On trip-strange engine "shudder" need advice

[whlav]

Emergency trip came up. Just finished 1200 miles in 19 hours. Noticed a few hours ago that at about 70mph when pulling out to gradually pass other cars felt a slight "shudder". Don't know how else to describe it except sort of like a small shake or vibration. This only occurs when gently pressing the gas pedal. If I hit it hard no problem at all. Does not do it at lower speed. No check engine light and car running otherwise great. Averaged 27mpg on the trip.

Anyone got any idea what it could be. Worried about the trip home!!

 

[rendyx]

I'd associate it with your tranny, but I can't be sure (not an expert on the autos). Any other signs of the tranny having issues? Hard and delayed shifts?

 

[Mr Anonymous]

Could be as simple as a slight imbalance in one of the wheels that is only noticeable in the circumstance you describe. It could also be a bad motor or tranny mount, with the outside possibility of an EPC pressure problem in the tranny at part throttle.

 

[whlav]

Thanks so far. Not a wheel problem. Tranny shifts fine through all speeds under normal operating coditions or at WOT. Only noticable as described, right about 70mph when lightly touching gas. Kinda like the feeling you get if you are poking along in 4th gear and the engine is lugging.
Hoping that driving more aggresively will keep it from happening. Got to turn around and drive 1200 miles home in a few days!

Any chance fuel injectors could cause something like this?

 

[sdpatt]

Sounds like a spark misfire under load. Since you didn't mention a CHECK ENGINE light, I would have to ask you about the age and brand of your spark plugs and plug wires and if there is any oil in the spark plug wells. This could even be a case of "arc tracking" where the spark travels down the outside of the spark plug because there is either moisture or oil between the boot and the plug. I would check the secondary ignition components (plugs and wires) first.

 

[SHOtimer]

My car used to do exactly what you are describing before I did my 60k. Once I did that, (plugs, wires, ect...) It ran like a champ, and has not come close to doing it again. Hopefully it is something that simple for you.
Doug

 

[whlav]

Thanks sdpatt and shotimer.Last 60k done about 6k miles ago(full 60k) including new Ford plugs and wires. I'll try to get a look at the plugs but its ass deep in snow here in Ottawa (now I remember why I moved from here to the Heart of Dixie and I'm parked in my buddies driveway with six feet of snow banks on both sides.

By the way the 60k was done at FPS in Georgia and the plug seals were done at the same time. New 155 fuel pump about 3k ago. Fuel filter was changed with the 60k service. New O2 sensors with PP y-pipe k ago.

Once again "No codes"

 

[HopefulSHO]

Torque converter unlocking?

 

[rangerj]

WHLAV,

Try a volt test of the throttle position sensor(TPS). You may have a flat spot, or wear spot, near that throttle position. At 70mph you are tach'ing about 2600 to 2700rpm in 5th gear.

With the key in the on position, but the engine off, put the volt meter probe on the sending wire, and the other lead on ground.

Then open the throttle by hand, slowly turning it to wide open throttle (WOT).

The voltage should start at about .5 volts and move up to about 4.5 volts. If you hit a spot where the voltage drops off, you have a flat spot in the TPS. Just a thought, rangerj

 

[BlackOnBlackATX]

i started a post about this about a week ago, i was having the same problem. it was suggested that i get my tranny flushed with a detergent of some sort then refilled. i havent done it yet though so i dont know. im suspecting it might be the band on my overdrive gear so im going to have them checked soon. let me know what happens if you figure it out, or ill let you know if i get there first. good luck!

 

[whlav]

Saw Blackonblack's post on similar problem. I'll get back to him when I find out what causes the problem. No other driveability issues right now and no place to do any work. I'll have to wait till I get home. Thanks for the responses so far.

 

[whlav]

Problem fixed. Thanks to SDPATT and RANGERJ. Checked TPS voltage and got readings of 1.1 to 3.8.
New TPS and idle reset soved the problem. Thanks guys! Now to fix the cxruise control. Any problem solvers out there?

BLACKONBLACK, MAYBE THIS WILL HELP.

<small>[ March 20, 2003, 11:34 PM: Message edited by: whlav ]</small>

 

[BlackOnBlackATX]

well, my TPS is new, but consider the idle reset this afternoon! thanks for the follow up!