Engine missing in 5th gear 1500 rpm

[Tozan]

When cruising at 45 mph in 5th or 6th gear around 1500 to 1900 RPM it starts feeling like an engine miss. This happens the most on a very slight up hill grade. If I accelerate or down shift it goes away. Sometime in the morning when I first take off I will get a miss while accelerating around 65 MPH.

Pretty much any other time it still drives normal... Hard accelerations it's fine, cruising at 65 plus it's fine. Idling is fine... Hauling butt off road it's fine.

Details on my Tahoe
240K miles
Rebuilt trans at 195K
Replaced plugs and wires last month (no change in performance)
Gearing 4:11s Tires 35's
Tuner installed
AFM Off
No codes...

 

[Geotrash]

When cruising at 45 mph in 5th or 6th gear around 1500 to 1900 RPM it starts feeling like an engine miss. This happens the most on a very slight up hill grade. If I accelerate or down shift it goes away. Sometime in the morning when I first take off I will get a miss while accelerating around 65 MPH.

Pretty much any other time it still drives normal... Hard accelerations it's fine, cruising at 65 plus it's fine. Idling is fine... Hauling butt off road it's fine.

Details on my Tahoe
240K miles
Rebuilt trans at 195K
Replaced plugs and wires last month (no change in performance)
Gearing 4:11s Tires 35's
Tuner installed
AFM Off
No codes...

The only way I know to diagnose this is to record live data while it's happening. With no codes, it's a guessing game otherwise. Potential culprits I can think of: intake leak, one or more weak coil packs, damaged coil or injector harness lead, bad ground, partially plugged injector.

 

[Dustin Jackson]

Some OBD 2 readers can show misfire data per cylinder but I don't know how accurate that info is

 

[Geotrash]

When cruising at 45 mph in 5th or 6th gear around 1500 to 1900 RPM it starts feeling like an engine miss. This happens the most on a very slight up hill grade. If I accelerate or down shift it goes away. Sometime in the morning when I first take off I will get a miss while accelerating around 65 MPH.

Pretty much any other time it still drives normal... Hard accelerations it's fine, cruising at 65 plus it's fine. Idling is fine... Hauling butt off road it's fine.

Details on my Tahoe
240K miles
Rebuilt trans at 195K
Replaced plugs and wires last month (no change in performance)
Gearing 4:11s Tires 35's
Tuner installed
AFM Off
No codes...

One more thought: are you still on the original fuel pump? If so, I'd want to monitor fuel pressures either electronically or with a mechanical gauge.

 

[tom3]

Son's truck was doing the same thing, exactly the same, we thought it was the engine with a lean condition. Turned out to be the torque converter failing in lock up mode. Disaster. Have you changed the trans fluid since rebuild?

 

[ivin74]

When cruising at 45 mph in 5th or 6th gear around 1500 to 1900 RPM it starts feeling like an engine miss. This happens the most on a very slight up hill grade. If I accelerate or down shift it goes away. Sometime in the morning when I first take off I will get a miss while accelerating around 65 MPH.

I'm leaning towards a transmission issue(torque converter), put the suv on neutral at that speed (65) and raise the rpms to 1500 thru 1900 and if the engine misses its an engine issue if not it's transmission related.

 

[Tozan]

Thanks for the ideas I will try them out.
I did check fuel pressure with my tester. I will have to duplicate the test under those conditions too.
I did change the oil last year and it looks clean.

One other point I missed mentioning. When I changed the spark plugs all the plugs on the right side had eroded ground straps and the plugs on the left side had heavily eroded center electrodes.

 

[donjetman]

Counterfeit spark plugs, etc has become common these days (amazon, ebay, etc).
https://www.tahoeyukonforum.com/thr...iring-at-idle-counterfeit-spark-plugs.146952/

 

[Tozan]

It was a torque converter... Replaced it with a billet TC and tore down the trans to inspect and clean it out also changed some springs in the valve body to improve shifting... Cost me $2864.