1995 m42..not revving out..labors past 4000 rpm.. read on
 

1995 318ti, m42, fresh top end/headgasket, new valve seals, lapped valves. All new vacuum lines, head shaved .010" to correct warpage from overheat when the Hg blew. New radiator, water pump, thermostat and coolant pipe (block). About 1000 miles since the engine went back in. Stock except for shielded K&N filter. 215,000 miles on the bottom end and other engine parts (MAF, DISA, injectors..etc)

She was running great, pulled strong all the way to redline until just the other day I noticed a big reduction in power. No difference in idle, nice and smooth. Labors to pull now past 4000 though..feels like I'm trying to punch thru if I keep going, whereas it used to sing all the way to 6800..in fact it was my favorite thing to do in 1st and 2nd :cool: . The induction noise is also very loud, even revving by hand from idle. I have had this car for 4 yrs now and I never recall noticing that before. Very deep howl coming from the intake when pinning the throttle to the floor.

I'm wondering if the DISA flapper is jammed, and I'm being forced to stay on the short runners thru the higher rpms and that is why it is feeling so restricted.

My first thought was actually a bad exhaust leak, but looking under the car I dont see or feel anything, and like I said, the idle is smooth..no telltale puff puff sounds, or excessive exhaust odor from the front of the car.

No check engine lights either, but I'm going to do the key on 5 steps on the gas later today and check it just the same. I have dropped MPG though.. I keep a close eye on it and usually get about 25-26 and now getting in the 24s. I have slightly undersized tires also.. so the OBC is not totally accurate, but my #s were always consistent .

I'm stumped crew. And I miss REALLY driving my Ti... Any ideas?

here's an update since I tested a few things on the way home from work this morning. Is DISA strictly RPM based, or does it take load/throttle position into account? in 2nd and 3rd gear if I only use part throttle then I'm able to pull past 5000 rpm. but if I go over half throttle it bogs and I get loud induction noise.
based on this I'm almost thinking fuel is the problem I'm going to check the fuel pressure regulator and pressure at the rail later when I wake up. lluckily I have another 95ti that I can borrow some parts from to try and figure this out.
looking forward to some ideas and input though.
Thanks

another update I just checked the check engine light codes 1 long flash followed by 4321. although my check engine light is not lit during normal driving.

cat converter clogged?

Im actually starting to think that may be it. There is a magnaflow on it so the PO replaced it before obviously. Guess ill pull it off tomorrow and check it out.

I did a compression test earlier to rule out anything there..not bad at 175-185 on a barely warm engine.
The plugs looked a little lean so I pulled the iridium plugs and put in a new set of normal plugs.
Swapped the fuel pressure regulator out after pulling vacuum line and smelling fuel in it.

Went for a drive and while it did idle a little smoother the was no change in rpm/power.

I just put a can of seafoam in the tank tonight so it can cleans things up there too.

So I pulled the exhaust header and cat. The brick was broken and a piece was lodged sideways blocking flow. So I gutted it but then decided it would be too loud and tinny, so then I cut the twister resonator out if one of my old race car exhausts and adapted it instead.

Problem solved, nice tone not loud at all..and she revs out all the way and pulls hard again.

It was a good day.