SVT with sudden rough idle, power loss - Page 8

TheCarGuy4All · 02-02-2013, 05:35 PM

Fair enough. I find it especially odd that it would go bad with no warning. And in my case, go bad and still run fine for 400 miles.
This is going to sound oddball, but could there be a massive exhaust restriction on a few cylinders so the backpressure is backfeeding into the combustion chamber? Or a seized valve? (I seriously hope not for your sake) Beyond that I'd think you'd need to look for a random electrical issue that is grounding somewhere unseen.

swansong · 02-02-2013, 08:01 PM

Yeah I really think its a silly electrical issue somewhere. I can't get it to start on its own, but if I do get it going with creative methods it runs like crap until it gets warm. When its warm it randomly switches from running 100% OK to total garbage. Given that it can run well when it wants to, I think its something simple and electrical.

esmith2039 · 02-02-2013, 08:31 PM

Have you replaced the coolant temp sensor? Not sure on exact name but its the sensor on the thermostat housing. The SPI is a different animal but had a odd problem with it. At cold it wouldn't start tried everything. Eventually it would but wasnt happy till warmed up. Finally one day the gauge literally went from one side to the other a few times or never would of found it. Good luck..

TheCarGuy4All · 02-02-2013, 08:42 PM

I dont' know. Something about it is bothering me. If you can get spark and fuel to all four cylinders so it will crank over and fire with ether or whatever, and it'll run up to operating temperature. So you've got fuel, spark, enough timing to keep both somewhat in line, but cold and hot you've got a problem.
So, it has to be oil, fuel, or electrical. A sensor would have to be very odd to have faults at two points within the range (as I'm sure you know), but mechanically, you might have variances.
Is the VCT working properly? The reason I ask is that there was a TSB on it way back when. If the oil pressure is varying and it is slipping the cam lobe off the tappit, or isn't aligned well enough to open and close properly, it could be a problem. Also, oil chambers in Ford's of this vintage can have really finicky oil passages, so you could have a clog. But that seems unlikely given the mid temp ability, but not the high temp.
Definitely confusing as all hell.
Let me know your progress and I will continue to think on it.
As for my own predicament, there was also an old TSB that dealt with stuff I thought was just the character of the car. I'm going to try a reflash and hope it works.

BC_ZX3 · 02-02-2013, 08:58 PM

Quote:

Originally Posted by swansong

Yeah I really think its a silly electrical issue somewhere.

x2. I would suggest after reading your tthread and all your symptoms, you check the coil and coil connector thoroughly.

I had intermittent good/crappy running conditions such as yours and it turned out to be the coil connector. What I believe was happening was that, once warm, condensation or moisture evaporated or simple minor expansion of wires under heat restored the continuity of the wires enough to make the car run normally (still somewhat intermittent under load); during cool off, it was back to hard starting and poor runninng and the cycle would repeat.

Can you beg or borrow a substitute coil to try also? The intermittent may be inside the coil as well as being related to the connector. I'd aslo unwrap the black plastic coil connector harness sheathing back a good six or eight inches to trace the wiring and make sure all is well.

swansong · 02-02-2013, 09:41 PM

Quote:

Originally Posted by esmith2039

Have you replaced the coolant temp sensor?

I thought about that, but temp sensor reports good readings, both on the dash gauge and in my SCT logs.

Quote:

Originally Posted by TheCarGuy4All

Is the VCT working properly?

Ought to be. No codes about it being wrong, and it acted normal up to 6k rpm on one of the test drives where it was running ok.

Quote:

Originally Posted by BC_ZX3

x2. I would suggest after reading your tthread and all your symptoms, you check the coil and coil connector thoroughly.

Can you beg or borrow a substitute coil to try also?

The wiring and coil look ok, but looks can be deceiving. I can borrow a coil, and had in fact arranged to do so before I got it running again and thought I fixed the problem. I think the coil being bad is a more likely scenario than VCT or ECU, but I didn't really realize it could allow my car to be semi-functional like it is. I'll check it out more thoroughly.