1.6 16v lanos 1999 running fault lumpy jerky

[shiner.32]

Hello
Please can anyone help?.
We have a 10yr old lanos with 46k miles. It starts fine and runs well for around 5 mins driving very smooth with not hiccup or splutter at all.
Once it reaches operating temp, it changes into the most frustrating lump of metal i have had the displeasure of owning!. I have threatened it with the scrap yard!
The previous owner tried and gave up ,meaning we got it cheaply, in the boot was the box of a new ignition coil pack and ht leads, both have been fitted and the old items are in the boot, i felt it must be something more variable as it runs fine when cold and the coil and leads would be needed then as well, realise they could get worse when warm but as they have been changed guess thats not the problem.
I had it running whilst hot ,( lumpy and hunting , and smelling very rich, its also doing loads of petrol) then whilst still running disconnected the o2 sensor and it improved massivley. ordered a new direct fit replacement and disconnected the battery for 30mins to clear ecu and restarted.
All seemed great but alas it was false hope as it still runs terrible when warm. worked out the current mpg to 16 !!. There is no signs of head gasket faliure, not oil in the water no water in the oil and no drop in coolant level , its not over pressurising and not overheating. Feel i must be missing something obvious, i have looked for an air leaks , vaccum leaks and can not find one . please help.....

[benzino]

when the coil and leads were replaced, where the spark plugs also replaced?

[shiner.32]

yes the plugs were replaced along with the coil pack and leads, They came out today for a clean and were all as equally sooty as each other.Put them back in and it was much better than before they were cleaned,but back to bad within 5 miles,so must be running rich. ?? .when it was jurking up the road i pulled over and disconnected the air temp sensor in the air intake pipe ,although it put the engine check light on it run better making me think that the sensor is indeed doing its job .
i have come to the conclusion as it is fine when cold, that somewhere there prehaps is a coolant temp sensor that is not letting the management system know that the engine has warmed up therefore making it rich when hot ? .
Also have cleaned the egr valve and throttle body - no change

[shiner.32]

hAVE FOUND ENGINE TEMP SENSOR IN BASE OF INLET MANIFOLD, OFF TO ORDER ONE

[Daniel]

hAVE FOUND ENGINE TEMP SENSOR IN BASE OF INLET MANIFOLD, OFF TO ORDER ONE

Should not a faultly temp sensor trigger a MIL?
Pls keep us informed when replacement is done

[shiner.32]

Will do , shall have the sensor in two days time . Would have thought so too, the mil light comes on when you disconnect either the aIR TEMP/MAF SENOR and coolant temp sensor so both appear to be working but something has to be wrong making it run in cold start settings. costing a fourtune to run. Also on top to the throttle body there are a further two vaccum pipes currently blocked. with either cap removed allowing it to draw in more air it really picks up and improves showing it is too rich and needing less fuel or more air, so frustrated and irritated !!!! let me know please any suggestions very welcome. thanks

[Daniel]

I guess you already changed air filter.
Blocked vaccum pipes is proly from factory as I've too some blocked on my 1.6DOHC Nubira without any driving problem.
You may crawl in online service manual under 1F section "engine controls" for similar problem description and cure.

Wish you fix this one.

[Trey05Woo]

Have you gotten the vehicle scanned at all? there are some codes which set but will not trigger the mil because daewoo engineers felt it not necessary. two of those codes have to do with tps which will affect driveability.

I would double check ignition system the condition of spark at the coil pack + wire ends. I would also make sure they are wired correctly.

but get the car scanned by a professional scantool. you might have a pending code waiting to be set but will not light the mil till the pcm runs certain tests and verifies a fault. these codes ae only viewable under pending codes with a technician quality scan tool.

[Daniel]

Have you gotten the vehicle scanned at all? there are some codes which set but will not trigger the mil because daewoo engineers felt it not necessary. two of those codes have to do with tps which will affect driveability.

I would double check ignition system the condition of spark at the coil pack + wire ends. I would also make sure they are wired correctly.

but get the car scanned by a professional scantool. you might have a pending code waiting to be set but will not light the mil till the pcm runs certain tests and verifies a fault. these codes ae only viewable under pending codes with a technician quality scan tool.

Good to know that. Thanks!