VOLVO 5.7 GSI backfire

[ToddP63]

I have a VOLVO 5.7 GSI PWTR that has a backfiring and power loss problem. Engine runs well at the dock, but under way with a load it starts backfiring and briefly loses power. Thought it was a fuel problem so had fuel checked for water, and added fuel treatment just in case. I have changed spark plugs, wires, rotor, and cap. Mechanic told me one side of the fuel TBI fuel injection was not firing. Got entire new TBI unit and injectors. Still has not solved problem. Did seem to briefly flood the engine on initial startup. Got engine started and still have backfire problem. Can see both injectors providing fuel. where do I go next? Fuel pumps? what triggers the electrical part of the TBI?

 

[Walt T]

Re: VOLVO 5.7 GSI backfire

What year and engine serial number? Find another mechanic, he took you for a ride. Check fuel pressure first. You don't mention changing fuel water separator filter, but I imagine the so called mechanic probably did. From there I'd probably verify sensors starting with the throttle position sensor on the side of the TBI but its probably new with the TBI, but possibly not. Easy to check with an ohmmeter. Other sensors more difficult to check and do NOT try to check voltages to the ecm from the sensors as you can damage the ecm without the right equipment.

Stuff to check:
Ignition timing.
Ignition module in distributor. This is common. Check it with a timing light hooked up to different plug wires and observe flashes as rpm increases. If you notice the flashes turn irregular and appears to need Exlax well then I'd bet on the ignition module. Worth buying a cheap timing light with an advance knob and learning how to check your own timing n stuff. Harbor Freight. Wont help your own irregularity.
Make darn good and sure the oil is clean and has no water in it.
Check compression and look closely at spark plugs for any sign of water. Harbor Freight has compression testers.
Trying to give you some free or cheap and easy stuff to check here and you'll look like you know what you're doing. Which by the way I'm quite good at. I have perfected the art of sleeping under vehicles on a creeper. Oh and a pro tip: When under a vehicle and you see someone walk by reach out and grab their ankle and yell. Great fun. Another pro tip: Don't do this to the wife.

 

[jerryjerry05]

Re: VOLVO 5.7 GSI backfire

Check the coil.
Once it's been running for a bit.
Reach back and touch the coil.
It shouldn't be so hot that you can't keep your finger on it.