Diagnose 93 Suburban C1500 engine "skip" under load (towing)

93 5.7 C1500 193k miles: On the highway pulling a 1 ton trailer and typically under a load (e.g. climbing a hill) my engine will periodically intermittently skip - a definite abrupt loss of power for an instant. I've only noticed this while pulling a trailer and under load. I've checked and cleaned the Distributor cap, rotor and PCV valve; checked the plugs & replaced the fuel filter. Fuel pump was replaced about 4-5 years ago. Out on the highway without the trailer, I've not noticed this happening at all.

Additionally, on a trip last week, this behavior occurred and also my first tank full gave me 15 MPG and the second one on return gave me only 12 which is far less than I've ever gotten before. I usually avg between 15-17 when on the road with the trailer.

Since this is load related, I'm not expecting an ignition problem but something else.

Anyone had similar behavior and can offer any suggestions? Thanks.

Reply to
KR
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Describe the skip, is it a backfire back into the intake? Any preignition?

Reply to
A. Baum

No backfire or preignition. Just a momentary loss of power which feels like a slight lurch and totally intermittent - only noticed under load.

Reply to
KR

Does the RPM drop? If it's an auto transmission, it might be overheating and causing that lurching sensation. Do you have a towing package, transmission cooler or is it a manual transmission?

Reply to
A. Baum

Happens so intermittently and quickly I haven't been able to notice if RPM drops. It has the towing pkg w AT & trans cooler, etc.

Reply to
KR

Have you checked the transmission fluid for smell, signs of burning and color? It should not smell burnt and will smell burnt to anyone, not just someone who has worked on them as I have. Also the fluid will be a reddish clear. If it is even slightly rust colored, it and the filter need changed. A pressurized flush also to purge the torque converter. The pan needs inspected around the magnet for parts/shredding etc. When was the last time you had the transmission completely serviced? It's something I would not rule out and would lean more towards than the power plant since it makes no pop or backfire and is limited to tows uphill.

Reply to
A. Baum

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