Could use a little help here.

[Balatgek1]

My 19 GT350 has a slight miss with a drop in rpm at idle, when that happens the A/R ratio fluctuates. No codes. Dealer did a hx evap test that passed and checked VCT wires and cycled the VCT solenoids, tested plugs, coils, all ok. though maybe an injector so he put in a can of BG44K injector cleaner. Here's what I did, new PVC and vapor canister valve, fuel filter. Cleaned MAF sensor, throttle body and air filter. Any advice on what the dealer should check/test next?

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[wingnutt]

Double check your air filter and entire inlet is cranked down tight. Mine did similar after I had cleaned it and forgot to give it some beans

 

[Balatgek1]

Thanks, done, no change.

 

[wingnutt]

Ok, let’s back up…what’s the actual rpm after the drop?

and does it affect drive-ability?

mine is 16feet away, so I can cold start and tell you my own drop!

EDIT…mine goes from about 1300 to about 800, which is normal

 

[Mrhavasu]

Watching

 

[wingnutt]

Waiting

 

[Unbridled5.0]

Commiserating

 

[Balatgek1]

It doesn't seem to effect drivability. Once warmed up RPM is 650-670 then will drop between 100-200 (stumble)

then go back to normal. Also, when this happens the A/F ratio fluctuates. Not sure if this helps but at idle the bank 1 short-term fuel trim for go's from between -0.8 to 18.8% the LTFT is steady @ 7.0%.
Bank 2 STFT -0.8 to 6.3% LTFT steady @ 4.7%.

 

[Joe Gonsalves]

When you figure it out, post it. Mine does the stumble cold. It's not a miss-fire it's more like it cut out for half a second. Only does it once when cold and not every time. Car drive fine no issues with the engine at all. My theory is, it's a glitch in the engine programming.

 

[Balatgek1]

Will do.

 

[traktrbeam]

Interesting. I just changed my air filter the other day and noticed it dropping RPM's during cold start. Would drive like normal on the road. Drove to a drive thru to pick something up and noticed a RPM drop again and the AFR fluctuating up and down from 15-13.

Got home and revisited the air filter box and found I had not seated the front tabs correctly and there felt like a gap between the top and bottom pieces. Reseated everything and now it runs smooth again, FWIW.

 

[jheissjr]

Are you thinking the gap in the box housing caused a decrease in vacuum in the intake? Why does RPM drop from loss of intake vacuum?

 

[wingnutt]

Are you thinking the gap in the box housing caused a decrease in vacuum in the intake? Why does RPM drop from loss of intake vacuum?

…mass air flow vs. speed density?

 

[Zenaxia]

I had a similar issue on my 19 gt, they swapped the whole engine and that didnt fix it, and I shit you not, this is not rage bait, I used a bottle of chevron techron injector cleaner and it fixed it.

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