Well I'm pretty much stumped. I can't get rid of this stumbling / misfire. No CEL. Majority of the time it happens at low rpms, below 2 grand. Randomly happens at mid and high rpms. I just replaced all plugs and properly gapped them all. I bought a new COP and swapped it into all 8 cylinders with no change in driveability. Replaced the fuel filter, cleaned the maf, cleaned my K&N, checked for vacume leaks, none. Ran BG fuel injector cleaner through my fuel rail, added BG fuel treatment to my tank, checked all electronic connectors. tried to disconnect the egr, didn't affect the stumble / misfire ( I was thinking it might be sticking open). IAC is working properly. I did a compression check. all cylinders around 165-170psi. TPS working properly. O2 sensors cycling like they should be. I disconnected the fuel pressure regulator putting the car into full rich mode. Car ran worse, so I was thinking it could be running rich all the time. So I created a vacume leak after reconnecting the fuel press. regulator, still ran like crap. Tomorrow I'm gonna hook up a fuel pressure gauge to the rail and check fuel pressure specs. Then I guess I'll check vacume readings at 2500 rpms for a minute and see how efficiently my cats are flowing, but I doubt a clogged cat would cause this problem. Lastly, I've never removed injectors from an engine to clean individually. Is it possible to open the injector up and clean the screens inside of them? I thought one or more could be semi clogged and the BG chemical I ran though it couldn't clean it completely. Well thats all I can think of. Hopefully I can get some more ideas from you guys. Thanks for the help in advance.
99 GT still missing......
- Thread starter Kappa2006
- Start date
mustangkid05
New Member
- Mar 10, 2006
- 199
- 0
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Distributor huh? 
You can pop the injectors out individually, just make sure you use a compressor to blow all of the crap around the base of them away. You don't want anything to get down in there. I took mine out, and hooked them up to a 6 volt lantern battery, and pumped some acetone through them. At least 3 of them were just kind of barely squirting. Now they fire like brand new.
Do you have a performance chip in, or possibly a tune? I know they can cause some issues sometimes. Also, do you have a K&N filter? Mine was idling rough once, because the filter oil got on the sensor in the MAF. I cleaned it up real good, and the car ran like a champ.
Rickey_Bobby
New Member
I had a similar problem on my 99gt. Check this:
water or coolant around spark plugs. Remember NEVER wash down the engine
I had coolant coming out of the intake manifold gasket. Just barley, not enough to drip on the ground, but enough to make moisture in 2 plug holes.
if you EVER had water in a plug hole, you probably killed a coil or 2.
You can narrow your problem by doing the following. This will tell you where the problem is, and if it is spark, or fuel related.
1. Get your car in a state where it is misfiring. It must be misfiring for this test.
2. one at a time, unplug fuel injectors while the motor is idle. The engine should have a noticable lope when you pull each injector. This is GOOD. It means the fuel injector is working. If you get to an injector that DOESN'T cause the engine to lope when disconnected, or causes it to lope less than the others, suspect that cylinder. Do this 2 times each for each cylinder to see if you get the same results. Most likely, this is not a fuel problem.
3. Rev the engine a few times and then let it idle for a minute and make sure it is still misfiring.
4. assure that all injectors are connected properly
5. One at a time, go around and disconnect the plugs from the coils. Again, doing this should cause a noticable lope. If you get to a coil that when it is disconnected, it either doesnt lope, or causes less of a lope that the other cylinders, suspect that cylinder.
Ok, so hopfully now you have narrowed you problem to a specific cylinder(s) For this write-up's sake lets say cylinder #5 is your problem, but your still unsure if it is the coil or injector because during both tests, the engine still loped, just not as much as the other cylinders.
6. swap cylinder #5 coil with a coil from the other side of the engine. (You will need a small 7mm socket and extension to remove the bolt holding the coil down. And the coils will come out without removing the fuel rail.)
7. connect both coils to the wire harness and start the car. It should still misfire. Use the method in step #5 of this write up to see if your misfire followed the coil, or is still happening at cylinder #5.
(If the misfire followed the coil, you have a bad coil. whats worse, is the others are probably on their way out too. Replace them all.)
