exhaust odor/idle MOT issue
07-04-2019, 10:47 PM
Post: #1
exhaust odor/idle MOT issue
Hello, I noticed this long time ago but still bothers me my exhaust odor is always peppery smell. In years i tried different fuel brands but no change there. Also sometimes it misfires on idle but it is not affecting anything while driving. Engine has normal response. Another matter is that just now i did not passed MOT because of higher idle was told to correct it between 700-850 rpm. I set distributor with timing light and set idle all according manual was able to set it to 800rpm but sometimes when i sharply hit accelerator pedal it drops under 700rpm it is complicated to set it like they want. With lights on it idles between 900-1000rpm. MOT values where CO - 0,42 and HC - 123 they have limits for CO - 1-2 and HC - 300. So it passed emissions. Last time i cleaned injectors and it helped solve the idle trouble so i am planning it doing again. Idle is not floating but still i cleaned the throttle body, accelerator cable goes smoothly, Fuel filter was not changed in years so i think i replace it for new one from toyo. It is stock AE86 with 4AGE engine, AFM model. Got catalytic converter installed but not mentioned in papers (no such cars in database in Slovakia, only non CAT versions).
Can the exhaust odor mean that O2 sensor is not working properly and catalytic converter is too old? Any hints much appreciated.

85' AE86 GT coupe lifetime project since 2005
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07-05-2019, 01:04 PM
Post: #2
exhaust odor/idle MOT issue
Try cleaning the throttle body. Use spray carb cleaner. Best to remove the TB for the cleaning. Make a line across the TB and the TPS so you align the marks for re-assembly. After cleaning the idle can be adjusted by an air bleed screw under the rubber plug on the TB. If you need additional idle adjustment there is a small allen set screw on the under side of the throttle linkage. I would also double check the throttle cable "free movement" and make sure you have just a little slack in the cable allowing the TB to completely return to the idle position. Check both throttle return springs for function and all vacuum lines for cracks and air leaks. Dave W
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07-05-2019, 02:17 PM (This post was last modified: 07-05-2019 02:18 PM by Ryo.)
Post: #3
exhaust odor/idle MOT issue
I think i already checked all things you described i am planning after cleaning the injectors and fuel filter replacement to dissasembly the whole intake manifold i own the car for 15 years but i never cleaned the butterfly valve assembly. The car not moves much i drive it only in summer and about 1000km a year. No much time for it just need to pass MOT every year so i need to drive it little. Maybe that's why there are these troubles.

85' AE86 GT coupe lifetime project since 2005
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07-06-2019, 12:50 AM
Post: #4
exhaust odor/idle MOT issue
I don't have a catalytic converter and I have never smelled "pepper" from
an ehaust... but I do read a lot Tongue Apparently, if the gasoline in your country
contains sulfur, the combustion process will produce hydrogen sulphide in
the exhaust. The cat is supposed to convert this to sulfur dioxide which is
odorless. But if the cat is not working properly or if the engine is rich or has
a misfire, some of the hydrogen sulphide will not be converted and you get
the characteristic "rotten eggs" smell.

If your car does not get driven far or often, you may be getting a buildup of
carbon from low temperature operation. It might be a good idea to take the
car for a drive on a motorway where you can cruise at 100kph for half an
hour or more. This will help get the plugs, O2 sensor and cat up to their
correct operating temperature and "self clean" to some extent. See if that
makes any difference.

Changing the fuel filter is a good idea Smile

Your car will have an "idle-up computer" that operates a small solenoid
valve to let extra air into the intake manifold. This will raise the idle speed
by around 100rpm when there is an electrical load such as brake lights,
head lights, rear screen heater etc.

Cheers... jondee86

The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.
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07-07-2019, 09:04 PM
Post: #5
exhaust odor/idle MOT issue
Anti freeze can make an exhaust smell like that.

An analogue brain in a digital World
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07-13-2019, 01:36 PM
Post: #6
exhaust odor/idle MOT issue
Thank you for your replies. Can someone tell me part number for O2 sensor i know on flos.ie i can get new one but i can look in our local store for a new one. My friend told me only number 5671 6t from the sensor but denso catalogue don't show anything with this number.

85' AE86 GT coupe lifetime project since 2005
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07-14-2019, 04:22 PM
Post: #7
exhaust odor/idle MOT issue
Can you tell me how should the idle set screw be set on throttle body before i adjust the distributor according the manual i lost the original position and want to set it correctly again.

85' AE86 GT coupe lifetime project since 2005
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07-15-2019, 09:17 AM
Post: #8
exhaust odor/idle MOT issue
(07-14-2019 04:22 PM)Ryo Wrote:  Can you tell me how should the idle set screw be set on throttle body
before i adjust the distributor according the manual i lost the original
position and want to set it correctly again.

You should be able to get close enough if you adjust the bypass air
screw to get the engine idling at 850-900rpm and then set the distributor
to 16-17 deg advance WITHOUT bridging the diagnostib plug. It may
be necessary to repeat the procedure twice if the distributor was a long
way out of position.

Then, if you follow the procedure in the FSM you should find that when
you bridge the diagnostib plug the engine speed drops by 100rpm or so,
and the timing drops to very close to 10 deg advance. If needed, you can
make a fine adjustment to the distributor to obtain exactly 10 deg.

Cheers... jondee86

The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.
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