Engine Lag Problem Getting Worse

[wayneh]

Hi -

I have a 2002 SportCross with 38K miles and over the last year or so,

both my wife and I have noticed an increasing problem.

After starting up and driving, the engine will seem to lag periodically -

the "mpg" meter jumps to 80, the rpm drops about 500, and it feels like

the engine dies - for about a second or two.

This happens irregularly.

It usually happens for a few miles then drives normally.

However, recently, after driving it 150 highway miles, then parking it in a

parking garage for 3 days, when we drove it again it was horrible.

We could barely get it out of the garage - it felt like it was going to stall.

Then it settled down, but by the time we got onto the highway again it

started 'lagging' again - but this time at 65mph. This continued for

over 10 miles, then stopped.

We've had our dealer try to diagnose the problem several times - they did a full

40K service, replaced an O2 sensor, updated the transmission programming,

and ran full electrical diagnostics.

Even though the Shop Foreman has (finally!) felt the problem for himself, they

can't seem to figure out what's causing this.

We're getting pretty *BLEEP*ed off, as well as concerned about driving the car anytime.

Does anyone out there have any ideas or similar experiences?

Thanks.

[smooth1]

Have you tried purging the fuel tank and going to a different gas station and fueling up there? I'm not talking about just going to E on the gas gauge and filling it, I'm talking about removing any water you may have built up in the tank. It's possible from your description that could be a cause that wouldn't be detectable by diagnostics. But it does sound like a fuel supply issue of some kind. If you pop the lower section of the rear seat out, you'll see a hatch on the driver side, open that up to gain access to the fuel tank and the fuel pump. Maybe take a look and make sure the hose isn't clogged, look for water in the tank, maybe even test the fuel pump.

[nutkin]

Yes, the fuel tank and fuel pump will be the reason.

My 2001 IS300 (almost 89,000km) always hesitate to go. It improved after cleaning the throttle body, MAF sensor. It improved a lot more after I change the cam belt and spark plug. But it still has a bit of hesitation occassionally.

So I bought a bottle of 3M fuel tank & fuel system cleaner and add into the fuel tank before fill up .

After a full tank treatment, the hesitation gone and the car is so quick response like new.

[nutkin]

however my fuel pump dead afterward. But it is amazingly that after I have a brand new fuel pump fitted, the car response improved even more. I can say much much better before the fuel pump replaced.

As a conclusion, I think the performance of the fuel pump do deteriorate as time goes by and it does affect the performance a lot.

[801mike]

? for you nutkin how much did the fuel pump run you?