Break Up, Misfire, Popcorn at 5k rpm

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04-18-23, 10:45 AM

#26

ptrhahn

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You sure you don't have a dying coil?

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04-18-23, 10:54 AM

#27

BXP088

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Quote:

Originally Posted by ptrhahn

You sure you don't have a dying coil?

I already swapped out with good used coils that worked fine with another car and it didn’t make any difference…

I assume the water damaged the alternator and it probably had a voltage spike that messed something up in the fuel system. Apart from the fuel pump and injectors what else should I look into that was probably messed up by the voltage spike? That’s if I did have one.

Last edited by BXP088; 04-18-23 at 11:06 AM.

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04-18-23, 01:54 PM

#28

DaleClark

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Quote:

Originally Posted by BXP088

Thanks for your thoughts, Dale. I’ve been focusing on the ignition (plugs, wires, coils, harness) for a while and since I tried the refurbished alternator today (14.5v idle from 14.1v) with no cure I am now going to look into the fuel system. Leaning out at 5k was what I thought the alternator might be doing not giving me enough volt at that rpm…

I always imagined the secondaries to be coming online with the first turbo also and not rpm based (is this correct?), I do get full boost with the first and no misfires. Only when I reach around 5k does it start to misfire then disappears at around 6k.

I installed a new fuel filter a week or so ago, found it was quite dirty. Before all this the car was stored for quite a while that’s why I was thinking I might have blocked secondaries too? I will also replace the tomei fpr but it tests fine with regards to pulling the vacuum hose off and back.

I managed to borrow an igniter, which is the last thing I have to try out in the ignition system. When I go for a test I let off immediately upon any sign of break up so it’s probably the last ignition related test I’ll do.

The secondaries are brought on when needed, at very low load it's a higher RPM and it's a lower RPM at higher load. It think it's partially when the ECU sees the duty cycle on the primaries gets to a certain point it cuts over to the secondaries.

Igniters basically never go out, they either work or they don't. Coil packs have a solid test in the shop manual, if they pass that resistance test they are good.

I think you are going into a goose chase, you really need to get hard data. Get some info from a wide band and/or get a fuel pressure gauge.

I would also try and run the car at low boost - like 7 or 10 psi - and see if it does the same thing. I'm really concerned that you could be getting into detonation. Possible that ECU could have a map that isn't tuned up to 14 psi or it's tuned for higher octane gas than what you can get - many factors. Again that ECU is a black box, you don't know what you have.

Dale