Been having some trouble with my injected '72 145 lately and wondered if anyone out there has any thoughts? Seems when it gets warm (a little over 200 degrees I'm guessing) it starts misfiring haphazardly. This get worse very quickly, until it starts dying when I let off the throttle, and won't really run under 3000 RPM. Smells like fuel. If it sits for a little bit it will start up and run great again.
Now, I have been the supervisor for an auto repair shop for nine years, so I have been through the all the obvious scenarios I can think of: 1) The engine is not overheated to a dangerous level---max temp when it does this is 195-210---I can keep my hand on the valve cover. 2) it has an electronic ignition conversion. I have tried putting points back in it as a test, but the results are the same. 3) The coil is less than a year old. 4) I have checked for fuel leaks/problems from the tank all the way to the fuel rail. 5) Fuel pump is good and with proper pressure specs. 5) Timing is correct, D-Jet trigger points in the distributor base are clean and within spec, and the distributor itself was rebuilt a year and a half ago. 6) Injectors are clean, TPS is clean and smooth. 7) Fuel filter is good.
Engine has roughly 100K on it and runs clean, doesn't burn oil, no mechanical problems whatsoever.A few things that might make a difference in trouble-shooting: It has an IPD fuel ratio dial installed, seems to run best (when it isn't acting up) at +10. Coil is an MSD, not a Bosch. It has an IPD header. IPD street performance cam. I was told it has a B30 fuel pressure regulator (not sure about the truth of this, the differences/possible incompatibilities, if any, just reiterating what the previous owner told me). Not sure how to test the two temp sensors that feed the computer, or how sensitive they are in the D-Jet system; there is one in the head and one in the sheetmetal next to the radiator, and they are both plugged in. If I unplug the one it the head the engine dies, if I unplug the one by the rad, nothing changes...This is one area of the D-Jet I am fuzzy on.
The only consistency I can think of with this problem is that the shift lever always feels warm down by the floor when it starts sputtering. I have wondered if this could mean that the fuel line is also hot, but it is on the other side of the car from the exhaust so it seems unlikely; also, it couldn't hotter than it is at the fuel rail, and that shouldn't be a problem. Other than that, it seems pretty random. It doesn't always happen when the weather is warm, or when the car is warm either, but any time does happen, the car is warm. Sometimes it bucks a little then is fine. Other times it gets really bad and poops out for at least half an hour. Once it has sat though, I can put it back on the road under the same conditions and it won't happen again that trip. It still seems like a timing issue to me, but I don't where else to look...everything from spark plugs to advance springs are new or carefully inspected.
Any thoughts? This problem is frustrating and confusing as hell.
