does any one know how exsactly can i put the car into a fied service mode to check if the air-fuel mixture is too rich/lean
thnx in advance
AK

 

Field Service Mode

On the OBDI ECMs, you can jump 'A' and 'B' terminals on the ALDL while the engine is running.

WARNING! This must be done after the engine is running. This is called "Field Service Mode" and will not harm the ECM.

If the ECM is in Open-Loop mode, the SES light will flash rapidly, about 2½ times per second. If it's in Closed-Loop mode, it will flash about once per second. When in Closed Loop mode, flashing less than once per second indicates the ECM is enriching the mixture above the 128 count base line. Flashing more than once per second indicates the ECM is leaning the mixture below the 128 base line.

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Later,
Vader
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If you want to beat the World, it might reach up and pull you down...
Adobe Acrobat Reader

 

ok, i did the test, and its flashing really rapidly, that means the ecm leans the mixture, right , so that means is running too rich by itself right?
how can i fix it , or do i need to fix it?
because my gas milage is really bad now .
about 17 L per 100 km
thats around 15-14 MPG and thats a 2.8 v6 with manual. engine rebuilt 1000 km ago /2 month
can any1 help me plz

 

Were you getting any trouble codes from the computer before (ie the check engine light was on)? If you were you should read the codes in the computer...might help you find the problem. Sounds to me like you have a coolant sensor or oxygen sensor keeping the engine in open loop mode, which would explain the bad gas mileage.

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Red '87Formula Firebird
-mostly stock 5.0L LG4 w/cowl induction setup borrowed from '83 TA and T5 tranny.

My newest Ride:

'85 Silver L98 Corvette w/4+3 manual tranny. not bad for $3500.

 

Hi 88 Camaro.

It the SES is flashing very fast it means that the ECM HAS NOY yet entered the closed loop. Let the car warm up or better place the jumper wire at the terminal A and B (after the car is started and thouarly warmed up) and drive it for a while while observing the SES light.

If you are getting poor gas mileage check the following:

- secondary ignition (plugs, wires, cap, rotor, adjust your timing) you should advance it by couple of degrees (helps fuel mileage)

- when was the last time you have changed the oxygen sensor?

- tire pressure?
- air filters, pcv valve?

I hope this helps. Good luck.

It shold not flash very quickly while you are driving.



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89Iroc, 305 TPI, WC T5, 3.08 Posi, Headers, Hooker Y-Pipe, 3 inch over the axle, Flowmaster 80, No Cat, Aluminium Driveshaft, Ported Plenum, Air Foil, K&N, AFPR, All free mods,

 

thnx for the advices
i'll check it out and keep u posted
AK

 

now im confused , when its cold it flashes rapidly , but when it warms up it starts flashing really slow, so what is going on?

is it running too rich or too lean?, how can i fix that

thnx in advance
AK

 

So your car eventually got into the closed loop.(flashing slowly).

Here is what the book says:

"if the SES light is on more han it is off, then the engine is running rich"

" if the SES light is off more than it is on, then the engine is running lean.

Just go by that but this will only work when your car has entered the closed loop.

Good luck.

 

ok i found out my engine is runing lean, now what , how can i fix it ?
oh and how can i check the O2 and temp sensors ?

thnx allot
AK

 

can any1 help ?

 

88,

The oxygen sensor is difficult to test for calibration. There is a fairly simple "go/no-go" test that will tell you if the sensor is working at all, but short of installing a second sensor and testing the output, the apparatus for calibration testing is pretty involved. For the cost of a new sensor, you should probably replace it if yours has more than 30,000 miles or has been contaminated by sealants, lead, or antifreeze solution.

Once you have a reliable O2 sensor, the ECM should be able to accomodate the mixture and maintain it correctly. The normal failure mode for a sensor is a slowly degrading signal, which tells the ECM that the mixture is lean. The ECM will try to enrich the mixture to compensate until the O2 reading is "correct". Weak sensors often are first noticed by poor fuel mileage.

