Need help, please, idle and coolant temp
 

The car has had a Reverant-built MS2 for several years, but a year ago it started behaving a little odd. When the car is warm, the idle oscillates between 1,100 where its set and 2K rpm, sometime going even higher I did a data log today, it's attached.

More recently, the car started overheating. Its a Normally aspirated '2000 dedicated autocross car, not really driven on the street. It overheats during the run Coming back, idling and popping the hood open takes the gauge right down. I can't really run a laptop during a run, so don;t know the real temp, but the dumb stock gauge goes above 2/3rds, which is not good. Last week I've replaced radiator, radiator cap, thermostat and two main hoses. Tried today wit a laptop (with TunerStudio), Drove around t high RPM for a while until the gauge started moving up. The laptop, however, showed no more than 190F. OK, tried sitting there with car revving at 5K RPM.m Saw the stock gauge move up to about 2/3rd again and temp on laptop went to 200F, at which point I let it idle and teh temp backed to 185F. Odd

So... could it be a faulty coolant temp sensor? Are these issues (idle, fan coming on at low temp and overheating) possibly related or not? Any and all help is appreciated, I'm quite lost.

Gentlemen, any help or ideas?

So, diving more into my longs, including some from 2012 and 2014, it appears that wideband sensor (innovative LC-1) might be dead? Does anyone see anything else that's weird?

I doubt its your clt sensor. If tunerstudio/MS is getting a reading then its fine. What is your AFR at idle?

Just found out that AFR is flat at 7.4:1 as the LC-1 wideband appears to be dead or wiring is broken.Could that be the reason for any of this stuff? Will be checking LC-1 output this weekend between races.

Alsom on CLT... On NB, I believe the same CLT sensor is used separately to send a signal to ECU (that TunerStudio also reads) and a separate signal to temp gauge. Unlikely, but it could be some issue with the side that sends signal to dash temp gauge. Would be strange failure mode, though.

I would not drive the car until you get the wideband fixed. 7:4:1 is a default error. Look in the manual and it will tell you what to do

7.4:1 is not a real reading. It's an error.

Dash gauge is fed from the same sensor but doesn't not affect the engine at all.

I'll be looking at the LC-1 controller and sensor itself this weekend. Im sure that 7.4:1 means that either the sensor is dead, controller is dead or a wire is broken/disconnected somewhere.

However, I'm not at all sure how this can be related to overheating. Thoughts? Aidandj, what do you mean by: "doesn't affect engine at all"?

OK, a bit of an update after an autocross today, upper 80s ambient temps.

First, it collectively dawned on us to disable EGO correction, so the 0 signal from the wideband is eliminated. That had some effect, car doesn't heat up as much. Second, went to open loo[ on idle control, also to eliminate wide band and close up the idle control screw. The idle stopped hunting (mostly). But there were other issues, so I'll go through them and will need more help:

- The gauge still moves a bit after the runs, but not much. The Tuner Studio never showed above 208F. Better, but still not a total solution, as far as I'm concerned.

- This is where is gets weird. As I was getting a bit happier, started the car after all the runs and instructing... idle shoots up to 4K RPM and stays there. Consistent and stable.

- Disconnect Idle Control Valve, set the idle by the set screw to 1,100 RPM. seems stable.

- Shut it down, try to re-start... the car suddenly refused to start. It does start fine with a screwdriver over the starter terminals, battery is fine, jump pack had no effect.

- Measure Alternator output. 15V, which is high.While running, it's 13.6 at the battery, so drop of 1.5V. Too much over a (long) cable?

So, it now appears that there's also a bad positive battery cable? An/or something else? Does disconnected Idle Control Valve have any effect on starts?Thoughts, ideas, anything?