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My 94 ford ranger was running fine the last 600 miles. Noticed backfiring in tje exhaust at idle. I cleaned the IAC checked the plugs and they all looked fine. Still seems to run fine under load. MAF sensor is clean and the throttle body doesn’t look bad. I did notice a littl bit of fluid in the back of the intake manifold. Unsure what that is. Thought of checking the injectors and pressure testing the cylinders. Any thing Im missing. Also thought about the emissions system. Any clues? Oh and the engine is a 4.0 ohv with 213000
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[quote=”TL408″ post=124250]My 94 ford ranger was running fine the last 600 miles. Noticed backfiring in tje exhaust at idle. I cleaned the IAC checked the plugs and they all looked fine. Still seems to run fine under load. MAF sensor is clean and the throttle body doesn\’t look bad. I did notice a littl bit of fluid in the back of the intake manifold. Unsure what that is. Thought of checking the injectors and pressure testing the cylinders. Any thing Im missing. Also thought about the emissions system. Any clues? Oh and the engine is a 4.0 ohv with 213000[/quote] Backfire is usually caused by fuel in the exhaust aka running too rich. A backfire in the intake is usually due to running too lean. Sounds to me like you are running rich and burning fuel int he exhaust. I would look to the fuel system.
A common backfire situation occurs when there is a small leak in the air injection system that feeds the exhaust system. This can cause unburned fuel to explode suddenly. One of the most common causes is a stuck or faulty air intake or gulp valve near the exhaust manifold.
Backfiring can also occur with a sudden drop in fuel pressure. This may be due to a faulty fuel pump or a plugged fuel filter. Correcting problems in the fuel system usually resolves these issues.
Incorrect ignition timing to the spark plugs is another cause of backfire. Adjusting the ignition distributor, if the engine is so equipped, may resolve this problem. Adjusting engine timing is not difficult and can be done with a timing light by following the timing adjustment procedure for your car. If you do not know your car’s ignition timing procedure please visit our car repair manual page. A vehicle that is not timed properly will not idle, run or operate correctly and will often backfire rapidly. On newer cars you will need to scan the pcm to check for CKS (crankshaft angle sensor) and CMS (camshaft position sensor) related trouble codes.
Strange thing. After checking all the things above the problem disappeared as quickly as it came. Put in a new thermostat and coolant temperature sending unit to fix another issue bit the mis fire:-) has not returned. I purposely created a check engine light to make sure it works and it did. Could plug wires be a source? Im thinking i may see tjis problem again. Thanks in advance
[quote=”TL408″ post=124493]Strange thing. After checking all the things above the problem disappeared as quickly as it came. Put in a new thermostat and coolant temperature sending unit to fix another issue bit the mis fire:-) has not returned. I purposely created a check engine light to make sure it works and it did. Could plug wires be a source? Im thinking i may see tjis problem again. Thanks in advance[/quote] Plug wires can certainly cause a rich running condition due to the fuel not being burned and going out the exhaust. You would have a misfire though due to the plug not firing. If the spark is getting to the plug but is weak due to resistance in the wiring is another possibility.
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