Misfiring
11-13-16, 02:14 PM
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Misfiring
Good afternoon everyone, finally have my 94 fd. Currently trying to track down a misfiring issue with her. It runs and revs fine on light acceleration and throttle all the way to redline, however there's an intermittent misfire while idling and it always breaks up and pops under full load at full throttle. Changed plugs to ngk platinums, 9s for the top two and 7s for the lower two, but the issue persists. Taking it apart now to replace the wires and coils. The front most lead plug did have quite a bit corrosion and rust where the wire connects to the spark plug on both the spark plug and wire. Cleaned the connector in the boot as best as I could. Hoping that is the issue. 93k miles and the car is bone stock. Changed oil already and will change the filter as well and double check all ic piping ect. Any other possible causes or things I should look for? Completely new to the platform.
11-13-16, 02:25 PM
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11-14-16, 07:48 AM
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11-17-16, 12:45 PM
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Misfires can usually be traced down to the plugs, wires, and coils. I prefer the NGK stock replacement wires as they seem to fit the best and all BUR9EQP plugs.
You are going to need a volt meter, power fc, or the mazda sst to set the tps. It would also be beneficial to see all the other sensors are reading correctly.
If those don't do it I would look into the fuel filter and the injectors.
You are going to need a volt meter, power fc, or the mazda sst to set the tps. It would also be beneficial to see all the other sensors are reading correctly.
If those don't do it I would look into the fuel filter and the injectors.
11-24-16, 05:51 PM
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Making progress, new air filters, fuel filter, plugs, fresh gas, pettit ecu, down pipe& mid pipe and the dale clark fuel pump rewire all done. Car runs great above 3000rpm. Installed a boost gauge and it is making full boost. Anything below 3000 rpm and it buckles and acts up. Idle is a bit lumpy as well. pulling 15-17 in.hg of vacuum on idle.
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11-25-16, 12:01 PM
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Will double check again as well as the plug wires. Also pulled a code this morning for the air intake temp sensor I believe. Code was #11. No one seems to carry the sensor in stock and really looking to get this squared away before heading back to work next. Only free time I have really. Thinking of getting a generic sensor that'll work with the car and taping it into the intake elbow. Any recommended air intake temp sensor to replace the factory one? Will also mess with the tps today
11-25-16, 01:00 PM
#10
Intake temp sensor will default the car to rich which will cause it to run ike garbage. Test the sensor's resistance per the fsm. You are better off getting the fast-acting triumph sensor. I would not move the sensor with the stock ecu or a chipped one as there is no way to tune for it.
11-25-16, 02:56 PM
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I'll try that out. Anyone know what size wrench is needed? I'll try bending one to fit in there rather than removing the whole manifold. Also is the triumph sensor a direct fit, or will I need to re drill and tap the existing hole in the manifold?
Last edited by rotorXray; 11-25-16 at 04:21 PM.
11-26-16, 03:36 PM
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It won't let me edit my post again, but a quick update. Tps voltages are all within range. Checked them using Robins guide with the car warmed up. However, I started it up and let it warm up with the air temp sensor unplugged this time, and the issue didn't get any worse. Ran exactly the same actually. Getting steady 14.4 volt reading at the alternator and battery so all is well there. Hopefully it's just the sensor. Will update when it is changed in case any one else is experiencing these issues.
12-02-16, 07:45 PM
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Measured sensor resistance and it actually checked out good, no longer getting the code for it. I will still replace with a fast acting one however. The easiest way to replace this sensor is a stubby 19mm wrench with a 12 point slanted end, Lowes kobalt brand. Remove the pressure chamber and go in under the manifold to loosen. I got code 40 today, but accidentally left the hose to the intake elbow unhooked while putting it all together. Will see if it stays clear after resetting. Trailing 1 plug wire was toast. Replaced all wires with 8.5mm and I have spark on all coils. Haven't done a compression test, I did remove L1 plug and while turning over, got 3 loud pops sounding exactly the same. Same results with removing the L2 plug. Engine was warm when I did the test, car fires right up everytime as well, cold or hot. I also replaced the fuel pump with a 340lph unit today. Idle is still pretty lumpy and random bogging or stuttering occurs above 3000 rpm it seems and at wot sometimes. Staying out of boost until issue is resolved. I will remove my two 7 plugs and run all 9's.
Last edited by rotorXray; 12-02-16 at 10:27 PM.