Misfiring 2006 LGT; fix

[Squib308]

I have a 2006 LGT with about 120k miles on it. I bought it with about 108k mi, and it spun a bearing in the first 2k miles. I had a guy (sp?) rebuild the motor with a new EJ257 short block. I put a cat-less stainless up-pipe on it almost directly after the rebuild. Recently, I put a downpipe on the car, and took it to Dave/Cryotune in Denver for a tune. Too many misfires.

 

I thought the car shook because its motor mounts were shot, but not so. I was getting a lot of misfires in cyl 1 & 4. He (dave) pulled the spark plugs, which were the wrong ones - they had a 0.04x gap. Apparently Keith put in the wrong plugs. Dave put in new, properly gapped plugs, and that HELPED, but didn't eliminate the misfires.

 

Couldn't tune it that day with so many misfires. Ppbt.

 

I was thinking it was a loose coil pack contact, since the problem got BETTER, but not all the way better with a smaller gap. The cyl 4 misfire went away almost completely with the correctly gapped plugs, but the cyl 1 misfire was still present.

 

Swapped the 1 & 3 coil packs. Seemed to run better for a day, but the misfire was back the next day. It was an intermittent problem, BTW. So no dice with the coil packs.

 

I pulled the 1 & 3 injectors, they were obviously dirty on the sides of the tips, but looked clean where the atomizer holes were. I had them off the car, so I dropped them in an ultrasonic cleaner (cheapo harbor freight one, low power) for about 4 hours, with simple green and 409 as a solvent. Popped the filters off the side, as well.

 

I then used a rubber hose, that would slip over the tip of the injector, filled the hose with carb cleaner a number of times, and backflushed the injectors while activating the solenoid with a 5 volt power source, and 20psi from the compressor. Did that a few times, and stuck them back in the ultrasonic cleaner for a bit.

 

Blew the cleaning fluid out of the injectors with the compressor, put the o-rings back on, lubed them up, and popped them back in.

 

Car ran pretty rough for the first few minutes, dunno why, but smoothed out, and was not getting misfires on cyl 1 anymore.

 

Decided that it would be a good idea to keep things symmetrical, and clean cyl 2 & 4 injectors the same way.

 

Did that, and now I get maybe 1 misfire in about 30-60 minutes of driving.

 

No more shaking at idle at a stoplight, all smoothed out.

 

Problem, and fix. Prior to pulling the injectors, I ran a couple bottles of injector cleaner through the engine, with no apparent variation in the misfire rate.

 

Dave/Cryotune DID do a smoke test to ensure that there were no vacuum leaks or boost leaks, so I was 99.99% confident that the problem was not vacuum related. I was 95% confident it wasn't a mechanical problem, since the engine was just rebuilt.... I would have been more confident if Keith had put the right plugs in the motor after he rebuilt it, but whatever.

 

For what it's worth, your mileage may vary.

 

I also made an injector pulling tool from an old coat hanger. If you are doing this procedure, you will understand. I read one write up where the author had used a shop towel wrapped around the jaws of his pliers to pull the injectors... That didn't seem like it would work very well for me, so I made the U-with-prongs shaped puller tool, to make sure I didn't screw up the plastic on the injectors. I had to pull pretty hard to get them out, I don't think the pliers method would have worked, at the very least, I would have probably screwed up the top of the injectors. I had to pull pretty damn hard. Because of the things in the way of the injectors, I also tied a piece of cord to a dowel, that pulled on the end of the coat hanger turned injector-puller tool - this gave me a better handle (literally) to pull the injector with.

[Squib308]

I was not getting a CEL or any codes, BTW - apparently you need over 30-40 misfires in some (?) amount of time to trigger the CEL or a code. You could see the misfires with a OBD2 cable & some logging software (either romraider or btssm). I was getting a count of 7-16 misfires on cyl 1, and a handful on cyl 4. But the engine would shake at idle at a stoplight or in the garage.

 

I sure am glad it wasn't a mechanical problem. :o

[StkmltS]

I've been battling misfires for a couple years and you definitely spent more time cleaning your injectors than I did. I have the same HF ultrasonic cleaner you mentioned so I may try cleaning my injectors (again) like you did, although I think my problem is coming from somewhere else.

 

Did you really have them in there for 4 hours?

Do you remember the water/solvent ratio you used?

 

Sent from inner space.

[hero2zero]

But the engine would shake at idle at a stoplight or in the garage.

 

I had exactly the same symptoms that eventually triggered a CEL (P030X). Once I determined it was a fuel injector, I sent them off to be reconditioned. However, that did not work for me. I eventually had to purchase a new replacement injector. After that, engine idle smoothed out and no misfiring.

[Squib308]

Did I REALLY do 4 hours in the ultrasonic cleaner? Heck yeah! I figured it was like, 1/5 of the power of the more expensive ultrasonic cleaner, so it needed more time. Is that true? I dunno, but I figured it couldn't hurt at this point. What I did to make the cleaner run continually, was put a mouse mat over the opened lid, so I could get a C-clamp to stay in place (rubber - better traction) holding the 'on' button down. Then I just plugged and unplugged the power cord to turn it off and on. Not an ideal method, the C-clamp slipped off a couple times when I moved the unit, but worked well enough to keep the unit on for a long time.

 

I used about 50% simple green cleaner, and about 50% 409. I figure that 409 is dilute enough anyway, and must be cut with water, so that's what I mean when I say a water/solvent bath. After running it for about 2 hours with the solvent, I took the injectors out, blew them out backwards with the filter off with compressed air, a 5 volt power supply (old phone charger or something) & a momentary switch, and part of a hose filled with carb cleaner. The hose was 3/8" diameter, and was flexible enough to slip over the tip of the injector, and the metal ring that holds the small O-ring on.

