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Discussion Starter #1 (Edited)
Car has 130k on the clock. Turbo around 125k.


I recently did some work to the SVT, which was running fine. This behavior didn't change immediately upon the work, so I think it's unrelated, but it's the install of a new, smaller watercooled ball bearing turbo, and a LSD in the trans, as well as cleaning up a bunch of exhaust leaks. It started with intermittent cut-outs, but now the car is undrivable at any kind of load.

Looking at the log, it seems like the advance bogs to zero every time I hit any sort of load - but I don't know if that's cause or symptom, much less how to fix it! Here's a picture of that behavior:

(The advance isn't ramping over time, that's just an artifact of the graph, there are no points. It drops from 16 to zero in <1 second when throttle exceeds 500!)

I unplugged/cut out the KS to eliminate it completely for this run. My tuner says that the KS is eliminated. The behavior didn't really change. Boost is stable at ~8psi on the wastegate currently.

It seems to make boost OK, but at partial OR WOT it does a kind of BRRAAAPPP and does not accelerate hardly at all - it's undrivable above about 40 mph, it's not just "down to NA power" or similar like a big charge pipe leak.


In terms of leaks, I thought it was maybe the vacuum line that references the fuel pressure sensor, so I redid all that tubing and checked all the charge piping connections.

Checks the plugs as well and they look fine - no real signs of fouling or detonation. They're just the standard motorcraft coppers, which were working fine before. Idle and neutral rev (log attached) work fine. Should I get and gap new fresh coppers just in case? Something else? I did the coil and wires at 95k and they look fine to the eye.

I changed the fuel filter, ran through some seafoam on a 1/8th tank in order to flush the fuel system of any bad gas, then filled up with fresh 93 - no change.

I have NOT run compression tests yet, but I have checked both oil and coolant for the telltale signs of headgasket failure and it seems fine. It starts and idles very well so compression and ignition hardware issues seem less likely to me. Cruises like a totally normal car as well.

I looked at the logs but I couldn't find anything obvious (AFRs, fuel pressure dropping), but you can see how the RPM signal is "notchy" - it stops accelerating, then goes a little, and so on. Could this indicate a crank signal dropout issue?

The spark values seem a little low to me - I did notice that the coolant temperatures are higher - it's a 180F thermostat and the temps read higher - this is likely due to the location of the return line from the turbo causing some extra heat, but I'm not sure if this might be adding some retard to the spark calculations. Could it be something on the MAF side of the load calculation?

The only code it is throwing consistently is for the knock sensor - I'm not sure if that needs to be fully turned off given that I cut the wires or if I need to bypass it with a resistor, or if it doesn't matter at this point since it's supposed to be fully off in the tune and tables zero'd.

All I can think to do is:
New plugs, compression test and maybe fuel pump replacement (fuel pressures look a little low but aren't dropping under load really). I'm fine doing any sort of maintenance schedule as I pretty much have the rest of the car completely rebuilt already.

Any help would be hugely appreciated! I'm definitely considering a switch in Tuner as the car is useless to me as is. . .


16,182 Posts
Look close at ignition, you have at least one cylinder totally dropping out at times there. The coils can go bad like popcorn on these, I've failed them in less than 30 days before. RPM readings add to that.
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