Bucking/hesitation at 1800 RPM

[hank szeto]

1974 3.0csi: Any ideas what causes the bucking at RPMs below 2,000? Problem goes away with I down shift (increasing RPM). Seems like it is starving for air or gas.

Hank

 

[rsporsche]

Hank

has the car run fine and this is this a recent development? always best to start with keeping it simple. first check for vacuum / air leaks. and make sure you have good spark to the plugs and that all of the ignition is in good condition (probably is since it runs at rpm). then make sure you don't have any water or trash in your fuel filter. sounds like the fuel pump is working if it runs at high rpm and there is good draw of fuel / air.

how old is the gas? next question, have you ever had the injectors flow tested / cleaned? i have had injectors stumble / stick in the transition from fast idle to running. one time i ran injector cleaner and it solved most of the issues. another time i had the injectors cleaned. anyway you look at it, it sounds like a combustion problem - either spark issue or gas delivery issue. a car that runs well at higher rpm is generally getting decent flow of air / gas and good ignition.

good luck and hopefully some of the people like SFDon can shed more technical light on this subject.
scott

 

[hank szeto]

Bucking/Hesitation at 1800 RPM (74 3.0 csi)

Thanks Scott.

This is a recent development. Vacuum good and no air leaks. I drive the car on the weekends and probably fill it up every 2-3rd week.

I'll have injectors cleaned and tested.

Whos is SFDon and how do i get a hold of him?

Other than low rpm problem, the car runs great.

Hank

 

[rsporsche]

Hank,

SFDon is on this forum, hopefully he will read this and weigh in. you might try running BG44k injection cleaner. you put it in the gas tank -

since this is a recent development, you might should check the fuel filter - might have some water or trash in it. taking the injectors out and having them flow tested and cleaned usually means you have to send them to somebody who does that kind of work.

scott

 

[sfdon]

Hank,

SFDon is on this forum, hopefully he will read this and weigh in. you might try running BG44k injection cleaner. you put it in the gas tank -

since this is a recent development, you might should check the fuel filter - might have some water or trash in it. taking the injectors out and having them flow tested and cleaned usually means you have to send them to somebody who does that kind of work.

scott

Pull your plugs- what do they look like?

 

[Sven]

since this is a recent development, you might should check the fuel filter - might have some water or trash in it.

I agree. One of the first things to do, if in doubt, is to replace the filter. Especially if you are sensing a starvation issue. I once spent many hundreds of dollars and dyno time chasing down a problem that turned out to be the fault of this $10 part.

 

[Stevehose]

Certainly worth a go. In my experience usually fuel filter blockages reveal themselves at higher rpms.

I agree. One of the first things to do, if in doubt, is to replace the filter. Especially if you are sensing a starvation issue. I once spent many hundreds of dollars and dyno time chasing down a problem that turned out to be the fault of this $10 part.

 

[hank szeto]

Bucking/Hesitation (74 3.0 csi)

Thanks. I replaced the fuel filter two weeks ago, when the problem developed. Still have problem.

Hank

 

[pamp]

Check Points and timing? Dist. cap?

 

[30csl]

I would disconnect the MPS and TPS separately, I think I'm right in saying the engine runs without them. See if that helps isolate it.