Rough Idle My car idles intermintanly rough and does'nt seem to accelerate past 40mph

Have you cleaned the throttle body bore and plate of carbon/deposits ? This can cause idle and off idle symptoms .

engine light flashing means a problem needs immediate attention ----have the vehicle scanned most auto stores offer this service for free more than likely the viberation is what is setting off code

Rough Running Engine - James on Engines #2 - Bell Performance

https://www.bellperformance.com/blog/rough-running-engine

Apr 21, 2015 - When diagnosing an engine with a rough idle, there are certain things that must be ... If the problem does not reoccur, the codes will be erased by the computer. ... when accelerating the vehicle, which causes a higher fuel demand. .... it was water in gas...added added Gas LineAntifreeze/Water Remover.

The car does have a maf, but it is rarely the cause of rough idle. Rough idle is usually caused by vacuum leak, pvc issues, or idle air control valve. What does it do, specifically, and is the engine light on?

You can add whats known as a "Test Pipe" To verifie that is the issue, Or simply disconnect the cat and drive it around the block. Although you can bypass it, Its NOT reccomended you do so. Hope this helps..

For this types of problem,there are few help inks to troubleshoot the problem.Click the link below to go through the troubleshooting procedure to resolve the issues :----Idles rough and quits when gas pedal is pressed less? http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html-----------van idles rough? http://howtobyme.blogspot.in/2012/01/2004-ford-freestar-van-idles-rough.html
--------------runs lean and idles rough? http://technoanswers.blogspot.in/2012/02/ford-runs-lean-and-idles-rough.html
-----------Car still runs Rough after tune up? http://howtobyme.blogspot.com/2011/12/car-still-runs-rough-after-tune-up.html
------------Idle flair is noticed on car? Rough idle? car will not idle? Erratic idle speed? http://technoanswers.blogspot.in/2012/02/idle-flair-is-noticed-on-car-rough-idle.html
----------High rpm in neutral? Inconsistant high RPM in neutral? http://technoanswers.blogspot.in/2012/02/high-rpm-in-neutral-inconsistant-high.html
------------Engine Backfires? http://technoanswers.blogspot.in/2012/02/jeep-backfires.html----------- Nissan stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

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Nissan Pathfinder Backfires? http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-backfires.html
---------How to adjust rpm? http://schematicsdiagram.blogspot.com/2011/12/how-to-adjust-rpm-on-2009-dodge-charger.html
------------Engine cuts out at 3000 RPM? http://schematicsdiagram.blogspot.com/2011/12/engine-cuts-out-at-3000-rpm.html
----------This will help.Thanks.

try cleaning the IAC (idle air control) sensor and check the hoses going to the MAF (mass air flow) sensor, i have found both causing me problems with erratic idle. the IAC was totally gunked up with carbon on the pintle and i had found that the screws holding it down were loose ( but only clean this with throttle body cleaner, not carb cleaner it might damage the sensor, and replace the vacuum hose to the MAF sensor, i found mine was cracked and old and brittle, a car that has been run poorly for a long period of time might also cause a problem with an oxygen sensor and this would lead to poor fuel economy also, try to clean that up or just replace it. Also have the transmission fluid serviced, i have seen this problem lead me to think i had an engine idle problem or rough perforamance when accelerating. can you rate this!

Idle air control valve would be my next bet , the TPS usually just makes it rough on acceleration. Is it rough on acceleration(loss of power) ?

has anyone checked for a vacum leak? a vacum leak will cause rough idle at idle. check the lines from the pcv valve.

no problem. If you are getting that low of voltage on a load then you might want to test the alternator as well to make sure it is running at capacity.