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. Thinking about a throttle position sensor. Anybody have any suggestions?

[This message has been edited by cowboykent (edited 01-22-2001).]

 

MIGHT be an EGR problem. Unhook the vac line from the valve and go for a drive. If the surge or miss is gone, you probably have a vac regulator problem for the egr.

 

i have the same problem w/my 6. I think it is the oxygen sensor making it run rich. Have not coughed up the $40 yet but its in the very near future.

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1987 F-150 300 L6 4sp 2wd
K&N, flowmasters

 

I just got the truck back from the shop and they checked all of the sensors and the ignition. They said everything looked good. So they cleaned the fuel injectors and this seemed to help a little but occasionally it still does it. How much is a new EGR valve? And do you have to have a special tool to replace that and the oxygen sensors?

 

Cowboykent, when does this happen?? My '87 did that when she was cold (just started up) and I was running around in 3rd gear at about 2000 - 2500 rpm. I believe, if memory serves me correctly, the guys (mechanics) thought is was the O2 sensor, in that the motor is still cold that the sensor is flipping back and forth till the truck becomes warm. After she warmed up and I was to do that same speed it wouldn't happen. I hope this helps.

Have Fun & Keep on Truckin'
Dean

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1994 F-150 XLT Supercab, Long Box, 302 EFI, K&N FIPK, Bosch Platinum +4 Spark Plugs, Automatic, Single Catalytic converter, followed by a Raven Z-55 muffler and finished off with chrome tips (2 1/2" to 3"), Royal Blue in and out, Captain Chairs. Chrome Rims 15x8's, Michelin LTX M/S 105S 235/75R15 (Summer), OEM Aluminum Rims 15x8's, Michelin LTX M/S 108S (Winter), Lightly Tinted, Soft Tonneau Cover, Ford Receiver Hitch Cover & Lock, J&J Enterprises Stainless Steel AirDam with KC driving lights, Lund Supersteps, Lighted Grab Bars, VTech Slotted Taillight Covers, Alpine CDM-7829 Head Unit, PPI 4800 Amplifier, Kicker 10" Solo Baric Sub with Custom Box and Kicker Impulse 6.5 Mid & Tweets.

 

I have had my 93 F-150 A-T 4x4 to the dealership several times about the same problem. It audibly skips between 30 - 50 mph, bad enough that it feels like a washboard. Response from the 5 star Ford Garage: Drive it or trade it, we cant find a problem. They changed the EFI Manifold gasket, Throttle position sensor, Plugs, Wires, Cap, Rotor, EGR Vent solenoid valve, plugged in a new O2 sensor, Checked the injectors, decarbonized the manifold and cant find the problem. The shop manager has a 94 that has the same problem. Another used Truck on the lot does the same. Mine has 85K on it K&N filter, and 3" Stainless Gibson performance exhaust. The problem isnt showing up on the computer. I am looking for help as well. I am looking at an aftermarket chip and computer, because the problem doesnt seem to be a part failure, but more a defect in the computer curves and timing set up in the chip. Just guessing though. My brothers 95 does not have any problems. The skip isnt there when accelerating, only at low loads, typical to city, easy driving. The garage is no longer taking my calls unless something new breaks.

 

This was the first morning I drove it to work since the injectors were cleaned. It still does it, but not near as bad. One other suggestion is to get a fuel additive to remove any water and moisture from the fuel tanks. It does it usually in 3rd and 4th gears. I don't have a tach so I'm guessing aroung 2 grand. It idles, accelerates, and runs great if I keep the rpm's up. But when I am on level ground, not accelerating or deccelerating, just barely pushing in the pedal it feels like I forgot how to drive a manual transmission. It was worse this morning when I first took off, but I let it warm up in the driveway before I left. I'm going to try unhooking the vacuum line from the egr valve this weekend to see if that fixes the problem. I hate to get rid of the truck, so I want to determine exactly what the problem is. When I do fix it, I definitely will post it here. By they way, I can tell a BIG difference when accelerating after having the injectors cleaned. Mechanic suggusted every 30,000 miles or so.

