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Tech Tips, Tech Questions / Engine making pops out of the intake
« on: September 03, 2013, 10:22:10 am »
Hello everyone,
I few months back I bought an 1985 GT V6 2.8. One thing I've been struggling to figure out is a pop that comes out of my air intake. When then engine is under load, mostly is 1st and 4th, with low RPMS on acceleration the engine will pop several times over my left shoulder. It seems to occur once the engine has heated up. It won't do if you give it a lot of gas and power through all the gears. But slow casual driving with not so much gas and lower rpms seems to trigger it.
I checked all the cylinders and they are all firing to some degree. (noticeable shake and sound on ever unplugged plug). I have not done a compression test.
I've changed: Plugs, Wires, Cap, Coil, Oxygen sensor between engine and cat, fuel filter, air filter.
I also discovered two vacuum hoses on the throttle body that were unplugged and one on the ECM. The hose on the ECM is rotted out and I plan on replacing all the vacuum lines here shortly.
I've also run two bottles of Gumout through the tank and just last week a bottle of Seafoam. I've also tried running ethanol free gas through the tank.
After doing all the above the engine purrs and runs really smooth. I've noticed significant power increase and it no longer feels like its struggling. I wasn't noticing the pop anymore so I was intentionally trying to get it to do it by slowing down to 30 in 4th and giving it gas. It would not pop for me. Even in first on a very slow casual start (right on red), it would not pop. It popped once then entire 45 minute ride and it was unexpected, in first after a stop sign.
My two thoughts on the matter are either a vacuum problem or possibly a semi clogged injector still. I ran the Gumout through the engine about two month ago and the seafoam just last week but perhaps the seafoam finally did the trick in mostly unclogging an injector? I've heard arguments for both, or even for a bad Valve. However none were from Fiero owners.
I few months back I bought an 1985 GT V6 2.8. One thing I've been struggling to figure out is a pop that comes out of my air intake. When then engine is under load, mostly is 1st and 4th, with low RPMS on acceleration the engine will pop several times over my left shoulder. It seems to occur once the engine has heated up. It won't do if you give it a lot of gas and power through all the gears. But slow casual driving with not so much gas and lower rpms seems to trigger it.
I checked all the cylinders and they are all firing to some degree. (noticeable shake and sound on ever unplugged plug). I have not done a compression test.
I've changed: Plugs, Wires, Cap, Coil, Oxygen sensor between engine and cat, fuel filter, air filter.
I also discovered two vacuum hoses on the throttle body that were unplugged and one on the ECM. The hose on the ECM is rotted out and I plan on replacing all the vacuum lines here shortly.
I've also run two bottles of Gumout through the tank and just last week a bottle of Seafoam. I've also tried running ethanol free gas through the tank.
After doing all the above the engine purrs and runs really smooth. I've noticed significant power increase and it no longer feels like its struggling. I wasn't noticing the pop anymore so I was intentionally trying to get it to do it by slowing down to 30 in 4th and giving it gas. It would not pop for me. Even in first on a very slow casual start (right on red), it would not pop. It popped once then entire 45 minute ride and it was unexpected, in first after a stop sign.
My two thoughts on the matter are either a vacuum problem or possibly a semi clogged injector still. I ran the Gumout through the engine about two month ago and the seafoam just last week but perhaps the seafoam finally did the trick in mostly unclogging an injector? I've heard arguments for both, or even for a bad Valve. However none were from Fiero owners.