LQ1 didn't feel right

[Padgett]

ever since I bought it. Was OK with occasional misfire and I put the 12 mpg down to excessive idling. That said for me plugs are a part of routine maintenance and I had a bunch of Rapidfire #14s I use in 3800s with Delco ignitions  For that application I gap them at .060 (.045 #3s for Magnavox). The LQ1 has the same coils I use in the Reattae so gapped .060 also.

 

So using two screwdrivers as levers to raise the plug sheaths I find that the plugs seem to have been installed by a trunk monkey with an air gun. Took some tapping on a 18" breaker bar to get the front three loose but once loose they spun out clean. Put new ones in with a 3/8 ratchet and about 15 lb-ft torque.

 

1 & 5 look OK but #3 seems waaay too tight (see pic. ) Is less than .020. Plugs look almost new, just that one is misgapped (dropped ? No sign of hitting something.). Seems to idle a lot better. 

 

Which brings up the question of the back bank. Is there a way to change the rear plugs without removing the intake ? Seems like almost enough room to the firewall but not certain what angle the sheaths come out at. Is this possible ? Service manual seems to want you to remove the engine. Advice welcome.

 

ps a magnet on an extension is handy to fish plugs out when your 5/8 plug socket has lost its sponge.

 

[94 olds vert]

The rear plugs aren't that bad. Remove the weather stripping on the firewall. If needed remove the upper engine mount. (The one on the core support). That way you can rock the engine forward to get some more room back there.

[Psych0matt]

I always pull this back up every time I go to do the plugs. I can do all six plugs in probably about 10 minutes

 

DOHC rear plugs, easy solution

http://www.w-body.com/index.php?/topic/46639-DOHC-rear-plugs%2C-easy-solution

[94 olds vert]

I have slots in my firewall for a long extension. No need to do anything besides pull the FSTB and weather stripping.

[Padgett]

Think I'll try the pull dogbone/rock this time. Don't forget I needed a 18" breaker to get the front plugs out and expect I may need same to start the rears. I replace at about 15 lb-ft so all the extensions make sense if I do it again.

 

Rolling method is a little difficult when in a garage on a lift.

 

 

Does beat changing the clutch in a 70 Buick GS on a big oak tree root all to heck.

Edited March 12, 2016 by Padgett

[Psych0matt]

yeah, if they were that tight then that might be a better plan of action for now.

[rich_e777]

Someone forgot to put the anti-seize on the plugs when they put them in, also Rapidfires? Ive been told by several legit mechanics, GM mechanics, that those are junk. I seem to have the best luck with just the ACDelco platinum tipped plugs in my Cutlass and probably what I`ll use in the GTP unless it needs something else.

 

Something else that might help out with the hard to reach plugs is to cut the plug end off an old spark plug wire and use it to install/remove the loosened plugs, helps me out on my 3100. I don't envy doing the same on an LQ1, there is just no room in those bays.

[Schurkey]

Drops right into '91--'94 3.4L.  Have used it on '92 and '93.  Removing the weatherstrip helps.

 

No promises on '95-up.

 

"I" would be unlikely to use a .060 gap.  Until someone proves differently, I say that anything wider than .045 is wasted.  Worse, it provides excessive voltage stress to the secondary ignition system.  Leads to potential misfire under heavy-throttle conditions, or as the plugs wear and the voltage required goes up.  This MAY mean that you need to select different spark plugs, as the side electrode will almost certainly be taller for plugs intended to be gapped at .060 compared to plugs intended to be gapped at .045.

 

Anti-seize is handy on almost anything torqued into aluminum.  Some folks are concerned that anti-seize will screw-up the heat transfer from plug to head.  If you're worried about that (I'm not) you can buy Champion Spark Plug anti-seize p/n 2612.

http://www.amazon.com/gp/product/B01BN647VW?keywords=2612%20anti%20seize&qid=1457822866&ref_=sr_1_1&sr=8-1

 

I use plain ol' ordinary Loctite/Permatex Copper anti-seize.  I looked for an Amazon link, there's about a hundred, and the prices seem out-of-line.  I buy it at NAPA, but it should be available at nearly any automotive parts house.  I buy the 4-ounce brush-top tub.  4-oz lasts me years.

 

I have used other brands and types in the past.  I don't think it matters much WHAT kind of anti-seize you use, as long as you apply it carefully.

 

DO NOT OVER-TORQUE fasteners or spark plugs when used with anti-seize.  Lubricated threads do not need as much torque to be "tight".

 

Some spark plug brands are advertising an anti-seize plating directly on the plug shell.  This probably works  ONCE.  If you re-use the plug, you'll need replacement anti-seize.

[rich_e777]

Interesting about the gap, I know you guys are talking LQ1 here but would you still think the same for plugs in another engine like the 3100?

[Padgett]

My first LQ1 but have had quite a few 3800s and with the Delco ignition they like .060", is the factory spec but those are 5,000 rpm engines, for 7,000 it may want a tighter gap so could change to .045 which is the LQ1 spec for a R44LTSM (copper core). Anti-seize in an aluminum head is a good idea but these were not seized (threads in photo are clean) just way over torqued but once I got to move at all, they spun freely. Believe me I know what a seized plug in an Aluminum head feels like.

