Are we NO for ignition?

[blacktail]

Hello,

I’ve been reading through some older threads, but wanted to make an inquiry.

06 expy, 180,000 miles. 2nd owner, always well maintained. Have put significant highway miles (~15k) towing ~5,000 lb trailer last few years.

Recently, I noticed what I initially thought was a small exhaust leak.

Popping sound when giving it gas, under load, at ~1500-2,500 rpm. Difficult to duplicate and isolate sound when not driving.

I considered a misfire, but it’s not throwing any codes or check engine light.

Had a mechanic look at it and he thought it was possibly a bad coil. He “power braked” it and was able to replicate the sound in the garage.

He recommended changing all the coils. Which, based on all the threads I’ve been reading, seems like overkill.

I would like to go ahead and get the plugs changed. Not sure if the original plugs were changed at 90 or 100k, but figure it’s about time.

I have had an issue previously years ago with one of the coil connections getting loose. At that time the engine light came on and the car went into limp mode. Played around with and cleaned the connections resolved the issue.

Owing to that experience I’m wondering if the “popping” sound is even related to ignition.

Definitely sounds like an issue with a single cylinder, but not loud enough to be an exhaust manifold leak.

Any thoughts are appreciated.

 

[whtbronco]

I really can't think of something specific to look for. That said I'd check the coil on plug connectors and the fuel injector connectors since you had an issue once before. Electrical cleaner makes it easy to clean them unless there is significant corrosion.

Even if your spark plugs were changed at 100k at 180k they are overdue in my opinion. 50-60k is the limit for me. The plugs are pretty cheap and with this ratchet they aren't bad to replace. The 2 on the passenger side rear are hard to get to without this ratchet.

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Amazing deals on this 3/8In Dr T-Bar With Flexible Ratchet at Harbor Freight. Quality tools & low prices.

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[ManUpOrShutUp]

Had a mechanic look at it and he thought it was possibly a bad coil. He “power braked” it and was able to replicate the sound in the garage.

He recommended changing all the coils. Which, based on all the threads I’ve been reading, seems like overkill.

Based on this alone, I'd find a new mechanic. He's throwing parts at the problem without having any idea what the problem actually is. While the coils do go bad on these trucks more than most vehicles, they're not a routine maintenance item and there's no reason to replace them if they're not bad. I've got nearly 211k on my truck and still the original coils.

 

[SafariGoneWrong]

I'll second whtbronco and ManUpOrShutUp's recommendations. In addition, with these engines and their age and you have an '06 3V (like me), it's so important to get powertrain data in real time or logged from the PCM. ForScan Lite runs on a pad or phone and works nicely with a bluetooth OBD adapter like OBDLink MX+. I'd be interested in your misfire count ("NM") especially. I use it a second set of "gauges" on the iPhone while driving, looking at parameters such as VVT operation (advance degrees, error, solenoid duty cycle), misfile count and a host of others. Back to your issue, is the popping an internal engine sound, or like a backfire through the intake or exhaust?

 

[blacktail]

Thank you whtbronco, ManUpOrShutUp and SafariGoneWrong for your insight. Agree with your concerns about the mechanic. This shop had recently done some work replacing the yoke and rear differential seal for me, but it was the first time I had used them.

I have always done my own tune-ups with other vehicles, but hearing about the spark plugs breaking has me intimidated to do that job. I have been running lucas oil or some other gas treatment in just about every tank to hopefully minimize carbon buildup. In anticipation of getting the plugs changed next week, I followed recommendations I have read to put a bottle of sea-foam in 1/4 of gas (~3oz/gal) and am driving that around for the next few days.

The one thing that gave me a bit of confidence in the mechanic was his explanation of the specific procedure he used for removing the plugs to minimize the chance of breakage, as well as what he would do in the event one broke (additional hour of labor).

SafariGoneWrong - The sound sounds like muffled back fire coming from under the vehicle. I can only hear it when driving with the radio off. I will be cruising along in OD at 30-40 mph, apply gas and I hear it when accelerating at ~1500-2500 rpm. Sound immediately goes away when not pressing on the accelerator.

I tried to replicate the sound in park with my 9yr old daughter keeping it at ~2000 rpm, as well as looking for any noticeable leaks in the exhaust manifold. Thankfully, the exhaust manifold seems fine and I had trouble even hearing the sound, let alone isolating it. Seems to only occur when accelerating under load.

Regarding your suggestion about the OBDLink MX+ and ForScan, will I be able to monitor misfires even if there are no codes showing? I did take the truck to the parts store and had them check for any codes - nada. If a program like ForScan would allow me to monitor misfires that don't initiate error codes, I would love to have something like that.

Thanks again!

 

[blacktail]

Update: Just tried to replicate the sound again in park. Started it cold, let it run for a minute, then gave it gas.

Engine won’t rev past ~2750 rpm. Starts to oscillate the tach. Have not noticed this before, but I drive it pretty gently.

 

[SafariGoneWrong]

Our ‘06s are rev limited to about 3K RPM in neutral and park. I see 0 or 1 misfires counted per drive, with the lone misfire happening on startup, best I can tell. Yes, you can see the misfire count in real time. I’m not sure if ForScan Lite can break it down by cylinder. I’ve never used the full ForScan software for computers, but know it has more capabilities.

 

[blacktail]

Thank you. That makes sense, as I have never had an issue getting the RPMs up on the highway.

I recall when I had the prior issue with the ignition connection, misfire and limp mode, the OBD scanner told me exactly which cylinder was having the issue. But, it was throwing multiple codes, limp mode and check engine light too...

Thanks for the ForScan rec. Looks like this chart breaks down the differences in functionality:

Comparison of FORScan applications

 

[blacktail]

I did some driving this evening with an OBDlink MX+ and Forscan lite running.

Recorded 5 misfires heading to the store. 1 on the return trip.

Recorded at 2750 rpm and 20% load.

I think the popping noise sound might be an exhaust manifold leak. It occurs at a rate matching rpms, but only when the engine is reading ~55-80% load. Sounds like a helicopter, if that makes sense, at 80% load.

I can’t replicate the sound in park or power braking, only in that high load range.

When I’ve had exhaust leaks in previous vehicles - you and the neighbors knew it. So I’m confused.

 

[GaryH]

What sounds like an exhaust leak could possibly one of the spark plugs worked a little loose and is getting ready to blow out of the engine. A known problem with the Gen 2 Expeditions.