Chrysler 300C & SRT8 Forums banner

1 - 9 of 9 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1 (Edited)
Ive got a little issue regarding my 08 300c hemi 5.7 wagon.
Can anyone tell me why or what would cause my vehicle to surge/rev up and down at 60ks? If i put the car in neutral still doing 60ks and give it a rev she doesn't come down but goes all the way to 7500rpm at that point i have to turn off the ignition, stop and start her again. What the f#%k
And what would cause the beast to drive itself, literally foot off the gas! Its like cruise control is on but it isnt.
Does any one have any ideas they could throw my way regards stevie
FYI
I have a new throttlebody OEM part
New air filter
Eng oil etc
Plugs etc
PCV valve in good cond
Trans service fluid filter etc
300s only got 112tho ks
Please any advice would be appreciated.
 

·
Registered
Joined
·
393 Posts
Welcome to the forum. First, are there any diagnostic trouble codes showing? Your 5.7 engine, if stock, will not rev. to 7500 RPM, unless it is extensively modified to support that high RPM, and the rev. limiter in the PCM has been changed. The rev. limiter on a stock 5.7 is set to around 5800 RPM and will not go higher than that....the fuel will cut off at the set limit.

Did you install the new throttle body yourself? If so, you probably need to do a throttle relearn. To do it correctly, you need to have a diagnostic scanner with that capability. The relearn only takes a minute or so and basically synchronizes the throttle body with the PCM. In most cases, when done correctly, this should resolve your issue. If it continues, you'll need to do a "Follower Test" to insure the throttle body is working properly. This checks for linear movement as the throttle is advanced. First check for codes though and then go from there....easy, inexpensive stuff first. Good luck and keep us posted.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #3
Hey mate, my bad over exaggerated the rpm she is all stock and solid. Beautiful car. My 300 was behaving the same prior to the throttle body changeover however strangely enough after having installed the new part it did help a little with her behaviour. As for codes their is none and that is frustrating. I will do what you have suggested first and go from their i appreciate it cheers mate.
 

·
Registered
Joined
·
66 Posts
This might sound like a stupid question... But..

Is your pedal getting hung up on your floor mat?

Had that happen a few years ago on the highway, she got stuck running wide open till I turned the key off.

Probably not the issue lol, just figured I'd toss the thought out there.

Sent from my SM-N900V using Tapatalk
 

·
Registered
Joined
·
6 Posts
Discussion Starter #5
I thought the same hey, but the potentiometer/foot pedal is sweet i even went to the extent of pulling it out to check the resistance of it and she checks out great.
Its bazzar no kidding its strange cruising at the speed limit flick her in neutral give her a flick on the gas and bam shes revving right out..... what the.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #6
Welcome to the forum. First, are there any diagnostic trouble codes showing? Your 5.7 engine, if stock, will not rev. to 7500 RPM, unless it is extensively modified to support that high RPM, and the rev. limiter in the PCM has been changed. The rev. limiter on a stock 5.7 is set to around 5800 RPM and will not go higher than that....the fuel will cut off at the set limit.

Did you install the new throttle body yourself? If so, you probably need to do a throttle relearn. To do it correctly, you need to have a diagnostic scanner with that capability. The relearn only takes a minute or so and basically synchronizes the throttle body with the PCM. In most cases, when done correctly, this should resolve your issue. If it continues, you'll need to do a "Follower Test" to insure the throttle body is working properly. This checks for linear movement as the throttle is advanced. First check for codes though and then go from there....easy, inexpensive stuff first. Good luck and keep us posted.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #7
Hey fellow chrysler junkies,
Ive had a auto electrician recently do a relearn on the throttle body and reset the computer, however to no avail. I did myself disconnect the egr valve "out of curiosity" and lowen behold wow what a difference "touch wood" also even with the egr valve disconnect their is no fault code WTF. Anyway i can't explain it but so far cold starts are perfect at 1000rpm.
For now we will just monitor the situation.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #8
Hey kareba, the behavior is still present, im still baffled by the egr valve being disconnected and yet no warning signals.
I baught a new dealer MAP sensor thought what the hell ile by oem and again its better but still evident im lost for ideas im thinkin that perhaps i may need to go down the path of having the ECM wiped clean or replaced.
 

·
Registered
Joined
·
393 Posts
You certainly should be getting EGR code(s) with it disconnected, so it is very strange that you are not. One of the symptoms of a bad EGR Valve is low speed surging. It also does it at higher engine speeds but is not as noticeable. Other symptoms of this are poor performance and fuel economy and erratic, sometimes stalling idle. If the valve is failing/has failed, what sometimes happens is it kind of takes on a mind of its own. If you have it hooked up to a scanner when it is surging and set to monitor "Commanded EGR" vs. "EGR Error Correction" you'll notice the valve is rapidly opening and closing to strange percentages, sometimes even (supposedly) above 100% and the PCM is trying to correct the opening percentages and can't keep up....hence the surging. At lower RPM, if the valve is open too far or at idle (it should not be open at all at idle or when the engine is cold), the engine will run rough and/or stall or almost stall. This also adversely affects the performance and fuel economy because when all this is going on the PCM is also continually adjusting the other engine and fuel management settings......timing, fuel delivery, etc.

Another area to check is the cam and crank sensors. Usually they either work or don't but, if they are not properly synchronized or there are wiring issues, you could possibly get surging, stalling and/or no start conditions. First, I'd sure want to know why there are no EGR codes with the valve disconnected though.
 
1 - 9 of 9 Posts
Top