There is a guy on ebay selling genuine motorcraft coils for dirt cheap. I have them on my car and they work flawlessly. Here is the auction.
http://cgi.ebay.com/ebaymotors/8-OEM-Coil-on-Plug-DG508-Ford-F150-4-6-5-4-6-8-TRITON_W0QQcmdZViewItemQQcategoryZ33689QQihZ009QQitemZ190040945028QQrdZ1QQsspagenameZWDVW
If the problem stays at cylinder #5, then suspect your injector.
8. Use compressed air to blow dirt off the motor before doing the folowing procedure!!
9. Using a 5/16'' wrench or deep well socket, remove the 2 nust holding both fuel rails down.
10. Remove the intake plumbing. PITA i know, but it is well worth it.
11. Lift gently and evenly on the fuel rail until all 4 injectors are clear of the manifold. It is a Bioch to pull, so just go slow and steady. Repeat on other rail.
(there is no need to releave the fuel pressure, you will still spill fuel, just let it drain on the motor, it will evaporate in a minute)
(And, duh... I know most people don't work on their engine after cruising the interstate for hours, but if you do, please do this when the engine is sorta cool so you don't blow up.)
12. Visually inspect the injector, don't clean it yet even if it is dirty or looks clogged.
13. Switch it with an injector from the other side of the engine.
14. re-install everything and start it up. See if the misfire followed the injector. IF it did, clean or replace the injector. If the misfire is STILL at cylinder #5, then your only possible causes left are:
1. The sparkplug (you said you checked these already)
2. mechanical problem within cylinder #5
3. the connector or wiring to cylinder #5's injector or coil
Hope this helped. IF you follow this without cutting corners, you WILL find your misfire.
Note that a multiple cylinder misfire should be aproched using this same method, just make sure when you go to swap coils and injectors, you are swaping with known working cylinders.
-Steve
water or coolant around spark plugs. Remember NEVER wash down the engine
I had coolant coming out of the intake manifold gasket. Just barley, not enough to drip on the ground, but enough to make moisture in 2 plug holes.
if you EVER had water in a plug hole, you probably killed a coil or 2.
You can narrow your problem by doing the following. This will tell you where the problem is, and if it is spark, or fuel related.
1. Get your car in a state where it is misfiring. It must be misfiring for this test.
2. one at a time, unplug fuel injectors while the motor is idle. The engine should have a noticable lope when you pull each injector. This is GOOD. It means the fuel injector is working. If you get to an injector that DOESN'T cause the engine to lope when disconnected, or causes it to lope less than the others, suspect that cylinder. Do this 2 times each for each cylinder to see if you get the same results. Most likely, this is not a fuel problem.
3. Rev the engine a few times and then let it idle for a minute and make sure it is still misfiring.
4. assure that all injectors are connected properly
5. One at a time, go around and disconnect the plugs from the coils. Again, doing this should cause a noticable lope. If you get to a coil that when it is disconnected, it either doesnt lope, or causes less of a lope that the other cylinders, suspect that cylinder.
Ok, so hopfully now you have narrowed you problem to a specific cylinder(s) For this write-up's sake lets say cylinder #5 is your problem, but your still unsure if it is the coil or injector because during both tests, the engine still loped, just not as much as the other cylinders.
6. swap cylinder #5 coil with a coil from the other side of the engine. (You will need a small 7mm socket and extension to remove the bolt holding the coil down. And the coils will come out without removing the fuel rail.)
7. connect both coils to the wire harness and start the car. It should still misfire. Use the method in step #5 of this write up to see if your misfire followed the coil, or is still happening at cylinder #5.
(If the misfire followed the coil, you have a bad coil. whats worse, is the others are probably on their way out too. Replace them all.)
There is a guy on ebay selling genuine motorcraft coils for dirt cheap. I have them on my car and they work flawlessly. Here is the auction.
http://cgi.ebay.com/ebaymotors/8-OEM-Coil-on-Plug-DG508-Ford-F150-4-6-5-4-6-8-TRITON_W0QQcmdZViewItemQQcategoryZ33689QQihZ009QQitemZ190040945028QQrdZ1QQsspagenameZWDVW
If the problem stays at cylinder #5, then suspect your injector.
8. Use compressed air to blow dirt off the motor before doing the folowing procedure!!
9. Using a 5/16'' wrench or deep well socket, remove the 2 nust holding both fuel rails down.
10. Remove the intake plumbing. PITA i know, but it is well worth it.
11. Lift gently and evenly on the fuel rail until all 4 injectors are clear of the manifold. It is a Bioch to pull, so just go slow and steady. Repeat on other rail.
