Extreme fumes

[John Deere 4240]

Ok so I got a normal 98 sierra, gm crate motor with only 56,000 miles. Got rid of the cats a while back and some where along the line the exhaust started to smell bad, now it's just raw fumes coming out of the tail pipes. No need to pass local emissions but I know it's getting way too much gas in the cylinders and would like to fix the problem if it's possible? Don't know the fuel pressure btw.

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[19trax95]

I think 96+ had a o2 sensor after the cat. So what did you do to deal with that? You may be over fueling the engine and not burning all the fuel. Is there any smoke? Also, how does thw power feel? Is it the same or less? I know that no cats will make you smell the exhaust more but not as bad as you say. I would say that your best bet now is to read the codes and report back here with what they are. Autozone has a service where they will do it but im not sure what type of scanner they have. I think you would need a diagnostic scanner.

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[John Deere 4240]

The #2 oxygen sensors are plugged in and breathing fresh air, mechanic grandpa says that those report the performance of the cats, doesn't control the air/fuel ratio like the #1 sensors do. Only code it throws other that ABS brakes, not sure if the fuel regulator is going out, that part has 280K miles on it

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[bluex]

Ya the after cat sensors have nothing to do with fueling, they just check to see if the cats are working.

How old are your front oxygen sensors?

 

[John Deere 4240]

.....good question, knowing my father they are original lol

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[someotherguy]

Whether it fixes the issue or not, go ahead and invest in a good brand coolant temperature sensor (CTS, or also referred to as ECT) - this has a huge amount of control over your fuel mixture, way more than the O2 sensor tends to have, and they go bad gradually - as they go bad, they give a false reading of colder and colder than actual coolant temp, which richens up the mixture. My belief is they should be replaced every couple of years just as preventive maintenance.

It's inexpensive, easy, a very common problem, and may just solve the issue for you.

How you're gonna pass smog without cats is another story.

Richard

 

[John Deere 4240]

Don't have to pass emissions here, and I have an acdelco CTS. I put in last winter.

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[John Deere 4240]

#1 oxygen sensors in each bank is kinda sounding like the problem but don't wana pay that right away

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[someotherguy]

Don't have to pass emissions here, and I have an acdelco CTS. I put in last winter.

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My bad. I misread you saying "no need to pass emissions"; all I saw was "need to pass emissions"

Year-old CTS is probably fine; my guess would be then you're looking at failed regulator as you suspected, or more likely, leaking poppets. Have you done the MPFI conversion yet?

Richard

 

[John Deere 4240]

My bad. I misread you saying "no need to pass emissions"; all I saw was "need to pass emissions"

Year-old CTS is probably fine; my guess would be then you're looking at failed regulator as you suspected, or more likely, leaking poppets. Have you done the MPFI conversion yet?

Richard

Idk what that is, elaborate or link please good sir

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