Basically I took everything I replaced for the old engine, and that was expensive: Injectors, Ignition Module, CamShaft sensor, if I'm not mistaken.
Today I unscrewed my ECM, and let it stay indoors overnight - no change. Spoke to another mechanic, who mentioned that it's been pretty common that the persistent problems were getting cured by the replacement or upgrade of the PROM.
Tonight was pretty warm 48F (+7C), so nothing would be freezing inside, and yet I hit the same 20mph with eventual stalling if I was trying to force beyond that speed. After 5-10 minutes it became slightly better.
I'd still love to see the results of swapping the MAT sensor... can't shake the feeling that it's "telling" the engine that it's nice and warmed up even though it's really ice cold...
But, failing that, before you splurge on the big buck items - how about unplugging enough sensors to force it into limp home mode, see how that performs ?
I like Mr. Weitzel's idea to systematically unplug various sensors to find out if your machine is affected positively. If it runs half way decent with the sensors unplugged then you could plug them in one at a time to find out which one (or ones) is (are) giving you fits.
Don't know for sure, but I'm assuming that the engine will not run at all with the crankshaft position sensor unplugged, and if so, then obviously, it cannot be disconnected for purposes of this test (others more knowledgeable are welcome to correct me if my assumption is off base).
If it is the ECU as you suspect then your recent experiment showed that the ECU itself is not temperature sensitive so perhaps it is mishandling the output from one of the sensors that is temperature dependent. Could it also be possible for the wiring/connectors to a particular sensor to be affected in some bizarre manner by temperature changes? Grounds, opens, looseness, shorts, and the like. Admittedly if would have to be something really off the wall to be so repeatable.
As an aside, I replaced the starter on my daughter's Grand Am three times in very quick succession. After the third one it was time to look further. It turned out that the insulation on two wires in the starter solenoid circuit had rubbed through and the process of replacing the starter disturbed the wires so that the starter worked fine for a short time after each replacement. Long enough for the wires to gradually return to their natural resting position on a metal frame in the engine compartment, after which the machine would not start.
Sure hope you're not dealing with something that weird.
Back to the subject at hand, it seems to me that your problem falls into one of these three general categories:
Reduced/restricted fuel flow Reduced/restricted combustion air flow Restricted exhaust flow
Are there others that are eluding me?
Please keep us informed. Your problem is intriguing.
I haven't heard anybody say that the exhaust has been unhooked to see if the problem would clear, old mufflers and cats will do a lot of tricks. I've seen engines changed out of frustration only to find out later that loose bafuls were packing up against the back of the muffler. Sometimes you will hear the exhaust hiss when you step on the gas hard.
ECM & PROM upgrade didn't help. Car is being checked for exhaust problems tomorrow - will post updates later. In the meantime, the weather warmed up, so I'm not hit as badly (or maybe it was an ECM contribution indeed).
Current feeling - that something has to warm up enough inside the car, and it has to happen while driving - idle doesn't seem to have such an effect as 5 minues of trying to break through the cut-off speed.
Good to hear from you. Thought you might have dropped off the face of the earth. Hang in there with the car problem. Hopefully your logical approach will find the culprit(s).
That's a pretty neat idea. I have replaced the fuel pump to another one shortly after the engine change. The old one lasted only one day. So fuel pump itself doesn't seem to be connected to the behavior. Mechanic checked for restrictions in fuel delivery, and said that everything was ok. But cooling parts down to -50C (-60F) could help in tracing down the circuit. Worth the try.
a) ECM reads 100mph when the car actually goes at 30mph b) Fuel pumps runs at the lowest allowed range @32psi (specs define
32-40 range).
Negative battery cable was loose, fixed that.
A friendly mechanic, who tried to quickly troubleshoot the wounded beast, said that there was a lot of odd rattle in the exhaust system and also fixed some broken ground wires in the vicinity of the transmission. And then left the country. I hope my beautiful car didn't scare him to that extent.
I asked him about flushing the exhaust, he said that he never heard of such thing.
The weather keeps changing to warmer one, problem is becoming harder to catch.
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