Furb

iTrader: (2)

hi guys, i need some thoughts here with me!

have some probs with the TII for a while now, but haven't sorted them out.
i'll try to explain everything as good as possible.

i have a '91 S5 TII
my engine is still stock, now 30k after rebuild. (bought the car with 9.2k)
only modification done is the Apex'i air intake.


problems started a while ago with this:
- when still a bit cold, engine is hesitating at low rpm when pulling up slow.
- hesitating at 6,5k at full boost
- little lack of power

actions taken to solve problems:
- replaced MAF sensor (this solved the low rpm hesitation)
- blue connector from duty solonoid (boost pressure control) was loose

so we thougt that solved the problem, it also looked and feeled better, but after a very shoirt time had the same 6,5K rpm hesitation.

then we:
- replaced duty solonoid
- replaced boost sensor
- replaced hose to boost sensor

i suggested to just wait and see what will happen in a longer period of time, to find out what the exact symptoms were.

what i found out was, that after taking the car to a show, which was about 300km in one day, my 6,5k hesitation problems were all gone.
i even found out, that after having the car in the garage for 2 weeks, just making short drives, the hesitation problem returned.
when i took it for a long drive, again no problems, so my guess is that it's ignition related. (not enough juice?)
but after that, this problem hasn't occurred for about 4 weeks.
i also had more power, because my boost went up a little higher then it used to!
it never got passed 0.45bar and now got a strong solid 0.5bar

in the meanwhile, i've come across some other problems.

one time, it wouldn't start. thought it was flooded, but after pulling the fuse, and trying and trying it just wouldn't start.
then i heard a sound! my duty solonoid which was replaced was clicking then i pulled the connector and the car started instantly!
haven't had the starting problem ever since, but did have the clicking solonoid.

now i'm coming to the biggest of my problems, which i have now for a couple of days now.
- lack of power
- very irregular boost! it builds up, then lowers, builds up again. very strange!
- redline buzzer doesn't sound at the normal 7k, but it goes of at 6k. come to think of it, i've had this one time before, but didn't really think much of it.
- idle is normally at about 750 or 800rpm, but now at sometimes its at normal idle, but most of the times it almost drops dead. idles at about 400rpm i guess. when i play with the throttle a little, then idle will some times stay up at 800rpm.
it's no vacuum leak, cause idle is nice and steady. it's just at very low rpm

now i disconnected the battery, so i will check in a few days if that has given any effect...


i know, its a long story, but i hope you can make something of it!
tried my best to give as many details as possible

my guess is my ECU is passing away or something like that...

NZConvertible

The boost control solenoid valve has a black connector. It's the one clipped to the oil filler pipe seperate from the others. The one with a blue connector is the Relief solenoid valve, which is just emissions control.

Did you test these before replacing them? Testing components as per the FSM is much quicker and cheaper than replacing them unnecessarily.

I'm not sure why you think it's ignition-related just from that, but you should still make sure the system in good condition. If the spark plugs are more than a year old, replace them. If the spark plug wires are original, I'd replace them too. They do wear out with age, and can cause hesitations and poor performance.

It's supposed to click rapidly. The ECU pulses it open and closed at about 20-30Hz (from memory) and varies flow through it by varying the duty cycle. If it's not clicking then something's wrong.

Have you checked for leaks in the boost control lines? Any leaks in the lines to the wastegate actuator and boost control solenoid valve will cause erratic or high boost.

Have you checked that's not a low oil or coolant warning? The same buzzer is used for all three warnings.

A vac leak doesn't necessarily cause an unsteady idle. Considering the age of the car, a broken vac line or TID should be considered highly likely. It would be worth the effort to replace all the vac lines, and to remove the TID and inspect it thoroughly, particularly the turbo end. This gets very brittle due to many years of heat. If emissions checks are not required where you live, consider removing the emissions controls entirely. This is probably easier than replacing all the vac lines, and eliminates many possible leaks (if done right).

That would be the last thing I'd worry about. ECU's are extremely reliable and rarely go bad. It's far more likely to be the components attached to the ECU than the ECU itself.

Furb

iTrader: (2)

mine is Euro-spec, maybe that's different? but the rotary-specialist said it was the boost solonoid.

i did not replace them with new ones, just with good used ones we pulled of the shelve at the rotary specialist.

i do suspect the plug wires, so they are on my shopping list for this winter!
the plugs have only been in for about 7k km

you mean when the engine is running? when it clicks, it is when i turn on the ignition, but not starting the engine!

haven't checked yet, but planning on replacing a lot of this stuff this winter

both oil and water are fine

also planned for this winter

maybe, but i will wait and see what will come out...

Furb

iTrader: (2)

im going over to the garage this evening, i'll reconnect the battery and take it for a spin. i'll post my findings this week when i get back from Portugal