Rhythmic ticking, sluggish below 3k and idle issues

[markhinton]

Just recently my car’s been making a slight rhythmic ticking, which alters with revs, and led me to think it could be tappets. Checked the oil level and there’s no issues there, but another symptom which has always been apparent since I bought the car is the cold start idle, which fluctuates below 500rpm occasionally before retrieving itself with a rev to 1200ish to settle back to idle at 850rpm. ICV? Possibly, MAF? Also a consideration.

However, just this week I’ve noticed a more serious problem in that the car seems to bog down below 3000rpm. This doesn’t happen every time I drive it, only if I drive it for a short journey (not allowing it to get up to temperature) then restart the car a few minutes after - for example if I stop for petrol before making a journey. The car is hesitant to start, and when it does, it seems to be in limp mode below 3k. Once warmed up it doesn’t seem to change and the only remedy is to restart the car, which seems to reset it and all is fine.

From the symptoms it sounds like a failing VANOS system, and with them being so common on the M52TU engines I suppose there isn’t much harm in me replacing the seals.

I’m going to check the MAF and ICV before undertaking the work, but I imagine I’ll be ordering new seals this week.

So, to summarise;

• Rhythmic ticking with revs
• Poor idle at cold
• Bogging/sluggish below 3k
• Hesitant to start after short journey


Any help/advice on what to check would be appreciated. I’m going to plug it in to my friends diagnostics and see if any error codes, particularly vanos, appear.

[Del]

A history of lowish annual mileage and shorter trips than a typical daily user, can also cause the build up of "varnish" and "slight sludge" in a typical Z3. In the days of completely separate engine oil for petrol and diesel cars, it was often considered good practice to occasionally fill with diesel engine oil (with more detergents) to clean up older petrol engines. I had bad problems (sticky hydraulic valve lifters) with my 1.9 (no Vanos) cured by a succession of oil/filter changes using good modern petrol/diesel (e.g. API *SM/**CF) "thinnish" engine oil e.g. 0W-40 or 5W-30.

* S = Spark Ignition
**C = Combustion ignition

[Southernboy]

The rythmic ticking will be the injectors opening / shutting... that's normal...
Erratic idling sounds more lik an air leak in one of the hoses pre-intake manifold, or the engine pressure valve, which is fitted just below the MAF area.... This balances the internal engine pressure, and it's a good USA plastic item... over time this can crack and if it does, it will affect the idling as well as low speed / revs performance... as does any air leak in the hoses as mention previously... a careful check of all the hoses by uncoupling them, and bending them this way and that to look for any cracks in them is a good place to start... All things being well, you may need to add some injector cleaner to the fuel as an additive to ensure they are cleared / cleaned. Next are the spark plugs... if you're only doing occaisional short trips, the plugs may become fouled, remove and inspect them.... Finally, fuel... this is a trickier area since there's a fuel pump and a fuel filter... these both need to be functioning well...Filters are relatively inexpensive, pumps are another matter... Also check the fuel hose / pipe connections where they join up with the fuel rail... under the cover on the right as you face the engine...and if you're under there, you may as well use some contact cleaner to all the injector connectors too...be careful not to drop any of the little wire type clips used to secure them to the injectors...

[markhinton]

The rythmic ticking will be the injectors opening / shutting... that's normal...
Erratic idling sounds more lik an air leak in one of the hoses pre-intake manifold, or the engine pressure valve, which is fitted just below the MAF area.... This balances the internal engine pressure, and it's a good USA plastic item... over time this can crack and if it does, it will affect the idling as well as low speed / revs performance... as does any air leak in the hoses as mention previously... a careful check of all the hoses by uncoupling them, and bending them this way and that to look for any cracks in them is a good place to start... All things being well, you may need to add some injector cleaner to the fuel as an additive to ensure they are cleared / cleaned. Next are the spark plugs... if you're only doing occaisional short trips, the plugs may become fouled, remove and inspect them.... Finally, fuel... this is a trickier area since there's a fuel pump and a fuel filter... these both need to be functioning well...Filters are relatively inexpensive, pumps are another matter... Also check the fuel hose / pipe connections where they join up with the fuel rail... under the cover on the right as you face the engine...and if you're under there, you may as well use some contact cleaner to all the injector connectors too...be careful not to drop any of the little wire type clips used to secure them to the injectors...

I assumed injectors as well but I should have said, the noise is a bit clearer from the front of the engine - using a screwdriver as a stethoscope, it's definitely got some classic VANOS noise, no huge knocking but a definite gravelly noise around 2k

I tried running the car without the MAF briefly earlier and this seemed to get rid of the dipping revs, so perhaps a clean there will help. There's what seems like a hissing noise coming from the inlet manifold area, could be an air leak around there?

I'll be calling Munich Legends tomorrow for their advice, but I imagine I'll be ordering the Beisan Systems Vanos seal rings and rattle repair kit, as a precautionary.

Thanks for both your answers

[XVar]

I've been having similar symptoms recently, a pretty loud ticking noise that rises with revs, and when I start the engine from cold it seems to pull to 1500rpm briefly before dropping down. Going to start with an oil change since the oil service light has just come on (I reset it last time I changed the oil) but not really sure that's going to change much. What engine do you have? Mines a 2.8 M52 single vanos.

[markhinton]

Mine's a '99 2.8 M52TU dual vanos. Let me know how yours progresses and I'll keep this thread up to date, too. Best of luck!