Backfire and misses under load (Page 1/2) sjmaye FEB 20, 05:10 PM This is a 1987 GT. I haven't driven it in a year. I decided it was time to sell it. It started up like a champ. I took it out on the interstate. It ran like it always had. I was getting it cleaned up as someone was coming over to look at it. I thought I would take one last test drive to be sure all was good. As I pulled back into my neighborhood I turned the corner at the bottom of the hill and started up in 2nd gear the engine started bucking and misfiring, coughing. No matter what I did when I put a load on it to pull up the hill it bucked and misfired. I managed to get it home only by revving it above 3,000RPM and slipping the clutch. Of course it was embarrassing when the guy gets there and I can't even take him for a test drive. He still wants the car when i get this worked out. The car starts and idles fine. It is when taking off from a stop and pulling a load. At first I thought it was fuel related, but the bucking now makes me think electrical. I once had an engine do this when a tiny piece of carbon crossed the gap of the spark plug. I will check them in the morning. Any other thoughts would be greatly appreciated. Patrick FEB 20, 06:32 PM quote Originally posted by sjmaye: I haven't driven it in a year. I would suspect a fueling issue. If it's not something as simple as a near empty gas tank (hey, it happens!), then I'd look into the fuel pressure. 82-T/A [At Work] FEB 20, 07:00 PM quote Originally posted by sjmaye: This is a 1987 GT. I haven't driven it in a year. I decided it was time to sell it. It started up like a champ. I took it out on the interstate. It ran like it always had. I was getting it cleaned up as someone was coming over to look at it. I thought I would take one last test drive to be sure all was good. As I pulled back into my neighborhood I turned the corner at the bottom of the hill and started up in 2nd gear the engine started bucking and misfiring, coughing. No matter what I did when I put a load on it to pull up the hill it bucked and misfired. I managed to get it home only by revving it above 3,000RPM and slipping the clutch. Of course it was embarrassing when the guy gets there and I can't even take him for a test drive. He still wants the car when i get this worked out. The car starts and idles fine. It is when taking off from a stop and pulling a load. At first I thought it was fuel related, but the bucking now makes me think electrical. I once had an engine do this when a tiny piece of carbon crossed the gap of the spark plug. I will check them in the morning. Any other thoughts would be greatly appreciated. Patrick is probably right... however, I had this EXACT same issue with my Fiero once (87 SE / V6, basically same car just without the fastback). I don't know why... but something told me I should disconnect my MAP sensor, and so I did... and I was able to drive the car home just fine. I then replaced the MAP sensor and all was good with the world. Maybe totally not it. But try disconnecting the MAP sensor and see if it stops bucking. jelly2m8 FEB 20, 08:24 PM Also check the EGR valve , have seen those rust off the base and the exhaust pressure forcing it up cause similar issue. 1985 Fiero GT FEB 20, 09:23 PM Definitely check fuel pressure. My dad had that same problem on a 2014 Ford escape. Just kept getting worse until it couldn't even start. Turns out it was water in the gas tank, cost alot and 2 garages to figure that out. Perhaps you have a leaky gas cap or something and hose water got into the tank as you cleaned, or via the charcoal canister under the drivers side decklid vent. Perhaps drain some of the gas and look at it, specifically after the fuel filter, make sure you don't have rust and debris in the gas, while also checking for water, water is heavier then gas, so will get sucked up by the fuel pump, should be easy to tell if the fuel has some water in it by pumping some out from after the fuel filter. If you didn't know the aldl connector has pins to jump to just run the fuel pump. Stingray92 FEB 20, 10:03 PM When the car was parked what did you do with the fuel? Nowadays you can't let it sit for more than a month maybe sooner before it starts attacking things. How full was the tank? This sounds like a fuel supply issue, maybe a plugged filter/weak fuel pump or bad pressure regulator. I've seen 3 year old carb engines not want to start due to water! I would flush your fuel supply through the fuel rail and verify the pressure as you bleed the system, if that checks out you'll probably get a strong running engine. Stingray sjmaye FEB 21, 03:11 AM While reviewing old threads here it reminded to check for ignition arcing in the dark. I waited until the sun went down and started the car in pitch black darkness. There it was. There was arcing on the ignition coil. I am going to pick one up today and give it a try. Thanks for the suggestions. There may be other things wrong. Either way I will report back. jelly2m8 FEB 21, 04:22 AM Something so simple and easy that we all forget to check for jumping spark in the dark sjmaye FEB 21, 04:31 AM quote Originally posted by jelly2m8: Something so simple and easy that we all forget to check for jumping spark in the dark Exactly. Thank goodness I read the old posts here. It reminded me. Patrick FEB 21, 03:20 PM quote Originally posted by sjmaye: While reviewing old threads here it reminded to check for... That's what they're there for.