Just be aware that I got that number from strangers on the net and I myself took it for a brief 15 minute spin so far, so I don't know how it'll be in the long term. It did well at both low RPM and redline, no misfires or any sign of trouble so far. Apparently anything in the range of .030 to .035 is working good for people with both engines. I just chose my number because it was in the middle of the recommended range and I want to stay somewhat on the safer side.
Spark Plug Gap
- Thread starter Larry
- Start date
Just be aware that I got that number from strangers on the net and I myself took it for a brief 15 minute spin so far, so I don't know how it'll be in the long term. It did well at both low RPM and redline, no misfires or any sign of trouble so far. Apparently anything in the range of .030 to .035 is working good for people with both engines. I just chose my number because it was in the middle of the recommended range and I want to stay somewhat on the safer side.
So I checked this morning.
Hello everyone,
For the record, I take it with a grain of salt that a minor change in the gap of a plug will aid drivability or will yield better fuel mileage. I posted elsewhere on the site about shaking when the car is stopped at a light. I just got the car back from the dealer, and while they are very nice, unfortunately whatever they did failed to correct this issue. So I continued to read. Spark plugs! HUM, really, what the hell, give it a shot.
So this morning I pulled them. Yes, the gap was off on all of them. One was much worse then the rest. I also found that one of the springs inside the plug boots was ****ed to the side and did not seem as if it was going to make contact with the top of the plug. No sweat, little screwdriver and the spring snapped back. Gapped all of the plugs to .028 as shown in the book.
What do you know, the idle shake went away. Tried as hard as I could to force it to shake, NOTHING. Fifteen minutes of work and done. I am driving around all day today so I will be keeping an eye on it. As for better shifting and better mileage. I am not too hopeful this will do anything. Time will tell.
Ed
Hello everyone,
For the record, I take it with a grain of salt that a minor change in the gap of a plug will aid drivability or will yield better fuel mileage. I posted elsewhere on the site about shaking when the car is stopped at a light. I just got the car back from the dealer, and while they are very nice, unfortunately whatever they did failed to correct this issue. So I continued to read. Spark plugs! HUM, really, what the hell, give it a shot.
So this morning I pulled them. Yes, the gap was off on all of them. One was much worse then the rest. I also found that one of the springs inside the plug boots was ****ed to the side and did not seem as if it was going to make contact with the top of the plug. No sweat, little screwdriver and the spring snapped back. Gapped all of the plugs to .028 as shown in the book.
What do you know, the idle shake went away. Tried as hard as I could to force it to shake, NOTHING. Fifteen minutes of work and done. I am driving around all day today so I will be keeping an eye on it. As for better shifting and better mileage. I am not too hopeful this will do anything. Time will tell.
Ed
CoHPhasor
Active member
It'll work wonders my friend.
By changing plug gap you essentially change the timing.
It doesn't seem like the gap would make much difference in timing but remember, you're firing several times/second.
You're literally making a more or less efficient explosion in the chamber by changing the length of the spark.
Of course, this is worse than having all plugs off by the same amount.
In that scenario, you can readjust base timing to try to compensate, or the computer can try.
When all plugs are different the engine is out of sync, and it relies on synchronicity.
(That's why they fire in a specific order)
Glad you got out there, it can ONLY help to have them synched up.
Good on you! I hope your problem stays away.
(If it does, tell the dealer. They recognized a problem and if you show them it might get them to keep an eye out.)
By changing plug gap you essentially change the timing.
It doesn't seem like the gap would make much difference in timing but remember, you're firing several times/second.
You're literally making a more or less efficient explosion in the chamber by changing the length of the spark.
Of course, this is worse than having all plugs off by the same amount.
In that scenario, you can readjust base timing to try to compensate, or the computer can try.
When all plugs are different the engine is out of sync, and it relies on synchronicity.
(That's why they fire in a specific order)
Glad you got out there, it can ONLY help to have them synched up.
Good on you! I hope your problem stays away.
(If it does, tell the dealer. They recognized a problem and if you show them it might get them to keep an eye out.)
No, thank you!!
Actually sites like this are a very good reference for everything you need. I consider it a knowledge base. I would hope the manufacturer would be reading and taking notes. I know they see this but do they use it to make changes for the good? I would hope they do. As a side note, that spring thing did seem to be a but of a concern. I would bet the spark plug was not making contact. A slight bump of the spring caused it to drop down about 1/4 inch. If the plug did make contact it would have never been stuck in the up position.
Again, thank you!!
Ed
Actually sites like this are a very good reference for everything you need. I consider it a knowledge base. I would hope the manufacturer would be reading and taking notes. I know they see this but do they use it to make changes for the good? I would hope they do. As a side note, that spring thing did seem to be a but of a concern. I would bet the spark plug was not making contact. A slight bump of the spring caused it to drop down about 1/4 inch. If the plug did make contact it would have never been stuck in the up position.
Again, thank you!!
Ed
Glad yours is doing well now sonic-HWD. I think we need to start complaining to GM about this like they've tried to over at CruzeTalk and see if they'll ever release a bulletin to dealers. There is some pretty sloppy QC somewhere along the line and it seems that everyone's plugs are off, some by quite alot.
Well, guess what!!
It was running fine most of the day. All of a sudden it started up again.
Thought I had this sorted out. It's never that easy!
