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Roy
Roy, import/domestic specialest
Category: Car
Satisfied Customers: 5717
Experience:  ASE master tech for 40 years
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Daewoo Leganza: My 2000 Daewoo Leganza SE often is sluggish

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My 2000 Daewoo Leganza SE often is sluggish on takeoff. It sound like there is more air flow than fuel getting to the engine. As I press more on the accelerator (about mid throttle), it kick into passing gear as it should and just around 55MPH it sometime jerks intermitting. If I take off slowly it moves in sync with the accelerator pushdown and after it complete all the shifting gears and I give it more accelerator pushdown the engine RPM drops. If I continue to give more accelerator pushdown it slowly response and it will get up to speed slowly (Have felt more power in the past). I notice if I should let off the accelerator and immediately push down again, I feel an increase in power and then it goes back to a drop in RPM slightly and sound like there is more air than fuel getting to engine. Engine has 199M mile, parts that have been changed in the past 3 years are Idle air Control Valve, Throttle Positional sensor, Fuel pump, Both Oxygen sensor, Air filter, Fuel filter, spark Plug and Wire. Disconnected the PCV vacuum from purge canister searching for vacuum problem. What could cause the lack of performance? If the A/C is on or off does not affect this condition and the lack of power performance. Also when A/C is turned on, the engine does not increase speed nor does it loose speed at idle. A/C clutch engages and engine idle remain the same.

roy :

Hello my name is XXXXX XXXXX I will assist you today. It sounds like your cat converter may be clogged. A back pressure test will confirm the cat being open or clogged. The fuel pressure should also be checked as well. How old is the timing belt????

roy :

Roy

Customer:

Sorry Roy, But i did not want to mention this because it do not meet EPD standards and exposed myself. I removed the Pre-Cat catalyst that's attached to the Exhaust manafild and Post catalyst converter and remove the honey cones from both. This was the first thing I tried to correct the problem. My Plan was it if worked I will install new ones to get my inspection tag.

Customer:

Also, I have change the fuel pump and checked the [pressure. It's in spec range.

roy :

OK. Then the other thing is either the timing belt retarding the timing or the compression is low. Roy

Customer: Can the muffler be plug like the cat converter and cause the problem . How would I advance the timing with no distributor on this car.
roy :

Doubtfull the muffler is clogged. You cannot adjust timing. The timing belt may be worn and effecting the timing. Roy

Roy and 4 other Car Specialists are ready to help you
Customer: replied 4 years ago.
Hi Again Roy, The timing belt may have approx 25 m mile on it or less. The compression is good on all cylinder. I will check the purge control vale that is vacuum and electronic control that may open and close to create a vacuum leak affect intermittently because the engine perform can have good power performance and just loose it when excellerating
OK, what is the exact compression???

The other possibility is the injectors. They may be clogged with debris. You can try to have them professionally cleaned as additives have little or no effect.

Roy