Hi folks,
I thought that I was a pretty good shade tree mechanic but I have been beating my brains out trying to find the intermittent miss in the engine on my 1998 F-150 V/6 EFI. The miss only happens when you take off and when you are freewheeling. It calms down and runs good under load. I have replaced the oxy. sensors (3ea.), mass flow sensor(1ea.), spark plugs (twice),wires (twice), cleaned the little cigar shaped thing on the plenumm, sorry don't know what that is called. Someone said that it builds up carbon and probably needed to be cleaned out, did that. Checked the idle control sensor. I have checked for vacuum leaks on all the lines I can locate and around the manifold (none). All this with no luck. My next move will probably be the ignition block and rotor assy. if that doen't work I will have the injectors professionaly cleaned, MONEY PIT?? I don't know what else there is to check. My best guess it may be a clogged injector??? Also, it is using alot of gas!!!!! This truck has been a really good truck and this is the first time I've had any trouble with it since I bought it.
Also, another little problem. I do not have an interior light when you open the doors nor when you turn the dimmer for the dash lights all the way up which is suppose to turn the interior light on, it's never worked since I bought the truck(used) I have checked all the fuses and they are all good. The interior light will work if you manually flip the switch on the light itself.
Any thoughts??
Charlie

 

Do a SEARCH on intake leak, common problem on 4.2

 

Hello,
I have done the vacuum leak test with starting fluid and a small gas tank using propane all around the intake gasket. I did not hear any up rev. of the motor when I did this.

 

hello
welcome to the forum

have there ever been any codes or a cel

 

Could be a coil, but that usually happens under load.

 

As old as the truck is I would replace that coil - their only $30 @ Global Auto..

I would also look for FORD 19 lb (orange) injectors on ebay. I found my type 3 upgrades on ebay - NEW for $ 60 (that's for all 8 where you just need 6).

If you don't find type 3's - Just regular 19 lb'ers will work. Look for new ones, there's quite a few take offs on ebay that are sold cheap..

I have all fairly new parts on my 98 motor. Most of the parts came from Romeo Crate Motors that are parted out on ebay . Their motors are usually crown vic 4.6Ls. Allot of parts from that motor will fit yours , like the injectors. Ford used the same injectors from 97-03 on the 3.8L - 5.4L engines.

 

Hi folks,
I still have that miss in the engine at low speed when my engine shifts into second gear and when I'm freewheeling at low speed. When I give it gas or under load it smooths out. Even at speeds between 50 and 70 at the free wheeling state you can feel it missing. When it smooths out the engine lite stays lit but when it starts the missing the lite will blink.
Well let me tell you' all what I've done so far and what has been told to me.

Replaced:
Coil Pack, wires, plugs .54" gap, mass air flow sensor, oxy sensor's, compression tested all 6 cyl. 190 psi. new air filter, cleaned intake plenuum, checked for vacuum leaks with propane and with WD-40. checked all fuses.
Possible check outs:
bad injectors and internal intake gasket leaks. Injectors I can replace but the intake will have to be removed and gasket replaced if that is the problem.

Any ideas where this miss is coming from?????
Help!!!
Signed,
Stumped??? (Charlie)

 

Fuel Filter or Regulator maybe. You test the pressure @ the rail. You can check the regulator that way.

Always go through the fuel system first with this kind of problem , it's fairly easy to do ..If theres a pressure problem. Replace the filter and test again.

 

I thank you for welcoming me to the forum.
I am really at a standstill with this engine the only thing left is the injectors and maybe an internal vacuun leak in the intake gasket. I have checked all the connections and vacuum lines on the engine and everything is connected properly with no leaks. Even the old school hose in the ear trick to try to listen for the vac. leaks. nothing.
I guess I can drive it with the miss. I have been told it may possibly have a burnt valve but with 190 lbs psi. of compression on all 6, too even, very unlikely.
I remeber that I did not change out the rear oxy. sensor because I was told that it was just a flow sensor and had nothing to do with the fuel or firing. I did change out the 2 upstream oxy sensors.
I guess my shade tree days have come to an end.
Any one got any ideas??

