I just finished replacing the plugs, wires, cap and button, but still my '95 seems to be missing when I cruise at a constant speed at a relatively low RPM. I can't hear the engine cutting out, but the truck jerks like it has a miss. It runs fine when I am accelerating, deccelerating, or pulling a hill. It has 92000 miles, and I haven't replaced anything else with the ignition system. The fuel injectors have been cleaned and this helped the problem a little, but it still does it just not as often. I have posted this message in the pre-97's board also. All of the sensors were checked and they said they couldn't find anything wrong. Might be on the right track with the fuel system. Any comments?

 

5 speed or auto? I had a '91 with 5 speed and it seemed like it jerked alot also. Sold it for a '01 Mustang Gt, though. The truck had 130,000 on it and was still going strong.

 

Manual. So did you fix it before you sold it?

 

Could it be possible there is a bad injector? Or maybe water in the fuel tanks?

[This message has been edited by cowboykent (edited 01-26-2001).]

 

Is the rotor loose in your distributor? I had this problem in a car once. It turned out to be the bearings in the distributor had worn and it allowed the shaft to wobble just enough (hardly perceptible to the touch) to cause it to miss.

Otherwise bad injectors certainly can do it too. I have always had to replace them. Tried having them cleaned - didn't last. Not sure if the 4.9 is multiport injected, but they seem more susceptible because each injector is small compared to a single throttle body injector.

Also fuel filter?

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'99 f150 S/C 5.4L
Tow package, L/S, 3.55

 

For a cruise miss, I'd look at the following:

1. Don't recall if your truck uses a MAF, but if it does, make sure there are no air leaks in the hose between MAF and throttle body.
2. Check the TPS voltage; make sure the reisstance changes smoothly, and is spot on to the spec.
3. If the O2 sensors are original, consider replacement. After 90K miles, it's likely they may be "lazy", which could result in a lean cruise condition.
4. Make sure the injectors are clean; a can or 2 of techron thru the tank could do wonders. Check for sealing around the injectors and manifold for any 1 or 2 cylinder leaks.
5. Check out the EGR for stickiness or excessive flow, or clogging. Wrong EGR amounts will cause a miss.
6. Check the MAP hoses; an air leak will give the ECM a wrong signal. This is more likely to cause problems at higher throttle settings, but...

Low rev cruise used to be called "lugging the engine" back in the bad old carb days. With modern EFI we take low-rev drivability for granted, but it's a real tough environment to get the spark to completely ignite a mixture. Andy any component out of spec will cause a problem

 

dgipalo,
Found something! I unhooked the EGR Valve Vac line and the miss is gone. Plug it back up and the problem comes back. Do you think I have a bad EGR Valve, or a bad EGR Postion Sensor? I am getting no codes with the Vac line hooked up, of course I am with it unhooked. If I had a bad sensor, wouldn't it have thrown a code?

Wake,
To let you know, the 4.9 is multiport on the '95.

[This message has been edited by cowboykent (edited 01-31-2001).]

 

check your cats they could be clogged up my byd has a 94 4.9l and it done the same exact thing sure enough he spent hundreds of dollars and come to find out it was just the converters hit them with a hammer and see if you can hear stuff rolling around or moving inside them if so id pull them off and check them out
keep us informed
jj

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97 4x4 ORP
flareside supercab
rear blackouts
westin step bars(black)
side window louvers
lund shadow wiper cowel
true duals 5 in tips
k&n F.I.P.K
17in' wheels 265/70 Bridgestone dueler A/T's
ventshades
tinted windows 5%

 

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