Spark Plug Gap and Adjustment

Pops_20

Hi all,

I will be servicing my car (2006 Opel Astra 1.6) over the next few days and have a few questions to do with spark plugs.

1) The Haynes manual for the car recommends Bosch plugs but I have purchased NGK plugs. Is this OK?

2) The electrode gap is specified as 1.35 mm, but does this gap only apply to Bosch plugs?

3) I have a feeler gauge for checking the gap but no adjustment tools. Would it be ok to carefully bend the outer electrode with the tip of a screwdriver?

Thanks in advance for any suggestions!

cletus

Once you asked in the motor factors for spark plug for your car, you'll be ok. They also come pre-gapped these days, no need to gap them

sorry just noted your 3rd point, have you checked the gap and its not correct?

Pops_20

All 4 of them came with a gap of 0.7mm. The manual says 1.35 mm so I feel I should change them.

JP 1800

There is a specific tool to gap spark plugs but in the absence of this tool I usually use increasing widths of the feeler gauge between the electrodes to adjust the gap until the correct size is achieved. BTW the gap in plugs is important as is the correct plug as damage to coil pack may occur

Pops_20

Thanks JP. I might do this if I cant get my hands on a proper adjustment tool.

I just checked NGK's website and it suggests a gap of 1.1mm for my car.

I'm thinking I should just go with the gap quoted in the Haynes manual?

cletus

AS above, they will need to be gapped, but if you specified your make and model car to the guy where you bought them, he should be supplying appropriately gapped plugs

edit appears there may be issues re Haynes manual specs, see here

http://www.astraownersclub.com/vb/showthread.php?t=343499

mickdw

Id be inclined to think they are not the right plugs for your car or else you have the wrong gap figure. The plugs should certainly be much closer out of the box than what you are quoting.
You got NGK plugs. Do NGK list the part number you have bought as suitable for your car? If so and they give a gap figure too, I would go with that, not the gap as given in the haynes manual.

joujoujou

Pops_20 wrote: »

All 4 of them came with a gap of 0.7mm. The manual says 1.35 mm so I feel I should change them.

You probably got improper set of plugs (I mean - not for your engine).

All modern spark plugs are pregapped and end user is advised not to change it, as many of them are very gentle.

Here's just one example:



Tip is only 0.4 mm thin!

corkgsxr

I'd never gap plugs. Imo that day is gone.

Pops_20

Pops_20 wrote: »

...... The Haynes manual for the car recommends Bosch plugs but I have purchased NGK plugs. Is this OK?........

There are cross reference tables on the net, have a peak to ensure they gave you the correct NGK plugs

As mentioned by several people, you shouldn't have to alter the gap on the plugs.

Pops_20

Thanks for that link cletus. That poster appears to have had the same issue as me. Same engine and all.

I think i Will go back to the motor factors tomorrow and ask them to confirm if i have the right plugs.

However, i Will still be inclined to adjust the gap. As the poster in that link confirmed, the gap should be 1.35 mm, but the plugs in question were Bosch! Would people agree that the gap depends on the plug, and not the engine??

cletus

The gap should be the same for your engine regardless of the make

Pops_20

Just with regard to people saying that the days of gapping spark plugs are gone, the box that they came in has instructions on the back that say you should set them to the right gap, so I doubt they are pre gapped.

Cee-Jay-Cee

Pops_20 wrote: »

Just with regard to people saying that the days of gapping spark plugs are gone, the box that they came in has instructions on the back that say you should set them to the right gap, so I doubt they are pre gapped.

The majority of plugs are not car specific, they are made in a wide range of thread pitches, heat ranges and gaps and you buy the plug that corresponds to the requirements of your car/engine so if your car requires a 1.1 or 1.3 gap and the plugs you get are 0.7 then they are not correct for your engine.

Your car is a common model and if the place that supplied them are not capable if supplying a plug for a common popular car then they really shouldn't be in business.

Do not adjust a 0.7 gap plug to 1.3 thats almost 100% wider and increasing the gap that much moves the hood/ground electrode back from directly over the centre electrode causing a poor spark.

Bring the plugs back and get the correct plug for your car, if they supplied a 0.7 gap plug when your engine requires almost twice that gap then you can be sure the heat range is incorrect too.

gctest50

Might be helpful :

http://www.sparkplugcrossreference.co.uk

You should check the gap anyway, a plug may have hit something ( been dropped onto a surface? )

The gap will affect all sorts , need different voltage before it fires, exposure of spark to mixture and so on ===> a tiny bit to do with timing

Pops_20

gctest50 wrote: »

Might be helpful :

http://www.sparkplugcrossreference.co.uk

You should check the gap anyway, a plug may have hit something ( been dropped onto a surface? )

The gap will affect all sorts , need different voltage before it fires, exposure of spark to mixture and so on ===> a tiny bit to do with timing

Right, I've cross referenced the Bosch plug specified in the car manual (FQR 8 LEU2) with its corresponding NGK plug, and its coming out with NGK - ZFR5F, the exact number on the plugs I bought.

Am I making a big deal out of nothing? I should probably adjust the gap, pop them in the car and forget about it

dougie-lampkin

Autodata shows the listed plug as a Bosch FLR 8 LDCU with a .9-1.1 mm gap, to throw a spanner into the works :pac:

There's a few different flavours of the Z16, which seems to be the problem. There's at least an XE, XEP and XER that I can see, all listing different plug codes and gaps. There's a different of 5 mm between some of the quoted gaps, that's way too far to stretch an electrode. If it was me I'd be going to the nearest dealers with the VIN and see what they can tell you.

Pops_20

The engine in my car is the Z16 XEP. I'm going to go back to the motor factors tomorrow anyway to be sure they gave me the right plugs and I'll mention the fact that I'll have to pull the electrode back by 0.65 mm to see what they think of that sort of adjustment.

CJhaughey

The NGK come pregapped at 0.9 , the iridium version of your plug is pregapped at 1.1mm, ZFR5FIX-11 the suffix refers to the plug gap.
NGK don't make a 1.35mm pregapped plug, this is almost unique to Opel twinport engines.
Just adjust yours to 1.3mm and stick them in.
Plug tools hold the side electrode to bend it in or out, you want a sticky fit with a 1.3mm feeler gauge.

Pops_20

CJhaughey wrote: »

The NGK come pregapped at 0.9 , the iridium version of your plug is pregapped at 1.1mm, ZFR5FIX-11

I measured the gap a few times and its definitely 0.7 mm. The feeler gauge im using is hardly that inaccurate. I dont think i have the iridium plugs as i understand they are more expensive.
Full code on the box is ZFR5F stock number 5165

cletus

If ngk dont do a 1.35, you might have to ask tje motor factors for the bosch equvielent, which seems to have been oem

CJhaughey

Pops_20 wrote: »

I measured the gap a few times and its definitely 0.7 mm. The feeler gauge im using is hardly that inaccurate. I dont think i have the iridium plugs as i understand they are more expensive.
Full code on the box is ZFR5F stock number 5165

They'll be fine, just adjust them to the required gap and stick them in.

Pops_20

CJhaughey wrote: »

They'll be fine, just adjust them to the required gap and stick them in.

Thanks. Went into the motor factors this morning and double checked that they are indeed the correct plugs. The guy there had a look and he thinks they are find to adjust up to 1.35 mm.

Thanks everybody for all the help.

Pops_20

Well, just as I thought I had this sorted, I emailed NGK directly and they said that the gap should be set to 0.9 mm and they have had no issue with this. Talk about confusion!