A Few Issues With a 4.0L - Are they valid or am I going crazy?

I recently did a tune up on my 05 with 201k. New plugs, filters, oil and a thorough cleaning of the TB and MAF sensors with the proper cleaning fluids. The engine corrected itself after stalling a few times which I know is necessary for the system to re-calibrate itself now that the sensors have been cleaned.

Everything except the plugs went on at the same time. I recently serviced the plugs (3 days ago) with OEM ones gapped at ~.41-.43. After swapping the plugs I noticed a slight shake at idle when cold, mostly between 1000-1200rpm. This shake is also present as the engine warms into the 900-800rpm range. It isn't as apparent at operating temp but is still present. Anyways, I have also noticed what sounds to be an exhaust leak when I accelerate hard, at any temp.

I don't recall this vibration being there before and I don't recall this noise being there before. I can't exactly recall otherwise though. SO.... I think either I'm going crazy or there's something wrong here.

I made sure the gaps were correct and all plugs were torqued to 12lb-ft since I didn't want to push it with an HF wrench. There are no codes and the engine runs perfectly fine at highway speeds.

Please tell me I'm not crazy.

 

You can have cracked spark plugs and not ever know it (dropped during shipping etc), its hard to say if anything is really wrong but the only way to detect this is to use an OBD reader with a misfire counter.

I would double check for vacuum leaks and connections to ensure the work is good, but it's hard to say whats wrong if it only happens at specific conditions.

 

It’s a 13 year old truck, things get a little shaky. As for the exhaust leak? Defiantly get that checked out

 

Cracked spark plug.... hadn't thought about that.

I'd accept the shake on an old truck like this but it seems this shake is a recent development. That the problem.

I'm assuming any misfire would throw a code, am I wrong?

 

It should throw a P30x code where x = cylinder that is misfiring. I had a cracked plug last time I did mine, but I did have to run it for several minutes for it to throw the code. You said you did 12 lb/f, isn't the spec like 16 or something? Maybe you've got a plug that is not fully seated? That might account for a ticking sound and a bit of a shake to the motor and may not throw a code. That is just a guess.

The 4.0 has a lot of valve train noise. It may be something you are just now noticing.

 

I'll crank them up to spec today and see if that helps.

Maybe my sensitivity level has gotten a little high lately. I'm just not used to this truck doing ANYTHING out of the ordinary. 201k never looked so good.

 

If you used anti seize, I think 12 is about right??

 

I have the exact same issue. Have you found anything yet?

 

Typically the intake assembly is removed to clean the TB and replace the spark plugs. Could be an oversight, did you reconnect the small vacuum hose that goes behind the intake assembly facing the firewall after cleaning the TB and installing the spark plugs. That small vacuum hose can be easy to forget.

 

I see you have an '05 ...
... and you're positive that exhaust leak is at the manifold and not the head, yes?

I'm guessing you're aware of the '05 known head gasket issues

 

I had new manifolds installed on my ‘05. It couldn’t be that for mine at least, not sure about OP. I wasn’t aware of the head gasket issues but I do know that I will get an intermittent P0171 and P0174 code that means it’s running lean on both banks.

 

I definitely used anti seize. Cranking them up didn't help.

No progress to report.

All vacuums are nice and snug.

I can't imagine the truck would run so well with a head gasket issue of any kind. To my knowledge the truck has never overheated and the oil level is perfect. There shouldn't be a head gasket issue on this engine. I wasn't aware of the 05' gasket issues though.

 

I still tend to believe the problem is a loose vacuum hose. There are hoses on the drivers side that need to be disconnected, or may accidentally get knocked off when changing plugs. They may also appear to be in place unless you tug them. I've done this myself even knowing what I'm telling you.

 

Even if the vacuum lines are connected, they could’ve cracked or not be fitting as tightly due to age..

 

If one or more vacuum lines are the culprit, spray brake cleaner on all the suspect areas with the engine running. If the rpm's drop or stumble, you're found the leak.

 

I will tackle the vacuums as soon as I get home.

Vacuum leaks are pesky things aren't they. I thought by now they would have pressure sensors throughout to ensure proper vacuum operation.

 

I checked all my vaccumm lines, all are in good shape and are on properly... guess it can’t be my isssue

 

Brake cleaner or carburetor cleaner ? !!!
Do the intake manifold flange area also. Common area.

 

You mentioned “OEM” plugs. Copper core, platinum or irridiums? If you used precious metal plugs, gapping them is a no beuno.

 

Brake cleaner.