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Thread: Bigport 4AGZE Cold Start Issue and Flat Spot

  1. #1
    Junior Member Backyard Mechanic
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    Default Bigport 4AGZE Cold Start Issue and Flat Spot

    Car: 1987 Toyota Sprinter Trueno - Bigport AFM 4AGZE. Completely stock engine apart from a Nevo pulley and a blitz filter.

    Problem 1. When I cold start the car it will crank over for 5 seconds before starting to cough. I turn the key off, then 5 seconds later try again and it will cough into life after another 5 or so seconds then go to normal cold start rpm. On really cold mornings it may even need me to put the throttle in 1/4way to get the airflow in. It may be related that sometimes at idle at the lights, the rpm will drop from around 800rpm (normal) to almost stalling then it will catch itself and go back to idle again.

    Problem 2. The car feels like it has a massive flat spot all the time. Almost like the supercharger is not even working. Then at random times I'll have all this extra power come onboard, like a flick of a switch. Then 2 minutes later it will vanish and I'll be left slow again. Boost gauge prooves that the supercharger is working perfectly, I can hear the clutch kick in etc...

    Attempts of solution:
    Changed SC belt (doesnt slip)
    Pulled plugs out and they were clean allbeit a little white (lean???)
    Checked leads for resistance and they came up perfect (around 3ohms or less in each)

    Ideas?

    Could it be the airflow meter spring? A mates Mazda air flow meter was causing a flat spot and cold start issues and it was fixed by tightening the spring slightly.?

    Fuel filter clogged up?

    Timing adjustment way out?

    Water temp sensor?

    Thanks for your opinions in advance!

    Ben
    www.usell4me.com.au - We buy and sell cars for private clients
    www.scorpionaustralia.com.au - Australia's only street legal race car!

  2. #2
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: Bigport 4AGZE Cold Start Issue and Flat Spot

    how does it start hot?
    5 seconds is far too long for a modern engine to need to catch..

    it sounds like most issues are related to fuel.
    does it get really bad at higher in rev range (when more fuel should be used), or is it all the way thru the rev range?

    pump, filter, fuel pressure reg, etc?? can you chuck it on a wideband to check mixtures?
    "I'm a Teaspoon, not a mechanic"
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  3. #3
    Junior Member Backyard Mechanic
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    Default Re: Bigport 4AGZE Cold Start Issue and Flat Spot

    starts hot perfectly. I cant really tell if it gets worse high in the RPM as ive never driven a 4AGZE car to compare. What I might think it abnormal might be normal in these cars. It does feel sluggish at the top end. Its only happened 3 times in the last 3 months but I have felt a miss under load. Plugs seem ok though, so maybe its a lean miss?

    I have a emissions test facility at work, so I might go test it tonight and change the fuel filter while im there.
    www.usell4me.com.au - We buy and sell cars for private clients
    www.scorpionaustralia.com.au - Australia's only street legal race car!

  4. #4
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: Bigport 4AGZE Cold Start Issue and Flat Spot

    does it actually have a cold start injector? can you check if it has gummed up?

    sometimes igniters do similar kind of stuff, but they usually stuff up when hot, not cold
    "I'm a Teaspoon, not a mechanic"
    "There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)

    AU$TRALIA... come and stay and PAY and PAY!!! The moral high horse of the world!

  5. #5
    Junior Member Backyard Mechanic
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    Default Re: Bigport 4AGZE Cold Start Issue and Flat Spot

    Yes I believe it does have a cold start injector, but i may have a bigger problem.

    I just threw it on the emissions tester. AF ratio is comming up on cold start as "Normal AF Ratio" (14.8ish) to "Lean AF Ratio" (15.3) at idle. Once warmed up and given a few revs it goes to "Very Lean" with around 20 and even up to 22!!! After a minute at idle it will go back down to 14.8ish.

    Obviously something is very wrong. The fuel filter was changed less than 6 months ago, so i doubt its that. I have access to a 4AGE of the same era, can I swap anything over to check what could be the cause? IE: O2 sensor or fuel pump?

    Any help would be very appreciated.

    Ben
    www.usell4me.com.au - We buy and sell cars for private clients
    www.scorpionaustralia.com.au - Australia's only street legal race car!

  6. #6
    Junior Member Backyard Mechanic
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    Default Re: Bigport 4AGZE Cold Start Issue and Flat Spot

    anyone help?
    www.usell4me.com.au - We buy and sell cars for private clients
    www.scorpionaustralia.com.au - Australia's only street legal race car!

  7. #7
    Junior Member Backyard Mechanic
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    Default Re: Bigport 4AGZE Cold Start Issue and Flat Spot

    diagnostics came up normal with no faults. I'll get the TPS fuel pump and AFM checked out.
    www.usell4me.com.au - We buy and sell cars for private clients
    www.scorpionaustralia.com.au - Australia's only street legal race car!

  8. #8
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: Bigport 4AGZE Cold Start Issue and Flat Spot

    check your fuel pressure regulator as well.. it may be.. farked... (or chekc fuel rail pressure at same time as chekcing AFR)
    "I'm a Teaspoon, not a mechanic"
    "There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)

    AU$TRALIA... come and stay and PAY and PAY!!! The moral high horse of the world!

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