Off Idle Hesitation Stumble

[Torinate]

What I’m seeing is under lighter load. Pulling away from a stop if I step on the gas with 40-50% throttle the car bogs down, stumbles and hesitates then takes off. There’s that delay from pedal down to acceleration.

What are the usual suspects in that?

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[TX-Ripper]

Start with the easy stuff.

compression test while replacing plugs.

Next step would be pull the fuel injectors and have them bench cleaned or swap in a new set of injectors.

 

[Torinate]

Do you think low compression would manifest as an odd idle hesitation?

 

[TX-Ripper]

You’re asking me what’s wrong with your car and I am asking you what’s not wrong with it.

if you change the plugs, that Takes care of the majority of ignition issues which could be caused by many different things so it might temporary fix your issue but not permanently of something else caused the plugs to foul.

If you do a compression test and the compression is good that rules out one reason why a plug might be fouled which could definitely cause a hesitation.

After that I would go onto cleaning/replacing your fuel injectors.

It might sound expensive to replace but with the time involved with removing them and getting them cleaned unless you have someone local it might be easiest to replace them and then get your old injectors cleaned and sell them.

 

[TX-Ripper]

If you have access to a smoke machine you might wanna start with Smoke testing to find an intake leak from a gasket that’s gone bad that could cause a hesitation.

going back to what I first asked a lot of times you can see a problem in the fuel trims that might lead you to believe that there is extra air getting in and the engine is not running the correct air fuel which overtime can cause your plugs to foul

 

[Torinate]

If you have access to a smoke machine you might wanna start with Smoke testing to find an intake leak from a gasket that’s gone bad that could cause a hesitation.

going back to what I first asked a lot of times you can see a problem in the fuel trims that might lead you to believe that there is extra air getting in and the engine is not running the correct air fuel which overtime can cause your plugs to foul

I appreciate the assistance.

Plugs were all pulled and looked new. Gap was still 28. Vacuum on my gauge has been consistent and there hasn't been any change from pre-issue to post issue.

I'll pm you my logs at datazap. Let me know if you see anything the fuel trims that sounds an alarm. Unfortunately, I don't - but i'm far from any sort of expert!!

 

[TX-Ripper]

I will look at the logs.

I hate to say this on a public forum, have you contacted Edelbrock I seem to remember there being some issues with the supercharger casting destroying rotors and bearings.

if I remember correctly one of the Lund tuners had it happen on his personal car and had to have the supercharger rebuilt by Edelbrock and I think he sold it afterwards.

 

[Torinate]

No I haven’t.

Same as contacting Lund. I don’t see this issue as a tuning issue or a supercharger issue. Tune has been perfect for 2 years and the supercharger has been spot on.

I’m hoping to start small and eliminate things as I go.

I didn’t hear that about the EB blower... I guess you never know.

 

[TX-Ripper]

After reviewing the logs there more than a 20% swing and short term fuel trim around the hesitation.

my best advice is to smoke test the intake and supercharger system.

And as a wellness check replace the spark plugs and do a compression test if nothing else you have a baseline as of today going forward.

Intake leaking air, dirty fuel injectors, fouled plugs could all be the root cause.

smoke machine, compression tester, set of plugs are pretty cheap Compared to damaging the motor or killing a cat that then kills the motor.

 

[Torinate]

Thanks for that TX-Ripper. I didn't see that I guess. I don't even see where the hesitation occurs. I even blew up the logs huge and cut them to try to pinpoint the event. I'll have another look. Going from negative to positive or vice versa I presume. The one log is weird. for 2 milliseconds there is a spot that goes from .78 afr to 1.23 then back to .8 afr. Sort of coincides with the vct2_intake stopping and torque source dropping (below).

What is vct2-intake? Is there a reason that it just stops in a log? It went from -21.29 to completely gone. Variable cam timing I am assuming. tq_source_pid went from 7 to 0 at this same time. These events took place within 0.06 seconds. No idea what they are or if they're related.

Appreciate the time and advice. Any info on these PIDs?

 

[TX-Ripper]

My experience with the NGauge is sometimes PIDs just drop out and come back.

VCT intake is your intake cam PID and VCT exhaust his exhaust cam PID numbers one and two refer to bank one and bank two

 

[TX-Ripper]

If your car goes even 5% lean you’re going to feel that… 10% or more would be like closing your throttle as far as what the car would feel like

 

[Torinate]

I'll look again at the logs for when the issue is occurring and focus in on the AFRs. But it's just coming off idle at the moment the pedal is pressed. I didn't notice any AFR changes in those areas previously but i'll check again.

 

[TX-Ripper]

Do you have access to a smoke machine?

 

[Torinate]

Not at my disposal but can likely borrow one. As I said, I did a smoke test initially when the blower went on and my vacuum levels on my gauge haven’t changed. But I guess you never know.

Any place I should do is more attention on?

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