As for the CTS, you can test the resistance of the sensor at a given temperature. If the resistance is reasonably close to the resistances given in the table, the sensor is probably O.K. If not, check the connections and voltage of the 5VDC supply to the sensor. If everything is coorect, a new sensor is about ten bucks (US).



------------------
Later,
Vader
------------------
If you want to beat the World, it might reach up and pull you down...
Adobe Acrobat Reader

 

wow, thanks alot i'll check these out .
another question though, i just found a huge vaccum leak and fixed it, could it have been the cause for the poor gas milage ?

thanks for the help so far
AK

 

can any1 help.
if it helps , the vacum leak was a broken hose running from a cilindrical box at the left front of the car ( for fuel vapours or somthing) ,( i would also like t oknow what that is and does)
thnx allot
AK

 

88,

A "huge vacuum leak" = very lean operation. If the engine is runnign lean, the fuel mileage will be great until you try to make any power. As soon as the ECM rejects the lean condition from the O2 sensor and reverts to the Backup Fuel and Spark Mode, your mileage is gonna suck raw eggs.

------------------
Later,
Vader
------------------
If you want to beat the World, it might reach up and pull you down...
Adobe Acrobat Reader

 

k, but still, whats that cilindrical box does?
because all i did was plugging the broken hose at both sides, so i didnt really fix it per se, do i need to fix it , or is it just emission crap that the engine will run better without ?
thnx again
AK

 

can anyone PLEASE help
im sorry im asking so many questions its just that i want to know more about my car

 

If the lean condition is caused by a vacuum leak, then you need to find the leak and fix it.

If there is nothing mechanically wrong with the engine, then giving your engine more fuel is what is needed. The best way is a combination of properly sized fuel injectors, increasing the fuel pressure (don't go over 50 psi or you'll be replacing your fuel pump fairly soon) and altering the eprom.

If you are interested in learning how to burn an eprom, then go to the DIY Prom Board. But make sure you don't have a mechanical problem first. No point in burning an eprom in that situation.

 

still , whats that cilindrical box for
it has two hoses running to it from someplace in the manifold, one of them is broken into 2 not just cracked

 

If it's a sphere, it's a vacuum resevoir. If it's a cylinder, that's the evap canister/charcoal canister whatever you wanna call it. It' a piece of your emissions components in the car. It catches fuel vapors that can't be burned off immediately and saves them for later use. I'll go take a look at the one in my car to see how the hoses are supposed to run.. brb

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

Okay, I'm back. Now, the evap canister has two hoses on it, one on the top of the other. The one on the top is running to the engine somewhere, and the one on the bottom looks like it goes back to the fuel tank. I have a small valve on the lower hose on mine, it's about the size of a silver dollar. If you don't have that, maybe that's what's supposed to go where you're saying the hose is split in half.

I'm afraid I don't have a picture of it.. Maybe Vader can help there. He's got a way with the images.

 

actually its the cylinder and the top hose is torn , Vader, or anyone else ,what could it cause
shold i try to fix it , leave it as it is , or just buy a new evap canister.
could it have caused the bad milage
i filled up yesterday and i measured 16L/100 KM .thats aroud 15 mpg i think ....

so what should i do ?

 

also , if any one here has AIM because that way it will be faster , post your name or just find me im V6camaro1988
thnx allot for the help so far

 

so.... what should i do ?

 

Definatly fix that vacuum leak!!! Vac line is cheap and exremely easy to fix.. might as well do them all...

When I replaced my lines, I noticed a power gain and about 2 more MPG.

make sure tires are inflated properly... TC is locking up, tranny not slipping... ect.

Check your ingnition for weak components, replace as nessesary, definatly replace some of the more important sensors... O2 and CTS to start...

If it's still bad; fuel filter, have your injectors balanced and checked, exhaust checked for leaks, ECM checked for malfunctions...

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1985 Camaro SC - 2.8L, auto.

C'mon, spin 'em for papa...
http://www.xenodrgn.f2s.com/Frontright.jpg

 

its actually broken exactly at the entarence to the canister so that the vacum line itself isnt broken ,but can't be fixed
its not connected to the EVAP canister
(the exit from the canister is broken so i cant connect the line without having to replace the canister