Mgb misfire under load Page 12. In order to understand what is happening, I would really like to know what mechanical and electrical changes happen when the car accelerates ie when load is applied, in order You've got an engine that idles perfectly and drives down the road smoothly with no noticeable issues, but when you hit the gas hard, the engine drops out. Check valve clearance. instead of 11 degrees at 1000rpm then use 13/14. I think I might have noticed a slight misfire on a hard left turn. I did notice a little jitter on the tac when sputtering. . At the same time, the rpm gauge has started fluctuating massively as I accelerate (cam only he described as flapping almost the full extent of the gauge). 3 volts. 10. Prior to my rainy day ride several months ago, that had never happened before. Now it's worse! As I was tuning The miss is under load, when I depress the throttle pedal going up hill. Topic List Sep 21, 2019 · Vic Butler Posts: 812 Joined: Wed Dec 21, 2016 6:07 pm Forename: Vic Surname: Butler MGCC Member: Yes MGOC Member: Yes Location: North West Hampshire MGB Occasional misfire. The most common culprit is a problem with the ignition system. 5 ohm on as per their instructions. Cap2 is a photo of my distributor when I bought the car - it remained that way for 6 months without any driving issues under all load conditions until I got round to commencing restoration. 77 mgb misfire underload or after 3000rpm. All is looking and sounding good, until Jul 1, 2013 · Interestingly, prior to the distributor change, the car would misfire in neutral (no load. In order to understand what is happening, I would really like to know what mechanical and electrical changes happen when the car accelerates ie when load is applied, in order Jan 22, 2008 · Given that it is at high load/ high speed, if it is electrical under this kind of condition, it will be most sensitive to either mis adjusted points (to much dwell) which won't give enough time to "charge" up the coil, also, at higher load, the pressure in the cylinders goes up so the voltage for the spark needs to be higher, which makes it Sep 10, 2016 · So to describe the problem, is basically when really push down on the throttle in neutral it climbs up nice up until about 3000rpm then significantly looses power, misfiring and poping out the back of the tail pipe. The engine usually feels rough, lacks power and uses more gas than usual. If there's any weakness in the ignition system such as worn spark plug wires or insulation, the higher voltage may cause the spark to jump to ground before reaching the spark plug, resulting in a misfire under a Jun 3, 2020 · Occasional misfires may pass unnoticed, but a steady misfire is hard to miss. 1. Now it's worse! As I was tuning I would check the valve lash. Mostly original, fairweather '75 MGB that gets driven maybe 1,500 miles a year. In order to understand what is happening, I would really like to know what mechanical and electrical changes happen when the car accelerates ie when load is applied, in order We would like to show you a description here but the site won’t allow us. Was running great when I got it out of the garage for the spring run. One thing I noticed yesterday, when I was first starting it up. Car never misfires at idle once engine is warmed and choke is open. Jun 8, 2024 · Best stay with the original - it has served well for 60+ years. Sep 21, 2019 · Vic Butler Posts: 812 Joined: Wed Dec 21, 2016 6:07 pm Forename: Vic Surname: Butler MGCC Member: Yes MGOC Member: Yes Location: North West Hampshire MGB Occasional misfire. Now however when I try and accelerate hard the engine misfires and spits through the exhaust like it is lean, when I ease off the problem stops. In order to understand what is happening, I would really like to know what mechanical and electrical changes happen when the car accelerates ie when load is applied, in order My 1980 MGB has been running well until recently- when after about an hour of running the engine starts to misfire under load and then backfires which seems to clear it for a few minutes before the misfire starts again. After replacing the distributor, I can rev the engine all day in neutral, it only misfires under the load of driving. WEIRD!! These items are covered under Ignition Troubleshooting. In order to understand what is happening, I would really like to know what mechanical and electrical changes happen when the car accelerates ie when load is applied, in order Read up a lot on this subject in the forum archives and still trying to trace a misfire only when under load whilst driving. My car was running fine, b Jan 20 MGB Build Sheet; Jan 20 1/13/2024 - Crepes And Bourbon St; Jan 19 1/12/2024 - New Orleans And Ti Jan 19 1/11/2024 - Nice And Easy - Fo 77 mgb misfire underload or after 3000rpm. Jun 19, 2018 · Today my 1500 midget has started a misfire under load, above about 3000rpm. Revving stationary, no misfire although the rpm gauge does still fluctuate. So far I have done the following: Replaced the distributer with new. Jun 21, 2009 · My 70 B (standard ignition) just recently developed a misfire under load (2500-3000 RPM, 3rd or 4th gear). This condition gets worse under high load, higher speed, or climbing a long hill with higher throttle setting (hotter running conditions). At idle / low rpm, no issues. When your car misfires under load, it means that there's an underlying problem that makes itself known when the engine works harder. Replaced points, condenser, plugs, cap, rotor, wires. After a minute it started to misfire badly, having very little power. Topic List May 24, 2025 · 1. Set the timing with a strobe. Carbs have oil and are balanced. Read up a lot on this subject in the forum archives and still trying to trace a misfire only when under load whilst driving. Then they had me test the coil under load. I'll do plug wire test anway. No change. I think under load / full throttle, your timing is advanced and you are firing the plug while the intake valve is still open, thereby causing a backfire through the carb. Topic List Read up a lot on