My 2000 Ford Ranger with 62k miles starts up if I let it sit for a while, then it starts to sound real mufflie after about a minute at which point it bogs down and dies. Then, it usually won't start again or does just for 10-15 seconds. At this point, it just cranks over, and sounds like those street cars that have a "high-performance" muffler replacement.
The week before this happened, I sensed a little less power output. The day before, it really gave me trouble at moderate engine rpm. It felt like it was missing or something. I don't know.
It's been very mild here lately, but it was cold and so I put gasline antifreeze in the tank and changed the fuel filter. I also changed the two ignition coils. The secondary resistance of both coils were lower than spec., and the sparks were drizzlie brown. Changing the coils did not fix the problem. This 4 cylinder has 8 spark plugs and two coils. One plug fires during the compression stroke and the other during the exhaust stroke (why the exhaust stroke I don't know). The first night it gave me this trouble, I looked under the hood when it was dark in an attempt to see any arcing sparks from the wires to block. I saw none.
Also, I measured the fuel rail pressure and it remained at 64-68 psi even when the engine began to bog down and stall, so I believe the fuel system is good because this is within spec.
I tightened as many bolts as possible to stop any possible intake air leaks, but could not reach intake manifold-to-block bolts. I assume, that the oxygen sensor would pick up a lean condition, and report it by turning on the check engine light if this were the case. Am I correct?
Since the check engine light is not on, I also assume that the crank postion sensor is still good. I had a VW where the crank postion sensor failed intermittently, and the OBDII system set the check engine light, so I scanned it to find the problem. I assume the Ranger's OBDII would pick up any intermittent sensors causing this, so I kind of rule out any intermittent sensor problems.
The next test I plan to do is an engine compression test to check for a blown head gasket or leaking valve.
I also checked resistance from engine to ground and it was less than
0.5 ohm. That seems okay to me.Timing belt visually looks okay. If it were the timing belt, when I come back the next day, I believe it would not start up and run for a full minute before bogging down and dying again. So, I rule the timing belt out.
If I let it sit overnight, it will start back up and run for about a full minute then die. If it is intermittent, then it should be a sensor and the OBDII should give me a check engine light. If it were the head gasket, a leaky valve, or intake manifold type air leak, then it should not make any difference whether I let it sit overnight or not. Why does it go for about a minute before conking out of fuel pressure does not drop at the rail?
I am not familiar with throttle position sensor, MAP sensor and some of the others, but I assume that the engine will automatically go into its default settings when one of these fails -- and also trip the check engine light.
Can or should I clean out/test the fuel injectors? Any other/better ideas?
Thanks in advance for any help
Mike