 

Yesterday I spent over 6 hours working on the thing. All 6 fuel injectors have been replaced and the misfire is still there. The injectors made a big difference in how smooth and fast it accelerates. There is a test clip near the driverside fire wall that the factory guys unhook when they are setting the timing. Without a jumper completing the circuit the computer will not advance the distributor. This is the second time the Ford garage that has left the jumper off after returning the truck. Listening to the motor at an Idle, I removed the throttle position sensor lead. The flat spot or hesitation at the bottom is gone. Then I removed the air mix unit lead directly on top of the throttle body assembly, and the RPMs decrease and the skip becomes terrible. Not enough to make it quit, but the misfire is very evident. Listening very closely, it really sounds like a timing problem. Today I am going to work on replacing the pickup unit in the distributor. It sounds as if the timing is advancing to much, then correcting itself causing a misfire. As the factory guys said, there are no vacuum leaks anywhere in the system, verified with ether yesterday. There diagnostics state that there is a lean misfire with the EGR at max flow. With the EGR at max flow, the timing is missing. Still looking for insight from anyone who has every had such a problem with a 4.9. Could the PCM (Powertrain Control Module) be causing the problem? It is an automatic, and the skip is fairly close to the shift points.

 

Henshaw2001, Check out my thread under the same subject in the Engines department of this message board. Sounds like you are having the same problem also. Is the miss at the bottom end of the shift change? In other words, does it happen just after the tranny shifts up into the next gear?

 

Cowboykent, this weekend all six injectors were replaced with new ones. One seemed to be defective. However, the problem did not disappear. Since then the engine light has come on about 6 times. It is giving several troupble codes. The skip is very evident near shift on the automatic, but can be felt at several other throttle/shift positions. The codes it is giving point to the TPS, HEGO Sensor, and MAF. However, all sensors have been recently replaced. I talked to the Ford guy yesterday, and previously no trouble codes had ever been registered. There were seven after the first engine light warning came on. It is going to the shop this morning. It has gotten much worse. The skip is now affecting power, and has better than cut the fuel economy in half. One thing troubles me though. When I remove the mixed air solenoid on the intake near the throttle plate, the thing skips badly at an idle. According to my mechanic buddy, this should not occur. It should run rich, but not like this. Did you ever get the problem fixed on yours?

 

Henshaw2001,
With the tuck idling, when you raise the hood and opperate the throttle by hand, does your RPM's drop for just a second and then pick up when you barely move the linkage to crack open the throttle? If so, have you tried plugging the vacum line on the EGR valve? I did it last night and my hesitation is completely gone (knock on wood and keep my fingers crossed). I don't know if the regulator is bad or if it is the valve itself. But it felt like I picked up about 5 HP with the vacum line unplugged from the EGR valve. Check this out and let me know. I'll keep this thread updated with my progress as well.
Good Luck!

[This message has been edited by cowboykent (edited 01-30-2001).]

 

Well, the garage visit did absolutely nothing. Once again, they can't find it and "All Fords that year do the same thing with some miles on them". BS is what I say. I will try the EGR vacuum line and see if it makes a difference. With the truch at an idle, if you bump the throttle lightly, the truck hacks and coughs. If you feather it, you can make it quit outright. If you mess with it on the highway under load, just between OD and Drive, the engine light comes on.

 

cowboykent - have you replaced your fuel filter lately? A fuel restriction will cause this.

Also do a pressure check on your exhaust system to determine if you have a plugged catalic converter or muffler.

Let me know what you find out.

 

Henshaw2001,
Sounds exactly like mine except I never get a check engine light (with the EGR vac line attached). Let me know how the vac line check works. I am now trying to determine if the problem is in the EGR valve itself or in the EGR Position Sensor. I think maybe the valve is the problem since I am not getting the check engine light. What do you think? I'll keep you posted on my progress.
And I am going to take the advice of insect2 and change the fuel filter. It has been about a year since I have changed it.

 

Cowboykent,
The fuel filter had been replaced only weeks ago, the original having about 80K on it. The good news though: I unplugged the main vac supply to the EGR valve and wallah, no skip, better performance, improved fuel economy, smooth idle, and smooth acceleration. Ive got it plugged off for the time being. The new EGR valve, less solenoid runs about $95.00. Another mechanic said that if the vac line is unplugged, that it ruins the O2 sensor. The O2 sensor is only $41. Honestly I think its a mechanical problem with the valve itself. Either its not ceating properly, or the spring is weak or has completely let go. Just to give you an idea of the fuel economy increase, last week i got about 360 miles off both the front and rear tank. Ive gotten over 260 on just the front tank this week, about a 8 MPG increase. Im gonna leave it plugged off for now, cause Ive already dropped $600 this month in repairs. I appreciate the advise, it worked, and now I am off to giving the Ford Guys tons of *hit. What a lousy bunch of mechanics.