roadie13

Dear all,

Today, on the return leg of a 500 mile trip, my car started hesitating and misfiring, usually at revs around 3k and with very light maintenance cruising throttle. In that situation pressing gently on the throttle then resulted in fairly heavy misfiring; the misfiring was much less noticeable or gone at higher revs, or with more throttle pedal. I had my Foxwell scanner with me and found that it misfired mostly on cylinder 1.

My first thought was that something had gone wrong in cylinder 1 during my recent change of all plugs & coils, but after a while the misfires spread seemingly randomly to other cylinders on both banks, though cylinder 1 remained the main culprit. This was very intermittent, ie 10 minutes of cruising and then 30 seconds of misfiring.

The last few miles were stop and go city traffic, and then it got really bad at idle, with the car struggling and check engine light coming on. As I pulled into our parking lot the car was idling smoothly again, but I doubt it will last.

So, does this collection of odd symptoms suggest a specific failure mode?

Any pointers greatly welcome...thanks!

workhurts

Dunno but my first thought is if there was something off with cylinder 1 causing a misfire and engine vibration then all the other symptoms are probably a domino effect. Hopefully something as simple as a coil not being seated properly.

roadie13

Thanks!

rileyracing1

Plug her in and see what codes come up . Most likely a coil going south .

yelcab

That is always the first step. See what the car is saying.

roadie13

The only codes it throws are misfire codes on various cylinders.

ShaunP

Coil pack going bad

roadie13

So I only had time for some quick non-invasive diagnostics this evening.

1. Started the engine, let it go through cold start cycle, drive around the block, misfires, coughs, check engine light, mostly cylinder one. So no mystery healing overnight.
2. Tightened all the clamps from air box to throttle body to eliminate simple air leaks; no change.
3. Opened oil cap whilst idling, engine coughs and stutters, which is ok.
3. Unplugged MAF and started the engine, running roughly but no misfires counted by the Foxwell scanner! So unless unplugging the MAF somehow stopped the misfire counting algorithm this might be something. I might just replace the MAF anyways, as it's probably due after 50k miles.

Question: can one drive any distance with MAF unplugged or is this going to break something else?

Thanks!

roadie13

So turns out it was not the MAF.

Rather, the noob (ie, me) who recently changed the coils and plugs left the electronic connection on cylinder 1 slightly insecure. Rattled itself loose after 600 miles plus two track days at Watkins Glen, and that’s what caused the misfires.

Now connection firmly pushed in runs normal again, knock on wood!

Btw, the MAF looked brand new after 18 years and 50k miles.

workhurts

Yep, gotta hear it click.