misfire diagnosis and repair

[docraymund]

Good day ! Just want to ask if an engine misfire can be fixed without the use of code readers and how do you do it? Also can a faulty ignition switch cause misfire? Thanks.

 

[FordandPolaris]

It certainly can be done without a code reader, just keep replacing COP's and plugs until you solve the problem. That being said, it is much easier to get it read first. Most O'Reilly's and Autozones have a code reader they will let you borrow for 5 mins to go read them quick free of charge. Encourages you to buy the parts from them if you can find out exactly why the light is on. Many things can cause a miss, but I would definitely start with the COP and spark plug.

EDIT: I just read that you are in the Philippines, so I guess in that case you might not have the same parts shops like we do in the States. Still if you have an parts shop near you, I would still check with them if they have a code reader you can borrow.

 

[Thermo]

Doc, if you are suspecting a misfire, the first check I would do is to get your hands on a nice, bright flash light. Now, open the hood of your truck and look at the tops of each of the COPs (I am assuming that you don't have a 97-98 4.6L motor). Shine that flashlight on the clear tops of the COPs. Do you see a white line in any of the COPs. You see a white line, replace that COP. The ones you want to specifically look at are #3, #4 (the two on the passenger side, back by the firewall), and #7 (under the EGR tube, second from the back on the driver's side). These 3 seem to have 99% of the issues.

From there, like was said, you are going to end up pulling all the COPs out and doing a visual of the COPs. Also take a good look at all the boots running between the COP (black plastic piece) and the spark plug itself. Some members have found that these rubber boots break down over time and will start to get crumbly and the spark can actually jump through the rubber to the plug well, leading to the misfire. You should see a discoloration in the rubber where it has gotten a little warm, so, it will be a bit darker more than likely.

Like was mentioned, getting a code read is going to be much easier (assuming the CEL is on). If you look on places like E-bay and Amazon, you can pick up a code reader for under $50 that will work on your truck (I just picked up an ELM 327 for $15 that is bluetooth capable, then I downloaded a free app for my phone that I use to read codes on my truck and car). If you don't have a code, you can sometimes force one to come on by doing a long, hard acceleration (going 0-60 mph as fast as the truck will do it).

 

[khpony]

Doc another thing that you can try that might help is to raise the hood and watch the top of the cop's for intermitent sparks with it running. You need to do this while it's dark. Sometime a spark will show up and lead you to a specific cylinder.

 

[scraig314]

You can also check each COP with an ohm meter to make sure the resistance values are still consistent. Even if you don't know what the value is supposed to be you can single out which ones are not like the others and replace them.

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[Sasquatch]

Misfire

Hi. New to the site, but really like the threads. I have a 2000 4.6l 4x4 Exp. I began to have misfire problems about two years ago (approx 95k miles). Ran rough for a good amount of time before the engine light came on (code available)-turned out to be a coil. About a month later same thing with another coil, so I got frustrated and just replaced all coils and plugs. Ran well for about a year, and then same mis-fire condition. I bough a shop manual from LMC and used the specified Ohm reading ranges to test all the coils- turns out that #1 was slightly below the others-but within the specified ranges. I replaced this one with a good coil left over from previous swap outs and ran some Sea Foam through the motor-checkd all filters- cleaned MAF sensor and this worked for a while (few months) now it runs rough on acceleration.

The manual gives a trouble shooting checklist in sequence- its saying to check Throttle Position Sensor (TPS) and Exhaust Gas Recycler (EGR) sensor. I feel like Im chasing my tail...any suggestions? Acceleration is really rough on wet days and when engine is cold-seems to get better as operating temp comes up. Also, I've noticed a slight hiss coming from passenger side engine compartment-maybe an exhaust system leak?

Any input appreciated.

 

[scraig314]

Acceleration issue could be a bad fuel filter/bad fuel or maybe clogged injectors. Hissing could be vaccum tube or booster line. Just a guess.

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[FordandPolaris]

As far as the hissing goes, look to see if any of the studs that holds the manifold to the head are broke. Also same goes for the studs that hold the cats to the manifold. I am guessing it no longer gives any codes? I would start with the fuel filter as was mentioned, just cause that is fairly cheap and easy to replace. From there check vacuum lines etc. There is an elbow on the back of the throttle body that likes to throw a lean code (P0171 or P0174) and cause a rough idle, but I never had a problem with acceleration when I had this go bad. If it feels like a misfire, then I would also consider pulling each of the plugs and checking for cracks in the porcelain etc. Sometimes the truck misfires without throwing a code.

