Falling on its face

[Torinate]

Hey folks.
So first issue I’ve had.
I noticed it over the weekend but didn’t think much of it then as I was just cruising. Then yesterday I confirmed it.

When I try to get on it, the car just falls on its face. It doesn’t rev up or produce really much power and feels like jerk or like it’s missing. When I let off a little on the gas pedal it will pick up speed and become smoother and a little more power. Happens when I step on the gas hard only. Cruising it feels completely fine. Gauges look fine. Perhaps a little out of whack STFT but comparable to previous logs. No LTFT data. No codes.

Haven’t started any diagnostics yet. What is everyone’s thoughts on where to start.

I’ll take a log when I get a chance.

But where to start?

Thoughts? BAP or fuel pump going out under high load? Plugged cats?

Is there any way to log fuel pressure to see if it’s a fuel issue? Using nGauge.

Any way to tell if it’s the cats without pulling them off?

I don’t want to start throwing parts at it lol.

Any ideas and thoughts are welcomed!

I haven’t checked plugs yet either but only 5k on them gapped at 28.

Thanks for some direction!

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[turbofiveoh]

Stumbling and hesitation could be a number of things and in my experience fuel is usually the culprit but there's no way to know for sure until the condition is datalogged. If you don't want to throw parts at it then a datalog is the next step.

 

[engineermike]

Hard to say without a good data log.

I’ve been messing around lately with cat testing. I bought a back-pressure test kit and measured 15 psi on both sides at 7500 rpm and wot, which I believe to be normal. Next I’m going to measure it downstream of the cats to see how much the stock suitcase and mufflers adds.

 

[Torinate]

Thanks guys.

Yea, data log is my next step. I’d rather it be a pump issue than a cat issue. I know I’ve asked questions about cats many times and it’s always a concern. @engineermike that’s great you’re logging them! I have the factory cats and suitcase still as well...

I’m hoping after logs I’ll be able to see something. However, what will be the telltale signs? I also don’t want to push the car if it’s on edge either and cause a worse catastrophic problem. But I need to get data to see what’s going on.
Thanks again!

 

[engineermike]

There are so many things that can cause loss of power. With a thorough log you can see the torque source, which could lead to the throttle blade simply not opening. Verify it’s entering Power Enrichment, lambda is good, cams are going to Optimum Power schedule, spark timing is reasonable without excess knock retard, fuel pressure is at target, etc…

 

[StangTime]

What sort of air/fuel mixture readings are you seeing on your gauge? Cruising vs. getting on the gas.

 

[Torinate]

What sort of air/fuel mixture readings are you seeing on your gauge? Cruising vs. getting on the gas.

I really need to do a log and see. Watching the gauges and remembering is the challenge lol. Nothing that I saw where I really questioned it except for high STFT. As high as 20 at different times under different load conditions, but not wot. I looked back to see logs from 1 year ago to see if they were far off but they are comparable, at least what I see. The car has ran fantastic up to this point. I do see my idle rpm is around 850 which is where my tuner wanted it. Vacuum has 18.4-19.2 at idle at that rpm in park. A tad lower in gear though.

I think I’ll have to do a log and see what’s up and if anything sticks out. Maybe a cruise log and log under load. I fear doing a wot log if it is leaning out greatly though.

Thoughts or ideas? I’ll post it up when I get it. Hopefully tonight after work.

I’ll check for codes again but nothing has shown up yet and no check engine lights. I’m checking through the nGauge...

Thanks

 

[kevinvan6000]

Do you have access to a mechanical boost gauge? I'm not familiar with the Edelbrock blowers, but do they use a blow off valve at all?

 

[Torinate]

The Edelbrock has a bypass valve built in (separate though). I am using the vacuum / boost gauge in the dash enabled through forscan. Not exact but good reference. I do see boost build as normal but wasn’t watching when under load. No way to log boost though. No way to log fuel pressure itself either. Grr...

 

[Torinate]

Small update. No log yet. After dinner I’ll have a chance.

Pulled plugs and they’re fine. MAF sensor is clean as a whistle. Inside TB clean. By-pass valve visually ok but not tested. No codes no check engine light. Everything looks in order...

I disconnected the battery for half hour as well. Likely did nothing but who knows.

Will check BAP wiring before test though.

Next up is a log later today. Nothing visually.

 

[Torinate]

Ok. Well, back to normal. Went for a drive and low and behold it was fine. I did do a few logs but for whatever reason knock didn’t capture. SAFTOT did and shows my total timing of 18*. Man I was nervous. My pedal shows it. But afrs looked more rich than anything.

Here is a short log. Maybe I can’t see the forest through the trees.

Thoughts?

https://datazap.me/u/torinate99/log-1623889353?log=0&data=1

 

[Cory S]

Junky batch of fuel?

 

[Torinate]

You know what, that could be...

I always run Petro-Canada 94 octane. However, the last fill was with Mobil 93 from a station that is now carrying it close to me. I did top up with Petro-Canada 94 again so that could very well be it. I’m going to try to run another log and keep an eye on it. Just odd because it was so random.
Maybe someone will see something I missed in the log to throw light at it.
Not sure why the log didn’t show knock but I do see the full timing as tuned. Maybe need to rescan the nGauge but I always display KnockR and it displays correctly.

 

[brianbr]

Ok. Well, back to normal. Went for a drive and low and behold it was fine. I did do a few logs but for whatever reason knock didn’t capture. SAFTOT did and shows my total timing of 18*. Man I was nervous. My pedal shows it. But afrs looked more rich than anything.

Here is a short log. Maybe I can’t see the forest through the trees.

Thoughts?

https://datazap.me/u/torinate99/log-1623889353?log=0&data=1

Did you go wot in the log? Looks like max pedal percent is only 77, should be seeing 85 wide open.

 

[Torinate]

Lol. I was real nervous about not blowing up if going lean. The first one was only 50%. No WOT on this log. I did do one wide open throttle and it was similar as far as timing and fuel trims.

I had to work up to wot. I wanted to see what the car did when getting into boost and then watch fuel trims to make sure it wasn’t leaning out. I figured wot wasn’t a good idea right away.

Do you see anything that raises a flag?

Thanks.

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