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gav-

megasquirt popping/backfiring - random idle and load

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So removed all of the plugs and replaced them with Bosch WR7DC ones, however plug 7 was no were near as carboned up as the others. 

It started back up and the popping is still there but maybe not so often?? 

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You have two plugs not firing and the other pig rich. 

Check your coil packs for spark and wiring to them. 

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The other possibility rather than an ignition issue is a poorly injector or injector wiring fault on number 7. The popping will be it running very, very lean. As Bowie said, the rest have been running extremely rich. 

FFR: This is a great example of why EGO correction and/or autotune should only be used once you're sure everything is working correctly, and the lambda reading itself should be questioned until you've proved you've not got something skewing it. 

Looks like you're homing in on the problem, though :)

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11 hours ago, lo-fi said:

The other possibility rather than an ignition issue is a poorly injector or injector wiring fault on number 7. The popping will be it running very, very lean. As Bowie said, the rest have been running extremely rich.

I'd second this - when I rebuilt the 109 the injectors had sat in a box for so long it almost hydrauliced itself on raw fuel in several cylinders - several were leaking or stuck open, several were stuck closed or dead. I threw a new (used) set in and it fired straight up.

Also, I'm always wary of fancy spark plugs in V8's, NGK BPR6ES seem to give best / most reliable results.

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Thanks, is there a simple way of testing an injector? I’ll check out the wiring later but not sure on testing an injector?? 
 

(The Bosch Spark plugs were not planned, just a opportune buy a number of years ago!) :) 

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4 minutes ago, gav- said:

Thanks, is there a simple way of testing an injector? I’ll check out the wiring later but not sure on testing an injector??

Depends really; you can give it a few bursts of 12v (ground one pin, tap the other pin with a 12v wire) and see if it clicks as a very basic test (see if all 8 sound the same), slightly more advanced is trying to blow air or fuel through it whilst giving it a few pulses of 12v.

At this level you don't exactly need a flow-measuring test rig.

Also as Bowie suggests, check you're actually getting sparks on all 8 and that they're wired correctly, sooooo many MS problems have been down to mis-wired coil packs!

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Swap them round, if the lean cylinder swaps to the location with the suspect injector you've found your problem. They click quite loudly when working too, so use a piece of pipe from your ear to close to the suspect injector and listen. Doesn't mean it's flowing, but clicking means the solenoid is moving. 

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It’s looking like the no7 injector is blocked. It clicks ok with 12v applied and removing the plug can also test the ecu wiring. 
 

the spark is ok - checked with one of those visual colour tools that is fitted between the plug and lead. 
 

So now need an new injector, reading online - Vauxhall’s vectra are a good replacement??? They also appear a lot cheaper! 

 

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If they're definitely the same injectors? Otherwise you'll need a full set of 8 that match. Be careful as while they might look physically the same and fit, they may not behave the same as what you already have, which means mixing and matching isn't an option. 

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18 hours ago, gav- said:

So now need an new injector, reading online - Vauxhall’s vectra are a good replacement??? They also appear a lot cheaper!

I've never paid more than about £50 for an entire V8 inlet manifold & 8 injectors  :huh:

Unless the Vectra ones are identical flow and spray characteristics I'd say you're risking trouble, especially if you're not fitting a matched set of 8.

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I used to use the Vectra injectors with good results, but did buy a few of them and flow test on the bench to get a matched set of 8. Most of the tvr forums rate them, and at the time they were dirt cheap. This was on my ickle 3.5, I was surprised that idle was ok as they flow a bit more than standard LR specced injectors.

 

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4 hours ago, Quagmire said:

Most of the tvr forums rate them,

Is that just because fitting the wrong flow rate hoofs more fuel in for the same opening pulsewidth and it's a cheap mod bodge if you don't have a tuneable ECU? Like winding the fuel pressure up or tweaking the fuel screw on a TDi :rolleyes:

The stock Rover ones flow more than enough for the 4.6.

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On 11/28/2019 at 1:46 PM, Cynic-al said:

Are you running petrol or lpg? Are all 8 injectors working evenly, maybe one bank is putting more fuel in than the other and that's making the mixture jump? I put a plastic cup under each injector to measure what was coming out of each one. You just have be be very careful there are no sparks!

I thank you, phew it's getting mighty close to the end of the year I thought I wasnt going to be right at all this year  🤣

Perhaps a less dangerous way I've tested them before is to push them on the end of a hose pipe, apply 12v and spray them against a bit of wood. You can sort of see the pattern and amount of water coming through and compare them one at a time. You can also see if they leak. I know putting water through them isn't ideal but I figure your not going to set fire to anything and if you get a bit of petrol straight back in what harm is it going to do? 

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Are all Land Rover v8 Hotwire injectors the same (excluding the gems etc?) I notice some have a green band in the middle whilst others had a green band at the top. But both look the same other than that. Thanks 

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