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Hesitation, bucking @ low RPM, no codes

G

getsum111

Yes I am a Pirate, 200 years too late.
Joined
Apr 5, 2005
Messages
4,188
Location
Pillaging in Freedom, PA.
Hello all. Pretty much what it says. When I press the throttle at low RPM's (2000-3400), I get a bucking, really bad hesitation. It almost feels like it's misfiring, but it's not. I scanned it, but no codes are present. I recently changed plugs, wires, cleaned UIM, etc. I did break a vacuum line, but it was patched (the green one to the EGR). Any ideas of what I can check? If I give it gas in the upper RPM's, it seems better, ie. no hesitation or bucking. Thanks for any help you give. Happy holidays.
 
Is it worse when the fuel tank is low?

Try driving it with a fuel pressure gauge installed. If the fuel pressure drops off dramatically when it is acting up, you have a fuel supply issue. The likely causes are a plugged fuel filter, a plugged fuel pump filter screen (on late 99 with returnless system), or a bad fuel pump.
 
Big Jim, no difference w/ fuel level, plus I have a return system, she's an early 99 it would seem. New filter as well, so I'm not really thinking fuel pump, as it's kinda sudden. Just got done testing the TPS, it seems OK too.:confused: Before, I was having a misfire due to fuel injector issue (no signal to injector via noid light), but then it cauised a misfire in #6. Now i'm getting no codes, plus the #6 plug looks good, still pretty white insulator. Thanks for the suggestions, though. I do appreciate it.:cool:
 
My suggestion is;
Send it in for a real time scan (about $100) or buy a real time scanner (Actron 9145 or similar for about $200). Then post the PIDs. And we should be able to help you narrow it down.
 
Go check your IMRC cable, just for poops and giggles, it may be disconnected and the secondaries open.
 
Maybe it is a misfire, just not enough to throw codes or flash the CEL. Replace your wires/spark plugs, or even just really re-seat them good, and see what happens.
 
You summed up EXACTLY what is happening with my vehicle and I posted earlier under the thought that it might be a transmission problem.

After 4 days of diagnostics and bogus "ideas" as to what was wrong with the car, the dealership FINALLY took it out on the road. He replaced the Fuel Filter. It didn't aleviate the problem, and now I'm wondering if it's a fuel pump...but I ask:
If it IS a fuel pump, why is it doing this after I've been driving for about an hour at 100km/h? If I keep driving, it gets worse and worse, and eventually the bucking happens at lower speeds as well. If I let the car cool down for about an hour, all is well again for about a half-hour to an hour of driving. Can someone explain to me how, IF it were the fuel pump, why the car wouldn't just be gas-starved and just choke out and stop altogether?
I'm so frustrated!
 
kouksie said:
...If it IS a fuel pump, why is it doing this after I've been driving for about an hour at 100km/h? If I keep driving, it gets worse and worse, and eventually the bucking happens at lower speeds as well. If I let the car cool down for about an hour, all is well again for about a half-hour to an hour of driving....!
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The gas helps to cool down the fuel pump. As the fuel goes lower, there is less gas to help cool the pump. After letting the car sit for an hour or so, the pump is cooled enough for it to function again. And the fuel screen/sock probably also had some of the "crud" slough off after not putting any pressure on it.
 
Twocontours, I honestly don't know.

I don't have access to all the fancy gear that some people on here do (wish I did!). I am forced to use what I know about cars (limited since I've stopped reading up on cars), and have to rely on my smarts and what the dealership tells me, and try to decipher what's crap and what's not.

I used to be a car fiend, but with a family that wouldn't let their "prized daughter" be a mechanic, and being in University, I just don't have the time to be as car-smart as I used to be.

I'm just ready to give up!
 
Tony2005 said:
The gas helps to cool down the fuel pump. As the fuel goes lower, there is less gas to help cool the pump. After letting the car sit for an hour or so, the pump is cooled enough for it to function again. And the fuel screen/sock probably also had some of the "crud" slough off after not putting any pressure on it.
Click to expand...

Seriously, I love this place and everyone in it. Why did I not find this place when I got my car 8 years ago???
You rule my roost. Honestly.
 
kouksie said:
Seriously, I love this place and everyone in it. Why did I not find this place when I got my car 8 years ago???
.....
Click to expand...
ROTFL. I did not find this place until 9 years after I bought the car.:laugh:
 
Tony2005 said:
ROTFL. I did not find this place until 9 years after I bought the car.:laugh:
Click to expand...

*giggles* well I guess it's good that I found this place now...as I'm considering driving my car off a bridge! LOL. Kidding!!
I'm just flabbergasted by the amount of stuff that's gone wrong with it since I got it. Perhaps I baby it too much, because honestly, I've put so much money and love into this car, it shouldn't be acting the way it does. Makes my heart-parts cry a little...:cry:
 
kouksie said:
.... Perhaps I baby it too much, because honestly, I've put so much money and love into this car, it shouldn't be acting the way it does. .....
Click to expand...
I hate to be the one to break the bad news to you but.....
it is a car. It is supposed to break down. You just have to maintain and repair it. If it doesn't break down, it is because it is stored in the garage and not driven regularly.
 
Tony2005 said:
I hate to be the one to break the bad news to you but.....it is a car. It is supposed to break down. You just have to maintain and repair it. If it doesn't break down, it is because it is stored in the garage and not driven regularly.
Click to expand...

This is true. I think I'm in denial. :rolleyes:
 
Crisis Averted:

Crisis Averted:

Well, at least I'm crossing my fingers, but, it seems as though a new fuel pump was what she needed.
I put in the new fuel pump yesterday and took her out on the road for a total of 4 hours.
Prior to the change, the erratic behaviour only took about 20 minutes to start. I made it 2 hours north of my city without a glitch, and drove back 2 hours more, and nothing. If anything, the ride is very smooth.
Thanks for all the advice/ input!:cool:
 
Good deal Kouksie. Hope that was it. Well, I finally set of a CEL New Year's Eve, so I'm gonna get it scanned, then prob. just do a real time scan at teh stealership.:cry: We'll see what happens. Thanks guys.
 
getsum111 said:
I recently changed plugs, wires, ... I did break a vacuum line, but it was patched (the green one to the EGR). Any ideas of what I can check? If I give it gas in the upper RPM's, it seems better, ie. no hesitation or bucking. Thanks for any help you give. Happy holidays.
Click to expand...

My money is on the wires... who can cover?

I'm betting a wire is mis-routed, or not seated properly, or has been cut/scuffed during install. Those are exactly the problems I had when I accidently (ignorantly) swapped a couple of the leads on the coil. Two of the leads are switched & do not correspond to the cylinder location on the engine. If your car was running OK with the old set, re-install them & DOUBLE CHECK the plug wire routing at the coil.


The other thing to check would be the vac line that was repaired. How was it repaired?? Is it possible it is plugged up now? I doubt this is the problem, but worth a look if the wires check out.
 
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