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Discussion Starter #1
Hi Guys,

When I first imported my R34 GTR in 2018 I noticed there was a slight hesitation on boost and the car struggled to start sometimes.

I replaced the battery, replaced the spark plugs and cleaned the MAF Sensors. At the time this seemed to solve the issue.

Recently the issue has returned and seems to be a lot worse.

Symptoms are as follows;

  • Struggles to start, sometimes have to tap the throttle to prevent stalling
  • When cold there is a bad hesitation when i get to around 3000 rpm, can't rev any higher and car starts misfiring and backfiring from exhaust
  • Has stalled when at traffic lights
  • When warm struggles to start
  • Strong smell of fuel and incredibly poor MPG
  • Did the diagnostic check by bridging the pins on Consult Port, this gave Error Code 12 (Air Flow Meter)
When unplugging the top rear MAF the car cuts out. When unplugging the front lower MAF the car continues to run and increases idle to approx 2000rpm. Switching the MAFs over and unplugging again does not change what happens when unplugging the MAFs. It is still the top rear one which stalls the car and the front lower MAF that the car continues to run when unplugged.

I have checked the voltage on both MAFs with them connected, both are getting a 12V supply and both return a signal to the ECU ranging from around 1v to 4v depending on throttle position while car is running.

I have also opened up the MAF sensors and the solder joints seem pristine.

Car has standard ECU (I believe?), also running Apexi Intakes, Decat and Tomei Ti exhaust.

Any idea's what else could be causing this? Any other checks I should carry out to diagnose?

Any help would be greatly appreciated.

Thanks

Liam
 
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Liam, from our experience it will be an AFM issue , we have over the 30 Years been looking after RB Powered GTR.s have only a 50% repair fix after soldiering up AFM.s. They do deteriorate with age with dirt contaminating the wire and vibration damaging the internals.
 

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Here's how to fix them.
 
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We susseed that back out in the early 90.s on the R32GTR.s but it doesn't always fix the issue, moving forward you can now log the AFM voltages if you have a car that you can data log the AFM voltage with even if the car isnt tuned with AFM,s a link G4+ will allow you to data log the Output voltage from the AFM , this will show up slow response voltage dropping out , yes we always say to people try re soldiering the AFM but be aware it doesnt always cure the problem
 

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Discussion Starter #5
We susseed that back out in the early 90.s on the R32GTR.s but it doesn't always fix the issue, moving forward you can now log the AFM voltages if you have a car that you can data log the AFM voltage with even if the car isnt tuned with AFM,s a link G4+ will allow you to data log the Output voltage from the AFM , this will show up slow response voltage dropping out , yes we always say to people try re soldiering the AFM but be aware it doesnt always cure the problem
Thanks Mark

as mentioned, I did open them up and they looked perfect inside, checked with a multi meter also and both seem to give similar functional readings.

I was also advised to check the intake manifold and throttle gaskets for a leak, will report back today
 
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thats a good call, if the car still has paper gasket fitted I expect they will have gone brittle and fallen out causing an air leak, quick spray with brake cleaner will answer that question, there are 3 layers of gaskets , 1 either side of the throttle bodies and another between the inner part of the plenum set up and the cylinder head.
 

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i had a similar problem on an r33 gtr, and at the end the problem was caused by the coils
 

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thats a good call, if the car still has paper gasket fitted I expect they will have gone brittle and fallen out causing an air leak, quick spray with brake cleaner will answer that question, there are 3 layers of gaskets , 1 either side of the throttle bodies and another between the inner part of the plenum set up and the cylinder head.
Hi Mark

see below videos, one is unplugging each MAF and the other is brake cleaner on intake side. See what you think.


 
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Looks like intake manifold gaskets need changing , stopping the video and zooming in they are original paper gaskets.

With regards the Air Flow Meters I would say 1 is faulty but I would look at sorting the intake gaskets 1st Liam.
 

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Looks like intake manifold gaskets need changing , stopping the video and zooming in they are original paper gaskets.

With regards the Air Flow Meters I would say 1 is faulty but I would look at sorting the intake gaskets 1st Liam.
Thanks Mark appreciate your help
 
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