 

BTW a Rapidfire #14 is designed for .060", the #3 is the same plug designed for .045 (I use those with the lower power Magnivox system. Did a review a few years ago.

 

As mentioned have had good luck with 14s and have a few boxes so might as well try. Would go Iridium if I bought any. Appears to have Bosch platinum 6704s.

 

OTOH this is what AC Delco says:

 

 

[Padgett]

Got a plug socket with rubber insert and did the rear bank today. Took dogbone loose and rocked, then pulled weather strip. These were torqued properly so no problem removing. I used a long wobble extension and that helped.

 

Three more Boschs,  found five gapped .044 and one .015. Now have six Rapidfire #14 gapped .060 per Delco spec. & personal experience. Light schmear of anti-seize. Idles MUCH smoother and feels like more power/response. Pulls smoothly from 15 mph in third.

[Schurkey]

Interesting about the gap, I know you guys are talking LQ1 here but would you still think the same for plugs in another engine like the 3100?

I've seen GM specify gaps as large as .080.

 

I've also seen the damage that does to distributor caps, conducting buttons, and rotors.  What GM specifies is not what makes the engine run best, long-term.  Yes, I understand that the newer engines don't have distributor caps 'n' rotors.  They still have insulation that gets stressed.

 

Anything beyond .045 makes me unhappy, doubly-so in an engine that's expected to run hard.

[Padgett]

I hear you but as mentioned I've been running 3800s with Delco ignitions (if I get one with a Magnavox I upgrade immediately) with #14s & .060" gaps for over a decade and other than an occasional coil failure (I get the whole ignition: plate, screws, ICM, and coils from the recycling center) have not had a problem. See here.

 

You are correct I would not run this wide with points or a HEI but the LQ1 is a DIS system with AC Delco plug wires. I am a bit concerned about the ICM/Coils location under the header, may build a little air scoop

 

So going to give it a try and see how it feels. This is a different engine for me and in Fiero 2.8s I ran #1s at .045 since they have a distributer. But the Delco ignition here is the same design and coils as the 3800 one.

[rich_e777]

Posts like these are why I cannot possibly stay away from this site.

 

Looks like I`ll be doing a spark plug changing soon and I`ll re-gap to .045

[RobertISaar]

the plug gap you can get away with is essentially a function of how strong of an ignition system you're working with is and the cylinder pressure at the time of ignition(dynamic compression ratio, BMEP, whatever measurement you feel like using). I've worked on a few engines that run .080 gaps(I want to say an 84 oldsmobile 88 with a 5.0 was one of them), they run so little static compression and have such weak cams they don't have too much cylinder pressure to work against when they fire their plugs so far advanced of TDC(terrible chamber designs) that they kind of get away with it, at least for a while.

 

keep an engine away from its torque peak and you can get away with some fat gaps without stressing the secondary side of the coil. dropped sparks are hell on coils though, so should you notice an improvement near your peak torque RPM with a tighter gap, you should definitely be running that tighter gap regardless.

[Padgett]

Just for S&G, AC Delco recommends the same #14 and .060" gap for the L67 supercharged 3800. Am sure it would run fine with .045 but the place where a fat spark and a big gap makes a difference is in cruise at highway speeds when the mixture is lean. Also almost all of Florida is close to sea level & have no doubt Denver is different. YMMV.

 

That said I make the run down to south Florida quite often and can go 180 miles with a 70 mph limit and no stops (could go over 200 but I stop at Boynton). Just turn on the tunes, set the cruise, and go. Highest point is at the top of the Thomas B. Manuel bridge.

 

Just looked up the plugs for my 2012 Jeep and that calls for a .043-.045 gap. Since it is the closest to the LQ1 (3.6 liter DOHC 24 valve 6 cyl, 10.25:1 cr, 6500 redline - said I have a weakness for a good DOHC 6) the needs should be similar. Only difference is being OBD-II I can monitor misfires on my cell phone, for the GP I need to use an OTC 2000 with a 93 cartridge - suspect a 91 or 92 would also work but have a 93).

 

So if I feel any roughness under high speed load, I'll back them down to .045 but for now, .060 it is.

Edited March 14, 2016 by Padgett

[Padgett]

Just went to Lakeland and back, occasional hiccough but cruise at 70 was smooth. Turning 2425 rpm at 70 mph, under 2000 is best for economy. AC on MAX and about 5 miles of stop and go around Disney so guess 20.5 MPG average (filled at same pump) for 113 miles is not that bad.

 

Not sure what or if a thermostat is in there, travel out this morning coolant ran 170-174F, coming back with AC on 194-197F. Had a sound at idle when I got to Lakeland like a chain occasionally rattling, not there when I got home. May be first exercise the GTP has gotten in a few years.

[94 olds vert]

That's a normal trip for a 20 year old W-body.

[Padgett]

Except my 26 & 28 year old Reattae get more like 25 mpg on 87 PON but in OD/lockup the 3800s are turning 500 rpm less. Difference between a 3.67 rear gear and a 2.97.