Flashing engine light / no power under WOT or heavy load

[iamdub]

Older Vortec missing under load: I'd go straight to the MAP, MAF and CKP sensors. Small chance the CMP is at fault, but let's include it in the diagnostics. Can you datalog these four sensors specifically with your scanner?

First attacks: Clean the MAF, check the MAP and check the tip of the CKP sensor for scratches. Here's a nice how-to for the MAP: https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-map-sensor-1#1

...And for the CMP: https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-cam-sensor-1

To check the CKP, remove the 10mm bolt holding the sensor in place and pop it out of the socket. You might need to gently twist and/or wiggle it as you pull it. Check the tip for any small scratch lines.

 

[04SS99Denali]

Older Vortec missing under load: I'd go straight to the MAP, MAF and CKP sensors. Small chance the CMP is at fault, but let's include it in the diagnostics. Can you datalog these four sensors specifically with your scanner?

First attacks: Clean the MAF, check the MAP and check the tip of the CKP sensor for scratches. Here's a nice how-to for the MAP: https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-map-sensor-1#1

...And for the CMP: https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-cam-sensor-1

To check the CKP, remove the 10mm bolt holding the sensor in place and pop it out of the socket. You might need to gently twist and/or wiggle it as you pull it. Check the tip for any small scratch lines.

Yes I have a Autell tablet scanner. I’m sure I can monitor those sensors.

As stated my truck has a MAF code pending, I cleaned the MAF and went for a ride still has the same symptoms. Maybe the MAF itself is not reading properly. I will look into the map and cam position sensor. Makes sense that one of those could he the culprit since I removed the dist as well as the intake
When doing the gaskets.

 

[Doubeleive]

maf sensor could be bad or failing.

 

[OR VietVet]

https://www.rockauto.com/en/moreinfo.php?pk=1887184&cc=1355510&jsn=3398

https://www.rockauto.com/en/moreinfo.php?pk=87376&cc=1355510&jsn=3441

https://www.rockauto.com/en/moreinfo.php?pk=88851&cc=1355510&jsn=3455


Just in case.

 

[04SS99Denali]

Yea I ordered a new MAF and MAP sensor this morning. Going to see if it changes anything

 

[iamdub]

Yes I have a Autell tablet scanner. I’m sure I can monitor those sensors.

As stated my truck has a MAF code pending, I cleaned the MAF and went for a ride still has the same symptoms. Maybe the MAF itself is not reading properly. I will look into the map and cam position sensor. Makes sense that one of those could he the culprit since I removed the dist as well as the intake
When doing the gaskets.

On these older Vortecs, it's possible to get a MAF code even when the MAF isn't at fault. The input from the MAP is compared with that from the MAF, and if there's a discrepancy, the PCM tends to blame the MAF. Depends on what the pending code is/was. Watching their input side-by-side when it acts up is about the best way you could isolate it.

 

[iamdub]

Yea I ordered a new MAF and MAP sensor this morning. Going to see if it changes anything

Looking forward to the results!

Just throwing this out there: Has the trans been acting a little off? Maybe delayed or rough shifting?

 

[04SS99Denali]

Looking forward to the results!

Just throwing this out there: Has the trans been acting a little off? Maybe delayed or rough shifting?

I mean its original trans. 135k miles. 1-2 is good 2-3 is a not the greatest it does slip /shift rough under load/ throttle. I actually checked the fluid a few days ago it looks good. Pink and not burning. Level was a smidge low right at the top of the first "hot" level indicator.

Another thing Ive noticed is if I turn it off for a few minutes ( gas station or quick stop). When it turns back on it feels like its loss of power under very minimal throttle ( like 10-20% throttle) for a few seconds. Feels like its lost all timing and suddenly comes back in after a few seconds.

 

[iamdub]

I mean its original trans. 135k miles. 1-2 is good 2-3 is a not the greatest it does slip /shift rough under load/ throttle. I actually checked the fluid a few days ago it looks good. Pink and not burning. Level was a smidge low right at the top of the first "hot" level indicator.

Another thing Ive noticed is if I turn it off for a few minutes ( gas station or quick stop). When it turns back on it feels like its loss of power under very minimal throttle ( like 10-20% throttle) for a few seconds. Feels like its lost all timing and suddenly comes back in after a few seconds.

I asked about the trans cuz a wonky MAF can affect trans feeling. Most common is delayed shifting and/or sudden, more harsh shifts.

That power loss could just be common heat soak. The intake tube and IAT sensor gets warmed up as it sits in a hot engine bay. The PCM reads this as ambient air being really hot so timing is pulled. A few seconds of running cools the IAT so the timing is restored. This is exaggerated if you have headers, especially uncoated.

 

[04SS99Denali]

I asked about the trans cuz a wonky MAF can affect trans feeling. Most common is delayed shifting and/or sudden, more harsh shifts.

That power loss could just be common heat soak. The intake tube and IAT sensor gets warmed up as it sits in a hot engine bay. The PCM reads this as ambient air being really hot so timing is pulled. A few seconds of running cools the IAT so the timing is restored. This is exaggerated if you have headers, especially uncoated.

This is definitely not heat soak. The engine will not rev past 3000 in 2nd gear under load.