Some Unwelcome Symptoms

[sly]

The old girl let off a massive backfire tonight on the way home from the shops...


...yes I do mean the car... doing about 3000rpm, moderate acceleration, on LPG.

Anyway after I reflexively lifted off and switched back to petrol, it's dropped a cylinder or 2 and is making like a chaffcutter.

Too dark to see anything obviously amiss, the plug boots are all firmly on the sparkplugs, but there seems to be some side-to-side movement in plugs 3 & 4.

Had to ease home at around 1600rpm, over that it started making metallic noises.

More when I get a chance to look in daylight.

Inclined to think the backfire was a symptom rather than the cause of the missing, just seems odd that such a serious miss could suddenly start rather than gradually develop.

[FGII-XR6]

coil pack leads plugs common problem with gas all the ignition components need to be spot on or it will backfire and generally play up

[Mechan1k]

Just hope you haven't done some internal damage to it.

[Auslandau]

Yes it will chug along and sound horrible until you put the air tube back in at the back of the heads ..... probably cracked the airbox as well. You should notice it as you should see a thin hose not attached to an elbow up near the firewall.

These have to be spot on with leads and plugs to run without backfiring and they still will. Make sure you have spring catches on your airbox to stop it from breaking as it will back fire again. Usually after sitting at the lights and putting the foot down ..... its like they catch a breath .... blow .... and then drive rough.

[sly]

Coil pack, plugs, leads all new <6000km, plugs gapped 0.8mm Splitfires. I've had LPG on this car for some 180,000km and 7 years & can count the backfires on one hand.

Simon, I was just thinking the noises reminded me of a Dyna that snapped a crankshaft a few years ago.

Been looking for an excuse to put a V8 in...

Seriously, comp test is on the list of things to do, just to make sure all the pistons are going up & down.

[JC]

Originally Posted by Auslandau

Yes it will chug along and sound horrible until you put the air tube back in at the back of the heads ..... probably cracked the airbox as well. You should notice it as you should see a thin hose not attached to an elbow up near the firewall.

Fix this, and the chaff cutter sound should abate.

[Mechan1k]

Actually ,,, my Father-in-law's BFII had a mini backfire ... and found the hose off the PCV came loose ... might also be wise to check the hose to the brake master cylinder as well ... that vacuum hose can cause it as well.

Just hope you haven't done a rod ... chances are there may be a bent valve in there ... fingers crossed for you it's not the case.

[sly]

He's describing the rear PCV hose by the sound of it, the one that goes from the back of the rocker cover to the intake. The pressure wave from the backfire would have had to have passed through the impeller of the blower to pressurise that hose. That could be expensive...

[JC]

Originally Posted by sly

He's describing the rear PCV hose by the sound of it, the one that goes from the back of the rocker cover to the intake. The pressure wave from the backfire would have had to have passed through the impeller of the blower to pressurise that hose. That could be expensive...

Ouch - could be!

[T3man]

If two plugs are snapped your problem is very likely right there. Backfire caused by lack of spark. Hopefully refitting any air sources and replacing the plugs will get it running smoothly again.

Then you have to find out why the plugs "blew" - maybe need a colder heat range?? With LPG and SC combined you would need a very cold plug and damn strong spark. Maybe the plugs just blew becasue they couldn't handle the amount of spark?? Try an Iridium style maybe.

[YOB POM]

I had very similar problem with an EF.
Turned out the MAP sensor hose had come adrift and caused over fueling a sump full of petrol and BANG.
I'm assuming it could also happen with LPG systems as they start on petrol.

John.

[sly]

No hoses missing, no plugs snapped thankfully. Busy with other things today, so not much time to troubleshoot. Plug 6 lead might be an issue, the idle seemed to smooth out when I moved the lead slightly above the rocker cover.

Thanks all for your input, more later.

[Bushbasher]

Have you checked that all the plugs are tight in the heads? You mentioned sideways movement in a couple of plugs, If all the hoses are still in place and with a SC pressurizing the inlet system all that pressure has to go somewhere, maybe you've stripped a couple of plug threads or cracked the manifold somewhere or even blown out part of a gasket.
As for the cause of the backfire, just because the coils and leads are new doesn't mean you don't have a dud. I had the same thing happen to the Fairlane and it turned out to be a slowly failing coil pack that was undetectable under test conditions. On petrol it ran fine but on gas it was very marginal and under load it wasn't giving enough spark. Mine backfired at 110kph when I hit an uphill climb and blew off half the hoses, split the rubber flexi elbow on the inlet ducting and destroyed the airbox, yes it was a BIG backfire. If yours backfired that big and the pressure wave couldn't get past the SC then the pressure must have put a massive load on everything after the SC.


