4A-GE not responding well to full throttle

nyberrg
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4A-GE not responding well to full throttle

Postby nyberrg » Mon Jun 19, 2017 11:42 pm

I have a very street friendly upgraded 4age swapped in my TA62 Carina.

Bigport block and head
Smallport pistons
TRD 0.8mm Headgasket
HKS 256° Cams
Smallport intake (w/ T3 adapterplate)
Smallport ECU, injectors, distributor, etc. etc.

The car starts and runs fine but doesn't respond well to full throttle. I can make my way through the rev range with no issue if I dont go flat out but if I press the pedal to the floor the car loses its power and starts to struggle.

Does anyone know what the issue might be?

My guesses so far are
•Too much air
•Too little fuel
•Distributor timing is off

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davew7
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Location: Michigan

Re: 4A-GE not responding well to full throttle

Postby davew7 » Tue Jun 20, 2017 4:23 am

Check your fuel pressure. min is 40 psi. How old is the fuel filter? Check flow out of filter. Dave W7

nyberrg
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Re: 4A-GE not responding well to full throttle

Postby nyberrg » Tue Jun 20, 2017 5:58 am

Fuel filter isn't that old, maybe a year. There wasn't any issue like this with the stock smallport I had before so I assume the fuel pressure is fine.

Since it's a tvis engine with a non-tvis intake I thought it might get a different airflow than it wants which I guess would affect performance.

Compression should also be pretty high (10.8:1 or so) with the trd headgasket and smallport pistons. I dont really know if this can affect this stuff as well?

totta crolla
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Re: 4A-GE not responding well to full throttle

Postby totta crolla » Tue Jun 20, 2017 11:09 am

What provision have you made for the knock sensor and O2 sensor ?

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jondee86
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Re: 4A-GE not responding well to full throttle

Postby jondee86 » Tue Jun 20, 2017 2:36 pm

Could be too much ignition advance. Try turning the dissy as far as it will go
in a clockwise direction and see if the stumble goes away.

Cheers... jondee86
Give a person a fish, they eat for a day. Suggest they search before posting, and they learn a skill for a lifetime.

nyberrg
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Re: 4A-GE not responding well to full throttle

Postby nyberrg » Tue Jun 20, 2017 11:18 pm

totta crolla wrote:What provision have you made for the knock sensor and O2 sensor ?


For the knock sensor i welded a nut to the block where it would sit on a smallport block. I've had this engine in my car before but without the TRD headgasket. Didn't notice any issues with the setup back then.

The o2 sensor sits in the exhaust in the "1" part of a 4-2-1 style header

nyberrg
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Re: 4A-GE not responding well to full throttle

Postby nyberrg » Tue Jun 20, 2017 11:20 pm

jondee86 wrote:Could be too much ignition advance. Try turning the dissy as far as it will go
in a clockwise direction and see if the stumble goes away.

Cheers... jondee86

So you're saying it should ignite later, right? Like right now it might ignite when the piston is still on the way up?

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jondee86
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Re: 4A-GE not responding well to full throttle

Postby jondee86 » Wed Jun 21, 2017 1:57 am

The fuel always ignites when the piston is on the way up... for example at 35 deg BTDC.
What I am suggesting is that the spark might be TOO EARLY for your engine. You have
changed the operating conditions by raising the compression, and the timing map in the
factory ECU may have too much advance for the engine as it is now. The fact that you
said on another forum that you thought you had some knock points to this possibility.

The easy way to check is to retard the timing as I have suggested, and see if the engine
still has the problem when you try WOT to redline.

Beside knock causing the ECU to pull timing, there are other things like old spark plugs
or spark plugs with the wrong heat range, fuel mixture going lean etc that can cause the
engine to miss. You just need to eliminate the possibilities one at a time.

Cheers... jondee86
Give a person a fish, they eat for a day. Suggest they search before posting, and they learn a skill for a lifetime.

davew7
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Re: 4A-GE not responding well to full throttle

Postby davew7 » Wed Jun 21, 2017 5:13 am

Just pull a spark plug! It will tell you the mixture, timing, and if you have detonation. If it checks out good, then I would look at the TPS. Dave W

nyberrg
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Re: 4A-GE not responding well to full throttle

Postby nyberrg » Wed Jun 21, 2017 10:35 pm

jondee86 wrote:The fuel always ignites when the piston is on the way up... for example at 35 deg BTDC.
What I am suggesting is that the spark might be TOO EARLY for your engine. You have
changed the operating conditions by raising the compression, and the timing map in the
factory ECU may have too much advance for the engine as it is now. The fact that you
said on another forum that you thought you had some knock points to this possibility.

The easy way to check is to retard the timing as I have suggested, and see if the engine
still has the problem when you try WOT to redline.

Beside knock causing the ECU to pull timing, there are other things like old spark plugs
or spark plugs with the wrong heat range, fuel mixture going lean etc that can cause the
engine to miss. You just need to eliminate the possibilities one at a time.

Cheers... jondee86

The knocks came down to the distributor timing being way off and possibly a faulty distributor. I switched that out and now I at least can't hear any knocks. Gonna try to adjust more when i have time and report back. Thanks!

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mad_86
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Re: 4A-GE not responding well to full throttle

Postby mad_86 » Wed Jul 19, 2017 10:34 am

Try getting your injectors clean out many shop offer this service
i had mine done, out of curiosity and made a difference in a good running car
After i had them cleaned out felt like it pulled more and redline at WOT

RC Injectors
Torrance,CA

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