so my check engine light came on in my 97 explorer with a 4.0 in it. i checked it with my scanner and it came up like p0304 which was a misfire in cylinder number 4. i changed the plugs and the plug wires and the fuel filter but its still runnin the same....also it idles better in park and nuetral then in gear.....any ideas ???
Those are known for breaking valve springs also. a compression check might be easier and less expensive than going after fuel injectors right away due to how they are mounted and the parts that have to be disassembled. #4 on the OHV and the SOHC 4.0l have to have the upper intake manifold removed for access.
You can also check the injector while the engine is running with a mechanics stethoscope by comparing the intensity of the sound to the known good ones. If it does not have a good solid click like a good one, you will need to verify the wiring is good and then the PCM driver. The wiring can be checked as well as the injector with an ohmmeter electrically as Jamie said, but it still could be mechanically stuck and still test good electrically. The best home mechanic way to testing the PCM driver is with a NOID light. Should be able to borrow a set from some friendly auto parts stores.
thanks for the fast response guys, ill start looking into all these...by the way the car only has 108,000 miles and its been fairly well taken care of so i hope its nothing wrong with the engine.. my scanner only tells me the codes, will a really nice one give me more specific info?
The Ford specific scanner will give you a lot of tests that you can run, but very expensive. Some high end scan tools give you more functions but the costs for those are very high as well. >$2000.00. The abilities of the user are much more important than the tester itself. If you get in over your head, try and find a competent mechanic in your area and see if he might be willing to diagnose the electronic control system to verify that it is working properly and you can run the compression test and basic electrical tests to isolate the problem area. A decent mechanic familiar with that system will be able to at least narrow it down to a system ie: ignition, fuel, basic engine, etc. Injectors and bad plug wires/plugs usually result in the same codes (misfires, P030X) x representing cylinder, so isolating the system causing the concern becomes imperative. I always start with the easiest first and work my way up to the hardest test to run to save time and $. Sometimes you can swap components on the engine for example: #5 plug wire to #4, #4 plug to #6, etc, to see if it moves to another cyl. Remember that system is a waste spark system, so any problem on the secondary side of the system will affect it's pair. 3:4, 1:5, 6:2. a open in the #3 plug wire can cause no spark available to #4, and so on... Hope this helps
