misses and knocks like crazy

[charlieshick]

my 98 Explorer Sport was running great until about a week before Christmas when the thermostat went out. So, I replaced that and when I started it up to check it out it immediately started missing. That seemed a little odd since I had just repaired one problem and a new one started up immediately afterward.

Anyway, I replaced the spark plugs and wires, and still it misses and has a lot of spark knock. So, after that I took the coil into Auto Zone and had it checked, it's still handling a satisfactory 11 ohms. I don't know what to do next. An OBD II scan said that it's only missing on cylinder one. As far as how it's missing, the tachometer stays steady right where it should and my fuel mileage is just the same as it always was. It just shakes the truck pretty good. However, when I drive at a lower RPM for a while like in the city or anywhere below 55 m/h and then try to accelerate to highway speed it sputters and hesitates. This is remedied by turning off the OD and letting it run around 3500 for a while, then I turn the OD back on and it's relatively fine in that all it does is miss and not sputter.

In the end, I have no idea what to check next. I thought my plugs looked fine when I changed them but I'm going to check #1 again in the morning and I'm also going to check for coolant in the exhaust.

Does anyone have any suggestions?

 

[charlieshick]

so, i had another scan and it still reads a misfire in cylinder 1 along with a bad Oxygen sensor. I figure the sensor is a result of the miss but i'm still at a loss as to why. i checked my exhaust and there was no coolant blowing out, nor was there any on the spark plug from that cylinder. there was a little grease, but no moisture on it

 

[unclemeat]

Check your vacuum lines, open the hood at idle listen for unusual hissing sound. Check to make sure all vacuum lines are hooked up and sound.

 

[Ira]

Get a pair of insulated spark plug pliers. Start the engine, allow it to warm for a minute, and remove plug wires from plugs, 1 by 1 and hold wire about 1/2" from plug. Replace after testing each one. You should see a spark jump from wire to plug. If you move wire farther from plug, you should see a definite drop/miss in engine rpm. If you don't see a difference in wire off vs. on, this is a sign that cylinder is not firing/igniting properly. This could be caused by...bad plug (yes, I have had bad ones right out of the box), bad wire, bad injector, low compression on that cylinder, water in cyl, etc. If you find that #1 is the one giving the problem, remove the plug and exchange it with the plug from the cylinder next to it. If you see the problem move to the next cylinder, you know the plug is the problem. If it still stays there, you know it is something relating to #1 cyl...injector, compression, etc. This is a handy mechanics technique that is effective in diagnosing any kind of engine, be it automotive, marine, etc.

Not really familar with 98, but my 91 has a fuel pressure regulator that went bad. When this happened, it flooded the engine and O2 sensor. Since my 91 has no code for FPR, it eventually showed up as O2 sensor because the flooding caused the sensor to go bad. Possibly something else to look into.