Questions and Answers

Chevy One Ton Motor Home Backfire Q. Hello Vincent, I Have a motor home on a 1988 Chevy one ton chassis. 7.4 liter engine, automatic transmission, 54,000 miles, 4-bbl carburetor, P/S, A/C and cruise control. My problem is sometime it will backfire through the carburetor. Usually you will have to drive it for a couple of hundred miles before it will backfire.

The backfire will start when it gets in hill country and the engine seems to be pulling heavy. After this backfire it may not backfire for a day or two, all this when driving the motor home about two or three hundred mile a day.

We carry the motor out this week and drove it for about 100 mile on fairly level road trying to get it to backfire. We drove at different speed, floorboard, ect. We could not get it to backfire.

I had a tune up including new spark plugs, plug wires, distributor cap, PCV valve, new inline gas filter and new filter at carburetor. Any advice would be appreciated

Harry

A. Does it seem to run okay otherwise? I can remember my Dad having a tune up done on our old station wagon before heading out on a vacation to Canada, just to make sure it wouldn't let us down. We drove all the way to Canada with two plug wires installed on the wrong cylinders! Didn't notice anything until a hill in St John. Just a thought.

Re-check the firing order of the plug wires. Also re-check the base timing. The coil may be loosing it's zip. Also, you may want to run a can of Top Engine Cleaner through the intake to see if it's carbon deposits in the cylinders.