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Help! Another Massive Flat Spot

senilykSkylines

By senilykSkylines,
in Engines & Forced Induction

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senilykSkylines

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After researching I tried to fix this flat spot at about 3-4500rpm or so. I have tried setting the plugs at .8mm and it improved slightly. I have just bought yellow jacket coils and installed them thinking the old ones must have had it. If anything, it is now running worse! Good torque at up to 3000rpm and then it just goes flat and pulls a bit more at the end.

What on earth could it be?

Mods are:

Mail/road tuned Z32 ecu

Walbro GSS342 fuel pump

3" turbo back exhaust

GFB Boost T

K&N panel filter

Yellow Jacket coils

Running 11psi

cheers,

Dan

Edited by senilykSkylines
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https://www.sau.com.au/forums/topic/354399-help-another-massive-flat-spot/
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senilykSkylines

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I would get a real tune done as apose to one of those mail order bride ecus! You may be able to make the car run better but not every motor is the same to run the same settings!

I did have a mail order but then the tuner did a road test to check that is wasn't pinging and that all was running fine. I've only notice the missing a little while after the tune was done.

MrStabby Grand Master

MrStabby

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I did have a mail order but then the tuner did a road test to check that is wasn't pinging and that all was running fine. I've only notice the missing a little while after the tune was done.

So - The tuner reckons it was running fine during the road test (that is, no pinging OR flat spots OR missing) and you agree there was no flat spot or missing.

Since then its developed a flat spot and a miss - did those things happen at the same time? What has changed since the tune? How many kms has it been?

senilykSkylines Collaborator

senilykSkylines

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So - The tuner reckons it was running fine during the road test (that is, no pinging OR flat spots OR missing) and you agree there was no flat spot or missing.

Since then its developed a flat spot and a miss - did those things happen at the same time? What has changed since the tune? How many kms has it been?

It's done maybe 5-10,000 km after the tune. It seemed to run fine around the time of the tune an it has been gradually getting worse.

I thought a miss was a flat spot? As in a stall in power, failure to ignite... possibly?

The spark plug gap and the coils have changed since the tune but I did those because I noticed it after the tune (not immediately) I hope it is not the tune but I was thinking possibly the airflow meter maybe? or wouldn't it be?

MrStabby Grand Master

MrStabby

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It's done maybe 5-10,000 km after the tune. It seemed to run fine around the time of the tune an it has been gradually getting worse.

I thought a miss was a flat spot? As in a stall in power, failure to ignite... possibly?

Nah - miss is where the fuel doesnt ignite at all, so it is rough running, running on 5 cylinders. Flat spot is just low power, but smooth.

honan Collaborator

honan

Posted
Posted (edited)

I had a similair issue with a z32 ecu on mine..ended up going with a r32 ecu and seperate vct controller, the drama was the z32 ecu for some reason just stopped controlling the vct properly.!

Edited by honan
senilykSkylines Collaborator

senilykSkylines

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  • Posts: 115
  • Joined: 08-March 10
  • Gender:Male
  • Location:Whangarei, New Zealand
  • Car(s):R33 GTS25t 1997
  • Real Name:Daniel

97 would be series 2, which means no igniter pack.

Ya, one of the last R33's made, when I had the new computer tuned we even had to change around a few pins that would not usually need to be changed.

What I don't understand is why would having new yellow jacket coils make it worse? They are new and suppose to be better.

I really hope i am not leaning out or my engine would be frying itself. I would have thought running it rich rather than lean would be what makes it go slower? Fuel pump is only several months old, unless there is a leak in the line after i installed, but then it wouldn't be pulling hard in the top end I would have thought.

I've emailed the tuner...

  • 1 month later...
senilykSkylines Collaborator

senilykSkylines

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Dynoed it and turned out to be (in theory) the intercooler getting too hot which triggers the knock sensor almost always at 4000rpm. FMIC is on the next to do list.

SargeRX8 Grand Master

SargeRX8

Posted
Posted

How does heat trigger the knock sensor? It's on the other side of the block, it's not affected by heat and has nothing to do with the cooler. Unless the heat is causing the engine to ping which would be strange because you said your tuner said it want pinging.

put the stock ecu in before to cause any damage. I had a pfc which had a tune for stock car and little more boost, sure the highest ping was 38 but it ran like arse. Put my stock in there yesterday and yanked out the z32 afm and it runs alot better, alot more power. If the tune is not on your car it's not for your car.

senilykSkylines Collaborator

senilykSkylines

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How does heat trigger the knock sensor? It's on the other side of the block, it's not affected by heat and has nothing to do with the cooler. Unless the heat is causing the engine to ping which would be strange because you said your tuner said it want pinging.

put the stock ecu in before to cause any damage. I had a pfc which had a tune for stock car and little more boost, sure the highest ping was 38 but it ran like arse. Put my stock in there yesterday and yanked out the z32 afm and it runs alot better, alot more power. If the tune is not on your car it's not for your car.

<i> Unless the heat is causing the engine to ping</i>

This is correct. Tuner sensed a "little pinging" on the dyno but the knock sensor was pulling it back sometimes when it sensed knocking. So it is not knocking badly at the moment, only a little when it is hot which the ecu picks up and takes care of. Goin to get a FMIC and try 98 octane instead of 95. cheers.

Mayuri Krab Grand Master

Mayuri Krab

Posted
Posted

<i> Unless the heat is causing the engine to ping</i>

This is correct. Tuner sensed a "little pinging" on the dyno but the knock sensor was pulling it back sometimes when it sensed knocking. So it is not knocking badly at the moment, only a little when it is hot which the ecu picks up and takes care of. Goin to get a FMIC and try 98 octane instead of 95. cheers.

Your running RON 95 fuel on a GTS-T, and it has being modified for extra power? :(

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