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steveo3002

reasons for engine wont run lean /normal...runs ok pig rich

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car failed its mot today 10% co

 

gets home and fiddle with it , i can get the emissions down sensible levels but it runs terrible popping and banging out the exhaust

 

everything i can check seems all good condition /normal

 

it has a crude diagnostics that doesnt highlight any problems

 

stuck where to look now 

 

polo 3f engine code 

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Where to start! Is the timing correct? I would check that first, then I would go to the distributor to see if everything is behaving in there, then HT leads, then vacuum pipes, and finally the carb.

 

Clean stuff before the messy stuff!

 

An old Renault of mine ran like shit when professionally tuned with similar symptoms to yours. I found the timing was out and a few degrees of advance made a massive difference hence my timing suggestion initially

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mpi 

 

everything i can think of /read about has been checked /swapped ..all new service parts that are decent brands

 

cam and ign timing checked over and over ..ign timing doesnt help it when lean 

 

just sort of looking for generic ideas really...doesnt make much sense to me

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I've had 4 polos and each one has suffered with crankcase breathing problems from blocking up to actually being sick, everywhere. They were all carbs though. Don't know what an mpi is but I'm guessing like most things that age it's a single point injection shoved on an old engine.

 

There opens a whole new world. High co means it's not exploding properly and letting out unburnt fuel so it could be anything related to ignition, breathing or sensors. I imagine it has a coolant temp sensor somewhere? Despite what the gauge says, that'll run off a different sensor... Probably.

 

You'll need to determine that the information the ECU is receiving is correct and you can do that by testing the parameters of the sensors. The hardest bit sometimes is getting that information to guide you. Google is your friend.

 

Ooh, look what I found...

 

post-24545-0-94326000-1536772974_thumb.jpg

 

 

Check it's breathing properly, check your Sparks.

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Guest

I'd second an air leak,Polo's were terrible for this, but if not,junkman could be on to something, Most polo's had a spray bar which could block up and wear the lobes.

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Does this have a distributor & rotor arm?

 

My Saab 900 was behaving *exactly* as though it was leaning out excessively when it turned out to have been fitted with the wrong rotor arm (bloody Intermotor catalogue).

 

Odd thing was that it ran absolutely fine for a week before this problem surfaced suddenly and out of nowhere.

 

Took me a month of faffing around before I randomly tried sticking the old rotor arm back on...problem solved!

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i didnt note it all down ...i think it may have been 1300 ish , but at 9% it would be miles out no?

 

ive marked all the settings and can revert back to standard /also have a spare afm thats got all the anti tamper bungs

 

default /standard setting is about lean enough for a pass , but runs awefull , make it rich and its smooth /normal sounding 

 

i have a video i can wahtsapp to anyone that wants 

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should i be investing in a compression tester?

 

the engine did 1500 miles or so with a carb , zero issues passed mot with super low readings 

 

now with the inj fitted , starts on the button , no blow by out the filler cap /breathers , runs good above idle or super rich

 

not convinced its a low comp issue but runnng out of ideas  

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Does it have an idle switch on the throttle body if it's a cable throttle, if so is it clicking when throttle is released?

If it's not closing the switch it will go rich and upset the mixture

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Is the TPS adjustable?

If it ran well and clean on carb, then rule out anything below the inlet , If it runs well on throttle, then it has to be connected to the idle circuit. Find out the settings for the idle voltages for the TPS if adjustable and set it exactly before anything else, then adjust around this. The ECU needs to know the throttle is closed..

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