Car is jumping when I am going steady at 45 or 50mph

Topic: Car is jumping when I am going steady at 45 or 50mph (Read 2506 times) previous topic - next topic

Car is jumping when I am going steady at 45 or 50mph

December 21, 2004, 09:54:31 PM

OK here is the deal. I have an '88 5.0 EFI T-bird.
When I level off at 45 or 50mph my car will start jerking, it feels as if it is coming from the back end. If I left off the gas it stops and if I give it more gas it stops. Any ideas? :dunno:
I am not sure what is going on with it but I need to get it fixed before it becomes a bigger problem.

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #1 – December 21, 2004, 11:04:44 PM

OK you are giving enough gas to keep it at a constant speed at what should be low RPM's in 4th gear. When was the last time the car had a tune up? It almost sounds like you are getting a misfire from old plugs or wires at low RPM's due to the faulty part just starting to go.

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #2 – December 22, 2004, 04:26:31 AM

Does it do it in both 3rd and 4th gears?

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #3 – December 22, 2004, 04:32:43 AM

Yes it does happen in both 3rd and 4th. The odd thing is it doesn't happen all the time. Only when it wants to.

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #4 – December 22, 2004, 08:40:26 PM

It sounds more like a bad spot on the trottle position sensor to me.

i like the misfire theroy also, explained very short and sweet i might add.

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #5 – December 23, 2004, 03:42:53 PM

My 87 just started doing the same thing, this random sputter, so i did a complete tune up, cleaned out the iac, and raided the tps off of my mustang....still does it

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #6 – December 23, 2004, 04:05:55 PM

Did you adjust your voltage on the TPS?

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #7 – December 23, 2004, 06:10:15 PM

check your driveshaft bolts. mine came loose and gave the same symptoms. just at a different mph.

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #8 – December 24, 2004, 11:30:00 AM

My 302 and 347 do it, the 347 just started to before I put it away for the winter. I was told it was the the TV cabel out of adjustment? Everything eles is new on that car but I havent been abel to check it being winter an all but in the 347 its a big problem...way to powerful to jerk around like that!

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #9 – December 24, 2004, 05:57:18 PM

I have no experience with the EFI set up so this may not apply.
It sounds like it could be a "lean" miss. When at this cruising speed and warmed up is when the EGR valve is opened and also when the carbon canister is purged.
Try pulling and plugging the vacuum hose to the EGR and see if it goes away.

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #10 – December 25, 2004, 09:36:31 PM

i just slapped the tps on...didn't know I had to adjust the voltage

What do I look for?

Re: Car is jumping when I am going steady at 45 or 50mph

Reply #11 – December 28, 2004, 10:00:17 PM

replaced the plugs, the wires and the rest are less then a year old and I have had the jerking problem for over a year now. After I replaced the plugs it happened again but it seems to be at peace now.... untill she wants to hate me again and act up.

Oh one more thing My car revs on it's own when ever it wants and mainly does it at stop lights. I have looked and maybe I missed something but does anyone know of a thread for this issue or do I have to make a new one.