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Strange AFR / Hesitation then POWER! - SOLVED!
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TOPIC: Strange AFR / Hesitation then POWER! - SOLVED!
#65846
Strange AFR / Hesitation then POWER! - SOLVED! 8 Years, 5 Months ago Karma: 2
Hi guys. Im having my 3GEN 3SGTE do kinda stange things.

Example: When im driving down highway on fifth gear about 120km/h about 2500rpm
Im having AFR readings 14,7 - 15,00 Thats fine, but as soon as accelerate just a little "With the tip of my toes" I can feel the engine retard the timing and the AFR keeps in the 14,7 - 16,00 and the car hesitates.

This keeps happening until I hit 0,5bar (7,2psi) boost then POWEEEEEER!! and the AFR drops to 10,00-11,00

This does not happen if im doing WOT or 1/2 gas. AFR drops instantly to 12,00-13,00.
Hesitation only at light (1/4 pedal) acceleration.

Any idea what causes this?

Only mods I have done are increased boost to 1,0 bar (15psi) and changed fuel pump.
Solor
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Last Edit: 2014/05/22 20:48 By Solor.Reason: SOLVED
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#65915
Re: Strange AFR under boost: Hesitation then POWER! 8 Years, 5 Months ago Karma: 314
Are you on an aftermarket ECU?

I would start looking at simple things first, like check your leads, dizzy cap, plugs etc. Also look for boost/vacuum leaks. Have all of that 100% prior to looking at tuning issues.
Quandry
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#65974
Re: Strange AFR under boost: Hesitation then POWER! 8 Years, 5 Months ago Karma: 2
No Im running Stock ECU

I have replaced plugs, wires, rotor & cap, lambda, fuel and Air filter (K&N High flow cone)

I tried to adjust my TPS and check any exhaust / vacuum leaks and nothing

Only way the air is getting out of intakemanifold is by throught Idle control valve and back to the turbo intake pipe and I suppose that is normal?
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#65979
Re: Strange AFR under boost: Hesitation then POWER! 8 Years, 5 Months ago Karma: 19
I thing it could be either a fuel pump or fuel pump relay . not swiching to full power in time. I chanched my pump for wallbro for same reason and problem disapered but came back after one and a half year the same together with significant and noticeble noise from the pump it self.

No harm in checking fuel presure as well.
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Last Edit: 2014/04/29 22:28 By Fazzio.
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#66067
Re: Strange AFR under boost: Hesitation then POWER! 8 Years, 4 Months ago Karma: 2
I actually changed my fuel pump already to some after market one (not walbro but some other similar) I will try to check my fuel pressure next thanks! =)
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#66116
Re: Strange AFR under boost: Hesitation then POWER! 8 Years, 4 Months ago Karma: 19
How is your afr sorted ? Just asking as i had similar problem after fitting afr gauge in 200sx. as i remember it was soldered in to a harness just after connector of lambda probe. There is very small voltage upto 1.3 v as i remember so any interference makes ecu go bananas. problem dissapears when you go above 3500rpm on boost as lambda readings is disregarded by ecu a that stage.

Any way my money goes on this:
Maf mr2-s -rev 1 and 2 can act up because of cone filter and blow off valve. check the second one for leaks or not closeing properly. it could be a issue that it stays open until larger boost has enough pressure to close it and power surges than. on rev3 that would delay boost. on rev 1 to 2 will make it go nuts as maf readings would be way off.
Fazzio
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#66142
Re: Strange AFR under boost: Hesitation then POWER! 8 Years, 4 Months ago Karma: 2
Fazzio you might be right!

My AFR replaces stock lambda and I had to leave the white and two black wires unconnected.
I just today redid my connection and there was a difference how the car acted, but it still didn't take away the hesitation under the boost.
I think Im gonna get a new lambda for me and do the AFR a standalone setup...
Solor
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#66166
Re: Strange AFR under boost: Hesitation then POWER! 8 Years, 4 Months ago Karma: 152
i had this happen to me. it's your wastegate. it's stuck. you have to port it out.
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#66179
Re: Strange AFR under boost: Hesitation then POWER! 8 Years, 4 Months ago Karma: 2
My wastegate is definetly not stuck. I can hear it open and the boost pressure is desired (15psi/1bar) Its my AFR that keeps being at the ~15 until suddenly about 3500rpm under boost it drops to ~10

Edit:
Anyway I got myself a new lambda and ordered a new downpipe at the same time. I have to try out these. Anyone can confirm that DENSO number DOX0217 is correct lambda for GEN3 3SGTE (year -94) ?
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Last Edit: 2014/05/07 21:42 By Solor.
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#66225
Re: Strange AFR under boost: Hesitation then POWER! 8 Years, 4 Months ago Karma: 2
Okay this is getting interesting..

Today I did a recheck on my ignition timing and it was off I mean way off. With TE1 & E1 connected It was about 20° BTDC. So I adjusted it to 10° BTDC. I don't have a idea how it has gone there in the first place since I did check some time ago and It was correct that time...

EDIT:

Solved!

It was my knock sensor giving a false signal to ECU
Strange that it was not giving any fault codes...
Solor
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Last Edit: 2014/05/22 20:51 By Solor.
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