v8maro

iTrader: (4)

I have no idea wtf is going on with my car. All of sudden, I will be driving, and the temp gauge will dip down, the car loses some power, then it'll come back up.
Another time it will dip down, then my car will want to stall, then the rpms go up to 2-3k stay there, then the temp gauge goes to normal, then the rpm's go back down
Another time it'll goto 100*, stay there, come back up, then go back down
Another time it just stayed at 100*
Lastly, on the drive home, on a 45mph street, the car was hesitating really bad, so bad the rpms would drop to like 300, then jump, then drop.
I pulled over, shut it down
thinking WTF?
I next try to start it, took forever, like 5 long cranks
Drove home, no problems

WTF is going on here? What would cause the gauge to behave like that?
thinks i check and know...

Coolant is full
No coolant leaking anywhere
Temp sensor plug on head is plugged in
No leaks around that or anywhere else
Doesn't seem like a vacuum leak for the pure fact it doesnt stay that way, and it doesn't do it all the time

I took a pic of me driving on the highway, look what it just does

thanks for any help!


-Steve

Ferocity02

iTrader: (60)

I would venture to guess there is a loose connection or some frayed wires. The PCM uses the temp of the motor to control a lot of things, so if that signal to the PCM from the temp sender isn't coming through, the PCM will start adjusting things incorrectly. Have you washed the engine recently, you may have gotten some water in some of the connections. So I'd check the wires, or maybe take it to the dealer.

blk~2000~Z28

That plug on the drivers side seems responsible for alot more than just temperature readings. I would check it real carefully b/c your symptoms sound like my car when I left that thing unplugged.

v8maro

iTrader: (4)

It's plugged in, no wires are exposed or frayed. I didn't wash it, so I am really confused. Maybe it just went bad? Odd thing is, i just replaced it about 6mo ago when I did my H/C swap.

Ferocity02

iTrader: (60)

The sender might have gone bad then. You may have to get another one from the dealer.

v8maro

iTrader: (4)

How much are those about? Where is it located??
Anyway to test if the one in the head is bad?

Ferocity02

iTrader: (60)

Its in the driver side head by the #1 cylinder. The only way I could think to test if it works would be to use a volt meter to test the signal it gives off. I don't how to go about this or what kind of voltages to look for. I'd imagine if it gives off some kind of voltage, then suddenly none, you have a problem,

v8maro

iTrader: (4)

Is that the only sensor for the temp? If so looks like I will be replacing it again :\

Magnus

iTrader: (4)

Unplug the temp sensor and see if the car runs better.

If the signal wire for the PCM is grounded or shorted the PCM will act very weird.

Hawkeye2

similar thing happened to me after doing my headers. My fix was simple.

I just unplugged the sensor and plugged it in again. I've had no trouble
since. I was throwing a code P0118 - coolant temp sensor, but since
re - plugging it it's been fine. Worth a try!

LT1559

iTrader: (5)

Losing to an STi today and searching for this similar problem lead me here. My car was perfectly normal, stock 98' w/ longtubes and no tune. I took off in first and ran through gears till' top of 3rd and saw him pulling away. As I threw it in neutral the rpm was fluctuating all the way from 900-2500 rpms and I noticed that my temp had gone all the way down below 160 so i knew the temp sensor was disconnected cause i did a spark plug change maybe 3 hours prior and probably knocked it out of place(it's broken and barely hanging on but still works if it isn't all the way unplugged). When i came to a complete stop the idle was still fluctuating badly and almost completely shut off. Then I pulled over and pushed the end part of the sensor back in and it's fine now. The reason I haven't replaced it is because Autozone, O'Reillys, and NAPA all don't have the right coolant temp sensor. 98 has 3 prongs and 99+ has two prongs. Hope this helps cause it sounds like yours is on the verge of going out.

LT1559

iTrader: (5)

I've never lost to an sti before and this loss is just bothering me cause when I pulled up to the stoplight next to him I gave him the respect and said nice run and he comes back at me with "It's just a little four banger bro"!

jimmyblue

iTrader: (11)

Bad connector on the ECT sensor will act like this.

dailydriver

I'm sure you know, but just in case you don't; some of those Scoobies are making STUPID power on built engines with sky-high boost levels.

So losing to one of those with an untuned, bolt-on, LS1 4th gen is NO shame at all.