(there is no need to releave the fuel pressure, you will still spill fuel, just let it drain on the motor, it will evaporate in a minute)
(And, duh... I know most people don't work on their engine after cruising the interstate for hours, but if you do, please do this when the engine is sorta cool so you don't blow up.)
12. Visually inspect the injector, don't clean it yet even if it is dirty or looks clogged.
13. Switch it with an injector from the other side of the engine.
14. re-install everything and start it up. See if the misfire followed the injector. IF it did, clean or replace the injector. If the misfire is STILL at cylinder #5, then your only possible causes left are:
1. The sparkplug (you said you checked these already)
2. mechanical problem within cylinder #5
3. the connector or wiring to cylinder #5's injector or coil
Hope this helped. IF you follow this without cutting corners, you WILL find your misfire.
Note that a multiple cylinder misfire should be aproched using this same method, just make sure when you go to swap coils and injectors, you are swaping with known working cylinders.
-Steve
WashburnGT
New Member
There may also be a unicorn crapping in your air filter and poking holes in your catalytic converter.
In all seriousness though...I had a misfire at idlebecause some oil from my filter got on my MAF. I cleaned it with a q-tip and some Isopropal (sp??) alchohol. That cleared that right up. You also might check to see if you have any water or oil buildup where your coil-packs are. that could defiently cause a misfire.
If you have access to a scanning device, I would go ahead and scan it. Just because the CEL hasnt been tripped doesnt mean your not throwing a code.
Thanks for all of the ideas guys. In response to the misfire detection, the only problem with my car is the misfire is only under load at low rpms. I can't get it to misfire constantly at idle to check injectors and coils to see if they're working. Its not bad gas because I've filled up three times with no change in driveability. And when I was replacing plugs, there was absolutely no water/coolant/oil around any plug or coil. I did scan my car and found no stored, current, or pending fault codes. I already checked to see if a coil was just starting to go bad by replacing every one with a new one, one at a time, but the misfire never changed. So its not a problem with coils. and the plugs are brand new and properly gapped.
Rickey_Bobby
New Member
you have 8 brand new coils sitting around? WOW!
umm... Why arn't they on your car in the first place?
And are they "bramd new" or new as in not as old as the ones you have.
Because The symptom you describe is a spark loss, not fuel.
Injectors dont know load. All they know is "Hey, I'm running low pulse width" or "Hey, I'm running high pulse width" So if an injector was clogged, it would be crappy across the board. It's not like it can unclog when you rev up.
So you could still be losing spark somewhere I think. cracked or old boots will arc too.
Do that long list of crap I wrote up, but for each test, drive the car. Put it in 4th at a low speed and floor it. See which cylinder makes the least amount of difference. That will be your problem one. Then it will get you looking at the right cylinder at least. You can't fix a problem ifyou don't know where to start.
So pull a coil connector, and drive. pull the next, drive....
then do the same with the injectors.
Will take a while. So be patient.
umm... Why arn't they on your car in the first place?
And are they "bramd new" or new as in not as old as the ones you have.
Because The symptom you describe is a spark loss, not fuel.
Injectors dont know load. All they know is "Hey, I'm running low pulse width" or "Hey, I'm running high pulse width" So if an injector was clogged, it would be crappy across the board. It's not like it can unclog when you rev up.
So you could still be losing spark somewhere I think. cracked or old boots will arc too.
Do that long list of crap I wrote up, but for each test, drive the car. Put it in 4th at a low speed and floor it. See which cylinder makes the least amount of difference. That will be your problem one. Then it will get you looking at the right cylinder at least. You can't fix a problem ifyou don't know where to start.
So pull a coil connector, and drive. pull the next, drive....
then do the same with the injectors.
Will take a while. So be patient.
