Lanos 1.4 acceleration (lack of)?

[panther]

I have acquired a 1998 Daewoo Lanos 1.4 (8 valve). It has done 100k miles and has a full service history but there appears to be a distinct lack of power from the engine when accelerating. The engine starts and idles smoothly and seems to pull away ok but there doesn't appear to be any "Umf" and lacks response when accelerating, especially through the mid-range revs.  For e.g, if I build up to 40 or 50 mph down a straight duel carriageway road, to get any response and increase in speed I have to press the throttle peddle a long way down (sometimes to the floor) before it picks up speed.  I know it's only a smallish engine but there definitely feels a lack of power. I always drive economically and on all previous cars I've never needed to use more than half the throttle pedal during normal driving.  I don't know if this is related but I notice that the more throttle I have to use, the louder the rasping induction sound appears from the air-intake system (air filter looks new).  Any pointers welcome.

[Derek Edwards]

I think the noise might be the clue here. My guess would be either a blocked CAT or slipped timing belt.

Check the cam belt timing first.

Derek

[panther]

Thanks Derek.  Someone else mentioned a blockage in the exhaust or a faulty EGR valve as another common problem.  I'm inclined to go towards the blocked exhaust but will get the cam checked to be on the safe side.  The car runs normal on the flat during light acceleration but when you need that bit extra power it just ain't there, or come to an incline and it feels as though the engine is losing compression.  I've replaced the plugs and did a compression test and that's Ok with number 1 cylinder at 12.5 Bar (180 psi) all the others were 12.9 Bar (188psi)
Can exhaust systems & cats be checked for blockages in situ without having to remove any sections?

[panther]

I think I've located the fault to be the EGR valve.  If I suck the vacuum pipe leading to the EGR valve there is very little resistance felt and not enough to move the plunger, so I think the diaphragm inside the valve must be split!  I took the valve off and cleaned it the best I could but it also does not appear to be closing completely.  If I open the valve by hand and blow through the bottom opening I can easily blow through to the other chamber, but even with the valve in the closed position I can still slightly blow through to the other side!

What I've done as a temporary measure is put the valve back as it is and plug the vacuum pipe and disconnected the wiring plug at the vacuum sensor which leads to the EGR valve.   The "Check Engine" light remains permanently lit but I would say there is now a 30% increase in performance.  Probably be even better if the valve was shut tight as it  will now be acting as a vacuum leak.   I will see if I can get a spare  valve from a breakers but at least the car is now running much better.  Can it do any harm to the engine running it like this and with the check  engine light lit?

[Derek Edwards]

The EGR does help keep the combustion chamber temperatures down so don't do to much sustained high speed driving until it's fixed


Derek

[panther]

Looks like it could be the exhaust after all.  With the temporary EGR gasket in place it has slightly improved performance but the engine still appears to be holding back during the mid to high range of acceleration.  In fact, if I floor the throttle I still get that roaring sound from the air-intake and it feels like the car actually slows down before gradually building up speed.   My local garage took a look and discovered that there is very little vacuum suction from the inlet vacuum pipe that leads to the EGR. He says it shows all the signs of a blockage in the exhaust system and the back box is usually the culprit on these cars.  Will try it tomorrow with the back box disconnected and see what that does.

[bruce]

My neighbour had the same problem, including the roaring sound from the air intake. I've just been up and taken the camshaft cover off. Knackered cams on cylinders 1&2 exhaust. Presume roaring sound is because exhaust valve not opening, the exhaust gases are coming back out through the inlet valves. Previous compression test he says was OK, well it would be. acting as if they were closed on compression, just that they were closed ALL the time. Anyone got a spare camshaft for a lanos 1.4 (no sensor) or a cyl head ?

bruce

[starkicker]

in response to your lack of power problem, i have a daewoo lanos 1.4 se that failed the emission test on the mot,after investigation i found that the cam lobes had worn on inlet/exhayst valve on the number 4 cylinder.had the cylinder head reconditioned with a new cam and followers.passed the emissions test no problem but now has less power than before?!.having spoken to the garage this type of engine does have a common problem with heavy cam wear but he has no idea about the lack of power,he seems to think if the belt had slipped the car would not run smoothly at low revs like mine does