Bushbasher

[sly]

Says it all really...





...or maybe not!

What I'm attempting to show is that the plug from cyl #1 is rooted. The outer electrode has been slammed into the centre electrode, and the insulator around the centre electrode has smashed off. But that's not the whole story.

After refitting some low-mileage (maybe 20,000km) iridium plugs gapped to 0.8mm, it still had a miss. Some further testing showed that the spark to cyl 1 was ****weak, but spark to #6 was strong. For the uninitiated, AU coilpacks fire #1 and #6 from the same coil. So the prob's not the coilpack.

So my almost-new "Top Gun Max300" leads had to go. I wonder why I'm suspicious of hypey brand names? I was a bit reluctant to get them in the first place when the shop didn't have Eagle 9mm leads anymore.

Anyway, I had a set of Bosch Motorsport leads in the cupboard and a couple of hours available to fill with swearing, sweating and grunting. No fun at all, the leads are heaps easier to change when either the head or intake manifold are off the engine! Nonetheless, with the front up on axle stands and working underneath the car, I was able to plug in the new set of leads.

So now it doesn't miss on #1 any more, but there are other problems...

1. There is still an occasional metallic rattle on acceleration from a standing start.
2. At idle, the belt tensioner sometimes oscillates and rattles noisily (maybe related to previous point)
3. Compression on cyl #1 is down, reading 1200kPa v's 1425-1550kPa for the other cylinders
4. I have NFI why the (apparently) piston slammed into #1 sparkplug

So I'd say that after 360,000 generally reliable km's, I'm looking at an engine replacement. But it won't necessarily be like-for-like. I'm tempted by the thought of options like:

1. XR6T engine with ZF transplant
2. AU V8 transplant with existing Raptor head unit bolted on
3. AU I6 + turbo, built up then fitted
4. CMS 4.5 litre engine with Raptor bolted on
5. CMS 4.5 litre + turbo (remembering I still have a GT3582 & 6Boost manifold in the shed)
6. BF NA I6 + ZF with either Raptor or turbo
7. Any of the above with a manual conversion

All are on the table. Looks like I've got some quotes to get. Things might be quiet for a little while, but then hopefully then there'll be a flurry of dyno printouts in my sadly neglected build thread.

[Beer Baron]

Did it eat something ?

[sly]

Nothing missing from the intake.

[T3man]

It sure sounds like something has got in the cylinder. It may be a chipped edge off a very hot exhaust valve - been known to happen with turbo engines so I guess it could happen with SC as well.

PS. I also had bad luck with Top Gun leads and will not use them again.

[XRGhia]

BF XR6T with ZF 6-speed...

[bodes-sh]

have to agree on the top guns also. i had a set on mine which i was suspect on, had a few backfiring issues too (turned out to be the coil pack, it was fairly new, but i put the old one back in and it has been fine since...) anyway, i tested the resistance on them and they all came up worse than the bosch leads i had on there previously (which were probably 6 + months old) so i put the old bosch ones back on and binned the top guns...

as for the mangled spark plug, it doesn't sound good. i would say a piece of valve too possibly, inless your raptor has somehow chipped a blade and it ended up in cyl 1. it would be handy to get a snake camera setup (like you see in the movies) to look in through the spark plug hole and see if there is anything in there and what it is...

as for the conversion options, being that yours is a s1 (or 1.5 as you have it), unless you have a s2 front end on it (or high series 1) you will need to do that if you went the ba/f motor and box route as it won't fit under the au1 / xr type bonnet... i reckon a supercharged au stroker would go down well, but i was under the impression they stopped doing them because of reliability issues..? or was that the 4.8l version?

anyway, good luck with whatever you decide and if you find out what went wrong throw some pics up too

[FGII-XR6]

fordpro smithfield will do a vct engine with under 100Ks 950 fitted

[sly]

Thanks Brett, I was going to ask if you could recommend someone to fit an engine, IIRC last time I did a comp check, you did too...

Bodes, I think the 4.5 is sorted, but I haven't checked with Joe yet.

