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egt gauge problems


eclipsed at 3am
01-06-2007, 10:40 AM
is there any reason a mechanical egt gauge would be pointing to 6, when im at 5500+ rpms and accelerating hard?

usually it would be at like 11-12. last night, it seems to be running ok, just stays low all the time. sometimes it actually seemed to be higher when i was going slower, unless i was just imaging things.

when my car is at idle and even sometimes when im cruising, the egt needle bounces around a lot. i mean REALLY bounces, it would bounce from 6 to 10 repetedly at like a million mph. could that have to do with vibrations in the exhaust?

also, what does an egt gauge actually consist of? the guy who had the car before me put it in, so i never saw it. I know there is the power wires for the light, but is there like a vaccuum wire or anything, or like one big sensor wire?

david-b
01-06-2007, 12:49 PM
It should be one big wire. EGT is basically a thermometer in the exhaust. Nothing too advance. But I see that is mechanical, so actually I'm not too sure then. I would think it would just be a wire tho.

Blackcrow64
01-06-2007, 12:55 PM
Yeah, its pretty much a thermometer. One signal wire to the gauge and all the gauge needs is a power and a ground... Are you sure you have it all tuned correctly? It should run hotter the harder your driving it, not the easier you drive it.

eclipsed at 3am
01-06-2007, 01:29 PM
yeah everything is tuned fine, and the gauge was usually at the right spots before. one day out of the blue it just had this one problem of the needle vibrating raipidly between 6 to 10. no changes in drivability at all. and now last night, it just wouldnt go up very high. still drove fine though.

i think that the rapid needle has to do with something i fixed. 2 months ago i got a new exhaust manifold. when i was putting it on, i noticed that it was very loose where the downpipe connects to the actual exhaust pipe. the bolts were the locking kind, but there wasnt enough spacers in between, and so i guess it loosened up over time. i put some more spacers in there and tightened it up, and now everything seemed to run a bit quieter. i dont know if that has to do with the egt or not, but the problem happened about that time. the egt probe is connected to the exhaust about 6 inches below the spot where the two pipes (downpipe and exhaust) connect.

Blackcrow64
01-06-2007, 01:48 PM
The EGT probe is supposed to be off of cylinder 1 in the exhaust manifold you realize.

eclipsed at 3am
01-06-2007, 02:12 PM
The EGT probe is supposed to be off of cylinder 1 in the exhaust manifold you realize.

um....wow.

well its not lol. is there a major cooling difference between the exhaust manifold and the exhaust piping?

also, i have the evo 3 exhaust manifold, and there is a small hex bolt right by cylinder one, i think. its the far drivers side of the manifold. i thought it was for an external wastegate. could it be for an egt?

david-b
01-06-2007, 02:19 PM
Sorry to hi-jack the thread, but I'm going to be getting an EGT probe for my car. I know N/Ts really don't need it, but I want good tuning. I was going to place mine b4 the cat. Is that good, or do I need it closer to the header?

Blackcrow64
01-06-2007, 02:29 PM
well its not lol. is there a major cooling difference between the exhaust manifold and the exhaust piping?
Yes, theres a huge difference. It is supposed to be metering the temperature off of cylinder 1. Not the combined temperature of all 4 cylinders and then however much heat it loses between there and where you have your EGT probe.


also, i have the evo 3 exhaust manifold, and there is a small hex bolt right by cylinder one, i think. its the far drivers side of the manifold. i thought it was for an external wastegate. could it be for an egt?
That is indeed for it. It should thread right in there.



Sorry to hi-jack the thread, but I'm going to be getting an EGT probe for my car. I know N/Ts really don't need it, but I want good tuning. I was going to place mine b4 the cat. Is that good, or do I need it closer to the header?
The closer to the header it is the more accurate it will be. Also, like I said before, you should be metering the temperature from cylinder 1 instead of the combination of all 4 cylinders.