Ed
It was running fine most of the day. All of a sudden it started up again.
Thought I had this sorted out. It's never that easy!
Ed
Do you fill up at the same gas station every time? Bad gas can cause rough idle and hesitation.
CoHPhasor
Active member
Sounds like this could be temp related?
Had you fueled up just before it went away?
If you're running 87, after a fuel up it runs the "high tune" until it detects detonation.
If that's the case, while it was cool out it has less tendency to detonate then when it gets hot that changes.
If this is the case, run the tank down(low), fill it with high octane and see what happens.
Had you fueled up just before it went away?
If you're running 87, after a fuel up it runs the "high tune" until it detects detonation.
If that's the case, while it was cool out it has less tendency to detonate then when it gets hot that changes.
If this is the case, run the tank down(low), fill it with high octane and see what happens.
MisterClean
New member
I came across the information regarding the spark plug gaps being different than the owners manual. Decided to go ahead and check them because the car feels like it doesn't have any more umpf than a NA engine. Also the car has had a rough idle when in gear and stopped.
All four plugs measured .025 gap and I was surprised how black n crusty they were. One of the plugs was a little wet. I didn't unplug the battery so it may take some time to realize any difference. Car has 3600 miles.
Drove about 10 miles and did notice less lag when accelerating. Was shocked when it hit 5000RPMs with moderate acceleration on the highway. Time will tell if this helped.
Little bummed about the lack of quality control with the car. Lately I've been having issues with the paint flaking on the front bumper, when checking the plugs I saw a cable with a plug that should have been popped into the hole and also clip onto the transmission on another part of the same cable not attached, and now the spark plug not being gapped according to the manufacturer.
Anyway I'm just rambling now...hopefully get some more power and MPG from this change.
All four plugs measured .025 gap and I was surprised how black n crusty they were. One of the plugs was a little wet. I didn't unplug the battery so it may take some time to realize any difference. Car has 3600 miles.
Drove about 10 miles and did notice less lag when accelerating. Was shocked when it hit 5000RPMs with moderate acceleration on the highway. Time will tell if this helped.
Little bummed about the lack of quality control with the car. Lately I've been having issues with the paint flaking on the front bumper, when checking the plugs I saw a cable with a plug that should have been popped into the hole and also clip onto the transmission on another part of the same cable not attached, and now the spark plug not being gapped according to the manufacturer.
Anyway I'm just rambling now...hopefully get some more power and MPG from this change.
CoHPhasor
Active member
^ Yes.
I've heard talk of disconnecting the battery for a certain amount of time to stop GM's idiotic correction program.
Apparently some moron thought:
"Most people haven't driven turbo cars before and are unaware of their performance. Since we're using it for fuel economy, Joe Blow won't know that cold night air makes turbos scream and will think their car is running poorly when it's hot. Can we make it run like **** to even it out?"
The computer will assume after a certain point that the car is seeing improved performance by some ungodly cold streak apparently and de-tune itself.
I wouldn't guarantee that this can be fixed by a battery disconnect but it's what the Cruze guys suggest.
(I don't think this is like the benefits of modded parts so it shouldn't need a tune)
I've heard talk of disconnecting the battery for a certain amount of time to stop GM's idiotic correction program.
Apparently some moron thought:
"Most people haven't driven turbo cars before and are unaware of their performance. Since we're using it for fuel economy, Joe Blow won't know that cold night air makes turbos scream and will think their car is running poorly when it's hot. Can we make it run like **** to even it out?"
The computer will assume after a certain point that the car is seeing improved performance by some ungodly cold streak apparently and de-tune itself.
I wouldn't guarantee that this can be fixed by a battery disconnect but it's what the Cruze guys suggest.
(I don't think this is like the benefits of modded parts so it shouldn't need a tune)
The computer won't compensate for properly gapped plugs...
So What I am up to now..
Hi Guys,
Great suggestions. Keep them all coming!
Keeping in mind the car as about 700 miles on it.
I have been running regular 87 octane. I am going to bump this to 89 or
mid grade and see what happens. After that, super or 91 octane.
Lets see if that has any effect.
I am going to go under the hood again and look for any loose connections, etc.
Maybe that has something going on.
Turbo mentioned a new reflash to stop this. Don't know how he know this is on
the way but it can not be too soon.
Car is great otherwise.
Keep ya all posted....
Ed
Hi Guys,
Great suggestions. Keep them all coming!
Keeping in mind the car as about 700 miles on it.
I have been running regular 87 octane. I am going to bump this to 89 or
mid grade and see what happens. After that, super or 91 octane.
Lets see if that has any effect.
I am going to go under the hood again and look for any loose connections, etc.
Maybe that has something going on.
Turbo mentioned a new reflash to stop this. Don't know how he know this is on
the way but it can not be too soon.
Car is great otherwise.
Keep ya all posted....
Ed
That might be worth a shot. I've been running 93 since shortly after I bought it because even my 1.8 engine sees a (admittedly minor) benefit in mileage and feel. I'm going to go ahead and assume that it's not the root of your problem though. Both Sonic engines are designed for 87 and run well on it.
That's what they say on the Cruze side as well. IIRC it was determined from contact with GM that the smaller gap was the correct one I don't know if there's a big difference between the .028 and .035 as long as they're all evenly gapped but I'm happy with where mine are at.