 

Backflush with carb cleaner in the black hose with about 20psi of compressor air (I just sprayed carb cleaner in the hose until it was full) a couple of times for each injector, then back into the ultrasonic cleaner for another couple hours. A couple more flushes with carb cleaner... Another half hour with just water in the bath - figured I should make sure there was no solvent left over in the injectors. I blew them dry with the compressor, too, used the air gun attachment to blow backwards through the injector (with the solenoid on), through the holes, got them totally dry.

 

I did this twice, once for each pair of injectors, so I guess 8 of ultrasonic bath total. I don't know if you can say 2 hours per injector in the bath, I don't know if that matters. Maybe I could have put all 4 in at once? I don't know if the cleaning energy gets divided up like that.

 

It could be that the carb cleaner was the trick, it could have been the ultrasonic bath, I didn't do a controlled test one way and the other. Maybe it was the relatively high pressure carb cleaner going through the atomizer holes?

 

It worked, but only because my injectors were apparently dirty. If you have a different problem, it probably wouldn't help. My problem was intermittent, sometimes it would shake at idle, sometimes it wouldn't. 'Injector cleaner' as in the type you add to your gas tank didn't help a bit.

 

Dave/Cryotune did the smoke test & inspected for vacuum/boost leaks, so that was 99% probably not the problem. New plugs with the right gap, so probably not the problem.

 

I popped the filters off & left them in the bath for the time the injectors were in it, FWIW. Also rinsed & dried them off before reassembling the injectors.

 

I would NOT try carb cleaner in the ultrasonic bath, the bath got pretty warm (hot even) by the end of the process, and I suspect the acetone in the carb cleaner would have eaten away the plastic on the ultrasonic cleaner. I had a few times where the hose blew off of the injector (there wasn't anything to secure it except the elasticity of the rubber hose) and sprayed carb cleaner everywhere, which melted various plastic things around my work bench.

 

hope this helps. Pics of one pair of injectors straight out of the car; the old power adapter I adapted to turn on the solenoid, with momentary switch; the rubber hose and blow gun attachment I used to backflush with carb cleaner.

[Squib308]

Also, my symptoms appear to occur under light load, like idle, or revving the engine in neutral, but not as much under load. Could also be the computer/sensor was simply unable to sense misfires at load, or maybe just the low duty cycle was atomizing the fuel poorly.

[Squib308]

In retrospect, I was lucky that this method worked for me - If it hadn't, I would have gone down the road of compression testing, leak down testing, etc, and it would have taken me some time to come back to injectors. I wasn't sure if this method would work at all, and I called a bunch of local shops (fort collins, colorado) to see if they did bench cleaning and flow testing, and no, no one locally does that sort of thing. All the shops that offer 'injector cleaning and rehab' do the on-the-car method, where they disconnect your fuel pump, and run concentrated injector cleaner through the fuel rails and whatnot. I could have still had one or more injectors that were plugged with gunk & not known it, had I gone that route. My way wasn't any better, but at least it was off the car, and if they hadn't flowed backwards, like, at all, I would have known.

[Crawlerado]

Hello former Six Star Car customer!

 

Did Dave say why the plugs I installed were wrong? Or was it just the gap?

 

I no longer have access to that information but I assume they were either 7913s or maybe 2309s.

 

They come gapped around 30. Some builders knock them down to 28. I find it very hard to believe they were over 40.

[Squib308]

I didn't verify the gap, but he said (and I am looking at) NGK LFR6AIX-11 plugs which have the larger gap... Something to do with the part numbers being the same as the ones with the correct gap? The rate of misfires went down with new plugs, but wasn't eliminated.. The problem was with the injectors.

[Max Capacity]

Have you check the ground wires yet ? make sure they are all clean.

[Squib308]

.42 is what i measured

(after ~10k miles on plugs)

 

I would check the ground wires if cleaning the injectors did not help, but it did, so problem solved.

[Crawlerado]

I'm happy you got it resolved regardless.

 

A word of advice, be careful when using an individual's full name when posting.

 

I'm sure you wouldn't want a snarky forum post popping up in a Google search of your name.

 

All the best! KP

[Squib308]

I should be so famous anyone would write about me! Let alone search for me on the google! Or maybe it's easier to search than write, I dunno. Either way...

 

I talked to a couple of mechanics, one said 'talk to the guy that rebuilt your engine', which, I couldn't find the guy's contact info, and apparently he'd moved out of state. Another mechanic said that if there weren't vacuum leaks, I should start looking for mechanical issues, even if the engine was just rebuilt. All I have is confidence that even if things are acting up, that the basics are correct..

 

Fortunately, it was dirty injectors. How they got that dirty is another issue, I dunno, maybe bad PCV? Previous owner thrashed the car, rebuilt the engine (poorly), who knows, they pulled parts off of another car to rebuild it, maybe they pulled injectors from a much higher mileage engine, too.

[StkmltS]

I should be so famous anyone would write about me! Let alone search for me on the google! Or maybe it's easier to search than write, I dunno. Either way...

 

I'm pretty sure he was (politely) asking you to consider editing your original post to remove his last name.

[Squib308]

Ahh... Well, I suppose I have to make allowances for people with different life experiences. I interpreted that completely differently.

[Squib308]

Update - about 2 weeks has gone by with the cleaned injectors, a tank or two of gas, still almost no misfires. By 'almost no' I mean every few trips I will see a misfire on one of the cylinders driving around town. I don't know if that's exactly perfect, maybe it's par for the course, maybe not. Shakes are still gone. Looking good. Feeling good, I guess would be a more accurate description.