: over 70Ks in overdrive



dustypatch101
09-09-11, 10:28 PM
I am having a problem with my 1989 4.5 Allante, driving in town it's wonderful but once it kicks into overdrive at 70 Ks it develops a miss if I drop it down into 3Rd it's back to normal runs great. I am unable to use the DIC as it's 50% black. Any suggestions I have been thinking it just m,ay be an ign. miss or a fuel miss only wish I could chek the injuctor values.
Stu
Vancouver B.C. Canada

cadillac kevin
09-09-11, 10:44 PM
can you describe the miss more in depth? does the car get very sluggish?
does the transmission seem like its slipping or engaging and disengaging (surging)?

carnut
09-10-11, 11:41 AM
Most times when this occurs you are in torque converter lock up as well as overdrive. Once the engine and trans are "locked" any secondary ignition fault will be felt on light throttle. There is no cushion between the 2. I would suspect a cracked spark plug or arching plug wires. If either are 40 to 50,000 miles old, replace them as a normal maintenance and report back. Rather than downshifting when this occurs, just rest your left foot lightly on the brake pedal, that should unlock the converter and keep the trans in overdrive. Does this miss "chuggle" improve?

dustypatch101
09-11-11, 11:06 PM
Hi Kevin, the car is sluggish, the trans is not slipping or disengaging. even running her at 100 plus Ks it still has a miss. If I put my foot into her without the transmission kicking down into 3Rd it will act normal, once the car settles down to a sustaned speep or going up hill I can feel the miss. The plugs have about 2000 miles as well all new ign. wiring cap & rotor.
Thanks
Stu

dustypatch101
09-11-11, 11:13 PM
Hi carnut, the plugs have no more than 2000 miles on them but that does not mean I don't have one cracked whick I will be looking into. I also changed cap, rotor, and ign. wiring at the same time. thanks for the information on light break pressure ( I never thought of trying that ) I do find her sluggish going up hills, we do have steep hills here on the west coast.

Thanks
Stu