chain tensioners change on a 4.2
11-05-2015, 07:45 AM
#11
AudiWorld Super User
ok, so far so good. We changed both tensioners, started the engine and drove the car about 500 km. What i don`t like is that the car has no power, especially in lower revs. Vagcom shows now faults but the car remains somehow sluggish. What bothers me is that we might have not aligned the chains correctly.
In accordance to what i have read and what i saw as i got my tensioners changed by the local dealer, there is a slight difference between the number of notches/ chain links on every bank/side. While between the camshaft marks on bank 2 (right side when you stand in front of the vehicle) the distance has to be exact 16 notches/links of the timing chain, on bank 1 it is a few mm less than 16 notches. Is that correct? If not, i`m afraid the gear of the camshaft might have skipped a few degrees? Any hints or ideas?
In accordance to what i have read and what i saw as i got my tensioners changed by the local dealer, there is a slight difference between the number of notches/ chain links on every bank/side. While between the camshaft marks on bank 2 (right side when you stand in front of the vehicle) the distance has to be exact 16 notches/links of the timing chain, on bank 1 it is a few mm less than 16 notches. Is that correct? If not, i`m afraid the gear of the camshaft might have skipped a few degrees? Any hints or ideas?
But instead as a different idea, if you are feeling it is weak in the lower revs, also check the intake manifold vacuum switching. Make sure all the vacuum lines are on correctly, the diaphragms work under vacuum, the linkage from them isn't broken, and the internal manifold flaps can actually move. If it isn't working or stuck in the high RPM position, it can feel sluggish. Working properly, you can feel some surge in the power curve in the mid 3000 RPM range, at least back on my 2000 A6 4.2 with the same general set up.
11-06-2015, 10:51 PM
#12
AudiWorld Senior Member
I would change all of the idlers. Tho bearings in the idlers are well past their prime. With new idlers, new belt, water pump, etc. the noisiest thing on the engine while idling are the injectors. Everything else is almost silent.
11-16-2015, 10:25 PM
#13
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what do you mean with "idler", richard?
little update here: MAF is suspected dead. Reason - disconnecting it nothing changes. However last night we performed the MAF test, reading the values on vcds, group 2 - under max load it reached about 200 g/s which is about 68 g/s lower than expected (BFM engine has 335 hp x 0.8 equals 268), so a new one was ordered. What bothers me - why nothing changes when disconnecting and reconnecting the MAF at idle but the sensor works at higher revs even though not as a new one?
little update here: MAF is suspected dead. Reason - disconnecting it nothing changes. However last night we performed the MAF test, reading the values on vcds, group 2 - under max load it reached about 200 g/s which is about 68 g/s lower than expected (BFM engine has 335 hp x 0.8 equals 268), so a new one was ordered. What bothers me - why nothing changes when disconnecting and reconnecting the MAF at idle but the sensor works at higher revs even though not as a new one?
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