"Bucking"

[David M. Hip]

Howdy folks (my first Thread)
Our '89 SHO that we have had since almost new has a very intermittent bucking problem. It will go for months without a problem and then do it some more. I have had the local Ford dealer do most of the work since new and they have replaced and checked over most everything that has been mentioned in the many of these threads. It seems to make no difference cold or hot, slow or cruising, it doesn't seem to buck under hard acceleration. This has been going on for about four years. My family refuses to drive this machine and I'm concerned that it will quit or at least make my trips to NY and Chicago less than pleasant, consequently it has to stay local, and as you all know these things need to be driven! I stopped by and had the codes read last week- code 14 & code 19 - the mechanic cannot find the cause.
Any insights and solutions would be greatly appreciated.
Thanks
Hip

 

[itwonder]

On the ignition side, the CID deserves attention. But I'll bet they have replaced that, possibly multiple times. Is the CID cavity being flooded with oil from a leaking seal? Is there possibly a problem in the wiring to the CID?

There's guesswork here, Have they replaced the fuel pressure regulator? Fuel pump?

 

[FREAK_SHO]

14-Profile Ignition Pickup Circuit Failure

19-Cylinder Identification Sensor Input Failure (3.0L SHO)

sounds like a cam sensor on the way out and or crank sensor.

 

[spiegeltuxer]

+1 on the cam sensor.

 

[93rev2sev]

Needs a front 60 before driving long distances...unless you know the age of your crank sensor waterpump and timing belt is less than 60,000 miles.

 

[1993MTXSHO]

ok this might be stupid, but my 93 mtx had a bad bucking problem, ended up being the battery hold down was contacting the terminal on the battery, which in turn was grounding out on the engine compartment wall. Just an easy check to see if thats it, if the battery moves a little it contacts, shorts, melts the metal away, and then doesn't contact it again for a while.

 

[ashedd]

ok this might be stupid, but my 93 mtx had a bad bucking problem, ended up being the battery hold down was contacting the terminal on the battery, which in turn was grounding out on the engine compartment wall. Just an easy check to see if thats it, if the battery moves a little it contacts, shorts, melts the metal away, and then doesn't contact it again for a while.

I had the same problem with a top post batt I was using. It would short out through the "sho" hood pad and cause the car to stall or the eatc to go nuts! Like all the lights on the eatc display would light up. I had a hunch it was the batt so I put the proper side terminal in and never had the problem again.

 

[Kens1992mtxSHO]

A lot of things can cause this but...

+2 on the cam sensor.

also, check the DIS. Had the same problem and a new one fixed my problem.

 

[Storm-Chaser]

I thought I would mention this, since people's definition of "bucking" is not always them same.

I recently had the fuel pump fail without notice - or so I thought. I would get intermittent missing/bucking at high rpm, or hard acceleration, or when the fuel was below ~ 3/16 of a tank (before the fuel low light). After replacing the bad pump, the missing (which at times was a intense as a rev-limiter) was eliminated.

 

[David M. Hip]

Thanks a bunch. I know that most of the parts mentioned have been addressed, with your thoughtful replies I will start back through the list.

 

[Shopower400]

99.9% it's your Cam sensor. I had the exact same problem. Replaced it and it was a night & day difference. As far as your fuel pump, see if you can hear a whine coming from the back when you turn the key 1/2 way on, or the accseory postion. Chances are it's not to far behind the sensor, due to the age. A loud whine means it's close to it's end. Also if your car seems a bit sluggish on the top end(from 80-120) that's another pretty good sign.(Providing all the other basic maintenence is kept up) Replaced my pump as well, and there is a signifigant improvement on the top end. If you can't afford to replace the pump, the filter is a good temp. fix & should help to quiet down the pump some + give it a little more life. Hope this helps!

 

[Storm-Chaser]

You cannot always rely on the "fuel pump priming" noise to indicate pump operation. I reinstalled the fuel pump that was removed in October due to a bad sending unit (I used the "old" pump with the working sending unit). When the pump was removed, the assembly had a green "**** remanufactured" label on it, and the pump was a Walbro unit with engineering number F3DU-9350-CA stamped on the case.

Even with everything off in the car (radio, heater, etc.) the pump makes virtually no noise. Operation was verified with a fuel pressure gauge - during startup, static engine runs to 6,000rpm, street runs to 7,300rpm, and a regulator bleed-down check. So I know that it is working properly.

 

[jthod]

Sorry for the hijack, but mine has been doing a little bucking latley too, and seems to be either fuel or ignition related.

The usual situation is while cruising (not accelerating or decel.) at 35-40, and I hit a bump (railroad tracks, washbords, etc.) it seems to stumble. I started just letting of the throttle when I know I'm going to hit a bump. I noticed tonight, when I do let off and push in the clutch and hit the bumps, in this case a fairly smooth set of railroad tracks, the tach dives to ~600 RPM, and jumps right back up.

Funny thing is, it just started doing this after being in the shop for a clutch.

 

[FRDSHOGRL93X3]

The usual situation is while cruising (not accelerating or decel.) at 35-40, and I hit a bump (railroad tracks, washbords, etc.) it seems to stumble. I started just letting of the throttle when I know I'm going to hit a bump. I noticed tonight, when I do let off and push in the clutch and hit the bumps, in this case a fairly smooth set of railroad tracks, the tach dives to ~600 RPM, and jumps right back up.

Funny thing is, it just started doing this after being in the shop for a clutch.

I would say this is loose battery terminal connection's. They prolly disconnected the battery when they did the clutch.

My 89 also "bucks" intermittently while cruising and for the life of us we can't seem to fix it. We have swapped out all of the sensors and checked the gap an the cam s. I think the next option is to replace the cam s alltogether, grrrrr.

 

[Storm-Chaser]

Replace the cams . . . ?




You need to take your car to a different dealer . . . .

 

[FRDSHOGRL93X3]

Cam sensor.

 

[Storm-Chaser]

Whew !

[looks for emoticon of wiping sweat from forehead]

 

[FRDSHOGRL93X3]

Off topic/refresh my memory/it's been awhile; the cam sensor is the "round looking" one and the crank sensor is the one that gets gapped/best way to swap is by going through the passenger wheel well, right?
If it's the cam sensor/round one thats an easy fix, whew....
Honestly I forgot that one was there and has not been replaced yet, it may indeed be the culpret.

Very sneaky

 

[Storm-Chaser]

Memory refresher 101



















(was C.I.D Removal w/ Pics. MTX/ATX cars)

 

[jthod]

Sorry for the hijack, but mine has been doing a little bucking latley too, and seems to be either fuel or ignition related.

The usual situation is while cruising (not accelerating or decel.) at 35-40, and I hit a bump (railroad tracks, washbords, etc.) it seems to stumble. I started just letting of the throttle when I know I'm going to hit a bump. I noticed tonight, when I do let off and push in the clutch and hit the bumps, in this case a fairly smooth set of railroad tracks, the tach dives to ~600 RPM, and jumps right back up.

Funny thing is, it just started doing this after being in the shop for a clutch.

Found mine! (I hope)

Loose memory lead wire off of the positive battery cable.