HappySalesman

iTrader: (3)

Car just started throwing a P0151 code yesterday. Doesn't do it consistently (I have a scanner so i'm able to delete the code) only in the mornings as I head up a particularly steep hill.

Question, what are the odds its an exhaust leak vs a bad sensor? Anybody know of a simple way to test for an exhaust leak?

Mercier

iTrader: (15)

Not knowing your car, I'd say 25% chance exhaust leak. 25% chance dirty MAF, 25% bad sensor or wiring, and 25% vacuum leak or fuel pressure issue. All relatively easy things to check but cleaning MAF is easiest and good maintenance anyway. Also have had IAC sticking and causing something that acts like a vacuum leak. That can be cleaned as well.

I've always looked for deposits around exhaust joints to indicate a leak. And sound/feel with the car running. Also look for damaged/dented or rusty areas. Maybe hit them with a wire brush and see if you have pinholes there. Check for carbon deposits around the exhaust ports on the heads as well.

Good luck.

HappySalesman

iTrader: (3)

After a few more drives I can definitely say its an exhaust leak. Under any hard acceleration I get a really loud ticking from the engine. Here's hoping that it's just an air gasket and I dont habe to yank the manifold. Might as well do headers if im gonna do that lol

HappySalesman

iTrader: (3)

Whelp, its an exhaust leak. Whole pipe where the flange meets the manifold is cracked, nearly 3/4ths of the way around.

Mercier

iTrader: (15)

Damn. Seems like that would have been poking you in the nose every time you drove it. But at least you know what it is now. Nice aftermarket pieces to to replace that pretty affordably right?

HappySalesman

iTrader: (3)

Sadly no, I just had two buy 4 brand new tires, so the wallet is a little empty. Fortunately I have a friend who works in a welding shop, so they welded the crack for cheap until I can get my aftermarket parts.

however, I now seem to have a fuel issue. The o2 sensor is still reading lean (now upgraded to p0151, p0174b, p1153 and p0300).

Not sure why, unless my sensor is fried as well. Gonna do a compression, spark and fuel test tomorrow and see whats going on

Mercier

iTrader: (15)

I wonder if the electrical current or heat from welding on the exhaust could tweak the sensor(s)?

HappySalesman

iTrader: (3)

Well they said they disconnected the o2 sensor and removed it when they welded... but I unfortunately wasn't there to watch.

I am getting a pretty consistent miss on bank 2. Mostly centered around cylinder 6, but cylinders 2, 4, and 8 are missing as well.

If the o2 sensor was reading lean, and the computer tried to compensate by dumping fuel (enough fuel to cause a misfire) into the engine, wouldn't it then start reading rich? Assuming a normally working o2 sensor.

Mercier

iTrader: (15)

That logic makes sense but the PCM should see a better signal from the O2 sensor now that the exhaust leak is fixed. You could try resetting the PCM(disconnect battery for a while). Also did you clean your MAF?

HappySalesman

iTrader: (3)

I cleaned my maf a couple of months ago, ill double check it. Fortunately my dad has a spare o2 sensor out of a 94 vette that im gonna throw on for a test. Ill reset the pcm as well

Mercier

iTrader: (15)

Are those the same part? They may not function the same. You can always swap sensors side to side and see if the problem moves around.

HappySalesman

iTrader: (3)

It turns out they arent. The sensor is the same but the plug is different. Fortunately the oreillys up the hill from my house had one so well see if it's the problem

HappySalesman

iTrader: (3)

So, it was the o2 sensor. I'm not sure entirely that the sequence of events was that ruined it but i put the new one in and it's running fine. Old 02 sensor was pretty covered in carbon, but not sure how that would cause it to read lean.