ECU Code 6/Engine quickly going through fuel...

[Susanoo]

So some preliminary research into this little ECT (Engine Coolant Temp) Sensor has told me that this paticular sensor has a lot to do with how the engine runs overall since the ECU uses its readings to make minor fuel/air adjustments on the fly...This is at least what my research has turned up. So is all this correct?

Also the reason why i titled it like I did is simple, I've got this code and I've gone through half a tank of gas in like double time and the car has yet to leave my garage since i completed the EFI conversion....

Also good to note...SOMETIMES (keyword) when I've warmed up the engine to normal idle temp, shut it off for whatever reason and restart, it starts fine but sometimes, like i said, the idle starts jumping up about 500 RPM's at a time from 1000 to 2000 and when this is occurring if you hit the gas pedal the engine starts to die but if you let go before it dies it idles back up to 2000 and the engine is louder then usual at 2000...

Is all this related to this one little sensor???

[pickupman6]

It could all be related. Won't know until you fix your known problems. The code six is causing your poor fuel mileage.

[Susanoo]

Well my fuel pump died today so yea...

[pickupman6]

Lucky you, its a super easy fix, but you alredy knew that from doing the fi swap I'm sure.

[Susanoo]

Haha Yea I did already know that, I actually replaced my old carb pump for a new one like 10 months ago but started the EFI conversion not long after i replaced it.

However I've still got a code six and i've replaced the ECT sensor for a new one...perhaps i crossed a couple wires when I rebuilt the connectors for the ECT sensor and TW(?) switch...So obviously im going to double check that..but does anyone have any other suggestions while Im checking the wire colors...

[Buzo]

There are other two factors in the basic equation to calculate fuel:

(MAP*RPM)/CLT

But you are lucky because you have your ECM telling you a problem with the CLT, but you can look for good electrical and vacuum connections to your MAP sensor & Tacho signal to the ECM as well.

Just more ideas, per your request

[Susanoo]

There are other two factors in the basic equation to calculate fuel:

(MAP*RPM)/CLT

But you are lucky because you have your ECM telling you a problem with the CLT, but you can look for good electrical and vacuum connections to your MAP sensor & Tacho signal to the ECM as well.

Just more ideas, per your request

I appreciate the ideas, so is it possible I have a bad MAP sensor? I dont know what you mean by "Tacho signal"...The only thing that comes to mind is the RPM signal?....

[Susanoo]

I checked the tw switch wiring and it was right according to diagram. so the other switch out of process of elimination from the only two plugs and four wires i was working with at the time I repined the plugs, the ECT must be wired correctly...

So why the code 6?

Also I checked on the MAP sensor and found that for some reason...It came into the box from the manifold and teed off, the input plugged into the side, the top of the tee plugged into the MAP and the other just ends with an open end...This didnt seem right and I assumed it would cause a vacuum leak and cause improper readings to the MAP sensor so i took off the tee and plugged the MAP straight in...but now im wondering why my car now idles at 2100 RPM's...can I just dial the idle back down? Or is that really how its meant to be?...

[pickupman6]

There's supposed to be a plug at the end of the short vacuum line coming from the t. Its there to help stabilize the vacuum pulse. It shouldn't matter too much if you don't have the t, I don't after deleting the black box, my idle is a steady 800 rpms. You could try adjusting your idle. Is it high both when cold and after it warms up? If its just when cold you could also try adjusting the fast idle valve on the back of the tb.

[Susanoo]

There's supposed to be a plug at the end of the short vacuum line coming from the t. Its there to help stabilize the vacuum pulse. It shouldn't matter too much if you don't have the t, I don't after deleting the black box, my idle is a steady 800 rpms. You could try adjusting your idle. Is it high both when cold and after it warms up? If its just when cold you could also try adjusting the fast idle valve on the back of the tb.

Well....thats the thing...I dont have the coolant lines connected to the valve because one of the stems broke off during the conversion and I never made a pepsi can gasket to cover the holes and basically delete it...So could this NOW be the problem?

EDIT: Also I knew it shouldnt matter because i've seen people's setups with deleted black boxes. They all have the MAP directly connected.

[import racer]

Yeah mines still runnin rich and i have the egr blocked off and that's the only code i get.Efi is a lot harder to figure out than carb.Got a new air filter cumin on monday so maybe that will help,also gonna try to bump timing.

