HwyStarJoe

Morning all,

I did a couple searches but came up empty.
I did the engine swap from an '06 GTO into my '69 Camaro a few years ago. I've been plagued with that exhaust smell issue inside the car and it seems to be worsening.

Complete engine\auto trans swapped, factory electronics\harnesses, 1.75" Headman headers into full Magnaflow exhaust system, no Cats, tail pipes exit below the roll pan. They point down at a 45 degree-ish angle but do not extend past the roll pan.

I haven't run diagnostics on it in a couple years...just been enjoying the crap out of driving it. There are no CEL's displayed and it runs just like it did since day one. I realize it's gonna stink because of the lack of Cats, but it's becoming an issue now. I thought maybe the exhaust was getting into the cabin somehow, so I went front to back and there's no loose exhaust connections and no openings from the body to the interior... at least not large enough that would choke me. I don't know if it's something that's coming more from the front of the car or seeping in from the back. Of course these old relics aren't known for being sealed like a newer car, so there's a million places for stench to creep in. But this is bad enough to burn my eyes.

I can put the computer on it and see what it says, but I'm not sure which specs to pay the most attention to. The 02 sensors are new last year. I don't think this is a rich vs. lean thing, at least I don't think so... I think it's more exhaust than anything.
I have tail pipe extensions, but haven't put them on yet because it means tail pipe surgery, and I hate to cut up my exhaust until I've 'exhausted' all other options.

Suggestions?
Thanks!

HwyStarJoe

To add something:
The only other thing I can think of is that it's coming from under the hood... the rear of the cowl hood opening is open, and it's coming through the cowl into the interior.
But everything is tight...and it doesn't burn oil.

Project GatTagO

iTrader: (7)

Do you have a stock cam?

Andrew

33willys

iTrader: (1)

The shape of a vehicle sometimes has an effect on the exhaust. My ****** sedan delivery had a backdraft which sucked/pushed fumes into the back door. I wouldn't think your exhaust turndowns would cause this but I would start with that. Can you cut the tips square and add pencil tips and bring them out at least even with the bumper?

HwyStarJoe

The engine is stock. Hell, I can't keep the rear tires from boiling as it is!
It did 372\370 on the dyno.

Well, I can modify the exhaust tips. But it seems like this is getting worse each year. I took it out a few weeks ago for the first time this year and it seemed worse than last year....and then for a second time yesterday. It was unbearable.
I'm at a loss.

unnatrl

iTrader: (1)

Do you have the ability to check air/fuel ratio with a wideband sensor? If it's running rich the exhaust smell will be amplified. A "stock" engine can still run on the rich side because of small changes in exhaust, intake or a sensor that's working "ok" (but not optimal).

Project GatTagO

iTrader: (7)

If you don't have a wideband, simply look at your exhaust tips. Is there a bunch of black soot inside the pipe, if so, then it is running rich for some reason. It could be a bad O2 sensor (or two...)

It's also not a bad idea to do a simple tune up. Check the plugs and plug wires. If one cylinder is missing spark, this will give a false lean reading to the ECU and it will start adding fuel. Pull all plugs and post pictures. Keep track of which cylinder they came from.

Andrew

HwyStarJoe

Plugs are new (couple thousand miles at most) but the wires are not. They all read the same continuity... approximately 750 each. 02 sensors are brand new...couple hundred miles on them.

I ran SCANXL just now, but I hate that program. I took data but the log is impossible to read, so I just took a bunch of screenshots. I'm having a hard time building a new map for the LTFT and STFT on Bank 2, so incomplete data there.

It always did seem to have a 'miss' as if a cylinder is having trouble, even at idle...but the injectors are cleaned, flowed and all have the same flow specs with new seals. Every time I replace something thinking it may help, it's still there.
I can't track it to a single cylinder with the scanner...just random misfires once in a while over all 8. Nothing stands out like it's one cylinder.

I have an Innovate MTX-L wideband, but haven't installed it. It's a pain in the butt to take the exhaust down and weld a second bung in, and run the wiring inside the car.
Lazy... so I'm selling it.

I'll see if I can crunch this data and post it.

HwyStarJoe

The image names are self explanatory. Everything is at idle, warmed up unless otherwise stated... 3200rpm.

JD_AMG

A really simple way to check for exhaust leaks is to run some kind of top end cleaner through the engine (seafoam, mopar combustion cleaner, gm top end cleaner etc.) The exhaust will smoke and you can check under your hood and under the car if it's seaping out some where from an exhaust leak.

Something else to consider is picking up a new maf from autozone, if you see no change then just return the maf and get your money back.

HwyStarJoe

I could try the smoke screen method cheaply enough.
As for the new MAF, I'm not sure they'll let me return an electronic part. I can always ask though. Thanks.

truckdoug

iTrader: (25)

i had a '64 442 that would draw exhaust in through a gap in the trunk seal. after trying everything i could think of including tons of body work to the seal area I simply chopped the tail pipes in front of the axle and added 45's and angled turndowns that pointed at the rear tires. i do all my rigs like that now.

i am not too familiar with that scan tool but those fuel trim percentages look okay to me.

does it get the smell just idling in the driveway or only on the road?

HwyStarJoe

I can smell it while just idling, but not nearly enough to burn my eyes. I had it running for 30+ in the driveway today while scanning it and either there was a breeze, or its just not as bad just sitting. Of course it's more noticeable at the rear where they dump.

I have Torque on my phone with a Bluetooth OBDII adapter...going to scan with that also and see if the readings jive with ScanXL.

If I'm not out shooting tomorrow I'm gonna do a lot of snooping around.
The door vents above the strikers were never replaced so they're wide open...they're getting blocked off as well as the hood cowl opening.

truckdoug

iTrader: (25)

you might try some ghetto fabbing just to test...like some dryer vent to get the exhaust out of the "dead zone" draft area at the back of the car.

HwyStarJoe

I'm gonna weld up something like this today...

truckdoug

iTrader: (25)

haha lol

1981TA

iTrader: (7)

where is your battery mounted? If it's in the trunk, you'd be amazed how much exhaust stink can get through the hole where the hot lead passes through. Or through trunk seals. Or the drain plugs (if they're not sealed). Mine's running rich too (CAI, LTH w/ 3" dual exhaust, 50LB injectors, cat delete, pipes dump just before the rear axle). I'm weighing my options now for a mail-order tune.

Aston Tibs

iTrader: (3)

I think it is a function of the 1st gen F-body. My 68 has done this for years, with several small blocks and now with the LS-1. My engine was tuned and I have my exhaust coming out past the back about even with the rear bumper and I get this as well although not as bad as you describe. My exhaust system is very tight, but I did have some water leakage coming in through my taillights which I just recently resealed, so I am hoping that will alleviate the exhaust problem. Check all you seals in the back of the car.

HwyStarJoe

I haven't played with it in a while, weather, pets, other hobbies...
But something dawned on me the other day...

It may not be totally exhaust smell.
I have a small leak from the oil pan which gets on the exhaust by the trans while I'm driving. I think it might be the oil burning that I'm smelling.
It's not enough to smoke...but it's enough that I'll see a couple drops on the ground after sitting overnight, and discoloration on the collector.

I have a new oil pan gasket...
That's a project I have no desire to take on. If it wasn't for all the wiring, it'd be a snap...but this thing is tied in big time.
Bummer...

Aston Tibs

iTrader: (3)

You are probably on to something there. Mine is much better since I sealed the rear taillights better.