Timing may be off. Have you checked it? Back firing could be valve timing problem; could also be too much gas-check injector spray pattern-should see a cone shaped pattern of fine mist on the throttle plates when cranking engine-this is if you have throttle body injection.
For $20-$30, you can buy a compression gauge tester and check engine compression. On a warmed up engine, pull all spark plugs, disable ignition and fuel delivery (pull injector fuse or unplug injectors), hold throttle wide open, and check compression on each cylinder by cranking engine over about 7-10 revolutions-the same amount for each cylinder, about 4-5 seconds each. All cylinders should be nearly even and balanced. Lowest cylinder should be at least 75% of highest reading cylinder. For any low reading cylinder, put a squirt of oil (about a tablespoon) in that cylinder and retest compression: if compression rises, rings are worn. If compression does not improve, valves are the reason for low compression-valves may be burnt or not sealing good.
I would do the compression test-on an engine that old, before putting expensive parts into it, you should know if the engine's internal mechanical condition is good first.
SOURCE: 1996 ford ranger -3.0 ltr
Had a similar problem and it just ended up being the sensor for the EVAP controls. Stupid I know but it fixed the rough idle. Error code was P1443. Worth a try.
SOURCE: I have a 1991 Buick Park Avenue. Runs rough in
Here are the common cause of surges, cold stalls, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours.
To correct this problem I want you to get a can of intake cleaner (ABOUT $5.00) from any local auto parts store like NAPA or Carquest, do not use carburetor spray, intake cleaner only or u will damage the Teflon coating inside the throttle valve and air bypass valve, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.
Testimonial: "Thank you, I'm sure if your advice it was I'm looking for. But at least if this works, it will save me a lot money from having to replace expensive sensors."
SOURCE: I unplugged the Mass Airflow
Most likely if there is no mass air sensor you actually unplugged the inlet air temperature sensor IAT. This is a little bead like thermistor that sits in the ducted air stream to measure incoming air temperature. Without an air mass sensor your engine will have instead a manifold absolute (air) pressure MAP sensor. This measures the absolute air pressure (the difference between the atmospheric air pressure outside and the drop in pressure inside) in the inlet manifold. The drop in pressure in conjunction with air temperature allows the engine control unit to calculate the amount of air in the engine to which it adds the correct amount of fuel per each injection cycle. The loss of the IAT signal is not critical as the ECU will assume a default value. However when extreme low temperatures are encountered the absence of the IAT may be become noticeable as the charge of air entering the engine will be denser and as a consequence the fuel mix will be much leaner; maybe to lean to start up.
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1991-1994 2.9L and 3.0L Engines Firing Order 1-4-2-5-3-6
1995 And Later 3.0L V-6 With DIS Ignition System Firing Order 1-4-2-5-3-6 191 views
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