Rpm's Jumping / Car turning off while idle

[neomadeit]

Hey, I've been having this issue for awhile now but could never find out what it is, im going to take it to a mechanic in a few weeks but want to get some input & figure out what the issue is

the rpms jump up and down when im at idle or stop while driving sometimes. For examples when i stop at a light from a few seconds the rpm would start jumping up and down. Sometimes the engine will turn off and go into accessories mode and i would have to start the engine back up agian.

From doing some research my thoughts are maybe bad fuel injectors, bad throttle body or maybe cracked manifold? I have been on e85 for a long time but i got the injectors clean a few months ago. My best guess is the throttle body or something is loose/leak hopefully

( don't mind the check engine light it was the cats)





Also noticed this hissing sound / click sound (at the start) not sure what is but i looked on the forums and i guess the hissing sound is normal coming from the tb area

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[njweatherman]

Hey, I've been having this issue for awhile now but could never find out what it is, im going to take it to a mechanic in a few weeks but want to get some input & figure out what the issue is

the rpms jump up and down when im at idle or stop while driving sometimes. For examples when i stop at a light from a few seconds the rpm would start jumping up and down. Sometimes the engine will turn off and go into accessories mode and i would have to start the engine back up agian.

From doing some research my thoughts are maybe bad fuel injectors, bad throttle body or maybe cracked manifold? I have been on e85 for a long time but i got the injectors clean a few months ago. My best guess is the throttle body or something is loose/leak hopefully

( don't mind the check engine light it was the cats)





Also noticed this hissing sound / click sound (at the start) not sure what is but i looked on the forums and i guess the hissing sound is normal coming from the tb area

Unfortunately, I cannot comment on E85. But, based on my past experience with my 2020 GT and others on here, the idle problem and the car shutting off, could be dirty/faulty VCT solenoids. Here's the thread on it:
https://www.mustang6g.com/forums/threads/idle-goes-rough-randomly-stock-tune.133398/

 

[NGOT8R]

Check the IMRCs too.

https://www.mustang6g.com/forums/threads/possibly-broken-imrc-shaft.183221/#post-3690082

 

[neomadeit]

thank you for the feedback! I’m going to check those two things out hopefully it solves the issue

 

[NGOT8R]

thank you for the feedback! I’m going to check those two things out hopefully it solves the issue

If your IMRCs do turn out to be bad, you can remove all of the hardware and lock them out. MMR sells a lockout kit (see the two anodized red pieces on the rear of the intake manifold). Installation is super easy. All you‘d need to do after installing the lockouts, is have your tuner turn off the IMRCs in your tune. I just went through this myself. I kept the two factory connectors circled in red, along with the vacuum hoses shown and plugged the factory wiring harnesses back up.

 

[SheepDog]

Sounds like a vacuum leak to me

 

[neomadeit]

Trying to find some VCT Solenoids right now I'm going to have my mechanic checkout the IMRC's i think im going to order the lockout kits to thank you for the advice! I will keep this thread updated when i get everything installed and checkout just incase anyone else has the same problem.

One question will locking out the IMRCs effect anything? & should i have my tuner send me a tune before doing it.

 

[neomadeit]

Unfortunately, I cannot comment on E85. But, based on my past experience with my 2020 GT and others on here, the idle problem and the car shutting off, could be dirty/faulty VCT solenoids. Here's the thread on it:
https://www.mustang6g.com/forums/threads/idle-goes-rough-randomly-stock-tune.133398/

Should i get VCT Solenoids. or VVT Solenoids. i can't seem to find any VCT's for 2018 mustangs

 

[NGOT8R]

Trying to find some VCT Solenoids right now I'm going to have my mechanic checkout the IMRC's i think im going to order the lockout kits to thank you for the advice! I will keep this thread updated when i get everything installed and checkout just incase anyone else has the same problem.

One question will locking out the IMRCs effect anything? & should i have my tuner send me a tune before doing it.

Locking them out won’t hurt anything.

Yes, you could go ahead and get the ball rolling on the tune. When I put my work order in with my tuner, I explained that I wanted to keep all existing tunes and just turn off the IMRCs.

 

[NGOT8R]

What IM are you running?

 

[njweatherman]

Should i get VCT Solenoids. or VVT Solenoids. i can't seem to find any VCT's for 2018 mustangs

Sorry, that I do not know the answer to. Somebody else on here may know?

 

[neomadeit]

Update:

The cars running like its brand new! huge shoutout to @NGOT8R & @njweatherman for the helping me out!

I replaced the VVT Solenoids, Intake Filter and installed MMR Lockouts. Cars running super smooth haven't had any issues so far! The car feels like its brand new again.

 

[NGOT8R]

That’s great news! Glad to hear you were able to get it sorted out.

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