RPM slowly decrease and the engine begins to vibrate

2CP-ARCHIVES

MEMBER
2002 FORD THUNDERBIRD
6 CYL
AUTOMATIC
76,000 MILES

2002 Ford Thunderbird mileage: 76,000. For the past six months I have noticed that as I accelerate lightly and the car reaches above 35 mph, if I hold the accelerator steady and not wide open throttle the rpm slowly decrease and the engine begins to vibrate until I let go of the pedal a bit and give gas again. During the winter when it's cold the car would run well until it warms up. I tuned it up, changed all filters, and many people tell me that it could be the EGR valve. Should I try to clean it or replace it? It feels as if the engine is losing power during cruising condition but while driving with full acceleration the car runs fine.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

This could be the EGR, but we need to do a couple things to determine for sure what is happening.

Let's start with checking for codes even if the light is not on.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If there are no codes, then we need to remove the EGR and inspect it to see if there is soot or carbon build up in it.

If the EGR is not the issue which I suspect it is not, we need to check through these guides that will walk through the common issues for low power.

https://youtu.be/U1RoG3I-Oww

https://www.2carpros.com/articles/symptoms-of-low-engine-power

The last thing that we need to check if none of this turns up any issues is a torque converter issue.

If the torque converter is not unlocking when it should, it can bog the engine down and cause low power and the engine will vibrate.

Think of this like a manual transmission that you leave in a high gear as you slow down then try to accelerate. The engine will vibrate, and you will slowly decrease speed.

To do this we need a scan tool that can monitor the torque converter make sure it is not engaged when you are decelerating.

Please run through this info and let me know what you find. Thanks

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