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Weird Bucking in lower RPMS.

T

Tourige

CEG's Resident Jackass
Joined
May 25, 2004
Messages
3,484
Location
Calgary, Alberta, Canada
No CEL, car bucks anywhere under 3500ish rpms. I thought it was something with the IMRC, but i dont see why that would cause bucking, and again no CEL. The IMRCs are clean and the butterfly plates are clean.

Shouldnt be the fuel filter because it runs like a champ above 3500ish.

Shouldnt be plugs or wires because they are decently new and again, no flashing CEL so its not a misfire.

Happens in every gear, it even backfired when i tried it in 2nd.
 
I'll second that. You need new OEM plugs and wires.

Mine started doing that shortly after I installed my Ford Racing wires. OEM wires and new plugs fixed it.
 
Tourige said:
No CEL, car bucks anywhere under 3500ish rpms. I thought it was something with the IMRC, but i dont see why that would cause bucking, and again no CEL. The IMRCs are clean and the butterfly plates are clean.

Shouldnt be the fuel filter because it runs like a champ above 3500ish.

Shouldnt be plugs or wires because they are decently new and again, no flashing CEL so its not a misfire.

Happens in every gear, it even backfired when i tried it in 2nd.
Click to expand...

Did you pick up another contour?

Like todras said, it sounds like wires.
 
Harrry said:
Did you pick up another contour?

Like todras said, it sounds like wires.
Click to expand...

No, its my old SVT that my brother has.

The wires are magnecore and we all know they never fit properly.

But wouldnt it be causing a CEL if it was misfiring from the wires? And it runs like a champ up higher.

Either way it needs new plugs and wires, its getting the full Turbo treatment this year.
 
no,not nesc. i've had many issues were the plugs and wires were bad and didnt get a misfire.
 
If I am getting the low RPM bucking, and hesitation, and the car feeling like its falling flat on its face in the high RPMs like 4500-6000 and at certain RPM's, does this still sound like Wires. or plugs, or coil?? I replaced my wires, plugs and coil and all this went away for a short time, then the problem came back. Any ideas???

thanks,
Adam
 
If it feels that you are fighting the idle air control trying to hold the idle speed up a little when the throttle is closed, it may be a normal condition. I have reduced the sensation by keeping the throttle body and IAC clean as well as adding the throttle hang fix (copper plug).

I feel it most on a hot day with the AC on when trying to drive at light throttle at about 30 MPH in 4th or 5th gear.

If that is not what you are feeling, look elsewhere.
 
BigJim, I am not quite sure what you are describing. What I am experienceing is surging in high RPM, when the engine hits certain RPMS it feels like it has no power for a bit. Also in low RPM it really bucks and hesitates. Does this sound like the IAC??

Thanks,
Adam
 
Big Jim said:
The title of the thread is weird bucking in LOWER rpms.
Click to expand...


I understand that...would the IAC affect why my car has bucking and no power in the lower RPM until it hits about 3.5k. The problem I have is almost putting the car in 3rd and flooring it from a stop.....it takes awhile until the RPMS get up there for the power to appear.


~Adam
 
Engine bucking on Tip-Ins

Engine bucking on Tip-Ins

Strangest thing, I'm running into what may be a similar situation. The difference is that my issue happens at nearly any RPM. Here is what I've done - please tell me if this looks/sounds familiar...
1-Replaced fuel filter
2-Replaced TPS (sensor)
3-Replaced bank 1 O21 and O22 (intermittent MILs-bank 1 lean-limit)
4-Removed UIM/LIM cleaned both carefully
5-Lightly port-matched UIM to LIM (HIGHLY RECOMMENDED!)

Still have the hesitation!

As of right now I've been running SCT Livelink data-logging through an XCAL2 whenver I drive it. The results are this->
1-The PCM is pulling spark advance on tip-in BIG-TIME (eg 28 Deg before tip-in to -10 on a 20% tip-in).
2-This seems to be caused by the IIMRC not working properly -STILL! (IIMRC position is part of the spark advance correction factor - SCT help-files).
3-I've gotten yet another 1519 MIL (Stuck-closed IIMRC eror).

As I have 150k miles on this car, I wouldn't mind replacing the IIMRC actuator if need be. However, I'd like to ask anyone who has rmoved the secondary butterflies how the engine responds and what the control impact is first. What do you all think?
 
97vulcan said:
I understand that...would the IAC affect why my car has bucking and no power in the lower RPM until it hits about 3.5k. The problem I have is almost putting the car in 3rd and flooring it from a stop.....it takes awhile until the RPMS get up there for the power to appear.


~Adam
Click to expand...

Once the throttle opens, the IACV is out of the picture. Hence the word "IDLE".
 
97vulcan said:
I understand that...would the IAC affect why my car has bucking and no power in the lower RPM until it hits about 3.5k. The problem I have is almost putting the car in 3rd and flooring it from a stop.....it takes awhile until the RPMS get up there for the power to appear.


~Adam
Click to expand...

What I described would be at a low enough speed that the IAC is trying to hold the idle higher than the very low engine speed you would have with a higher gear and low road speed. Roughly speaking that would probably be under something like 1200 to 1500 RPM. It could be higher if you are suffering from extreme throttle hang.
 
99SEinLivonia said:
As I have 150k miles on this car, I wouldn't mind replacing the IIMRC actuator if need be. However, I'd like to ask anyone who has rmoved the secondary butterflies how the engine responds and what the control impact is first. What do you all think?
Click to expand...

Just replace the IMRC and enjoy the secondaries opening up again.
 
Tourige,
I had very similar symptoms, turned out to be carbon tracking on the plug boots (magnecors). I needed to replace both plugs and wires at same time to eliminate the problem. Dielectric grease worked for about 2 weeks, but then it would return. Check out your plug boots for signs of carbon tracking.
 
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