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· Actual member since 2001.
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Discussion Starter · #1 · (Edited)
Well I have a misfire code being thrown by my 97 TT. The codes it throws are misfire 2-6 cylinder. While idling it leans out every 30 or so seconds to 16-17 on the AEM gauge. Some times so bad it sounds like a loud clunking noise. After it warms up, i could from time to time hear a single popping noise, like a misfire. While under WOT it drops to 10's, while crusing its about 14.5, while on the freeway at a steady speed (70 mph) it leans out to 16 for a split second then it goes back to 14.5. Currently its near stock with the twins in perm TTC mode and down pipe, 147XXX miles. The plugs are gap'd at 32. When the car is cold its very noticable, but once it warms up its less noticable. Also my gas mileage is piss poor. Anyone ever experience this?
 

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please list all your mods... you said you had an aem (wideband) gauge i assume... so just want to make sure we're not missing anything else that you might have.

it could be an issue with the fuel system, but if its staying rich at full throttle then i'm not sure why it would be lean at idle if it was a clogged injector, dying pump, or similar.

it could be a vacuum leak somewhere after your maf as well, or a dirty or faulty maf sensor, or idle air control valve, stuck throttle plate, etc.

not sure... but that should get the conversation started.
 

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Discussion Starter · #3 · (Edited)
please list all your mods.
The only other mods would be the fuel pump mod (12V).

you said you had an aem (wideband) gauge i assume.
Yes

I think the twins are going out because they will boost to 14 lbs then at other times they boost to 8 lbs. They boost high when the engine is cold. Also whine of death. But I dont think this has anything to do w/ the afr/misfire
 

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Vacuum hose

Check your vacuum line spray them with WD40 to see if your car runs better.
 

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Discussion Starter · #10 ·
The clunking noise the engine makes sounds like its comming from the engine block. ill try to post a vid, maybe that will help some one to identify the noise
 

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Clunk

Sound like a motor mount.
 

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Its possible that your mass air flow meter hotwire element is dirty either from mileage or the K&N filter oil. I've seen it more than a few times where maf cars will idle lean and lean miss because the k&n filter was over oiled.

Try and get some "Mass air flow meter cleaner" from a parts house and clean the element. I dont think you can see the hotwire in the TT maf sensor, so you can spray it into the center area through all the holes to clean it. This is not the proper way to do it, the proper way would be to replace the maf sensor.

Another think to check is if you have access to a scan tool. You can check the fuel trims. This will tell you if the ecu is adding fuel to compensate for a issue.

you could spend hours trying to find your issue, I would recomend taking your car to a trusted shop to diagnose your issue. It could be as simple as a vacume leak or dirty mass air flow meter. Just make sure you stay with your car for the time its at the shop.

Lawrence
 

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Discussion Starter · #14 ·
Update: Well I took my car to a local mechanic. He thinks it could possibly be a"sticky valve". He said he used a stethascope and he heard a clunk noise, due to the missfire codes, symptoms at idle. I read on other forums that seafoam could be used to correct this problem? He wanted $850 to tear it down and fix it, if that was the actual problem, I said no thanks.
 

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Sticky Valves

BG makes some killer stuff you just pull a vacuum hose off your intake and let the engine vacuum pull it through while you rev the motor and it cleans your intake, combustion chamber and valves. My dad use to use transmission fluid to do that along time ago but I'm not sure if its safe for sensors.
 

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Discussion Starter · #16 ·
BG makes some killer stuff you just pull a vacuum hose off your intake and let the engine vacuum pull it through while you rev the motor and it cleans your intake, combustion chamber and valves. My dad use to use transmission fluid to do that along time ago but I'm not sure if its safe for sensors.
Is this what your talking about
http://www.carfood.net/noname16.html
 

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Yes!!! :)))
 

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Discussion Starter · #19 ·
Upadate:
Twincharge suggested to replace the front O2 sensor which I did. After removing my old one and shaking it I heard a clicking noise. Obviousley something was broken internally. I also removed/cleaned the IAC. The car still misfired and rpms were around 500-600. An improvement but still not good.

Today I cleaned the MAF and removed/replaced lead wires to both VSV's on upper right side of engine and resoldered in place 1K Ohm 1/2 watt resistors(s). The VSV lead wires were green and full of cracks. I really dont know if this has anything to do with the way the car runs but it seemed to hold a better idle. (http://mkiv.com/techarticles/obd2_code_eliminator_after_removing_vsvs/index.html)

Now the now car maintains a idle of 800-600 rpms, most of the time, alot better then the last 3+ yrs. Now theres only and occasional clunking noise and a slight mis which is hardley audible in the exhaust, most likely the coilpacks since they have over 156K miles. I did test them and they were w/in resistance. I'll be replacing those soon. Feels good to have car that dont idle at 250-300 rpms...

(Can someone tell what how the EGR VSV comes into play at idle, Due to the wierd idle, I tested mine via a multimeter and it was at the outer limit, 33 ohms. Max being 34 ohms)
 

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The EGR vsv will function during cruise rpm, not at idle or wot. Can you hook up a scan tool and tell us what your short and long term fuel trims are?

Since you are 6-speed when the car missfires you will hear a "Clunk" noise from the duel mass flywheel. This is normal during missfiring on a older duel mass flywheel.

Most mass air flow metered vehicles will take the Maf over o2 sensor readings. Try and unplug your maf sensor and fire the car up.

If you were in my area, I would be glad to help you diagnose your car.


Lawrence
 
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