car stuttering at speed

[bobby300c]

i posted this on another forum, had 84 views and 1 reply. the reply suggested that i had a pedal position sensor out. i am hoping to get another couple of ideas to run with.

here is my post:

last weekend i went to my cousins house, i usually go every other weekend or so, 25 miles away on highways each way. this time however it started to stutter going down the highway. i could speed up and it would go away. but if i maintain speed it stutters.

it has done this all week long. everyday on the way to and from work. i work 10-15 min from home depending on the red lights. avg speed 35-45. yes a bit of speeding here and there. but it does it at this speed too. so i dont know if it is the mds doing it, which it hasnt done it until recently. it doesnt do it at idle anymore, however at one red light the rpms jumped from nowhere and lurched the car forward a little. i might have possibly hit the gas pedal by accident, but honestly not likely.

when it happens, i can watch the rpms go down about 200-300 then bounce back up. i have taken it to a transmission shop to check it out, they say the tranny is good and that it must be a power issue. the car accelerates good with no hesitation. i took it to the tranny shop cause i did have a stock TQ replaced last summer and thought maybe it had something to do with it. took it to the dealership, they cannot repeat the problem there of course, and they say it is ok. but this is a dealership that thinks that i cant use a plastic zip tie to check my tranny fluid.

i replaced the IAC about 2 mos ago. 6 mos ago i cleaned the TB, took it off completely to clean. 2-3 mos ago had a tranny flush at dealership. spark plugs replaced 5-10,000 miles ago by licensed mechanic. went with the stock replacements. i have had a k&n stock air filter on since i got it, but have cleaned it once or twice in the last year. the dealership said it did have a wheel speed sensor code stored, but attributed it to possible burn out, which it does NOT have any codes showing now.

i did fuel up before going to my cousins at a different shell station than usual, put in midgrade. i only put in 1/2 tank there. drove to cousins. on the chance it is bad gas i waited until 1/4 full then filled up with premium v power from my usual and expensive shell gas station and added sea foam to help clean up anything that needed it. i am back down to 1/2 tank now and i still have the problem. i did not top it off, so i am quite certain it is not from overfilling.

does anyone have any other leads i could chase down. all engine harness connections appear to be good and connected.

i apologize for the long post, but wanted to share everything going on with it for narrowing down possible solutions.

Thank you.

2nd post after reply of tps:

would the tps throw a code? as of right now my car isnt throwing any codes.

something new happened yesterday. stopped at a red light bout to make a left turn, had the ac, radio and turn signal on while holding brake. heard a pop sound, not loud, but the car lost electrical then regained it. i am pretty sure the pop was from the stereo, maybe from the speakers when it lost power.

when i got home i chased down all electrical i could without crawling under, as i personally dont own a jack. anyways i found my positive battery terminal was loose. i tighted it down. its too soon to know about the electrical problem, but it still stutters at speed.

if i didnt mention it before, i dont notice it stuttering when cold. only after it warms up for a few minutes.

i appreciate any ideas you guys could give me. as stated above, ive had it to the dealer, had it to another tranny shop. i dont know what to look at now.

Thanks.

[Daphod74]

Have you tried replacing the MAP sensor? Mine would surge around 45mph while maintaining speed - accelerating was fine. In park, if I wanted to keep RPMs at a fixed point using the pedal, say 1000, it would oscillate +/- 200 RPMs and would almost stall if I took my foot of the gas quickly. $15 part solved that problem.

[fnkychkn]

not sure what you mean by "stutter". is this an RPM surge or a high frequency shudder (like driving over rumble strips)?
also, please post a description of your car. YME (year, model, engine).

btw, welcome to LXforums.

[DSKREET]

Mine was doing this but only at inclines but the same speed as you, turns out my TC was going out. I put in a 2800 and all is well again. Hope this helps.

[bobby300c]

my apologies, it is a 2005 300c with the 5.7 hemi.

by engine stutter, i would describe it as a rpm surge i suppose. i can see the rpms dip 100-200. it feels like i am tapping the brake, but obviously i am not.

DSKREET - i had my TC replaced last summer, had a reputable trans shop here in town check it over again, they say everything looks good tranny wise.

Daphoid - i will try that this weekend. seems like a quick and cheap solution, possibly.

i would like to take a moment to say though, i upgraded the stock negative battery cable yesterday and added a couple of grounds under the hood, i know i read the thread on that subject, but it was a quick process so i said why not.

on the way home yesterday and coming in to work it didnt do it today. i drove it to get lunch and cash my check, probably 10-15 miles total. it didnt act up at all. this could be merely from resetting the pcm when i undid the battery cables. i will definately keep a close eye on it and report back any changes.

thanks fellas.