Oct 2022 – Engine running rough at idle schedule in new year for removal.  Codes occasional misfire and misfire cylinder 1.  Advised owner not to drive.  Also has tensioner adjustment range code for cyl 1-3

Feb 2023 –

  • Car up at IG, engine out, and disassembled.  It looks like Cylinder head 1-3 had been off and #3 rod is bent.
  • The customer states air/oil separator malfunctioned and the engine locked up while traveling 3 years or so prior.
  • Also later found out that the clutch and IMS upgrade performed about 3 years ago 125K miles?
  • #3 rod is bent out of crank plane, i.e. towards rear.  The piston is at an angle in the bore and the bore and piston are heavily scored.
  • Plan is to steel sleeve engine. since the same price for 96mm and 101 we go with 101 mm for 10% increase in displacement.

Engine built to 3.75 with 101mm bore and stock 78mm stroke

  • All new tensioners and ramps
  • New pistons rods and cylinders gapped as per instructions

Late July 2023 parts received, engine assembled and in car within about 2 weeks.

  • Has a rough idle. Engine runs well on long initial run. No codes present at the end of the drive
  • In subsequent runs engine starts running very rough and throws flashing CEL – Misfire damaging to cat, no other codes.
  • Troubleshoot as follows:
    • Swap injectors 1-2. No change same code appears
    • Swap igniters and sparkplugs 1-3 – same codes
    • Re-check cam timing, spot on
    • Check all sorts of things, nothing.

August 21 or so Call Tom at Brandywine Motorwerks, he asks me to drop it off.

  • Disconnect #1 injector to stop the misfire and drop it off.
  • Tom does similar swapping injectors, coils, and plugs – misfire status at #1 but the engine running way too poorly to be just one cylinder
  • Keeps car for 3 days, smoke for vacuum leaks, nothing, check tensioners and cams timing, spot on
  • Leak down 2-3% and compression about 160 on all cyls.
  • Nothing at all obvious. Following is 8/25/2023

August 28 – Pull engine

  • The thought is that it might be a
    • collapsed lifter or possibly a
    • bad wiring harness on either the engine side or chassis to the DME side
    • Possible collapsed lifter
    • Possible broken valve spring
    • Re-check cam-cam timing on both sides
    • Nothing else is obvious.
  • Plan A: Remove the engine and check the following:
    • Cam timing check and perfect
    • Fix oil leak on cam box 4-5.
    • Head off and cams out of 1-3 all lifters appear OK.
    • No broken valve springs.
  • Plan B: Swap the engine into Colonel Mustard and see if the problem follows the engine or chassis
    • Get 1999 C4 running properly
    • Fix fuel pump issues
    • All good running smoothly
    • When warm coolant from exhaust on cyl 1-3.  No go.
  • Plan A.2 – swap engine wiring harness from CM – 28K miles and in good condition.

Late September

  • Engine installed with items above.
  • Initially engine runs well with a slightly lumpy idle.
  • Three drives go well.
  • Fourth drive it decides to kick back into terrible running mode.  Tried many things to get it to run right, reset DME with Durametric, disconnected battery and touched hot to the ground to clear dme (not sure if this did anything), left the battery disconnected for days etc.
  • Back in bad driving mode.
  • Latest suspicion – DME issue.’
  • Makeup jumper from FI 3 to also run FI #1. this seems to help but still throws CEL and Misfire damaging to cat on #1

Early October

  • Swap DME, Immobilizer, and Key head from Col Mustard
  • Seemed to run better at first, then repeated syndrome.

October 20

October 24-28 – Mixture investigation

  • Add additional 02 sensor bungs to CM exhaust, swap that into car and install wideband O2 sensors along with narrow band sensors from DB.
  • Fuel Mixtire about 16.5-17.5  on 1-3 and 15.2 or so on 4-6.    This confirms the misfire on #1 indicating perhaps a bad injector, even though it’s swapped it still on the same bank, 1-3.
  • The plan is to check injectors and fuel pressure.

Nov 1-5 – Fuel injector tester purchased along with adjustable fuel pressure regulator.

  • Checked all injectors from both CM and DB.  Despite different color all flow exactly the same
  • Reinstalled injectors with swap from 1-3 to 4-6
  • Fuel pressure running 3.3 bar – about 48 PSI which is spec.
  • Installed adjustable fuel pressure regulator – set to 60 PSI running, about 25% high, should flow sqrt (1.25) or 12% richer.
  • Start car and with that pressure manage to get about 14.5 mixture significantly lean, As car warms up mixture goes so lean it stalls.

Injector Test Video (on 993 Injectors)



Nov 7 discussions with Paul. Wondering if O2 sensors are working improperly and driving the mixture to lean.  Need assistant to monitor and test drive, plan for 11/11

Nov 11

  • Disconnect narrow band sensors and monitor fuel pressure and mixture
  • Mixture climbs lean north of 18 and turns the engine off.
  • No change in behavior with sensors installed.
  • Update 6pm:
    • Disconnected 02 Sensors.
    • Pressure starts around 60 and then falls to 56 psi.  The Vaccum line is connected.
    • Mixture starts lean somewhat warm, 15.6-17-18-20.5 Stabilizes at 20.5
    • Both banks seem to climb in unison.
    • After the initial start mixture rises and starts popping 1-3 bank, which exits the passenger side along with some visible smoke that looks like unburnt gas.
    • Note Wideband O2 gauges are COMPLETELY independent and have been recalibrated.  They are not linked in any way.