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Why does my exhaust smell so bad?

 
vetprowanab
User
Posts: 85
Joined: 11/03
Posted: 09/13/05 04:32 AM

I have an 88 5.0 mass air car.  Car runs nice and smooth, but the exhaust has a very strong gas smell to it. Especially when the car is cold.  It does seem to get better once the car comes up to operating temperature.


Are the 24# fuel injectors too big?  Is the fuel pump too big?  Too much fuel pressure?  Are the oxygen sensors not working?  Is the gas not getting burned in the combustion chamber? Maybe a spark problem or a timing problem?  Maybe I should reconnect the vacuum lines back to the emissions solenoids on the passenger front shock tower and the EGR(the electronics there are still connected)?


It's drivng my wife and my kids crazy!!   By the way - this car needs to pass Denver emissions next month. 


Thanks y'all!

 

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EagleAutosports
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Posts: 729
Joined: 08/04
Posted: 09/13/05 06:14 AM

24 pounders?  What exactly have you done to the engine?  Unless you have over 330 hp, they might be a little too much for it.  A set of 19 lbs and around 38-40 psi fuel would be better for it if it's not built up quite a bit.  Especially at Denver's altitude, less fuel would probably let it run better too.  Try that and see how it does.   

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vetprowanab
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Posts: 85
Joined: 11/03
Posted: 09/13/05 06:36 AM

Hmmm...well the car puts out 266 hp at the tires so assuming a 15-18% loss that makes the flywheel hp 310-320ish.  Maybe the 24 # are too big.  Darn it!  I just bought a new mass air meter for the 24s!  Anyway, I'll put the fuel pressure gauge back on.  I believe fuel pressure was 42 when I removed the cowl mounted gauge. 


Car is basic mild build:  F1ZE GT40 cast heads, 1.6 SVO roller rockers, 93 Cobra computer with Ford 70mm mass air, BBK 70mm throttle body, E cam, Edelbrock Performer RPM II intake, full length BBK headers, 3.73 gears, manual trans, electric fan. 


Thanks Eagle!

 

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EagleAutosports
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Posts: 729
Joined: 08/04
Posted: 09/13/05 07:02 AM

I agree that it's around 300-320.  You're moving some serious air with that RPM II.  Actually, try reducing the fuel pressure first before you take the 24's off.  If it had to be one or the other, it'd be better to have the 24's and back the pressure down than to have 19's and sky high pressure.  I lived in Albuquerque at 4700 feet and I had 24's and it did better with less pressure.  Still a little fat but with the thin air, the a/f ratio was close.  One thing, is the fuel regulator working properly?  I had a plunger collapse and foul all the plugs out.  If you pull a plug, will it be black?  Does it blow black smoke when revved?  If so, it's obviously too much gas.  Best thing is to get on a dyno so you can read the a/f ratio when tuning.   

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vetprowanab
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Posts: 85
Joined: 11/03
Posted: 09/13/05 08:37 AM

Thanks for the quick response Eagle.  I agree, I'll reinstall the fuel pressure gauge first as that is already paid for.  The regulator is a BBK unit, but there could be something wrong with it.  Absolutely no smoke out of the back of any color. 


This car has only been to the dyno twice, but each time the techs say it is running rich.  Note: neither time was for tuning, just establishing a baseline.


What do you mean your car did "better" in New Mexico with the 24s?

 

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EagleAutosports
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Posted: 09/14/05 07:21 AM

I live in North Carolina and back in 1996-1997 I went to Arizona to attend UTI.  I then moved to New Mexico where I have family until I could come back to NC.  The tune up I had in NC was totally different then what was needed in the desert of Arizona and NM.  I backed the timing down from 14 to 12 and the fuel from 48 psi to 42.  Before I did it, the car would load up, start coughing and at cold start up would give me fits.  After, the manners came back to where it was acceptable.  It had 24's the whole time and out there it acted like I had a huge carb.  Here, it's fine.  I have TFS heads and Track Heat intake, Comp Cams Nitrous cam, DSS short block, full MAC exhaust, all the other bolt ons too and puts out 310 to the rear wheels, naturally aspirated.  The heads are the old TFS Street Heat with the raised exhaust ports and 195 cc intake runners so I needed the 24's, 190 lph pump and 48-50 psi.  It's just what it wants and is happy there.  Imagine going from near sea level to 5000 feet or even 6900 in Flagstaff AZ.  Let's just say the car had some serious attitude until it was retuned.  Yes, I drove it 2200 miles one way from Greensboro NC to Phoenix AZ.  It almost beat me to death. 


Check for any carbon build up in your tail pipes.  If they're clean, it can't be too far off in the tune.  If it's built up a little, the oxygen sensors might have a little build up too and they're really sensitive.  Just something else to look into. 

 

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vetprowanab
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Posts: 85
Joined: 11/03
Posted: 09/14/05 08:55 PM

Thanks again.


Put my fuel pressure gauge on tonight.  Attached it directly to the nipple on the back of the regulator. With the car running at a normal 800rpm it okay showed 36 psi.  I gave it some gas and it increased every so slightly but only for a moment then promptly settled back at 36.  I left it alone. 


I also removed spart plug # 5.  Text book boring.  Except for the gap perhaps being a little too large, it looked great.  Of course I put in new plugs when I installed the GT40 heads on 5/1.


Didn't pull out the oxygen sensors as things were too hot. Also, the tail pipe looks clean. 


Huge car show this weekend.  500 - 600 cars.  Should be awesome!


Interesting note.  throttle position sensor started out at 0.996, then every time I checked it tonight it dropped by 0.001 until it bottomed at 0.992.

 

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EagleAutosports
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Joined: 08/04
Posted: 09/15/05 05:28 AM

Everything sounds ok so it might be just the injectors after all.  What's the heat range on the plugs?  A set of colder plugs might help.   

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darkfenix101
New User
Posts: 1
Joined: 07/07
Posted: 07/29/07 07:41 AM

I had the same exact problem.  NOx levels were triple what they should be and I failed inspection for it.  Check the little tubes going into your egr.  I plugged mine back in and everything was fine.  (passed inspection thereafter)  I'd check other tubes around the TB area and make sure they're all plugged in.  

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Frelhubb
New User
Posts: 35
Joined: 02/09
Posted: 04/23/09 07:52 PM

i have heard others say that the fowl smell of odor is caused by not having any catylatic converts(thos things we get rid of first).? I bet you dont have any?.
i dont have any and i have the fowl smell of gas?.. Also  

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