?
I assume 02 sensor or MAF faults would show up as a fault code?
Fuel pump fault?

Thanks in advance for all the great advice I have had from both this and the other forums in pistonheads

[miniman]

I'm going for temperature sender fault. The car is up to temp, only the send thinks it isn't and the ECU adjusts the mixture accordingly. Don't forget that the sender for the ECU isn't necessarily the same one that controls the gauge.

[gav2612]

sounds like it makes sense. About the only thing I havent thought of! Any idea where the temp sensor for the ECU is?

[< FORZA WEST]

Several possible causes;

Poor signal from the inlet camshaft sensor.
Crankcase breather blocked or the diaphram has torn.
Air intake pipe to throttle housing os perished and torn (look around the short pipe that joins to the idle valve) Best way to check is to remove it as its not always easy to see on the bends.

[phelix]

What fault codes were in the ECU before you cleared them?

Can whatever you used to clear the fault codes read the data stream from the car? If yes see if the engine temp corresponds to what common sense tells you it should be when the engine is hot.

[gav2612]

Thanx guys

Would crankcase breather being blocked, air intake pipe leak not all show up when engine was cold as well? Already had the intake apart to look for tears, leaks but none visible. Where exactly is the crankcase breather? Is it under the inlet manifold? It could possibly be the CPS failing when hot. car runs like a dream for first 15 minutes/ 10 miles or so but almost like clockwork on struggling at the same point every time when heated up.

Basic code reader used for diagnosis so doesnt have live data for temps(will need to get carsoft) Error codes prior to clearing were traction control fault and airbag fault codes. No codes present now after over 200 miles although car is still running the same

Thanks again for the input

[gav2612]

Have just scanned the car for codes again and it has thrown codes 83 and 69. 83 is CPS sensor malfunction, with 69 being a fuel pump relay fault. will the CPS sensor be the inlet manifold sensor? does anyone think the 69 code could have been thrown due to the CPS fault or is it likely to be a seperate issue?