Missing,Backfiring, Rough Idle
Question:
I have a 91 explorer XLT that all of a sudden started to miss so chekced the plugs and were all O.K. Changed out the plug wires since they had over 90K on them and the miss is still there and the vehicle is now backfiring horribly and runs really rough. I checked the psark plugs again and made sure that they were all set the correct gap specifications which they were. I thought that maybe the Fuel Regulator might be bad and maybe needs replacing. Would appreciate any ideas on this.
Response:
>I have a 91 explorer XLT that all of a sudden started to miss so chekced >the plugs and were all O.K. Changed out the plug wires since they had over >90K on them and the miss is still there and the vehicle is now backfiring >horribly and runs really rough. I checked the psark plugs again and made >sure that they were all set the correct gap specifications which they were. > I thought that maybe the Fuel Regulator might be bad and maybe needs >replacing. Would appreciate any ideas on this.
do these trucks have a point distributor? if so check the cap. Oooo. .oooO ( ) ( ) ) / ( (_/ Friends help you move. Real friends help you move bodies.
Response:
> I have a 91 explorer XLT that all of a sudden started to miss so chekced > the plugs and were all O.K. Changed out the plug wires since they had over > 90K on them and the miss is still there and the vehicle is now backfiring > horribly and runs really rough. I checked the psark plugs again and made > sure that they were all set the correct gap specifications which they were. > I thought that maybe the Fuel Regulator might be bad and maybe needs > replacing. Would appreciate any ideas on this.
My 91 XLT is doing the same thing. I took it to a tune up shop and they did the basic $49 new plugs job. They also did some diagnostics and claim that I have a problem in the valve train – most likely a sticking intake valve. The tune up did help it run a tad better, but still misses and idles rough. My question to the newsgroup is: Assuming I have a sticking valve, how long do I have until a catastrophic failure or a valve burns to the point that the engine will barely run? Should I do a valve job on it now or wait until a valve burns?
Response:
jim: Don’t assume you have a sticking valve– check the compression to see for sure. A sticking valve will show up as a very low cylinder. A quick-and-dirty test for this is a vacuum gauge. The gauge will jump each time the weak cylinder (sticking valve) goes through an intake cycle. A more likely problem for your year is one of the following: 1) A vacuum leak. Search first for a hose or cap that has fallen off of the manifold fitting. Next is intake gaskets at the manifold/head joint. 2) Explorers have a problem with failing fuel pressure regulators. Dark smoke at idle, high fuel consumption, and maybe a ‘check engine’ light from the overloaded oxygen sensor are symptoms you might see in addition to the ones you list 3) Plug Wires. My ‘92 needed wires at about 55k, and got another set at 110k. Both were cures for a miss under load. The idle smoothed out a lot when this was done. The old wires tested OK with a meter, but failed in the real-world trailer towing test. 4) Look for a cracked head and/or a head gasket problem. If you are losing coolant, this is a problem area worth looking at. Look carefully at these possible problems before you start chasing a sticking valve. Like most vague problems and expensive "cures", this one deserves a second professional opinion. My impression of the "tune-up masters" guys and the like is that they know what to do if everything is OK, but are short on troubleshooting skills and experience. You might consider paying the Ford dealer to plug in the diagnostic machines and let you know what they think. My guess is it will be money well spent. Please let me know what you find out in the end. Helps me expand my knowledge base a bit… dr bob – Hide quoted text — Show quoted text -> I have a 91 explorer XLT that all of a sudden started to miss so chekced > the plugs and were all O.K. Changed out the plug wires since they had over > 90K on them and the miss is still there and the vehicle is now backfiring > horribly and runs really rough. I checked the psark plugs again and made > sure that they were all set the correct gap specifications which they were. > I thought that maybe the Fuel Regulator might be bad and maybe needs > replacing. Would appreciate any ideas on this. >My 91 XLT is doing the same thing. I took it to a tune up shop and they >did the basic $49 new plugs job. They also did some diagnostics and >claim that I have a problem in the valve train – most likely a sticking >intake valve. The tune up did help it run a tad better, but still >misses and idles rough. >My question to the newsgroup is: Assuming I have a sticking valve, how >long do I have until a catastrophic failure or a valve burns to the >point that the engine will barely run? Should I do a valve job on it >now or wait until a valve burns?
Response:
It sounds like you may have a timing problem. Mitch
Response:
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