Can I identify a faulty injector?

Wilky1974 · August 27, 2016, 15:36

Earlier today I fitted some new yellow injectors and a MAF spacer ( a.k.a the MAF mod ). The car started first time and on the test run performed really well. it's a great little mod. However since returning home I've found that the car struggles to start unless you keep turning it over. It does eventually start with a little throttle and then runs fine, The kit I bought was from a member on here and I know he did experience a similar problem. So I'm guessing the fault must be one of the injectors. Is there a way of detecting which is at fault possibly using an OBD reader? Or will I just need to send them off to a specialist to be reconditioned. I don't really want to revert to the standard injectors as this mod definitely does add some low down torque.

Any suggestions or advice for working this problem through would be appreciated.

Cheers,

Paul.

wotugonado · August 27, 2016, 17:07

I would double check but iirc there's a how too on you tube, where you put the injectors still attached to the rail into clear plastic bottles and prime the pump. That way you can check the spray pattern and volume the injectors are flowing individually. Injector tune did my refurb with printout of before and after the ultrasonic clean, highly recommended if you need to get them cleaned.

Wilky1974 · August 27, 2016, 19:37

Thanks! Hadn't thought of checking YouTube! Will take a look now s:)

s:) .

Tomo70 · August 27, 2016, 20:15

I thought the injectors had been serviced. Could it be a case of the of injector seal leaking while its stood. Seems from what you have said that you are starting the engine with too much fuel in the cylinder if you are having to push throttle down on start up

Wilky1974 · August 27, 2016, 20:47

....yeah the injectors had been serviced before I bought them but to be honest it's the only thing I can think of. Raising the MAF alone wouldn't cause the starting problem I don't think? s:(

s:(

Wilky1974 · August 27, 2016, 21:38

..... I think I may have worked this out! Looks like I have removed the entire air horn from the air box when I should have just removed the air vanes! What a total idiot | am! Thanks for the replies s:)

s:) !

jvanzyl · August 27, 2016, 23:28

Hey Paul,
I'm sorry to hear you're having issues!
Please let me know how it turns out- those injectors went back to Simtek twice!
Cheers,
John

Wilky1974 · August 28, 2016, 08:13

Don't worry John!!!! It's not a problem. This is one of the best and most effective mods that I ever done to a car. I don't regret it one bit s:)

s:) . I'll just keep experimenting and see if I can pin this down. Ultimately if I can't trace it I will live with it. Will keep you informed just for your curiousity s:)

s:) .

shnazzle · August 28, 2016, 08:34

Quote from: "Wilky1974"Raising the MAF alone wouldn't cause the starting problem I don't think? s:( s:(

This would be the leading cause I would say.

The MAF mod is a very fine balancing act.
But, also remember that the car is programmed to put a certain amount of fuel in at startup, and it doesn't know it has bigger injectors now.
So, all it can go off is the MAF readings, throttle position, o2 sensors and knock sensor.

wotugonado · August 28, 2016, 09:51

Just a quick thought, did you do an ecu reset? not sure if this helps the process but wouldnt think it would hurt.

jvanzyl · August 28, 2016, 09:54

My pre O2 sensors were on their way out when I was trying this mod....I never tried it with the new ones... Thing is when they are on their way out they react slower... This could lead to the over fueling I think!

Wilky1974 · August 28, 2016, 13:55

... whilst tracing my steps I realised that I had removed the entire air horn rather than just the vanes. So just been out and replaced the air horn and disconnected the battery to do another ECU reset. I also have two known good 02 sensors as have just fitted a decat manifold. So I'll see what happens in half an hour and then change the 02 sensors too. Also there my be a little bit of 97 RON in the tank although I have filled up with Tesco Momentum in preparation. Maybe I need to run it for few miles and see what happens. Thanks for all of your help folks, really appreciated. s:)

s:)

Wilky1974 · August 30, 2016, 20:53

... and the winner was ..... a faulty O2 sensor! Replaced with a working sensor and the car now starts as normal. Thanks so much for all of your help folks. Loving my MR2 even more now it's got tiny bit more poke. The Focus ST is sat in the garage gathering dust s:)

s:) !!!!

shnazzle · August 30, 2016, 21:03

Sweet. Tell you what... I hate these o2 sensors. I wish there was a way around them that didn't involve a standalone ecu

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jvanzyl · August 30, 2016, 21:32

Dammit.... That totally means it would have worked after I installed the new sensors!!!

Oh well... Glad you're sorted! :-) :-) :-)

shnazzle · August 30, 2016, 21:54

Haha that's the first thing I thought but didn't want to say it

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lamcote · August 30, 2016, 22:00

That's odd, I didn't think the O2 sensors were involved at startup, I thought it was in open loop at that stage until things warm up a bit?!

shnazzle · August 30, 2016, 22:03

Makes you wonder why the o2 sensors have heaters....

But, having a duff o2 sensor definitely messes with startup. 100% certain of that

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