Anyone have any ideas about this.....
my 1995 SC400 with 82K miles tends to hesitate about 50% of the time from a stop, then runs fine. I have take it to the dealer who has changed the plugs ($220) and done a throttle body cleaning ($200), which helped; however, it still tends to pause briefly before accelerating. Car isn't quite right. Otherwise, it's the best car I have ever owned. Thanks for any help.

 

burnettebr,
What other maintenance has been done? Fuel / Air filters ?? PCV valve ? Cap, rotor, wires?? Your t-belt is 8-9 yrs old, should have been replaced at the 7 yr mark. It's 90k miles OR 7 yrs old whichever comes first. ( 60K if you are in severe conditions ).

If new plugs and a throttle cleaning helped but did not eliminate the problem, your car could be out of tune. If it was a mechanic, electrical failure with a properly tuned car, new plugs would not have made any difference.

Regards

 

You know, you're telling burnettebr to perform a $700-$1100 procedure on his car.

No matter what its age, the timing belt has nothing to do with the hesitation problem. He said it himself - the problem only occurs half the time.

 

PERRYinLA,
I am not telling burnettebr to replace the t-belt as a solution to his problem. Just asking if it's been changed and providing info that it should have been.
The problem sounds like a low speed miss. Most likely culprits are :
Clogged air filter
Faulty spark plugs ( obviously changed already )
Faulty spark plug wires
Cap & rotor
Fuel filter
all of the above are basic tune-up items. If the problem still persist you then need to look for :
Improper timing ( cam timing in this case ) since ignition timing is ECU controlled
Improper cam timing means a stretched t-belt so yes the t-belt COULD be the culprit ( however unlikely )

No mention of check engine light, so I assume it's not electrical/ECU related.

 

Well, I think it is great that you are trying to help him out, so I didn't mean to sound unappreciative. But he's asking for help with his car's hesitation problem, not its maintenance schedule. If he had only seen your first answer he might have gone out, gotten a new belt and still have some hesitation!

Yeah, I guess anything is possible, but if the timing was off due to a stretched belt (I did a search- that's never been reported as a problem on our V8s), then he'd be hesitating all the time, not just half of the time.

 

Is you car stock? Any aftermarket intake system? I use to have hesitation on 95 SC400 when I ran a aftermarket intake system with a cone filter. Cause was the hot air the engine is breathing. End up putting back my stock air box and filter but without the snorkel.

Chu...

 

Thanks for the feedback everyone. I'm impressed with the quick responses. The dealer checked the wires when the plugs were changed, and told me that the throttle body/fuel system cleaning should also clean the fuel filter eliminating the necessity of replacing the filter. I will check the air filter. The timing belt is original-been holding off replacing it due to the $450 fee.

 

burnettebr,
What about your cap and rotors? Is your car hard to start in the morning? Is there any smoke from the exhaust (black) when you accelerate from a stop?
A dealer told you that a fuel system cleaner would clean your fuel filter?!?!?!? A fuel filter is designed to trap any debris before it enters the fuel injectors, If some sort of "cleaner" breaks down the debris and loosens it from the filter, it's going to end up clogging your injectors or scratching your cylinder liners. What is this dealer service advisor smoking? It is true that with today's fuels, it is not often a fuel filter clogs up and due to the location, many mechanics shy away from replacing it b/c of rust, fuel spillage etc etc. But a fuel injection cleaner, even GM Top engine cleaner or BG 44K is designed to clean fuel varnish not break down debris such as sand, dirt, grit that can enter into the fuel tank.

PERRYinLA,
My apologies if you misunderstood, however the only thing my first post hinted at as to the cause of the problem was " car out of tune " which means it needs a tune-up. Nowhere did I say " it needs a new t-belt water pump" That first post was mostly asking for more info.

Regards

P.S. Sorry for sort of highjacking your thread burnettebr