Bad Injector - Perhaps??

[oldmako]

Genamins,

After one year and 19,000 miles of blissful and sublime driving my Q laid a turd in the punchbowl last night. I was hoping that some of you motorheads could assist me with the diagnosis and rectification of it's horrible malady.

The symptoms;

Big honkin constant, steady misfire. It's especially noticeable at idle and under acceleration. Associated along with it is a fairly high pitched fluttering noise with the same frequency as the mis. This is only audible at slow speeds. There is also a fairly strong odor of fuel when I come to a stop light. I'm thinkin an injector crapped out, and with the fuel odor it will be fairly easy to diagnose....but I am often full of it.

It happened at the conclusion of a long 80 mph highway jaunt. Fortunately it was only a few miles from my domo so I was able to slow and limp home. It was 3AM and I lifted the hood but there was nothing obvious given the limited area of vis.

I'll start with removal of the ornate gizmo and OHMing the injectors. And of course, the search. Any words of experience, wisdom or sharp barbs of criticism welcome.

Gimpy.

[qship96]

More likely to be failed coil pack,prohibiting spark plug from firing......resulting in unburned fuel smell and other symptoms you described.

[maxnix]

3 AM? I'm telling Mommy!

Without recent maintenance history and condition narrative, going to be difficult to diagnose. Back firing is something I don't recall on a VH41DE.

[goody90q45]

I'll start with removal of the ornate gizmo and OHMing the injectors. And of course, the search. Any words of experience, wisdom or sharp barbs of criticism welcome.Gimpy.

Bring a pencil.

[qship96]

You mention "flutering noise", like the sound of air leaking from a loose sparkplug maybe? that would also result in misfire and the fuel smell.

[maxnix]

You mention "flutering noise", like the sound of air leaking from a loose sparkplug maybe? that would also result in misfire and the fuel smell.

A recent plug change would be worthwhile information.

[oldmako]

Hopefully, it's just a bad coil pack. I'd much rather mess with them than the injectors. Too many threads regarding too many problems with those pesky little bastards! I suspect that it would be much easier to diagnose as well. I am told that non-eth fuel has been used here for most of the last year due to the area meeting anti-pollution targets. That might help rule out FI issues...but at 140K, I suppose that nothing can be ruled out.

As far as maint, I bought the car this time last year. At that time I replaced the plugs and reused the original coils. I used a TQ wrench, so I'd be surprised if a plug wiggled loose. Beyond a new air filter, cleaning the MAF and intake path and cleaning connectors nothing has been done under the hood. Given the coil over design, it would surprise me if the plug could get loose enough to allow it to make the fluttering noise. But, that's not to say that it's not the culprit. It would make sense that one would smell unburned fuel in this case as well.

I have had plugs come loose over the years on a variety of cars, from Detroit V8's to VW 4 bangers and yes, the noise is similar. My boat's 351 is notorious for it.

I have yet to restart the car. I am worried about the possibility of hydrolock if it is an injector problem. Is this an unfounded concern? Because if it is, having the engine at idle would facilitate identifying the problem. I have yet to finish my am coffee, nor have I had my AM constitutional. Consequently the big plastic gizmo is still in place. In fact, I haven't even ventured out as yet. It's a bit cold for beer, and I am out of vodka for bloodies. A run to the ABC establishment may be in order. Oh yeah, and the search.

Did I mention that the old gal easily hit 120 the other day?? Still pulling like a mofo when my lower extremities shriveled up and headed north.

[maxnix]

I don't know how a coilpack could cause a misfire, but I am not an authority.

I would revisit those connections and the MAF operation thoroughly.

MAF cleaning is highly over rated and seldom required unless air filter change interval is greatly abused or 3rd party filter like K&N is employed.
Modified by maxnix at 2:12 PM 11/29/2008

[Q451990]

Injector failure seems to be pretty rare from '97 forward, while coil pack failure is pretty common on the '97-'01. If you are concerned about hydrolocking, I would think in terms of pulling all of the plugs and coil packs to see if you can identify anything that way first.

Good luck!

Heath

[oldmako]

Modified by oldmako at 2:51 PM 11/29/2008

[maxnix]

My local Infin parts place is closed today, so I will call IOS on Monday and order one of each.

NOOOO!!!!! Call today or go online with the code to get the additional 10% discount for November.

http://www.infinitipartsusa.com

[oldmako]

OK Sportsfans, here's the scoop,

I fired the mother up and the problem was obvious (once the shield and intake were out of the way).

Either the plug (second one aft, left side) was insufficiently tightened when I replaced it, or it was a defective plug. In either case, it was in pieces. The outer tip of the plug was MIA. The hot gas had consumed the coil connector, and the contact end of the coil. I will try and post some pics later.

So, one new coil, connector, and plug and I'll be back on the road. My local Infin parts place is closed today, so I will call IOS on Monday and order one of each.

While I was at it, I removed the other 7 coils and checked the TQ on the remaining plugs. All were tight. I am leaning toward a bum plug because as I mentioned earlier I had used a TQ wrench upon initial installation.

The good news is that I will be back on the road for less than two hours work and 200 bucks. I have a lot of driving to do in December and I am very glad that it wasn't something more serious and/or costly.

As usual, thanks for the suggestions.

[oldmako]

OK....ordered online. Any idea if the connector between the coil and plug is included with the new coil? The site wasn't clear and I obviously need that as well.

Fleecy Navaids.

[maxnix]

No, the connector is separate, or more likely, included with the subharness. Junkyard unit might work.

Use a thin film of high temp anti seize lubricant on the sparkplug threads.

[Q451990]

If by coil and "plug" you mean coil and sparkplug (as I suspect), you should be fine. If you mean coil and plug, as in subharness, then no...

Heath

[sdkhalsa]

I just had an incident on my 94 Q(120K) where it chugged down about five gallons of fuel in less than ten miles. Upon doing a fuel pressure check(i.e. holding no pressure), I discovered that the tip on one of the injectors had come apart. This injector was about one year old. The moral of the story is that if you have a serious miss on one of the cylinders, I would pressurize the fuel system with a tee'd-in fuel pressure gauge and see if the system is holding it's pressure. In fact, this would be a good test to perform frequently and part of standard maintenance. In my experience, I have had more trouble with failed o-rings that injectors.

[Mint Q45A]

Out of curiosity: What kind of plugs did you use when you replaced them?

[oldmako]

The factory spec OEM NGKs. I don't remember the number......PFG 7s or something???

Hopefully the parts will arrive soon and I can get it back on the road. Road trips in my old pick-up just aren't the same.

I am worried that the plug port will have been compromised by the blow by during combustion. The plug I removed has a fairly significant carbon build up at it's base. I am concerned that the same will be found in the heads threads.

Zeds dead baby, Zeds dead.

[maxnix]

Run a little BG44K or Redline SL-1 through then change your oil.

High temperature anti-seize lubrication on the threads.