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Starting And Rpm Issues


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12 replies to this topic

#1
matt g

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Hi everyone.
Can anyone shed some light into my cars current issue please.

It's a H reg 1.6 gti running all standard equipment.
On initial startup from cold when turning the key the engine fires up and instantly revs to around 2500rpm then dies. After 5 or 6 attempts of the same the engine catches and runs but sounds a little lumpy but ticks over.
When not under load the engine revs freely but when being driven it won't rev over 4500rpm.

Anyone have any ideas please? It's the last niggle to sort before mot time

Thanks in advance

#2
Tom Fenton

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Are you expecting it to start off the key and run with no throttle input at all? If so you are asking a lot if the 80's injection system with no closed loop idle control.
Even the very best set up cars may need just a touch on the throttle from a cold start to keep them running for 5 sec or so until they stabilise.
Yours from your description doesn't sound well setup to be honest.

#3
matt g

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Hi. Thanks for the reply.

I'm more concerned with the inability to rev through to redline under load. Your prob spot on in saying it needs setting up correctly. Does anyone know of a mobile tuner that covers the South Wales area?

#4
Anthony

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What happens when you try? Does it feel like a really severe misfire like it's hitting a rev limiter? If so, ignition amp would be my first suspect - a limiter like symptom around 4000-4500rpm is their usual failure mode.

They're almost certainly different issues though - as Tom says, it's fairly normal to need to give it a little tickle of throttle to keep it running for a few seconds after cold starting, even if it is set up correctly, whereas no matter how far out the idle side of things is, that shouldn't really impact how it runs under full load.

#5
nomis

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I've spent decent amount on trying to get my 1.9 running as smooth as I can by replacing lots of the usual bits, such as hoses, leads, etc. It idles pretty much fine and pulls well...

But it always needs a bit of throttle to start.

The rpm issues sound very different to though, as mentioned by those with much more knowledge than me above.

#6
welshpug

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whereabouts in Cardiff are you Matt?



#7
matt g

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Hi guys. Thanks for the replies. I will try another ignition amp and go from there. Fingers crossed.

Welsh pug. I'm in Pontprennau. Near junction 30 of the m4

#8
matt g

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Hi all.

Just a quick update on my woes.

Tried changing the ignition amp but the symptoms are still the same.
It's still a pig to start when cold but fine when hot so I'm suspecting the SAD valve. Will check that tomorrow.

My major concern is the rev limiting at 4000rpm. Either the tacho is reading incorrectly, I have a limited Ecu or my car is possessed by a non revving entity. I'm open to all ideas.

Thanks everyone.

#9
toolie72

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I'd suspect fuelling issue myself, like lack off
OR a big air leak which would also lean mixture

What's plugs like?

Sad will probably be fine (and it's a knob to change!) very rarely go wrong

#10
matt g

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Just had a quick look at the plugs. All are black and sooty.

#11
toolie72

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Not lean then

Out of ideas-I'd have guessed fuel and/or mixture

#12
jackherer

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What was it doing immediately prior to you removing the plugs and finding them to be black and sooty?

 

If it was idling it might just mean it is running rich at low load and/or RPM, it could still be lean at high load/RPM.

 

As I think has already been suggested run it to 4000 RPM or whatever the highest it will go to is, cut the ignition, coast to a halt then take the plugs out.

 

Also was the new ignition amp known to be working? When you got it was it already mounted on a heatsink plate?



#13
Gaz205

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What was it doing immediately prior to you removing the plugs and finding them to be black and sooty?
 
If it was idling it might just mean it is running rich at low load and/or RPM, it could still be lean at high load/RPM.
 
As I think has already been suggested run it to 4000 RPM or whatever the highest it will go to is, cut the ignition, coast to a halt then take the plugs out.
 
Also was the new ignition amp known to be working? When you got it was it already mounted on a heatsink plate?

Out of interest what does this test for when running it to 4K then coasting? When you say take the plugs out is it to check to see if they are flooded with fuel?

Edited by Gaz205, Yesterday, 10:13 PM.