QuestionQUESTION: HI, I have a 2000 chevy pickup k2500 with vortex engine. After driving for some time it starts to misfire and bogs down above 2000 rpms. If I shut it off for a litle while, it runs fine for a little while then acts up again. I had these parts replaced already: fuel pump,fuel pressure regulator,map sensor,cap, rotor,spark plus and wires,fuel filter,ignition module, I already tried unhooking the exaust at the flang and i have not cat problems. This thing is acting really wierd! Also replaced the two o2 sensors that upstream. The only codes the computer is showing is o2 sensor #1 bank 1 low voltage, and is showing the code for ignition control bad OR misfire. Some days i can go 20 miles before trouble starts and other days less. Please help if you have anything to try. The only thing that has not been replaced on the ignition system is the coil and the pickup in the distributor. I had it at a goodyear service center that does a lot of work for us,but i'm trying to solve this myself. Money spent on this thing is getting out of control. I seen in some of the posts about checking the fuel pressure. Is 60 to 65 the correct pressures i should be looking for?
ANSWER: The specified fuel presure for that vehicle is 414-455 kPa (60-66 psi). It sounds like you have a bit of a head scratcher. In my mind there are only two other possibilities. The Mass Air Flow Sensor (MAF) or the Crankshaft Position Sensor (CKP) You have replaced all the other good stuff. The MAF is easily replaced, if you can get your hands on a loaner swap it in and try it. Quick and easy. The CKP on the other hand is a little different. If you do end up removing it, get a flash light and look up inside at the reluctor ring, rotate the engine by hand and inspect it for cracks or any othe defects and look at the end of the sensor for signs of contact.
Below is a description of the two.
Hope this helps. Get back to me if they both check out ok and I will try to helps somemore.
The crankshaft position sensor (CKP) is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has 4 slots 60 degrees apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in four pulses (4x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the distributor. The relation between the crankshaft position sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap.
The mass air flow (MAF) sensor is an air flow meter. The control module supplies the MAF sensor a signal circuit. An ignition positive voltage circuit and a ground circuit are supplied to the MAF sensor by independent circuits. The MAF sensor heats a wire element, or grid, within the MAF sensor in order to maintain a calculated temperature. As inlet air flows across and cools the grid, the MAF sensor increases current flow to the grid in order to maintain the constant grid temperature. The MAF sensor converts the grid current flow into a frequency signal. The control module converts the MAF signal frequency into a grams per second value. During low air flow rates, such as at engine idle, the MAF sensor produces a low frequency signal. During high air flow rates, such as at wide open throttle-road load, the MAF sensor increases the frequency signal. The control module monitors the MAF sensor signal frequency in order to calculate the flow and mass of the air entering the engine
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QUESTION: I replaced both of them and still having the same problem. When i road tested, it started to act up and was getting worse the farther i went. I pulled over to the side of the road and shut it off for about one minute. When i restarted it and went on it was ok at first the started to bog down and missing again. I also replaced the pickup in the distributor. Gear inside distributor felt good. Very little slop in gear mesh. Anything else you can think of??
AnswerHmmm. I must admit I am struggling with this. It is so much easier to diagnose something when you can feel and hear it for yourself. Lean misfires, ignition misfires etc etc they all feel and sound slightly different. The way you are describing it, it sounds heat related.
Are all of the parts that you installed known good parts?
Is it possible you have bad fuel?
Is your EGR valve functioning properly?
Are all the other sensors reading correct values?
Do you have access to a scanner, not just a code reader, but a scanner that you can read live sensor data on?
Have you consulted a dealer?
Have you replaced the ignition coil itself, you mentioned the module but not the coi?! Try unplugging the coolant temp sensor and driving it, it should force your pcm to stay in open loop mode, essentially eliminating the 02 sensors and a couple other sensors. Aside from that I am hesitant to recommend anything else, just throwing parts at it is expensive and time consuming. Consider the things above and try the couple things that I mentioned.
Hope this helps
