Bucking/Hesitation

[Jack_Flash]

Now, I know there's another thread on here that has the same title but that one hasn't been posted on in forever and I really would like some input on my problem. I've been having the same problem as that getsum guy but the only thing is... it works when it's full tank but once it gets down to about 3/4 tank it'll show signs of it and progressively get worse as the tank is diminished. Now, I've spoken with a friend who know cars as much as any mechanic and from what he tells me is that my kind of fuel pump is the kind that either works, or it doesn't. In which case my car wouldn't start. One other thing: does the rpm problem I've been having have anything to do with it too? The rpm problem being that most times when I put it in neutral while driving the rpm's will either stay where they are at for a few seconds or shoot up about a thousand rpms and then slowly go down.

I've ran countless bottles of injector cleaner through it...changed the plugs and wires...and changed the fuel filter.

 

[thegadget]

Yep

Yep

CAR: 2000 SVT Coutour/2.5 Duratec/96k/MTX
I am in the same situation. I have ran lots of injector cleaner through, and have already replaced the fuel filter. I am planning on getting spark plugs and wires maybe tomorrow. It is really weird, sometimes it works, and some times not. I was looking through the forums, and someone was saying that the fuel pump itself could be the problem. I guess there is an internal filter? (screen maybe?) Anyway, I will be working on this, and hopefully figure this out. I really wish someone would write up a series of checks on this issue.
Here is what I have figured out...

1. Usually right after I start the car, I wait until the engine temp is to normal. It usually doesn't buck/hesitate. Only after, say 20 min or so it starts loosing power. (Could be a heat issue.. Ignition?)
2. After I replaced the fuel filter, it seemed to get much better. But now, after the replacement, still have the problem.
3. Yesterday, After I replaced the windsheild and got a tint job, it actually started bucking/hesitating even at low rpms. No more roar, almost sounded like the little dodge stratus 4 cyld.
4. I opened the IMRC? on the front of the engine, and it seems that the motor and links are movable. I haven't checked anything else yet. I am getting really fusterated! I have only had this car a few days, and it has proven very underpowered.

True, I do drive a 1997 BMW M3, and a 1998 BMW 328i; but shouldn't this car be comparable to the 328's power (190 HP)? I absolutely hate loss of power!! Any help would be greatly appreciated.

More reading.... I noticed that water can cause this. When I bought this car, the guy had the car detailed for me (nice jesture) but could have caused the problem. And I just did an full synthetic oil change and counldn't find the funnel. So I cleaned the engine off again. (just a little on the front). I wonder if this could have started this from the beginning? Any comments? Thanks!

 

[LauraSVT]

...One other thing: does the rpm problem I've been having have anything to do with it too? The rpm problem being that most times when I put it in neutral while driving the rpm's will either stay where they are at for a few seconds or shoot up about a thousand rpms and then slowly go down...

This particular malady may be tied into the idle air control (IAC). Two particular symptoms are common with failures of this part. 1) the car won't hold revs and dies unless you keep your foot in the throttle, or 2) the throttle hangs when you step off the go pedal. There have been some discussions to both effects on this forum. You may be able to find a bit more info with a search. Regardless, the IAC is not a particularly expensive part -- under $100.

 

[Big Jim]

Now, I know there's another thread on here that has the same title but that one hasn't been posted on in forever and I really would like some input on my problem. I've been having the same problem as that getsum guy but the only thing is... it works when it's full tank but once it gets down to about 3/4 tank it'll show signs of it and progressively get worse as the tank is diminished. Now, I've spoken with a friend who know cars as much as any mechanic and from what he tells me is that my kind of fuel pump is the kind that either works, or it doesn't. In which case my car wouldn't start. One other thing: does the rpm problem I've been having have anything to do with it too? The rpm problem being that most times when I put it in neutral while driving the rpm's will either stay where they are at for a few seconds or shoot up about a thousand rpms and then slowly go down.

I've ran countless bottles of injector cleaner through it...changed the plugs and wires...and changed the fuel filter.

It is always helpful if you tell us the year, engine, and trans.

An extremely common problem with the late 99 and early 00 with the returnless fuel system is the plugged screen in the bottom of the fuel pump module. It is too fine and too small. It is also not needed as there is a conventional sock filter inside the module before the pump.

If you have a late 99 with returnless or an 00 V6, pull the fuel pump module out of the car. There is a how to FAQ with pictures. Remove that filter and throw it as far as you can. Confirm that the tank is clean and put things back together and go on your merry way.

It would not hurt to run a fuel pump pressure test and get a pressure reading while it is acting up.

Your mechanic needs further education.

 

[Bowerbird]

I'm thinking that it's the fuel pump. I have a 2000 and I had this problem with about 1/3 tank of gas and it steadily got worse till having 1/2 a tank of gas or more was necessary to drive without the hesitation. Replacing it cured the problem. The running till it stabilizes reminds me of the IAC problems though... The fuel pump problems i had were only related to acceleration and amount of gas in the tank.

 

[Jack_Flash]

My car is a 2000 svt mtx with about 115K miles on there

 

[getsum111]

Jack, sorry for the delay, I was putting in a set of headers over the weekend. So much fun. :crazy: :laugh: My particular problem was similar to yours, as I read from your reply to my thread. I had swapped/changed/tested/ the following. New plugs, wires, CPS, swap coil, injectors, PCM, cleaned UIM, LIM, fuel lines, gutted precats, installed MSDS headers, tested TPS, CKP sensor, new O2, probably more. Here's what I think about your problem (BTW I'm not a professional mechanic. :laugh: ):

Your fuel pump will work or not, that's true. But as Brapple said, if the screen is clogged, it won't work as well as it should. Check out your fule pump screen, it's easy to get to under the rear seat. you may need to trim the hole over the fuel pump to get the housing out. Don't worry, no one will see it. :laugh:

But first I would do a complete UIM/LIM rebuild as per Ray's how-to on the old forums. It will deal with the most commonj sources of the problems you're dealing with. Use Berryman's B-12 to clean everything out.

My particular issue was caused by dirty sockets getting my new plugs dirty, which apparently caused carbon tracking along the outside of the plug. Brand new plugs, shot with less than 1000 miles.

Check out the fuel pump screen first, it's almost free. Then do the UIM/LIM cleaning, and check for carbon tracking across the plugs. Then post up and let us know what you find. Then we'll see where to go from there.