Rickey_Bobby
New Member
I agree that it is a spark related issue. Because you described that it happens at low rpm under load it could really only be one of two things. Your coil is taking a ****, or your spark is arching. Like said above check all spark boots, make sure they are good condition and moister free. Also a good check to see if your coils are putting out. Pull each coil out from the head one at a time and stick a screwdriver into the end of the coil. Have a buddy fire up the car and hold the shaft of the screw drive about a half inch to an inch from a engine ground. I know on my car I can get a good solid inch of blue spark from each on my coils. If you can't produce at least a half inch of spark then your coil is taking a ****. It becomes apparent under heavy load when more demand is placed on the coil it's self. just make sure you don't pull the coil out and leave it hangin in mind air with no ground. This maxes out the coil and eventually fries it. So keep it close to an engine ground, then fire up the car, shut it off and replace. GOOD LUCK!
what i said about the coils was that I purchased a brand new one and swapped it into each cylinder, one at a time and test drove. but the hesitation never changed. never got better or worse. This is why I was ruling out the ignition system. But I will give what you mentioned a try. But if I run the engine iwth coils unplugged. its gonna run like crap everytime. guess I'll try my best to figure out which doesn't hurt the engine as much as the other 7.
Rickey_Bobby
New Member
Tou WANT it to run like crap every time. What your looking for is the coil the DOESN"T make it run a lot worse when it is unplugged. Since the bad coil is already misfiring, having it unplugged wont affect the engine as much.
Are they genuine stock coils, or "remanufactured ones"
Are they genuine stock coils, or "remanufactured ones"
jstreet0204
Active Member
Check the EGR. Mine was sticking open and would cause a sort of stumble under load around 1800 rpm.
I did test the egr valve with a vacuum pump, and it was working properly. I went ahead and unplugged each coil at a time, i couldn't see a difference in the misfire from each. So I decided to go to the maf sensor and do some electical testing.
-Tested my power, got battery voltage at connector
-Tested my ground at connector, .1 ohm of resistance key off engine off.
**but then I noticed the resistance went up to 32ohms when key on engine off.
-Tested reference voltage from PCM at MAF connector using the ground at the MAF connector, got .87 volts
-Tested return signal from MAF to PCM at connector using ground at MAF connector, got 0v.
-Tested resistance of MAF signal wire and ground on MAF itself, .01 ohms.
I'm going to follow an alldata maf diag chart tomorrow at work and see what I come up with.
-Tested my power, got battery voltage at connector
-Tested my ground at connector, .1 ohm of resistance key off engine off.
**but then I noticed the resistance went up to 32ohms when key on engine off.
-Tested reference voltage from PCM at MAF connector using the ground at the MAF connector, got .87 volts
-Tested return signal from MAF to PCM at connector using ground at MAF connector, got 0v.
-Tested resistance of MAF signal wire and ground on MAF itself, .01 ohms.
I'm going to follow an alldata maf diag chart tomorrow at work and see what I come up with.
I bet you have a few weak COP's you will need to run a ignition test using a WDS or IDS or some other professional scan tool that can measure duration and KV's
Where are you located? if you are in my area PM me I can fix it for you, because I can see this getting really ugly with a lot of parts getting thrown at it since you don't have the right equipment to diag the car.
Where are you located? if you are in my area PM me I can fix it for you, because I can see this getting really ugly with a lot of parts getting thrown at it since you don't have the right equipment to diag the car.
This test made sure the hot wire inside the MAF wasn't damaged. you want low
resistance. I followed the DC from alldata last night, the MAF circuit checked out good. and I found another MAF in an 01 mustang, and its doing the same thing after swapping the two. Tonight I'll be doing a balance test on all injectors, checking fuel pressure, and running a resistance test on all coils. Sooner or later I'll find the problem, hopefully sooner!
resistance. I followed the DC from alldata last night, the MAF circuit checked out good. and I found another MAF in an 01 mustang, and its doing the same thing after swapping the two. Tonight I'll be doing a balance test on all injectors, checking fuel pressure, and running a resistance test on all coils. Sooner or later I'll find the problem, hopefully sooner!
Your saying when you tested the MAF, you put one test lead on the signal, and one on the ground wire? Or did you ground to the case of the MAF. I was assuming that you meant grounding to the case, which i couldn't understand because it's a plastic housing. O well, miscommunication is a bitch. Have you tried a DC for the symptoms you are have? If everything checks out it may come down to a PCM.
Yes, I followed some DC's and it directed me towards fuel and ignition tests. I just finished the MAF ones and they checked out ok. Now I'm going to do the fuel tests tonight (fuel pressure, injector balance test, injector resistance tests). and if I have time I'll so some tests on the coils. One thing I forgot to mention is that I found a ford TSB stating that some pcms need to be reprogrammed due to hesistation when accelerating. I kind of pushed this to the side since the hesitation is pretty bad, but if everything else checks out, I might have to look into pcm programming options.
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