1g-gte misfiring on first few seconds of startup - common?

[auto351]

Would be interested to see what ECU & static timing is used on the 1G's that are hesitating & what Fuel is getting used?

[jimmmayyy]

Hi,

Auto351 I tried leaving the car on ignition for a few seconds before turning it on, doesn't help.

thats because the fuel pump runs through the circuit opening relay on toyotas.. the fuel pump doesnt run until you turn the key.

[JetspeedCamry]

Couldn't this just be a case of the engines cold, and that there isn't heat in the cylinders yet to provide a clean burn of the mixture? I've got 2 carby v8's that do this kinda thing (run rough when first cold and sound like there misfiring). I always thought it was normal for older cars to be like that.

[JustCallMeOrlando]

Mine never did this, pre or post BHG, with any of the 3 ECU's attached to it. Not beyond a normal level of roughness I'd expect from a cold engine.

[Z2TT]

Would be interested to see what ECU & static timing is used on the 1G's that are hesitating & what Fuel is getting used?

Well, I have a Gen 2 Stock ECU, M_Green has a Gen 3 Stock ECU.

I have used 91 and 98 Ron, doesn't make a difference.

[auto351]

thats because the fuel pump runs through the circuit opening relay on toyotas.. the fuel pump doesnt run until you turn the key.

So are you saying the fuel pump will not run until the key is turned to the start position, once started it continue to run?

[JetspeedCamry]

So are you saying the fuel pump will not run until the key is turned to the start position, once started it continue to run?

That's correct yep.

[auto351]

Just looked at the wiring diagram for the 1G and it looks like its not just the key to start which starts the fuel pump but a switch in the air flow meter, this would mean fuel presure would be low for a few seconds on starting.

Do the people who dont have the problem, still run the factory AFM?

[Kedderz]

factory afm but 2 bitchen aftermarket pumps and surge tank.

[auto351]

factory afm but 2 bitchen aftermarket pumps and surge tank.

Did you use the existing power conections from the original fuel pump or run a new power feed to your pumps, if so where did you pick up the 12V from?

[jimmmayyy]

So are you saying the fuel pump will not run until the key is turned to the start position, once started it continue to run?

As jetspeedcamry said, yep. Pressure is low for a short peroid of cranking until it fires. If it doesn't fire, then obviously it gets shut down through the circuit opening relay. One thing that i noticed with most oldish toyotas is that they need a few more cranks before firing than other cars, such as Nissans that pressurise first.

To Z2TT i'd say, if it only does it for a short period after starting and goes away within minutes.. whats the problem really? My 7M was also the same some of the time when it was particularly cold. Just let it warm up a little before you drive off... after all you did say it runs fine once it's warmed a bit.

[LT1986]

...mine deosnt do this either...but it makes sense that it could be a fuel pump that hasnt built pressure in the rail...

...explain why factory cars have this problem and celica conversions dont because we all have to run custom setups (surge tanks, lift pumps etc) which might be more efficient and prime when turned to 'on' rather than 'start'

...possibility?

[jimmmayyy]

very much so i would think.

[Z2TT]

I thought the fuel pressure should remain in the hoses/rail once the car is turned off, isn't there a 1 way valve that could be faulty?

[jimmmayyy]

one way valve????

i think you are misunderstanding the whole concept of a return fuel system there matey. excess fuel is returned to the tank, it doesn't stay pressurized; only if the pump is running.