[pickupman6]

Well....thats the thing...I dont have the coolant lines connected to the valve because one of the stems broke off during the conversion and I never made a pepsi can gasket to cover the holes and basically delete it...So could this NOW be the problem?

EDIT: Also I knew it shouldnt matter because i've seen people's setups with deleted black boxes. They all have the MAP directly connected.

Bing that's your problem. It thinks the engine is cold so the valve stays open and creates a vacuum leak, causing the rpms to be high. Still won't solve your poor mpg's though.

[Susanoo]

Yea I blocked the holes off with a pepsi can gasket and bolted it back on, It ran way better and with the MAP sensor connected directly now, the whole engine runs extremely better and the exhaust no longer sounds like a machine gun.

So back to the ECT(Code 6) error...where do I go from here? I replaced the sensor...the only other thing i can do is test continuity...

[pickupman6]

That's about all that's left to do besides testing the ect to be sure its good. And if both check out good it could be an issue with the ecu. What color was the plug on the ect sensor you changed? Just making sure you changed the right one because most parts stores will give you the fan switch instead. The green plug is for the fan control. I'm sure you know this, just throwing it out there.

[Susanoo]

That's about all that's left to do besides testing the ect to be sure its good. And if both check out good it could be an issue with the ecu. What color was the plug on the ect sensor you changed? Just making sure you changed the right one because most parts stores will give you the fan switch instead. The green plug is for the fan control. I'm sure you know this, just throwing it out there.

Well actually I debated that when i changed it because I thought the ECT was the big one and it was actually the little one. I dont remember which is which but I think ECT is green? My fans work so it must be correct..

I'll have to do the continuity test later today. Even with the MAP sensor getting a good reading now, the engine runs twice better and I can tell from the exhaust smell that its using much less gas then before. I just want to fix this ECT issue before taking it through emission testing :P

[pickupman6]

Ok I remember this much the ect is the one closest to the block, I just checked and its the green one. The manual says to check voltage between ylw/grn(+) and body ground, there should be about 5 volts. If there's not trace the y/g wire bac to the ecu (c6). Next be sure there is 5v between y/g(+) and grn/wht. If thers not trace the g/w wire back to the ecu(c12).

[Susanoo]

Ok I remember this much the ect is the one closest to the block, I just checked and its the green one. The manual says to check voltage between ylw/grn(+) and body ground, there should be about 5 volts. If there's not trace the y/g wire bac to the ecu (c6). Next be sure there is 5v between y/g(+) and grn/wht. If thers not trace the g/w wire back to the ecu(c12).

Indeed, it's the exact same on mine. I'll check for this voltage and get back to you....

[Susanoo]

So i checked on that voltage and with + on the yellow/green i got a little over 3 volts for both readings, - to body ground and to the green/white. This was while the car was running.

[pickupman6]

Hmm well it says approximately 5v so maybe that's ok, idk. I will try to check mine out tomorrow but my guess is that's a little low. Have you tested the ect?

[Susanoo]

Well no, i bought a new one so i assumed it was good :/ i know the testing procedure for it but it may be a couple days before i get back on that. Could the ecu be bad or "weak"?

[pickupman6]

Its possible. Sorry I never got the chance to check mine, been working 16 hour days. I will try tomorrow.

[pickupman6]

Oh yeah I'm thinking you need to unplug it to get the 5v, the ect is a thermo resistor, which changes the voltage as the car warms up. At least that's how I figure it to work but I will try to check mine tomorrow.

[Susanoo]

Oh yeah I'm thinking you need to unplug it to get the 5v, the ect is a thermo resistor, which changes the voltage as the car warms up. At least that's how I figure it to work but I will try to check mine tomorrow.

Yea thats how i figure it would work...different voltages meaning different temps. However, I did unplug it to check the voltage :P I went to PaP today but there were no manual cars so I didnt grab an ECU. I dont know if theres a difference between ECU's with a manual or automatic tranny. I have a spare one I pulled from an automatic...

[import racer]

I know that people who have switch from auto to manual trans have used they're auto ecu but don't know if it works the other way,manual to auto.

[pickupman6]

Aww dang, I forgot to check mine out today.