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· Registered
81 Posts
Discussion Starter · #1 · (Edited)
So decided to go to the drags tonight.

Drove there (66km). Stopped the car and registered (5mins) Drove into the holding lane and turned the car off and waited for my turn to get ready (couple minutes)

Now here is where the issue starts.

I turned the car back on and it started to idle rough and everytime i went to try and rev it, it would start to idle worse. AFRs were reading 14.6 while idling. Oil pressure was 40psi which is something I noted to be normal when at optimal operating temps. While holding the accelerator down the boost gauge would just sit on 0psi.

The strange thing is thou If i slowly let the clutch out while in gear and start moving it still idles like crap and shakes and what not but get to 10km/hr or so and it starts to drive fine.

Did the stupid thing of running it down the strip just to see if maybe the injectors were fouling or the plugs maybe; but when I finished I went and collected my time slip (left the car on) and it was idling fine for a min then would start to go rough again until I started to drive forward.

I repeated the above process twice more and decided to see if i could get home. I managed to drive along the motorway to home without a problem and have now parked it. I checked for blown intercooler pipes and hoses and can not see anything out of the ordinary. Fuel lines are not leaking and all three fuel pumps are working (see build thread for more details) so I dont think it was a lack of fuel causing it.

Its strange. Works fine there and back; but while at the drags was just running like a dog even thou I hadnt raced it and it only started 5-10mins after I got there.

Its a gte with a single conversion running a vipec v88 and has had extensive work done on the fuel system / pumps.

Now this arvo I went and started the car fine, did a 3km loop and had it idling in the front ward and behold it started doing what I described above.
Least this time I was able to video it and take it for a very quick drive to show from a running POV.

At 5sec it shows the initial part of something starting to go wrong almost like it sounding backing off of the accl and back on
At 13sec is where the issue starts rearing its head and you can here the very rough idle.
At 35sec you can see my trying to coast into the car port and give it a little throttle and it goes lean.
At 45secs you can see the AFR gauge at 13.6 but with a really bad idle.
At 1.10 you can see using the throttle cable to get the revs up, but you hear the very obvious issue with the engine. (got no idea what it is)
At 1.18 you can hear the same noise through the exhaust note.
1.50 shows that idle itself in terms of revs isnt affected very much and you can see the oil press gauge jumping around a little bit.
And by 2.00mins you can see the AFR leaning out a little and as soon as I use the accelerator it leans even more but;
At 2.15 you see the AFR go back to where it would normally idle
And 2.20 afr leans out again with the popping sound from the engine in the background as I am trying to reverse down the driveway
At 2.48 you hear the engine start coming back to normality
At 3.05 you can hear I have the ability to rev again (which up until this point I was unable to and it would lean out)
At 3.15 you can notice I am able to drive forward and back with out an issue on my driveway.
At 3.30 shows that the oil pressue is still the same as it was during the issue so Im thinking it isnt an oil related issue.

Anyway here is the link of the video i am talking about.

------Issue Vid-------

Please any help with A) the noise from the engine when looking in the engine bay and B) what would be causing it.

PS. the noises in the background at the start and through the whole thing is the noisy bosch 044 fuel pumps.

6,719 Posts
my car does that when i start it at 6am and try and drive forward instantly. (cold start map)
it also misfires like a banshee at low throttle when in cold start mode.

my opinion leans towards AFR and/or ignition timing related, and/or on--off throttle conditions, and/or light throttle conditions.

aka tuning

· Registered
81 Posts
Discussion Starter · #5 ·
What is your battery voltage during the rough idle. It seams like your pumps are fluctuating because of the battery voltage? Does the voltage change when you start to drive again?
Pumps seem to be fine. They are working even during the engine issue, you can hear them in the background of the vid.
The defi gauge you see fluctuating is the oil pressure of the engine. Thou it is not on video, the FPR that i have stays constant before, during and after the issue arises.

As far as im aware, the battery is in good health. Havent tried testing the voltage when driving (bit hard being the only one around and cant drive and multimeter test the battery)

Kinda stumped with this one. So many possibilities it can be

EDIT: Forgot to mention that I have tested the voltage of the battery during the rough idle and its fine.

· Registered
2,151 Posts
Your car is doing exactly what mine is doing right now. And the AF ratios are identical to mine as well (fluctuating to 17.0 and back). Any updates?

· Registered
81 Posts
Discussion Starter · #9 ·
yeh i found the cause of it.

was a few things but the main issues were fouled plugs because one of the clips had disintegrated.

the other was a leak in the intake manifold gasket. we found this coz while the car was running we sprayed some cleaner around the block and all of a sudden, the AFR's went suddenly rich. Prior to this my mechanic was trying to figure out why every time he was touching the tune up; 2 secs later it would be different again.

hope this helps.
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