Spinnetti

1999 B5 1.8tqm 260k mi

Wasn't running great, with a full load stumble. Replaced plugs and coil packs, and stumble went away. I can floor it in 5th at 20 mph and it just pulls gently away. Anything less than WOT it hesitates. What could cause that? I replaced the MAF (twice) and the Throttle body is new too. I ran injector cleaner though thinking leaky injector, but it had no impact. I have a test pipe and fresh turbo too. After this many miles, should I replace the injectors? Is it a waste to have them cleaned? (Any DYI?)

thanks.

4Driver4

Did you do a throttle body adaptation with the new throttle body? That would be step one.

Prospeeder

Temp sensor will cause alot of problems. Did you use NGK or Bosch plugs? no Air leaks or boost leaks? Codes? EPC light?

Spinnetti

Can't seem to find air or boost leaks. I did throttle body adaptation with the vag. Denso iridiums (which I also us in my B6 and Touareg). No codes or lights other than o2 sensor

mtroxel

that fixed my stumble too, new Coolant Temp Sensor.

Spinnetti

Worth a whack... I need to check - I thought I changed that too, but that might have been my B6.. hard to keep all this VAG stuff straight!

RallyVermont

Check your "L" hose from the back of the intake manifold.. this is known to leak and cause mystery boost issues, throttle hesitation etc... also if disconnected you'll lose your brakes. FYI - take a peek.

Spinnetti

Vac hoses all look good. Coolant temp sensor didn't do it, but it was like $6, so why not right?

Still have the part throttle stumble. Full throttle is fine, just part. Maybe I'll try adaptation again.

One other thing it does, when you abruptly let off the gas under boost, it doesn't just bypass "cleanly".. diverter valve? is fluttering.. I presume the waste gate can't flutter, but it sounds funny. not sure how to describe it. I have a B6 too, and it doesn't do that.

M.S.G.

Try replacing the Denso Iridiums with a standard plug. Those caused all kinds of problems in the 1.8T when they first came out. I know first hand.

sparkster

I would plug the VAGCOM in amonitor what is is doing when it stumbles. could be a bunch of things.. First thing that comes to mind is the ICM/POS since you replaced a bunch of things already