 

The only codes I have seen are the ones that auto zone came up with:
1st time: misfire #1, lean condition bank 1 an 2. I didn't check the number for the codes, when I have the computer cleared I will note the codes and relay that info. to you folks.
After replacing the items I have listed above and also having a analizer check telling me their is nothing wrong with the truck. The truck was in idle state when the test was done.
Autozone reading was:
Mass air reading and lean condition bank 1 and 2.
The misfire reading did not show up this time??? DUH!!!
I don't know what is going on with this miss fire issue.
The saga continues
Any ideas???

 

With all youv'e done I would next investigate for an EGR fault.
Open to far, hanging open, not closeing completely etc. During cruise lite load, the EGR opens as a normal function. At this time the A/F ratio goes really lean making the ignition really sensitive to misfires or stumbling.
Normally the motor handles all this but with a fault, a miss can show up on an intermittant basis and may not be enough to cause a code related to any cylinder in peticular.
The EGR is a hose from intake vacuum to a regulator operated by the PCM, gates vacuum to the EGR.
If the regulator hangs open, the EGR does not bleed down as fast as it should, the EGR does not close up etc.

 

Hi all,
Thanks for the response you all have given about this nagging miss,
I apprieciate it.

I have since been told that it possibly could be an internal/external vacuum leak possibly inside the manifold and possibly fuel pressure, rails or injector problems.
I will check out the EGR for any problems there.
I have replaced alot of things on this engine, probably should have done this a long time ago. One good thing about all this, the parts that I have replaced that did not make a change I'll just keep for back ups.
This has got my curiosity up now, maybe after we all find out what it is we could help out someone with the same problem down the road.
This is strange.
Thanks much,
Charlie

 

I don't know - If it was me , I would have changed the fuel filter along time ago - It's one of the first things that should be done. It's a maintenance item that shouldn't be neglected and it could very well be the problem.

Keep in mind , you had a fault with #1 misfiring . #1 is the furthest away from the fuel pump. Very good chance you have a fuel supply issue.

Good Luck

 

Hi all, SUCESS!! maybe?

Well here's the scoop:
Went back to check out the EGR ststem and low and behold I found a small 3/8" 90 degree hose that hooked up to a sensor on the plenumm and I think went to the egr vacumm system, it was completly delappidated and in that I had found a major vacuum leak. As soon as I got another piece and installed it 98% of the vibration went away. Their may be some small leak elsewhere but for now that one piece of hose that didn't cost me a cent probably fixed the missing issue. I have probably invested 500.00+ because of a piece of hose. "Big" learning lesson. I had a feeling when this all started that it may be a simple fix but getting there was painfull.
I did test for leaks with propane and WD-40 and didn't find anything initially. I think the last thread that was entered about the problem I had was about the egr vacuum system.
Thanks for the help sir, I apprieciate it very much and to all that helped. I will let you all know if there is any thing else that arises with this.

 

If any one reads this, I need your opinion

I still have a vibration in the motor but it doesn't feel like a miss. I put the parking brake on and at idle took the vacuum line loose from the EGR pod and there was no change in the motor and it had a little vacuun on the line. It ran smooth. I had my daughter run the idle up just a little I slipped the vacuum line back on the EGR pod fitting and the motor started to shake like it had a miss.
I had mentioned in earlier threads that I had run a compression check and all six were at 190psi and I think that ruled out a burnt valve and that I had found a vacuum line that went to the egr vacuum lines to the plenum on the left of the motor in the back looking from the front of the motor that was delappidated and replaced it and the pvc valve and most of the vibration or miss went away. This vibration only occurs between 10 an 40 mph.
I am thinking it may be a bad EGR
Would a bad EGR make an engine shake like it had a miss at low speed?
Anyone got any thoughts?
BTW: I replaced the fuel filter a couple months ago and just replaced all 3 oxy. sensors,mass air flow sensor,wires, plugs,air filter and coil pack.