Low VREF voltages and speedometer going crazy after engine install.

Airbeast

New Member
May 30, 2007
22
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0
Johnson City, TN
I have some really weird electrical problems. 99 GT. I just got the engine back in (for the 2nd time) and my speedometer is going crazy. Sitting still, it will randomly jump all over the place and sometimes pegs 150 and my odometer runs at the same time. With the ignition on and the engine off it's usually normal. Also once you get about above 40, it acts normal. It's really puzzling. Another weird thing, if I unplug the cam sensor, my VREF voltage on the VSS sensor goes up slightly and the needle gets calmer. If I unplug the VSS sensor, it becomes steady too. The strange thing is that my vref voltage on the VSS is really low. 1.6v and if I unplug the Cam sensor, it'll go up to about 2v. I'm not sure how they're related exept that they share a ground going to the ECM. Also, I checked the coolant and IAT sensor VREF voltage and they're 3V and 3.5V. If I unplug the IAC, the VREF voltages will sligtly go up.

The engine will randomly run like crap. Sometimes it struggles to idle. Does the loping thing and black smoke comes out from running so rich. Other times it idles perfect. Also, it runs fine, then seems to lose power and not want to run unless you go WOT. Then it takes off and runs perfect as long as you're WOT.

It threw A cam sensor code earlier but I'm pretty sure that was from the low vref voltage.

Also, when I got ready to start the car for the first time, The cluster was going crazy lighting up all sorts of lights, the odometer said "-------" and relays were clicking, fan was running, the theft light was flashing. Of course it didn't start. Then I turned it off, turned it back on, let it go through all that once again and it went to normal and started up.

I think I must have a positive leaking somewhere or a bad ground somewhere. When I was taking the engine out for the first time, I forgot to unhook the crankshaft position sensor and tore those wires, but I resoldered them. They're on their own unrelated circuit and since the engine runs they're obviously ok.

The only other thing I can think of is maybe there's still water in the main connector when I washed the engine bay. I blew it out though and then used contact cleaner and blew it out once again. Maybe there's some trapped water on the bottom of it though? But I don't think so.

Tomorrow I'll check everything right at the ECU. Pretty clueless for now though...
 
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Problem FIXED :D :D :D

I don't know how but I had a TON of water in the connector to the ECU(inside under the kickpanel). No Idea how it could have got there. No trace of water anywhere else. When I took the connector apart, water just poured out.

Also found a Diablo Delta Chip plugged in which I'm sure was the cause of my pinging and broken piston. Yanked it out and the car runs perfect :)