canonicalman

I recently replaced the vacuum line to the fuel rack on my 98.5 1.8TQM, as the old hose was crumbling to pieces. Simply replacing this one hose made an enourmous improvemnt in engine performance. This also cured the detonation and rough idle problems that the car was having.

Now after a test drive -- pretty rough one at that -- there is a sewing machine like ticking and chugging sound from around the engine. The sound is faint but noticeable from inside the car. I am unable to pinpoint the exact source of the sound, but it is not the engine mechanicals itself. Rather the sound appears to come from under the intake or behind the engine. Also, the engine is starting to detonate occasionally under hard acceleration again.

I'm wondering if more vacuum leaks have appeared? For a modern, electonically controlled engine, this car certainly has a lot of complicated vacuum lines and components.

I would like to replace all of the vacuum lines to get rid of any vacuum problems at once so I won't have to chase them down one at a time if they appear. Does Audi, or anyone else, sell a vacuum line replacement kit? Also, the Bentley CD does not have a vacuum line diagram for the AEB engine. Does anyone have such a diagram?

Any other comments or suggestions?

ModifiedA4

pop the hood, and check it out.

8Rings

Under the IM, between runners 3 and 4 is the PCV valve, it Ts into the crankcase vent. My PCV split in half, the ruber T was torn on one side and the plastic hose to the crankcase vent itself was split open. The car ran like crap. under there as well is the vac line to the throttle body and the lines to the vacuum accumulator with lots of check valves and reducer/expanders.

The only way I can get in there is to pull off the radiator fill tank and then reach up under the IM but it's still like working with your eyes closed. I would almost recomend taking off the entire IM to get to all the vac plumbing.

Hopefully, by this weekend I will have it all back together. Fortunatly the parts, from the dealer, have not been too bad. $9 for the PCV valve, $12 for the T and $25 for the plactic hose.