At this stage I think I'm leaning towards the V8 option because the Raptor's an easy transplant and the tuning products for AU's are better sorted for 8's than 6's. Plus the generic tune for the V8 Raptor kit seems to work better out of the box for more people than the I6 one. And given the amount of custom wiring needed for a B-series conversion and the cost of the ZF box, I reckon the V8 option would cost me half any B-series based option.

I've been offered a 98,000km S2 XR8 engine/box/loom/ECU etc "dropped to the suspension", supposedly everything I need for the conversion, for $3500. Only reservation is, I believe the 200kW S2 XR8 has a high comp for iron heads (9.4:1) and needs PULP to start with. Not the best base to force-feed IMHO. If I can get a stocker for $1000-1500 less, I'd go a pair of alloy heads and higher-ratio rockers. I'll give Fordpro a call & see what they have.

[FGII-XR6]

they want an arm and both legs ( and whats in between too)for an AU 5L conversion . Ryan had an EB 5.o that needad a rebuild not sure if he still has it or wants to sell it

[sly]

Do you mean Fordpro, or wreckers generally (want an arm etc)?

Still keen to have a setup that can be engineered, so AFAIK I need an engine built same year (99) or later.

Last time I looked, I could get an XR6T engine for $4500, ZF for $2500. CMS offer a B-series NA retrofit to E-series for $5500 drive-in drive-out. That's a Barra 182/190 bolted to the existing gearbox, they probably source the engine for not much more than $500. That's not a complaint BTW, I've had quotes of close to $3000 for wiring alone, it takes a lot to get the B-series electronics to talk to earlier instruments, BCM etc.

So I figure $7000 for engine, gearbox & PCM, plus $5000 to fit. Then I'd need to fit a high-series bonnet & grille just for clearance.

I figure a V8 conversion should take 2 days or less for a good workshop. Maybe $1400 in labour. With some contingency, say $2000 tops, on top of the cost of the hardware. Then some hardware from Raptor and tuning. Another $3000 tops. All up around $7500.

Yep, makes a VCT fit look pretty sharp, even with tuning for the Raptor added.

[FGII-XR6]

I meant fordpro for the conversion I asked them a while back can't rember what they quoted but I know it was high

Originally Posted by sly

Do you mean Fordpro, or wreckers generally (want an arm etc)?

Still keen to have a setup that can be engineered, so AFAIK I need an engine built same year (99) or later.

Last time I looked, I could get an XR6T engine for $4500, ZF for $2500. CMS offer a B-series NA retrofit to E-series for $5500 drive-in drive-out. That's a Barra 182/190 bolted to the existing gearbox, they probably source the engine for not much more than $500. That's not a complaint BTW, I've had quotes of close to $3000 for wiring alone, it takes a lot to get the B-series electronics to talk to earlier instruments, BCM etc.

So I figure $7000 for engine, gearbox & PCM, plus $5000 to fit. Then I'd need to fit a high-series bonnet & grille just for clearance.

I figure a V8 conversion should take 2 days or less for a good workshop. Maybe $1400 in labour. With some contingency, say $2000 tops, on top of the cost of the hardware. Then some hardware from Raptor and tuning. Another $3000 tops. All up around $7500.

Yep, makes a VCT fit look pretty sharp, even with tuning for the Raptor added.

[sly]

Anyone closer to home who has a good rep in taxi circles? Someone suggested "Cars 2 Cabs" once but I've heard nothing rep-wise either way. PM if necessary.

[Barnaby]

Detonation caused the electrode insulator to disintegrate? Remnants of insulator got between piston & plug electrodes?

[FGII-XR6]

cars to cabs do good work but don't know if they would take on a conversion they are more plain vanilla mechanical work plus taxi specific electricals

[T3man]

Originally Posted by Barnaby

Detonation caused the electrode insulator to disintegrate? Remnants of insulator got between piston & plug electrodes?

Except his compression is now way down on No 1 - means there is broken rings or valves not seating.

[Barnaby]

Originally Posted by T3man

Except his compression is now way down on No 1 - means there is broken rings or valves not seating.

Yeah, I was thinking the shattered porcelain from the insulator may of had a hand in this too.

[Mechan1k]

I think Joe said his 4.5L engine is ready to go now from my understanding.

Don't go to FordPro to do a conversion ... I don't trust them ... neither for a few others on here as well. I might get the odd part I can't from anywhere else ... but that's all.

Have a chat with Joe about it.