Rough Idling on Ford F150

Bad gasoline?

That's actually a very real possibility. I filled up the 5 gallon tank on my boat last year and the gasoline was about 50% water, right from the station.........................separation had definitely occured.

Pulling a sample from the bottom of the tank would be a good next step.

We thankfully didn't get these here in Oz, however a bit of googling brought me to this entry in Wikipedia

A 4.2 L (256 cu in/4195 cc) version of the Essex V6 appeared in the 1997 model year as a replacement for the durable, but aging, Ford 300 straight six in the F-150. Like the 3.8 it had 12 valves and pushrods, but the 4.2 featured a longer, 3.74 in (95.0 mm) stroke. Bore diameter was the same at 3.81 in (96.8 mm). Initial output of the 4.2 L V6 in the F-150 was 202 horsepower (151 kW) at 4800 rpm and torque of 252 lb·ft (342 N·m) at 3400 rpm. Ford Power Products sells this engine as the ESG-642.

Ford experienced problems with this engine in the 1997 and 1998 model years.^[9] These included issuing all 1997 engines made at the Essex plant with a bad front cover gasket. The lower intake manifold has a bad reputation for cracking at relatively low mileages.

Ford ended production of the 4.2 L V6 after the 2008 model year, marking the end of the Essex V6. The engine's final recipient, the F-150, was only available with V8 engines starting with the 2009 model year until the 2011 model year, when the 3.7L Duratec was made standard.

Applications:

• 1997-2008 Ford F-150
• 1997-2005 Ford E-150

I've added the bolding to the manifold reference.

That's the trouble with bean counter engineering...

If you have replaced all the vacuum hoses and checked for leaking manifolds, then my only other suggestion is to check the HVAC system for leakage. Does all the functions of your heater/ac work? When you switch between Recirc to Fresh does the "door' move. Sometimes the diaphagms in the vacuum motors which operate the various "doors' in the HVAC perish or crack and allow the vacuum to escape. Also the switch/valve to operate the HVAC does it seem to be a bit noisey? Some of these things are more noticeble in a quiet passenger car not so noticeable in a rattly F truck..

Disconnect the vacuum feed to the HVAC system and plug it (at the motor end) see if that makes a difference.

Do you have a vacuum trailer brake system fitted? Is the vacuum booster tank perforated? Are the lines and connections ok?

Are your service brakes a bit hard? Is the brake booster leaking? You might have to have a listen under the dash while the engine is running.

Just some things to check.

thanks for all the help its not a gas issue i have checked that but i have had some brake troubles and have never considered that the booster might be leaking i will have to check it thanks again

This is probably unlikely, but I'll tell you anyway........it's kind of funny.

A couple of years ago my GMC truck started running/idling really badly, out of the blue. I thought I had checked everything and couldn't figure it out.

Long story short..........one day I was standing there looking under the hood wondering what I was missing, when I noticed some debris back by the distributor.

Turns out a squirrel had chewed out the elbow on a brake booster hose connector back by the firewall, creating a massive vacuum leak.

The hole was toward the firewall, so I couldn't see it just by looking.

Damn squirrels.

You need to take out the intake manifold both the upper and lower pieces. Check all the sealing surfaces and be sure to check all the seals around the bolts as we have found many 4.2 V6's run rough when the rubber seals around the lower bolts have been oiled and swollen. Too many deep in there places that vacuum can leak from that you cannot see or test!!!!

I would find a good place on the intake and install a vac. gauge. "T" it in is OK. We used them a lot with carbs. I still use them on cars today they will tell you alot. Sticky / burned valves valves, plugged exaust. early/ late timing, High even vac. 15"+ good. Low vac. wandering or a steady flux bad. The old Chilton's had a section about vacuum gauges. My 84 Caprice Classic has one in the instrument panel as big as the speedo, used for watching your fuel milage. Every mehanic should have and know how to use one. Most will read low positive pressures for checking manual fuel pressures. With the gauge hooked up you can spray carb cleaned around suspect leaks and watch if the gauge smooths out or increases. I've had 2 engines just lately that just had super wide plug gaps causing poor running. Is the Compression OK. Good Luck Let us know what you find.

This gentleman is not alone I have a 1998 E150 service van that keep's setting a service engine soon light on the dash. Every time we check it it complains of a lean bank 2. Then it decided to drop a cylinder and try to run on 5 cylinders and did not do that very well. We replaced the number 5 plug and found that plug to be completely closed up.Runs a lot better now with the new plug.But still still sets a code, I replaced the injectors with a new set of Venom 19 LB injectors. Still made no difference in the end. I was told about a problem these engines had with the EGR system that the manifold lower has A tendency to plug up the EGR passages for the runners. As I understand you have to remove the upper manifold and clean out the passages. I have not done so yet but it is next up on the agenda, as soon as I get the time maybe you might try the EGR circuit and see if that helps

Check that the carburetor and cruise control cables are not too tight

This version of Ford's better idea is fuel injected only. The transmission throttle valve circuit cable has nothing to do with idle it only controls the shift along with the ECM. Too many computer controls for the average guy to fix anymore without a computer bank of test equipment. currently I have 5 different scanners to try and keep up with all my service vehicle's and that is still not enough. Too many of the codes are set ot pending files that you have to use a manufacturer's proprietary scanner to open the files to read

i pulled ever vacume line i could find and plugged them still the same i think im just gonna have to pull the manifold theres got to be a leak that im not finding thanks for all the help

The only thing I would add to your post is that if the cylinders are experiencing a vacuum leak, the spark plugs should show it. They should be noticeably whiter than the adjacent cylinders. I also have had the 4.2 Ford intake problem.

If the EGR valve is sticking open it could act just like a vacuum leak causing rough idle. Also there is a sensor called differential pressure feedback EGR sensor, or DPFE sensor that is known to go bad. If it is malfunctioning it can cause same problem. It is the sensor with two vacuum (term used loosely) hoses running from the egr tube, and a three terminal electrical connection.

Hi there:

Ford issued a tech bulletin regarding defective EGR control solenoid. Roughly the solenoid controls opening and closing of the EGR. Simply remove vacuum hose from the EGR and plug it. Drive the car for 10min. If the Idle smooths remove the EGR and clean it the replace the EGR solenoid. The actual test is rather more complicated and takes some time. This workaround takes 20 min. and costs 0... ∑undog