Lack of power, strange running issues on S50 clone

[manofsteele]

Folks,

Hoping to get some feedback from some experts here.

Background: the car is an e30 (1989). M50 block with M54 rotating assembly (sometimes called S50 "clone" or stroker). S52 head including cams and exhaust manifolds. OBD1 with red label 413 DME, and Turner 4130 0004 chip. Wideband O2 sensor indicates that fueling is not an issue.

When I discovered the car, I had it inspected and driven by trusted 3rd party as it was out of state. So when I received the car, it was the first time I drove it. I didn't feel that it ran as strongly as it should for a 3.0 engine and was a bit noisy at around 3000 RPM despite being a freshly built engine. The car would randomly misfire under load at around 3000/3500 RPM and occasionally it would stall at idle. Now, I don't fault the inspection or the man who inspected it too much because the car came from high altitude so power loss is expected and the car did not misfire when he drove it. My subsequent inspection revealed interrupted crank signal probably due to a failed sheathing due to poor routing. So I updated some maintenance items regarding fueling and sensor feedback: new OE fuel pump in tank, VANOS rebuilt, new timing chain tensioner, new crankshaft position sensor, new camshaft sensor, MAF cleaned. I also pulled the intake manifold to check hoses and replace fuel injector seals. No major deficiency found, reinstalled. VANOS and tensioner calmed down the noisiness, and the new position sensors solved the misfire and stalling and smoothed out running a bit in general. But the car still feels way down on power to what it should be. No major air leaks according to smoke machine. ICV seems to be doing its job properly. Cold and hot starts are fine. I have also cleaned and improved grounding on some harness points.

2 major issues.
First, The car feels as though it does not have enough ignition advance in driving range. Last time at the track, the power output just felt very flat. AFR in the mid 12's, but just gutless. If I had to estimate, I would put it at maybe 170? HP based on some of the other vehicles that I drive at the track also. Others have dyno'd similar setups around 220hp crank or so.
Second, sometimes during street driving as I approach 3000 RPM with light throttle openings, the car seems to be accelerating normally in traffic and then suddenly seems to fall flat, as if the ignition has just retarded itself. It will still accelerate, but not as one would expect. It's not so "eager."

So my question is: is there a sensor feedback for this Motronic system that would retard spark? Failing coil pack? Are these Turner chips a known problem point? If the part number on the chip is to be believed, I understand that it is originally calibrated for a 2.5L engine but the ignition curves should not be vastly different and the fueling seems to be fine based on AFR and spark plug inspection.

If someone has a stock M50 chip I'd like to try it. Short of swapping an ECU, I'd like to at least troubleshoot what's there. Feedback welcome!

[hakentt]

You should run stock 506 chip from early 1995 M3. There are knock sensors that do go bad on Bosch system, they crack. That could cause timing being retarded all the time

[manofsteele]

Haken thanks for the reply.

Should I burn a new 27SF512 chip with the 506 bin as found on TunerPro? No problem to run that one in the 413 DME?

Is there a way to check operation of knock sensor? I do not have an oscilloscope.