Author Topic: Surge on deceleration, in gear and off the throttle, between 2000-3000rpms  (Read 1549 times)

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Offline SSS

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Anyone had this happen before?

I'm thinking either a) MAF or b) TPS.

Doesn't do it all the time, and only when off the throttle completely, in gear, decelerating from 3000rpm to just below 2000rpm. Feels like the throttle is *just* being tapped, or like it's just received another 5 or so degrees of ignition advance.

Pulls hard like normal, no other driveability problems apart from this (and well, apart from it being a 21 yr old car....)

It's fucking annoying because I use engine braking a lot instead of tapping the brakes all the time.

Help?

Offline roadkill91

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Hey  :) SSS.Have had crazy things happen Like fuel filter fault/surges usually are long Duration ones,Or like a while 2 drop revs, Vacuum Regulator Pod On the Fuel Return Rail !?! Vacum-Pod  :-\. Fuel pressure,But then depends on Surge type as like does the surge.Surge several times in the One Deceleration? :)  Timming,For the dizzy 2 change degrees does Vacuum come into play as in old school where weights are vacuum controlled or spring type operation 2 steady and counter 2 much change 2 fast etc  :-\ .Butterfly sticky on throttle body/not cutting Air back sweet enough.Still reading  Go. on air  sensor 4 a bit long.Maybe a top end cleaner if haven't already done,Just like air cleaner we forget and some times miss a simple thing :D . Um when Backing Off ? Belts are on opposite stress as in Timing Chain !?!  Hope a simple thing  is the case your way  ;)  .ps if motor is chocking or a bit rich it can cause a fuel after burn or glow in the chambers,Maybe, I am sure u will laugh when worked out.PS.
« Last Edit: Nov 9, 2013, 01:46AM by roadkill91 »

Offline Nomad

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I would have thought TPS, as in the closed throttle position. Sounds like its getting confused as to whether it's closed or not. Have you checked if the closed throttle voltage of the TPS is in spec? IIRC about 0.4V. But why would it change? Failing TPS?

Offline roadkill91

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 :) Hey.Good point.Why? Tndeed.UMM there is a shit load of back compression going on in that there Pillarless machine/Is that the SSS we talking about?The one doing Donuts with the GTIR Package  ;) .Well shit yeah  :) .Now some things are a bit vacant in my thinking here.Is it when u just back off at 3,3-2,4,5,6000rpm = If it is at the high end down than it doesn't make much sense 2 not do it throughout all the ranges  :-X ,If it is just from 3-2000 than the back compression doesn't apply as over the top as much,. ::) .SO maybe  ??? .Lets go back a bit,Surges as in Lunges/ not misses a beat Like u Hit the Brakes,So. A petrol motor Needs Fuel 2 Surge Forward/Spark or Ignition of any sort I cant see making a motor go with out being wet  :P ,IS the car doing it consistently,Cold extra fuel Rich,,Hot Vapour & if is getting even a little wet,!?! Hope food for thought :) , What could allow this type of a scenario 2 apply if it was the case say.?. ps  bigger  picture  maybe needed if not found yet  :) cheers.PS.

Offline SSS

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I would have thought TPS, as in the closed throttle position. Sounds like its getting confused as to whether it's closed or not. Have you checked if the closed throttle voltage of the TPS is in spec? IIRC about 0.4V. But why would it change? Failing TPS?

TPS voltage is 0.46v, so is no problem. However, when I went to swap it out with a spare yesterday, the head on the lower adjustment bolt had snapped off at some stage. So, TB off and into the mill to drill out the rest of the bolt before I can swap the TPS over. I'm pretty convinced it's a dying TPS, sometimes it'll be perfect, other times it'll carry on. Probably something to do with the idle contact switches playing up.

I'm fairly sure the O2 sensor is still good, I disconnected it yesterday for the drive home, and no change.

Offline roadkill91

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 :) Hey,Sounds about right,As even though backing off the machine is still in idle mode ;)
Hence the wet cylinder 2 enhance fuel 4 the surge! Cheers & good luck,pillar less or not ::)PS.

Offline SSS

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I'm pretty convinced it's a dying TPS, sometimes it'll be perfect, other times it'll carry on.

Hoping I'm right, swapped it over and it hasn't carried on again. Time will tell, although I only need to make the car last for another 6-8 weeks.

Offline SSS

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TPS was fucked. I has decent throttle response now. Wondering when it would fuck out considering the car has done 335,000kms.