Strange physical "hesitation" between certain RPM and boost levels

[Kittenpunch]

Take it out and check the caps for leaks, I guess?

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[Greg E]

In my experience, these hesitation issues are caused by one of the following:

Poor fuel pressure:
*dirty gas tank -> debree in the fuel pump, filter and/or injectors
*degraded wiring to the fuel pump
*bad fuel pump relay

Unmetered air
*intake leaks
*someone screwing with or messing up the MAF

O2 sensor feedback error:
*old/bad o2 sensors
*exhaust leaks before the o2 sensors (cracked manifold (TT) or leaking flex section in the down pipe (NA))

Poor compression
*carbon build up and/or pitting on valves
*bad rings or worn cylinder

Poor ignition
*old/fouled/incorrect spark plugs
*old/arching plug wires
*old ignition coils

The ECU is one of those things that either works or it doesn't. More than likely if it hasn't been repaired before, it will need to be but that's more of a preventative maintenance kind of thing.

[Kittenpunch]

As far as I know, my exhaust isn't leaking. I just had the car looked at and everything superficial seemed fine. I'll try the MAF fix and see how that goes, I'll check my compression, I'll test fuel pressure atbthe fuel rail (what should it be at?), and I'll look at my spark plugs and check current going to the coils.

Is there a way to test O2 sensors?

I'll keep you all updated on what I find.

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[Greg E]

Honestly, I would start by buying NGK plugs, OEM wires, new fuel filter and swap all them in when you test compression and the coils. Gap your plugs at .028-.032 and don't forget the lithium grease the wire connectors and put some kind of anti-seize on the plug threads.

Those 3 things alone will make a significant difference.

Cracks in the front exhaust manifold can be hard to detect without pulling the heat shield but start with what I mentioned above.

[KeithMac]

Seems to be a real problem with the 1st gen's my GTO had the same fault at 0psig 2500rpm.

I tried everything (ecu plugs leads injectors fuel pump etc), eventually adding fuel in via the Emanage sorted it but it wouldn't run properly at stoich..

Someone mentioned timing jitter, and looking at a video on here there is bad harmonics with the timing belt at 2500 rpm..

2nd gen on have seperate crank sensor to avoid this issue.

[Kittenpunch]

Seems to be a real problem with the 1st gen's my GTO had the same fault at 0psig 2500rpm.

I tried everything (ecu plugs leads injectors fuel pump etc), eventually adding fuel in via the Emanage sorted it but it wouldn't run properly at stoich..

Someone mentioned timing jitter, and looking at a video on here there is bad harmonics with the timing belt at 2500 rpm..

2nd gen on have seperate crank sensor to avoid this issue.

So the solution would seem to be...?

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[Greg E]

[Kittenpunch]

I don't want to throw money at this problem. Is there a proper way to diagnose any underlying issues the car might have?

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[Greg E]

I don't want to throw money at this problem. Is there a proper way to diagnose any underlying issues the car might have?

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The advice I gave you will expose any underlying issues. Fuel filter, plugs and wires are required regular maintenance items. 90% of the time, issues arise from a previous owner not replacing these maintenance items.

[Kittenpunch]

Alright, progress. I finally had a chance to look at the car. I pulled each coil out individually to check if there would be any difference in the way it runs. Turns out coil #1 isn't firing nearly as often as the other 5. Like, significantly slower.

What could be causing this issue?

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