Greetings all. I recently purchased a 2004 Mercury Monterey with 170,000 miles on it. I noticed while driving there is slight "shudder" under light acceleration. It doesn't really affect the speed or power of acceleration itself.

If the vehicle is under heavy throttle (50% or above) the shutter is not noticeable. If the vehicle is in park, and you lightly apply throttle, it has this same shutter as well. I do not notice it as prominent in reverse. It only occurs in the low RPM range (500-2000 RPM), fading the higher in RPM you go.

It is also more noticeable when the AC is on. If AC is off, it is noticeable, but if you didn't know any better, you would think its normal.

The following has been recently replaced:

Before purchase:
AC Compressor - Looks new
Alternator - Look semi new
Trans filter and fluid - Look new
Wires - Looks new
Plugs - Not sure (assumes plugs got changed with wires)

After purchase:
Belt Tensioner and pulley
Power steering pump and pulley
Serpentine Belt
Fuel Filter
Oil and Filter
Air Filter
MAF Cleaned
Throttle Body Cleaned
Sefoamed Through Intake Line

I am not an expert at automatic transmissions, since I haven't owned one in over 12 years, so I am unsure if this is a transmission issue. The trans shifts perfectly; no hesitation at shift points, no rpm fluctuation on shifting, no loud noises on shifting, etc. I was worried it could be the torque converter, but again, I am unsure.

I was originally thinking it was the fuel filter when I bought it, so I naturally thought, "easy fix". I am still curious it could be fueling, the injectors sound loud and clear. I ran some Lucas through it before as fill up just to see. No difference.

I checked the Ford site for recall under my VIN number for the TQ Converter, but see nothing listed...just the rear seat rust recall.

That's about everything I have to give in regards to back info. If someone could please point me in the right direction, I would greatly appreciate it.

 

This sounds similar to my issue, and my research on it says the coil pack is a likely culprit.

 

It sounds like a miss , don't assume the wires and plugs are good . Its either plugs , wires or coil pack . Replace them in any order you decide or if you can isolate which cylinder it is , try moving parts around to move the miss to a different cylinder

 

Thank you both. I had concluded the same results in regards to spark as well. I am fairly certain its the coil pack. It doesnt quite feel like the typical misfire, but then again...you never know. I will be xhanging out the plugs and coil pack next week. I have to drive 600 miles first to PA, so i am hoping all will be good until I get there. I imagine it will.

If this doesn't work i am thing a possible "flat spot" in the tps.

Again thanks for your help. I will keep everyone posted.

 

There is a very simple way to confirm if there is a misfire taking place at idle or low speed.
Just place your hand at the end of the tailpipe while the engine is idling, or in gear idling with someone holding their foot on the brake, and if you feel a steady puffing from the exhaust , it is usually the result of a misfire.
If you try this when the engine is running properly there should be a steady sound and regular flow from the exhaust. A very easy comparison to do.

If you do detect a misfire, then you can go to the other suggestions made in the earlier posts.

 

I took it to autozone and had it put on the scanner. No misfire is showing. Still a possible spark issue? Also what plugs? I was told bosch platinum was oem, but i was thinking motorcraft would have been stock, plus 6 bucls a plug is steep. I usually run vpowers in everything. Suggestions?

 

Motocraft plugs

 

I agree with diyautoelectric Motorcraft plugs work best.
There are many items that Ford uses and most experienced people in the trade will choose OEM parts because they usually work best. There are many tales of woe from highly advertised replacement parts that just don't cut it !!