**EDIT**
If you guys have ever looked up close at pulling tractors, they have an EGT probe and gauge for every cylinder in their headers... Like I said before, its all a tuning issue and getting an accurate reading. If you put the probe too far downstream then your gonna be thinking its running cool enough that you can lean it out some more. In reality though it will really be beyond meltdown temps and you will be replacing all the valves in your motor.

eclipsed at 3am
01-06-2007, 02:46 PM
[quote=Blackcrow64]Yes, theres a huge difference. It is supposed to be metering the temperature off of cylinder 1. Not the combined temperature of all 4 cylinders and then however much heat it loses between there and where you have your EGT probe.

ok then, blackcrow thanks for the info. also, i dont think the manifold would vibrate around as much as the exhaust pipes, so that would probably be good.

Blackcrow64
01-06-2007, 02:48 PM
ok then, blackcrow thanks for the info. also, i dont think the manifold would vibrate around as much as the exhaust pipes, so that would probably be good.
Yeah the manifold is a lot more sturdy than the downpipe is. lol

I'm just a big ball of useless information like this. lol :p

eclipsed at 3am
01-06-2007, 03:08 PM
Yeah the manifold is a lot more sturdy than the downpipe is. lol

I'm just a big ball of useless information like this. lol :p

excellent. could you tell me why my idle is funky?

Blackcrow64
01-06-2007, 03:21 PM
excellent. could you tell me why my idle is funky?
Well whats wrong with it? Does it surge or is it high/low?

eclipsed at 3am
01-06-2007, 04:33 PM
Well whats wrong with it? Does it surge or is it high/low?

my answer would have to be D, all of the above. and the needle is constantly moving, sometimes just cycling a few hundred rpms, sometimes a lot more. it never has a nice steady idle. ive tried adjusting the tps, ive checked the ohms on the iac, i adjusted the throttle cable. i have no idea what it could be. but i dont want to jack my own thread though. ill touch on it another time.

unless you have a magical answer?

Blackcrow64
01-06-2007, 04:47 PM
my answer would have to be D, all of the above. and the needle is constantly moving, sometimes just cycling a few hundred rpms, sometimes a lot more. it never has a nice steady idle. ive tried adjusting the tps, ive checked the ohms on the iac, i adjusted the throttle cable. i have no idea what it could be. but i dont want to jack my own thread though. ill touch on it another time.

unless you have a magical answer?
Ok, I was gonna say it sounds like the IAC is going bad but I can't say that in 100% confidence.

eclipsed at 3am
01-06-2007, 04:52 PM
the ohms should be like 32 right? 28-32 i think. the ohms on mine actually were about 48-50. when i asked someone about it, they said that a good working iac would say about 50 ohms, and older used iac should be about 27-32. do you know anything about that?

also, when your car was running, did it idle perfect? or, have you ever seen a perfectly idling dsm?

my dad's sportage, my stepmom's elantra, buddy's civic, another buddy's audi, my sister's accord, the idle doesnt move at all. not a single milimeter. even when the ac turns on, or the cooling fan, or anything. my idle is all whacky all the time.

Blackcrow64
01-06-2007, 05:04 PM
It is my understanding that when the ohms go up like that then it means its no longer any good... So I would say thats your culprit right there... But yeah, mine idled perfectly fine when it ran.

eclipsed at 3am
01-06-2007, 05:09 PM
nice....maybe i need a new one. im gonna check on one. thanks, ill replace that and get back to you. thanks a lot!

gthompson97
01-06-2007, 05:21 PM
You'd better check into that a bit more before just going and replacing the TPS, they're not exactly cheap. If I can get my damn Mitchell On Demand to work I can give you the exact specs and steps towards checking the TPS, but it's not cooperating right now. Check on dsmtuners.com or the vfaq, there might be something on there about it.

eclipsed at 3am
01-06-2007, 05:26 PM
well the tps is fine...i think. but i was gonna replace the IAC, which, if blackcrow is right, has gone bad.

about the tps, i dont know how to check if its bad or not. but i know how to adjust it. and it seems to adjust fine.


well...youare supposed to set it to a certain amount of ohms. then when i did that, and starrted the car up, it revved to 4k rpms... i dunno.

gthompson97
01-06-2007, 06:26 PM
You check it with an ohm meter to see if it's bad or not....

