GiggityH

Ok. I have a 90 gtus with a steel hood and 4.10 rear end. Power nothing. OK It gets stranger from there. Car is very hard to start but has perfect compression. Check engine light is on going to water thermosensor. Checking around the engine bay I find the gauge temp sender is unhooked but the gauge has always read right in the middle with no input. I hook the wire up and it reads it's overheating, OH ****, I shut the car down get my truck and bring it home. I try and replace the temp sender but my 90 gtus with the rebuilt engine only has the fitting for the 87 temp sender, the 88-91 won't fit it's too big, so i get the 87 after hours of trying to figure it out. Ok, So i replace the water thermo sensor, the gauge temp sender and the fan relay. Clean all the terminals, clear the ecu and the car will not start. Double check, everything looks good, triple check nothing out of place. So after cranking the battery dead I jump it. It starts up but the ecu throws up the water thermo sensor again. Explains why it was so hard to start. Change the plugs and it won't start again. It fires and runs nice. The factory temp gauge is reading really hot again from the get go. Put in aftermarket gauges and my engine temp is running about 180-200. Thats right for these cars right?

SO here are big questions..... Is there anything else that would flip on the C.E.L for the water thermosensor on that circuit. Why is it still throwing the code?

Second, why would only an 87 temp sender fit in my car? Thats F'd up. Unless in the rebuild parts were sourced but is that possible?

And are the temp senders the same output between the 87 and 90 models?

What do I do now?
Thanks for all the help guys, hope somebody knows something! G

WAYNE88N/A

I think you're getting the WATER THERMO SENSOR and the WATER TEMP SENSOR mixed up- they are two different animals...

GiggityH

thermosensor behind the altenator right?

The sender is below the oil pump right?

If I'm mixed up where is the thermosensor that is the 9 on the check engine codes?

Let me know if I'm getting a little mixed up
Thanks

WAYNE88N/A

the sensor that's throwing the code is the one behind the alt, on the water pump housing...

GiggityH

Yeah I already replaced it and cleaned the connector. I wonder where the problem lies now. I'm thinking about hardwiring it. Anyone know where it is on the ecu? where the wires are routed from, any help would be great

WAYNE88N/A

don't have the S5 wiring schematics on me, but when you do figure out which pin is the input to the ECU from the water thermo sensor, read it out with a meter and compare to the FSM specs- you might have an open or short in the harness, probably in the area that's on top of the engine near that connector...

GiggityH

turbo swap sounds like the easiest fix

WAYNE88N/A

LOL, I don't know if it would be the easiest, but it will certainly make you forget about the starting probs for a while