# Deceleration

**URL:** <https://community.cartalk.com/t/deceleration/54262>\
**Category:** Maintenance/Repairs\
**Tags:** mercury\
**Created:** [August 28, 2010, 3:54am UTC](https://community.cartalk.com/t/deceleration/54262 "2010-08-28T03:54:38Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![mirmax](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@mirmax](https://community.cartalk.com/u/mirmax)\
**Post date:** [August 28, 2010, 3:54am UTC](https://community.cartalk.com/t/deceleration/54262/1 "2010-08-28T03:54:38Z")

</div>

"99 Marquis,141K, decelerates to 30mph & will only accelerate after an incline.  
  
 So far hv replaced fuel pump,alternator,battery (after low voltage readings), and had major tune-up. Catalytic converter tests ok.  
  
 HELLLLP Pls. I’m running out of hills…  
  
 Thanks

---

<div class="post-metadata">

**Author:** ![kizwiki](https://avatars.discourse-cdn.com/v4/letter/k/7cd45c/32.png) [@kizwiki](https://community.cartalk.com/u/kizwiki)\
**Post date:** [August 28, 2010, 7:06am UTC](https://community.cartalk.com/t/deceleration/54262/2 "2010-08-28T07:06:31Z")

</div>

You have a bad automatic transmission. Or at best the trasmission fluid is low, which of course you should check first.

---

<div class="post-metadata">

**Author:** ![tardis](https://avatars.discourse-cdn.com/v4/letter/t/f0a364/32.png) [@tardis](https://community.cartalk.com/u/tardis)\
**Post date:** [August 28, 2010, 1:42pm UTC](https://community.cartalk.com/t/deceleration/54262/3 "2010-08-28T13:42:14Z")

</div>

If the engine races when you can’t go over 30, then it is the transmission.  
However, if the engine doesn’t race, then it is an engine problem.  
Is the check engine light on or flashing?  
Have you cleaned or replaced the MAF sensor?  
Have you checked the TPS?  
Have you verified fuel pressure (maybe a bad fuel pressure regulator instead of fuel pump)?  
You did replace the fuel filter, right?  
What did the old plugs look like when you did the “major tune-up”?  
Have you done a compression test on each cylinder?

---

<div class="post-metadata">

**Author:** ![mirmax](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@mirmax](https://community.cartalk.com/u/mirmax)\
**Post date:** [August 28, 2010, 3:36pm UTC](https://community.cartalk.com/t/deceleration/54262/4 "2010-08-28T15:36:03Z")

</div>

Hi  
Thanks so much for yr thoughts…  
Engine doesn’t race…a little stressful groaning or low whining.if I try to pump.  
no lights at all  
fuel filter replaced  
Old plugs were shot, gapped at 85 rather than 35

will inquire as to the rest of yr questions on Monday ,obviously I know ‘nuttin honey’  
& am at everyone’s mercy.  
Appreciately,  
Mirmax

---

<div class="post-metadata">

**Author:** ![mirmax](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@mirmax](https://community.cartalk.com/u/mirmax)\
**Post date:** [August 28, 2010, 3:37pm UTC](https://community.cartalk.com/t/deceleration/54262/5 "2010-08-28T15:37:13Z")

</div>

Hi  
Tranny lookin’ good so I’m told …  
Thanks for thinking for me.  
Mirmax