Not a mechanic so please bear with me on this. Noticed a couple of things have cropped up recently on my '02 SuperCrew (5.4L V8) with @103K miles.

First, it seems like it has started "missing" when driving at @55 MPH, especially up a hill. It's not a bad miss, but you can feel it. If I accelerate, it goes away until I go back to 55 or so and keep it steady there. Then it misses again. Doesn't happen all the time though. Not sure what could cause that? Does it sound like possible fuel injection needs cleaned or ?? Likely many possibilities I guess.

Second, it sound like I may have just developed an exhaust leak. When the truck is idling I don't hear it, but if I accelerate it sounds like air is leaking from somewhere. Assuming it the exhaust. Checked what I can ssee from under the truck and nothing is obvious. The exhaust is the original unit with no mods. It's quite rusty at this point. Noticed that at least one of the bolts that attaches the metal shield (assuming that's not the manifold ....) on the exhaust and the engine is broken. Talked to Midas on the phone and they are saying that is it possible that the manifolds, the Y-joint, the catalytic converter, muffler, etc all needs replacing but they need to take a look first. Sounded based on numbers he through out on the phone, that could be a $3K bill? Can somebody give a quick rundown on what I could be looking at so I can keep them honest? Want to make sure I do the right thing and probably keep it stock.

Thanks, David

 

1. The missing is most likely spark plugs, possibly one or more coils. At 103k the spark plugs are due. Have you been keeping up with the recommended maintenance schedule?

2. Talking on the phone or posting in a forum won't get you a good diagnosis, you need to take the truck to a good shop. I wouldn't go to Midas, I'd find a good independent shop that has a good reputation.

 

I agree with glc. Probably time for plugs and might be coil time but you could also have a vacuum leak. Pretty common issue and tends to diagnose very similar to what you are describing. You can get a decent scanner and watch a bunch of YT videos if you want to learn to diagnose and fix it or find a reputable shop.

I spent 1200 on a true dual cat back stainless exhaust with flowmasters and H pipe installed last year. So 3k ish with cats and manifolds doesn't sound unreasonable to me. Stainless might be a good idea too if you are in an area that gets salted every winter. Going to be more money but will last longer.

 

Thanks guys. I will check on the plugs and wires, think I replaced those at @90K miles. Will check coils too. The vacuum leak idea is interesting, need to look at that as well.

Thanks, David

 

There are no wires, there's a coil on top of each plug.

 

Ahhh, thanks, guess I might have figured that one out after lifting the hood again.... Told you I was not a mechanic. So do you typically just replace all the coils at once or only those needing it? And while the plugs may have been replaced within the last 20K miles, does it make to replace each one that has a coil getting replaced?

R/ D

 

Do you know what brand plugs were used?

If you are not a mechanic, I'd seriously consider taking the truck in to a good one.

 

Not sure on the plugs. As for the mechanic, thinking the same thing. Just don't trust the quality and $$ for local businesses around me. However, there is a mechanic about 1.5 hours away that a number of people swear by (not at). Thinking of getting my truck to him and leaving it for a week for him to give it a once-over and see what all needs work.

Thanks

 

In your initial post you gave a good hint on the misfire issue as being felt at 55 mph +/-.
There is very often a reason for it showing up at those speeds.
It involves being in Over Drive at which time the EGR is called into operation.
Under these specific conditions, the engine is forced to run in a Lean condition.
If one cylinder has a faulty coil with low output it does not fire reliably hence the misfire.
There is no code set for this type of fault.
Your shop needs to use a Scanner to look at Mode 6, test 53.
This is a look at the misfire totals for each cylinder.
Any cylinder with a high counts out of limits should have that cylinder's coil as a suspect for replacement.
The reason is the coil is not a hard fault but has shorted turns and low spark output.
This fault does not set a code or the check engine light.
Good luck.

 

Looks like I do have multiple issues, excuse the way I have called them out, some might not follow very well, problem #1, #2, etc.

The exhaust manifold gasket (problem #1) is in-fact leaking. Heard this is/was quite common. Have a mechanic repairing that now, not cheap for sure. Once that is done, need to figure out the rest. From getting underneath with 2 different mechanics both are recommending new coils and plugs (problem #2) along with a new head gasket (mine is leaking, so problem #3). While they fix that the engine manifold gaskets will get replaced as well. Also going to have the trans serviced, both told me that the missing problem (problem #2) could be the coils/plugs but could very likely be the torque convertor. They both stated that it possible that the trans could be drained and filter replaced along with new fluid that can help with this problem .... possibly. We'll see on that one. Then there is another found problem which I kinda expected. The brake hoses need replaced along with the calipers probably (problem #4). All of this looks to be in the $3 - $4K range which is almost what the truck is worth. But damn, don't want to buy a new/used truck either.

Thanks

 

Sounds like a lot of money. Learning how to work on your vehicles saves you a crap load of money. If they are going to do the head gasket they need to do both. While it's blown apart they address the other issues. I personally never heard of a trans doing that, Bluegrass has a ridiculous amount of knowledge and would know.

 

I changed my exhaust from a y pipe to true duals when my tip rusted so bad it fell off. I got all new piping and used the original cats because the shop said it wasn't bad and would recommend not messing with it unless the check engine light came on for it. Anyways it ran me 530 after tax on the parts with the installation service and I got flowmaster 40 series mufflers which has a great sound.