Carbon build up/ black exhaust

[redSUPRA '88]

Just a N/A 7m. Got my car running again after it sat for 7 months. replaced the fuel injector seals and the system has had new gasoline cycled through it. My problem is the car has a rough idle at 800 rpm and, as the title says, the exhaust is black. Also it would backfire every once in a while when its being driven. With those symptoms i know the engine isnt burning all the gas being squirted through the injectors. So i figured the spark plugs were bad. turns out i was partly right.....

:: angry :: So i replaced them, put it all back together, and it still runs the same.:nono: albeit a bit better but with the same amount of smoke. So my next step is to replace the wires?, and im contemplating changing out the coil. Is there anything else i need to look at? Thanks guys!:icon_surp

 

[IndigoMKII]

What is your fuel pressure? When was the last time the injectors were cleaned? You could have a pissing injector or one with a very bad spray pattern.

 

[AnubisMK3]

2 things, I had this issue and it turned out the cold-start injector was just pissing fuel into the cylinder, i had checked all the other injectors and they all checked out, i took it apart cleaned it and reseated it and the problem stopped. The other issue was on my 92, again same symptoms black smoke and backfiring, turned out the #4 injector was stuck open and just pushing fuel constantly, it needs to be fixed or your fuel pump will wear out quickly.

 

[jetjock]

^ The fuel pump will quickly wear out? Really?

...So i figured the spark plugs were bad. turns out i was partly right....So i replaced them, put it all back together, and it still runs the same.:...

That's because the plugs were effect, not cause.

 

[Nick M]

Take a picture of the top of the airflow meter. I want to see the plastic cover.

 

[redSUPRA '88]

Air flow meter? I'm sorry but is that just the whole stock air intake? Ill have to take a picture tomorrow anyways. As far as what y'all are saying about the injectors being stuck open or just malfunctioning in general makes a lot of sense. When I drove it, it only took 60 miles to go through half a tank of gas

 

[jetjock]

He means the thing right behind the air filter. I'm guessing he wants to see if it's been tampered with. My advice is to take the car to a mechanic because, like, damn...

 

[Nick M]

I have seen the wound up spring loosened on 7MGE's, and they smoke a little and run bad.

 

[EHumble]

I would definitely check out the cold start injector. That was the problem with my old 7m. I just eliminated it since i don't need it where I live

 

[Nick M]

Air flow meter? I'm sorry but is that just the whole stock air intake?

You might consider not attempting repairs to th EFI system if you don't know what the main input into it is.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=94

 

[AnubisMK3]

Yep, the cold start injector was keeping the fuel pump pushing full bore, it has the ability to flow much more fuel than a stardard 7m injector and I ended up with a toasty pump. Could have been on its way out at that point but it only had 50k on it.

^ The fuel pump will quickly wear out? Really?



That's because the plugs were effect, not cause.

 

[IndigoMKII]

Um, you do realize that the fuel pump is on 'full bore' the entire time? With a leaking CSI it would meet less resistance.

 

[Nick M]

Yep, the cold start injector was keeping the fuel pump pushing full bore, it has the ability to flow much more fuel than a stardard 7m injector and I ended up with a toasty pump. Could have been on its way out at that point but it only had 50k on it.

Fascinating....

The fuel pump is designed to operate at battery voltage. It is run through a resistor to slow it down at low loads. The CSI has no input in this operation.

 

[redSUPRA '88]

Here is a picture of the intake as you asked although it doesnt look like anything has been tampered with

And the air canister is partially melted because the previous owner drove the car with a BHG.

 

[redSUPRA '88]

Haven't done anything with my car yet. Also I'm not sure why this thread was moved to the the GTE portion of the forums. My car is N/A....

 

[89blackturbo]

Check ignition timing. Just for giggles. Not saying it will for sure fix anything. Cap and rotor replaced recently?

 

[redSUPRA '88]

Not the cap but the rotor was replaced about 10,000 miles ago

 

[redSUPRA '88]

He means the thing right behind the air filter. I'm guessing he wants to see if it's been tampered with. My advice is to take the car to a mechanic because, like, damn...

lol JJ if only i had the money id have done it a while ago, but id never learn anything about my car that way.::hang::
Just an update because i have more questions than awnsers. My fuel pump did indeed die so im not sure if that was part of the problem or what. Either way i dropped the tank and replaced it 2 days ago. It started right up after the install. Same symptoms. So i checked my codes and now its throwing a code 52. TSRM says that its a "open or short circuit in knock sensor signal". I looked around and saw that theres some way to rewire it? and why would i do a rewire? I replaced my knock sensor about.... oh say 500 miles ago. Because the old one literally fell off... so i'm honestly a little lost. Any input would be a godsend

 

[IndigoMKII]

lol JJ if only i had the money id have done it a while ago, but id never learn anything about my car that way.::hang::
Just an update because i have more questions than awnsers. My fuel pump did indeed die so im not sure if that was part of the problem or what. Either way i dropped the tank and replaced it 2 days ago. It started right up after the install. Same symptoms. So i checked my codes and now its throwing a code 52. TSRM says that its a "open or short circuit in knock sensor signal". I looked around and saw that theres some way to rewire it? and why would i do a rewire? I replaced my knock sensor about.... oh say 500 miles ago. Because the old one literally fell off... so i'm honestly a little lost. Any input would be a godsend

The KS wires become brittle over the years and since the ECU is very picky about the KS signal, it's just smart to run a new shielded wire.

 

[Backlash2032]

Since the ecu is so picky, what should the resistance be for the ks wiring?

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