 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Ford / Ford Explorer / September 2005HELP! Missing / Bucking over 4000 rpm
I have a 94 Explorer with 248K miles and at the end of my rope. After warm up only, it misses and backfires around and above 4000 rpm. I have replaced the following (in this order) in an attempt to correct it and am now broke. I lost the "let's replace this sensor game". plugs (3 different sets, autolite / bosch / motorcraft) wires (2 sets, just to make sure) fuel filter crankshaft position sensor throttle position sensor fuel pressure regulator both oxygen sensors fuel injectors (fuel pressure reads 33lbs at idle and 39 under load) EGR valve & tube (it broke) MAF (Ford dealer = lying sack o' crap) coil pack Ignition control computer (up by the battery) It idles fine and runs fine up to around 4000 rpm. If you start it up cold and just run the crap out of it, it doesn't pop or backfire at all until it has warmed up. It you just drive with a steady throttle at above 4000 it just bucks and pops and sputters. Same while sitting in park. There are NO error codes in the computer, it thinks everything is dandy. The Ford dealer put it on their computer and it also said that everything was dandy (while popping and backfiring at the same time). I have the fuel pressure gauge and vacuum gauge duct taped to the windshield and no hood on the thing. I am out of ideas. Shawn If you're hovering around 4K rpm, there may be something else wrong. My 93 4.0 5 spd typically cruised at 80 mph turning about 3000 rpm. My current 96 EB V8 AWD turns about 3K rpm running at 80 mph. >I have a 94 Explorer with 248K miles and at the end of my rope. > [quoted text clipped - 28 lines] > I have the fuel pressure gauge and vacuum gauge duct taped to the > windshield and no hood on the thing. I am out of ideas. >I have a 94 Explorer with 248K miles and at the end of my rope. > [quoted text clipped - 28 lines] >I have the fuel pressure gauge and vacuum gauge duct taped to the >windshield and no hood on the thing. I am out of ideas. It's probably a long shot but at that mileage it's possible that the valves stems have build up enough crud that they are sticking and at the high rpms they don't always close all the way. Chevron Techroline is very good at reducing carbon buildups. If it was mine I'd buy 4 bottles of it and put two bottles in each of the next two gas fill ups. I'm wondering if weak hydraulic lifers could cause this too, perhaps when cold they don't act up but when hot they do. Is there any sort of "clatter" noise when it acts up? Not clatter that I can hear, just the popping. To check timing, where is the "spout" connector that is mentioned? Without disconnecting it, the timing marks never moved thru the entire RPM range, I was expecting them to advance some as the RPMs increased. Is that normal? - Shawn >Without disconnecting it, the timing marks never moved thru the entire >RPM range, I was expecting them to advance some as the RPMs increased. >Is that normal? Timing should advance - I am assuming you checked it off a plug wire. The one thing I don't see in your list is the cam position sensor, which the engine uses for timing once it has started. So I guess I would take a look at the cam position sensor next based on your timing problem. Is there any way to test this short of just replacing it? Autozone has it for $369 and that is a little steep for testing purposes. I can watch eBay for a used one of get one from a junkyard if symptoms point to it. - Shawn Is this "no load" or in gear and driving.... you do realize that the PCM also acts as a rev limiter, right? > I have a 94 Explorer with 248K miles and at the end of my rope. > [quoted text clipped - 28 lines] > I have the fuel pressure gauge and vacuum gauge duct taped to the > windshield and no hood on the thing. I am out of ideas. Either way once it has reached operating temperature. When it is "cold" it is fine, but after it reaches operating temperature it starts doing its "thing". I have been just dealing with it, but on those occasions when you need some power (passing, merging, etc.) it just pops and sputters instead of actually going anyplace. Again, it is only at higher rpms. It you pull out and mash the gas it runs good until right before shift time, when it starts popping. It shifts and runs fine again util the higher rpms. Try checking the fuel pressure when the problem is occuring..... there's also the possibility that stray RFI is affecting things.... You can try disconnecting the alternator (just the regulator plug should be enough) to see if the concern may be excessive ripple. IIRC, your 94 will have a cam position sensor... these have been known to fail though it is pretty rare.... > Either way once it has reached operating temperature. When it is "cold" > it is fine, but after it reaches operating temperature it starts doing [quoted text clipped - 7 lines] > runs good until right before shift time, when it starts popping. It > shifts and runs fine again util the higher rpms. I am driving as a true hick with the hood off and the fuel pressure gauge and vacuum gauge duct taped to the windsheild. Fuel pressure stays about 33 at idle and about 37 when driving (and having the problem). Vacuum reads in the green (20 inches I think) at idle and about 5 in while driving at a constant speed. I did try pulling plug wires one at a time and driving. Of course there is a constant miss, but it still does the bucking / popping thing at higher speeds. If it was a sticking valve, my thought was that would NOT pop when it unplugged the wire on the cylinder with the sticky valve. - Shawn |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.