Blackcrow64
01-06-2007, 06:29 PM
The book gives you the different ohm ratings for different parts. If the the ohms are above or below those set ratings then the part is bad. That is how you test it properly if I remember correctly.

eclipsed at 3am
01-07-2007, 11:25 AM
well the haynes manual i have, which sucks by the way, doesnt say how to test the tps. it just says how to adjust it. i guess the IAC would be bad then if its reading higher than normal. I was just always under the impression that if it was bad the ohms would constantly move around or go to infinity or something....or rip a hole in the universe

Mikelb
01-08-2007, 09:14 AM
^you have an AFC... does it show the throttle as being 0% when you're idling?!? if not, then the TPS is bad or you have a faulty connection...

if you think the IAC is bad, unplug it and try to idle... it won't be going back and forth, and you might get a better idle... that's what I had to do to mine to set the BISS, turns out I had mad boost leaks... after I got everything set, I plugged the IAC back in and it idled fine...

^oh, and my car has no metal clips on the TPS or Injectors, and after driving hard, the TPS connector comes loose sometimes, and when that happens, my idle goes crazy... I check the Throttle position on the AFC and it shows the idle position changing, and I just plug the TPS back in, and idle returns to normal...

eclipsed at 3am
01-08-2007, 08:42 PM
^you have an AFC... does it show the throttle as being 0% when you're idling?!? if not, then the TPS is bad or you have a faulty connection...

if you think the IAC is bad, unplug it and try to idle... it won't be going back and forth, and you might get a better idle... that's what I had to do to mine to set the BISS, turns out I had mad boost leaks... after I got everything set, I plugged the IAC back in and it idled fine...

^oh, and my car has no metal clips on the TPS or Injectors, and after driving hard, the TPS connector comes loose sometimes, and when that happens, my idle goes crazy... I check the Throttle position on the AFC and it shows the idle position changing, and I just plug the TPS back in, and idle returns to normal...

that was a very imformative post... made me really think about this...

see, the afc does show that the tps is open sometimes. only sometimes will it actually say zero, and even when it says zero it sometimes has a surging idle. but most of the time it will bounce between 0 and 2.5 percent. if i floor the gas pedal really quickly and then let up quickly, it goes to zero, and the rpms usually sit at about 900-1000. i figured this was a problem with the throttle body. but the throttle has a nice crisp open and close, but when i attach the throttle cable, it gets spongey and doesnt close all the way. one thing though, if the throttle sits long enough closed without moving at all, it will "stick" in the shut position, and be a tad hard to move by hand, with the throttle cable on or off. but after i move it, it moves fine after that.

it normally idles at 1100 rpms, and usually it will stay at about that point on days that its running good. but if im driving and i let off the gas slowly, it will idle up to about 1500 or so and the afc will read about 2 percent throttle. so i cant really tell if its a sensor, or too tight of a cable, or mechanical or what.

one question i had but was afraid to ask because it seemed hard to ask, was....when i attach the tps to the throttle body, it seems the spinning piece INSIDE of the TPS has to be rotated just slightly to be able to sit on the throttle body, and in order for the two screws to line up at the same time. is this normal?

eclipsed at 3am
01-08-2007, 08:48 PM
alright one thing...my car is cold hasnt been driven in about 4 hours. i just unplugged the iac and started it, and it ran like it normally does. i didnt want to pisss off my neighbors at night, so i just ran it for a minute or so. but when i plugged the iac back in, still running, it didnt change a thing. also the tps read 3 percent throttle before and after i plugged the iac back in and i hadnt even touched the gas

gthompson97
01-08-2007, 11:17 PM
Alright I got the program working so here's how to test the TPS.

Total resistance (between terminals 1 & 4) should be 3500-6500 ohms. Varialbe resistance (between terminals 2 & 4) should change smoothly between 3500 and 6500 ohms as the throttle valve is moved from closed to wide open.

http://img218.imageshack.us/img218/5457/tpspinoutvb7.jpg (http://imageshack.us)

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