modified 1z hesitation misfire problems

So, I noticed I had a bit of hesitation/stutter at wot and high RPM's (over 3000). This problem got a bit worse as the days went on, and I assumed it was a fuel delivery problem and replaced the filter even though it was only 10k miles old. After replacing the filter, for the short test drive I took, the wot stutter seems to be gone, but if I stuff the pedal from a near stop in 1st or 2nd, the car loads up, smokes terrible and barely runs until I let off and let it clear up. After it clears, and I'm rolling along, I can floor it and it pulls hard.

I've got a BV-43 VNT turbo, Malone tune, my IQ is around 5, nozzles are PP764 and injectors were balanced, boost builds fast and holds steady at 25PSI, and injection timing is near the top line. I've got no CEL or codes coming up. Anyone have any guesses? Is my IP on its way out? Initially I though I may need a bit more IQ fueling, but with the car falling on its face from a hard start it acts like over fueling.

Thanks

It could be starving for fuel due to high inlet restriction before the fuel filter (Might be time for a lift pump or sending unit mod). It could also be valves floating and you may require dual valve springs.Beacuse it smokes I would say its getting fuel and its likely a valve float issue.I have ran into the valve float issue many times with modded engines. Just My 2 cents

Interesting, I never considered valve float. I've been thinking about a stage 2 cam, perhaps it's time I do the cam and dual springs.

One piece I forgot to mention. I recently upgraded my internal 2.5bar MAP to an external 3bar map and swapped my old 21 PSI tune (that originally matched my old GT1749VA turbo) for the new 25 PSI tune (that Malone created for my BV43 turbo). With the old tune and MAP, my car was a tad laggy, but I never had the (possible) fueling issues I'm having now. I also had my IQ maxed out through VCDS (instead of hammer mod) which brought it to around a 4.0 instead of the current 5.0. Could having the adaption setting maxed mask a possible issue with the IP quantity adjuster? Also, I have verified that my boost gauge agrees with the MAP pressure reported to my ECU.

Have you installed a keystone?

andy2 said:

It could be starving for fuel due to high inlet restriction before the fuel filter (Might be time for a lift pump or sending unit mod). It could also be valves floating and you may require dual valve springs.Beacuse it smokes I would say its getting fuel and its likely a valve float issue.I have ran into the valve float issue many times with modded engines. Just My 2 cents

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I've heard and have confirmed that there shouldn't be issues with valve float until you're >4500 or even 5000. The stock fuel filter is fine for this setup and the head, even stock, has dual valve springs

fletcher0780 said:

Interesting, I never considered valve float. I've been thinking about a stage 2 cam, perhaps it's time I do the cam and dual springs.

One piece I forgot to mention. I recently upgraded my internal 2.5bar MAP to an external 3bar map and swapped my old 21 PSI tune (that originally matched my old GT1749VA turbo) for the new 25 PSI tune (that Malone created for my BV43 turbo). With the old tune and MAP, my car was a tad laggy, but I never had the (possible) fueling issues I'm having now. I also had my IQ maxed out through VCDS (instead of hammer mod) which brought it to around a 4.0 instead of the current 5.0. Could having the adaption setting maxed mask a possible issue with the IP quantity adjuster? Also, I have verified that my boost gauge agrees with the MAP pressure reported to my ECU.

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Though I don't recall mentioning it in my thread, I'm running the TechTonics valve springs due to avoiding those same concerns and also possible oscillations at 30 psi.

G60ING said:

Have you installed a keystone?

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^^^ I'm lucky I've not had problem myself, but I forgot about this gem and can account for your problems. I believe you can still get them from Whitbread.

installing a keystone is a royal PITA, i tried once and gave up. some people tack weld it with great success. that's what i'll be doing if it ever becomes a problem...

Petroleum jelly also helps out.

keystone? I've not heard of it, I'll do some reading on it. Upon more testing, I've discovered I generally only experience the issue when stuffing the throttle from a slow start in 1st or 2nd. After changing the filter I have zero wot throttle fueling issues at speed.

here is how we found the issue on my car:
http://forums.tdiclub.com/showpost.php?p=3545761&postcount=137

The valve float issue I have seen is mostly due to High emp's.The Stock dual valve springs are not stiff enough when the emp's are more than double stock IMO.

The issue can be much worse if the engine oil is not at full operating temperature also.

VNT's can make emp spikes that will cause the exhaust valves to float then the hydraulic lifter takes up the slack and you start to loose compression.As soon as the excessive exhaust manifold pressure is gone then the lifter slowly bleeds down and restores full compression to the engine.

Not saying that this is the OP's issue but if nothing else is found then EMP's could be checked.

andy2 said:

The valve float issue I have seen is mostly due to High emp's.The Stock dual valve springs are not stiff enough when the emp's are more than double stock IMO.

The issue can be much worse if the engine oil is not at full operating temperature also.

VNT's can make emp spikes that will cause the exhaust valves to float then the hydraulic lifter takes up the slack and you start to loose compression.As soon as the excessive exhaust manifold pressure is gone then the lifter slowly bleeds down and restores full compression to the engine.

Not saying that this is the OP's issue but if nothing else is found then EMP's could be checked.

Click to expand...

This actually seems very similar to what I'm experiencing. I'll do some more testing and logging before I start buying any parts.