Need help troubleshooting and fixing a backfiring Milano 2.5

958 Views 6 Replies 5 Participants Last post by BAB, Aug 30, 2011

Peter Lundquist

Discussion Starter · Aug 29, 2011

Good Evening All,

I need your help. My brother is driving his 1987 Milano Platinum (2.5L engine is bone stock and the car has approximately 120K original miles) from Sacramento, CA to Seattle, WA, and has developed some backfiring problems just north of the Oregon border.

The car starts fine, but when he rolls on the gas the car starts to backfire, runs rough, and loses power. He thought he had some bad gas, so he ran some injector cleaner, but no difference. He has checked all the grounds on the Bosch system (taken them off and cleaned them), checked all the electrical connections to the Bosch system, checked the AFM butterfly, checked the AAV connections, checked the distributor and coil leads, pulled the main fuel filter, and checked all the vacuum hoses on the Bosch system.

Any roadside tips I can pass on to my brother?

Thanks,
Pete

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ghnl

· #2 · Aug 29, 2011

Sounds like what happened to us during our drive home after picking up a GTV6 in Houston. We stopped for gas and then for coffee. A mile or two later the engine would start & idle OK but if I tried to accellerate it would buck & run terrible. I feared we had bought some bad gas.

The main air duct connection to the Air Flow Meter was slightly loose. At idle with the engine sitting fairly still the air duct was close enough - touching the AFM - to run OK. But when the engine moved due to torque reaction it pulled the air duct away from the AFM. The accordian section of the air duct can also tear causing similar symptoms.

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alfaparticle

· #3 · Aug 29, 2011

No backfire but vibrating so bad that I initially thought that I had a driveshaft problem. Turned out that the spark plug wire extensions had a carbon film and were arcing over. It came on suddenly when I was driving in heavy rain.

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bshorey

· #4 · Aug 29, 2011

ghnl said:
Sounds like what happened to us during our drive home after picking up a GTV6 in Houston. We stopped for gas and then for coffee. A mile or two later the engine would start & idle OK but if I tried to accellerate it would buck & run terrible. I feared we had bought some bad gas.

The main air duct connection to the Air Flow Meter was slightly loose. At idle with the engine sitting fairly still the air duct was close enough - touching the AFM - to run OK. But when the engine moved due to torque reaction it pulled the air duct away from the AFM. The accordian section of the air duct can also tear causing similar symptoms.

I'd second air leaks as the first thing to check. Also make sure the plenum is well seated.

bs

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ghnl

· #5 · Aug 30, 2011

Was any of this helpful - has it been fixed?

If he uses the throttle when cranking the engine that can initate a backfire that loosens (or sometimes blows right off) the plenum.

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Peter Lundquist

Discussion Starter · #6 · Aug 30, 2011

All,

So far, so good. Marc drove for a while today, but he is not sure what helped (the checking of grounds, the tightening of the vacuum lines, etc.) but I asked him to pull the accordion hose and inspect for leaks when he gets to Seattle.

Thanks again for the help.

Sincerely,
Pete

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BAB

· #7 · Aug 30, 2011

did he refuel?
i had this issue yesterday, went away next fuel change

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