 

[docraymund]

Thank you very much for your inputs. I will certainly try all your suggestions and will give a feedback. I only use this once or twice a month and the other day after driving for about 10 kilometers it suddenly hesitated and barely ran at all I managed to bring it home and noticed that the ignition key temporarily got stuck in the acc position. I tried to restart it and it started again and the hesitation disappeared. I dared not to drive it again cause it might appear again. It starts fine everytime but with a mild misfire at low rpm. It has a previous problem of battery drain which I was not able to resolve yet I just disconnect the neg bat terminal and reconnect it again if i will use the truck. Thanks again and I hope I can fix this labor here is high especially if it's a ford expy!

 

[BANGEREXPO76]

1st Change all spark plugs and all coils.
This just solved my misfire issssue.
I have changed all 8 coilpacks and plugs twice since I have owned the truck and thats about 5 years now. Just did the second change last week after having a misfire on my #8cyl. The plugs were all pretty shot. Now the truck is running extremely well. I dont trust the change one coil here or there thing especially without changing the plug that goes with it. Your probably going to end up having to change them anyways. So my advice is to get them all fresh and go from there. Good luck!

 

[toms89]

Hi. New to the site, but really like the threads. I have a 2000 4.6l 4x4 Exp. I began to have misfire problems about two years ago (approx 95k miles). Ran rough for a good amount of time before the engine light came on (code available)-turned out to be a coil. About a month later same thing with another coil, so I got frustrated and just replaced all coils and plugs. Ran well for about a year, and then same mis-fire condition. I bough a shop manual from LMC and used the specified Ohm reading ranges to test all the coils- turns out that #1 was slightly below the others-but within the specified ranges. I replaced this one with a good coil left over from previous swap outs and ran some Sea Foam through the motor-checkd all filters- cleaned MAF sensor and this worked for a while (few months) now it runs rough on acceleration.

The manual gives a trouble shooting checklist in sequence- its saying to check Throttle Position Sensor (TPS) and Exhaust Gas Recycler (EGR) sensor. I feel like Im chasing my tail...any suggestions? Acceleration is really rough on wet days and when engine is cold-seems to get better as operating temp comes up. Also, I've noticed a slight hiss coming from passenger side engine compartment-maybe an exhaust system leak?

Any input appreciated.

I would associate hiss with a vacuum leak. The common exhaust leak that expys experience is at the manifold due to rusted and broken studs and it makes a ticking sound due to you hearing individual cylinder firing. It is possible you have an exhaust leak from the collector back but not as common and generally has a pulsating sound.

Note that the a/c can also make a hissing sound. Turn it off when your trying to diagnose.

 

[scraig314]

I had the same issue with misfire again and this time it was finally solved. Turns out I needed a reprogram from the ford dealer with the most recent updates. Drive much different/better than before. And it didn't cost much at all.

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[toms89]

I had the same issue with misfire again and this time it was finally solved. Turns out I needed a reprogram from the ford dealer with the most recent updates. Drive much different/better than before. And it didn't cost much at all.

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Just for reference. What year expy do you have?

 

[scraig314]

2006


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[tjenkse]

Check the PCV valve and hoses. In these Expys the hose has rubber elbows that can rot and leak causing the engine to run rough. Just an idea.

 

[Sasquatch]

Thank you for the advice. I'm going to take a shot at it this weekend. I've been contemplating doing some other things to the truck-I'm the original owner, and I swore that I would never get rid of this truck. Another post for another time I guess.

 

[omegalita]

And why you don't wanna read the codes? It's so easy... Software is for free in the net, all you need is a OBD/USB cable to your laptop...

 

[Sasquatch]

What brand of coils have you guys bought for your replacements-and where did you find good pricing? The first time that I did the swap out, I was under the gun for time-couldn't wait on mail order, and I bought whatever was available from Auto Zone. Not so sure the quality was the best.

 

[Sasquatch]

As for the codes, I was told that until the check engine or service engine light comes on, the codes have not been recorded and cant be read....Is this correct? That was one of my frustrations-putting up with the rough running until the engine actually threw a code.

 

[Sasquatch]

Hey Tom, Thanks for the info. I just had the chance to watch the you tube video of your Exp.- that was awesome. I'm the original owner of my 2000. I bought it at the end of 2000,when I was working as a pilot in the aviation business, and life was good. Well after 9/11 things got tough for a while and I left aviation to start my own general contracting business. I swore that I would never get rid of that vehicle for the sentimental reasons of it being with me through the tough times. My thought is that I'd like to keep it looking fairly "stock" but do some really cool things with the engine/suspension. My problem is that I dont know what options I have- do i want to work with the original block and make mods from there? Do I buy a block? Do I keep the air suspension and make mods to it (I know about the nightmares that people have had with it, but mine has served me well)?

Being new to the site, finding past articles, "stickys", etc.. is a little challenging. Can you point me in the right direction? Any advice in general is appreciated.