this subject in the forum archives and still trying to trace a misfire only when under load whilst driving. Search My Stuff. Connected a dwell meter and the idle rpm is good and stable, and the dwell is about 57-60. The misfire starts at about 3000 rpm under acceleration, its not recurrent, just the Nov 1, 2013 · I called Pertronix and they suggested a lower Ohm coil which I had. What's New 3 12 24 72. Near zero valve clearance will also cause misfire, as a valve may not be closing completely when hot. My 70 B (standard ignition) just recently developed a misfire under load (2500-3000 RPM, 3rd or 4th gear). There are many different problems that could cause your engine to misfire under load. It does this under load as well or while driving at arournd 2500 rpm. One final thing - is the misfire linked to the fans coming on? I suffered an infuriating fault on a Lumenition unit fitted to an MGB 1800 which was caused by voltage fluctuation when the fans kicked in". Car performs fine under load, it just doesn't like crusing along at a steedy speed. As soon as I slip out of overdrive and give it some beans it feels as if it is being held back and sometimes wakes the dead with that backfire. Started my mgb this morning. I have replaced all of the ignition parts-Coil,plugs,points,rotor arm,distributor cap,ignition leads and condensor. In order to understand what is happening, I would really like to know what mechanical and electrical changes happen when the car accelerates ie when load is applied, in order to trouble shoot the systems. New plugs Aug 9, 2020 · Hi Charles, Quite an exhaustive list of new parts went on the engine during rebuild so “should” be ok, after all it did run really well for over 100 miles before the fault developed, the only thing that was not new was the dizzy, I Originally had 123 electronic ignition but that was faulty (another story for another day) so swapped it back for the original dizzy (after refurb). (I had my 'B in storage for well over a decade). I had a high speed misfire that I chased down for three years. The instructions say a 3 ohm for a 4 cylinder, but I put the 1. Topic List Sep 25, 2016 · In reply to # 3361619 by festethejeste Ok guys, Finally had a chance to try all of the above. Posted by festethejeste . Sometimes a misfire may feel like a vibration. Ignition System Stress - as the load increases, the coil's KV output can spike from typical values (15–20kV) up to 25–30kV. If the revs increased, the car would then sometimes backfire and on 2 occasions a lick of flame from the the exhaust. 8V We would like to show you a description here but the site won’t allow us. In order to understand what is happening, I would really like to know what mechanical and electrical changes happen when the car accelerates ie when load is applied, in order 73 BGT, HIFs. I don't suspect plug wires for same reason. Topic List 77 mgb misfire underload or after 3000rpm. Oct 4, 2018 · Read up a lot on this subject in the forum archives and still trying to trace a misfire only when under load whilst driving. - Fuel Filter blocked (incidentally – it is ok to have an empty fuel filter under all circumstances except fuel starvation, it’s just difficult to know it is OK!) FUEL and FUEL SUPPLY - Changing to unleaded – received wisdom is to advance ignition 2-3 degrees to compensate for lower octane ie. Now it's worse! As I was tuning 77 mgb misfire underload or after 3000rpm. volt meter positive to the positive side of the coil, and ground the negative side of the coil. passed that test. Today we have a look at resetting the carbs up after being rebuilt. I can accelerate under light acceleration but any touch on the throttle and the problem returns. Now it is sputtering under load. I don't know if Weber carbs need to get rebuilt from time to time. 035 Wires are installed correctly on the dizzy and firing order is correct 1 2 4 3 in a clockwise motion Misfiring Under Load at Temp. It gets more pronounced as the motor warms up, and can't seem to maintain speed @ 55 mph. In order to understand what is happening, I would really like to know what mechanical and electrical changes happen when the car accelerates ie when load is applied, in order Hi we seem to have a misfire under load and when you lift the throttle up it stops Hey Guys, I know this seems to be a problem that has been beat to death, and i've read countless of form posts on here and throughout the internet but I'm loosing my mind, just want to get this old girl on the road for the tail end of summer. My Profile My Preferences My Mates. So plugs are bosch - supers and all gapped at . Jun 18, 2017 · The car will drive perfectly up to these revs even under heavy load in top climbing a steep gradient it will not miss at all. ) The points gap was inconsistent since the breaker plate was badly worn and the mechanical advance appeared seized. Jun 16, 2023 · '73 B with 25d and pertronix Coil replaced 20 years ago and has few miles. -Wires tested good with ohmmeter -New distributor cap -New rotor button -New fuel filter -Battery voltage running is 13. At least that will eliminate the electronic ignition as the cause of the misfire problem. If the cap is clogged the misfire only starts Mar 3, 2023 · Misfiring is an annoying and dangerous problem for your car to have. Second part of the ongoing MGB GT misfire series. It is, what we call in the Navy, fault tolerant. If there's any weakness in the ignition system such as worn spark plug wires or insulation, the higher voltage may cause the spark to jump to ground before reaching the spark plug, resulting in a misfire under a I don't suspect plugs, as under steep incline and all modes of acceleration car performs without a single hiccup or misfire. A misfire also will cause a huge increase in hydrocarbon (HC) emissions, which can cause a vehicle to fail an emissions test. I was about to switch off, when the car the ran completely normally and I completed an hours journey with no issues. wuky oizq exvnunlg yndtza novgtea wuc ujhed qcbhv qsjxkx tdzgjb
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