[Casper98GT]

Ok....here goes. I can help with a few options.

First off... stop going to autozone EXCEPT to get youre free scan check.

A 1516 is NOT youre IAC...keep letting them replace it actually. If it were me i would be a HUGE dick about it. Tell them they are worthless and its a very high status symbol to own a Mustang COBRA...hahahaa. It would be funny. because they are gonna KEEP putting in IAC's....

Not youre problem man. Youre IMRC controller is either bad, or youre IMRC's are sticking so bad its causing a fault because youre controller isnt strong enough to open them up.

OPtions...yank that intake like i said and replace that controller. You should beable to either Ebay one, or check this and other Mustang forums to find a IMRc controller. And then while you replace it youre gonna need to clean out youre IMRC's.

Second option...i see you like to mod youre snake. So...search online for a IMRC delete. This will remove the controller and IMRCs. You will need to tune youre car for this though and have them turn off the IMRCs. Any local Mustang performance shop will know this mod.

Those are youre options. If you do the second modifcation you will STOP worrying about this code and other IMRC problems that could arise. You will loose slight power down low because thats what the IMRC's are for. BUT you wont really notice it.

Sounds like youre snake makes you happy and it should. But stop letting Autozone diagnose youre vehicles.

BTW: if youre getting rid of the Borla stuff let me know.

[Flatline]

Ok so on my lunch break I ran up to BnT and they ran the codes for me this is what I got from them. This may ALSO be helpful for **OTHERS LOOK HERE** This is straight of the printed Diagnosis.

DTCs P1518, P1537 and P1538 indicate IMRC is stuck open. DTCs P1512, P1513, and P1519 can indicate IMRC may be stuck closed. ** DTCs P1516 and P1517 indicate IRMC input error **

Possible Causes:
Damaged Vacuum Lines
Damaged Vacuum Solenoid
Damaged Vacuum Actuator
IMRC Actuator Cables/Gears Seized
Cables Improperly Routed (Binding) or Seized
Damaged or Disconnected IMRC Housing Return Springs
Lever/Shaft Return Stop Obstructed/Bent
Lever/Shaft Wide Open Stop Obstructed/Bent
IMRC Lever/Shaft Stick/Bind or Disconnected

I still am not sure where this puts me I mean I feel like the input error must refer to electronic signal meaning IAC which we have ruled out (however I will take the free replacement lol) the only other thing I can think of would be the sensor on the Air Intake itself because it was in a wreck not too long ago a woman ran a stop sign and hit the front right fender and did 5g's of damage however the engine looked untouched but the wiring for the air intake run in that same fender and I am wondering if it might have been damaged. The dealer repaired it all and gave lifetime warranty and they did a ridiculous job fixing it I am thinking it still might be something else.

The thing that shocks me the most about it is ** I replaced the IAC and warning light went away for 2-3 weeks then it came back ** and I DID NOT have them reset the codes either it went away by itself. I am beginning to wonder if it has something to do with something very close to or in conjunction with the IAC.

I'm going to replace the IAC one last time I mean heck it's a freebie. Then I am probably going to try to start inspecting the intake is it that hard to do I mean freakin I'm probably going to be doing this in my driveway I hope this won't be too difficult...

[Casper98GT]

..........i tried to help.

[Flatline]

Ok I took it up to the local machine shop that has done the IMRC cleans before with acid. Before I got there I picked up the new IAC valve and strapped that puppy on this time they gave me a new gasket with it the old gasket practically crumbled and blew away when I took it off (maybe it was leaking) anyway on the drive up the engine light went off. We checked the cables in the back and revved it they we're swinging open at the right RPM with no hesitation so they told me to just drive it for the weekend and see what happens.

I also called the Ford Dealership and talked to two techs and neither one of them had ever heard of IMRC cleaning before. So I pretty much hungup on them, I was trying to see if it was something they would offer to do b/c it almost sounds like a known issue with this model year but they we're saying they had never heard of such a thing. Idiots.

Casper I really appreciate your information so far you have been extremely helpful and I see how you give and give and give to the forum that's awesome, hopefully some of the information I posted on the error codes will help some others too.

I will continue to post until I see the issue is resolved maybe someone else has a similar issue and will find this thread even more helpful.

Thank you Casper! Keep in touch I will let you know what I do with the exhaust.

[Casper98GT]

Not a problem. Alot of "FORD" techs dont know much about the modding scene. I wouldnt expect them to know about the cleaning. AND...not many Cobras even come into dealerships.

[naughty girl 98]

I have a 98 SVT Cobra also. I put shorty headers and an X-pipe on mine and you would not believe the differance! I also put a cold air intake, and the last project was 4:10 gears. WOW!!

[luis9988]

Alright guys i got this problem i just purchased a 98 mustang cobra and its giving me the p1516 code when i got the car i was expecting it to be alot faster but it wasnt how much does this slow the car down????

[Matt0987]

I have a 96 cobra. I have been having hesitation at the 3K+ rpms when the IMRC opens for the last few thousand miles. I threw on the Enginuity software and got the right bank IMRC code. I was afraid I was going to have to go into the engine and repair or install the delete. I was concerned about the smog check if I installed the delete and the low bottom end torque I hear rumors about.

While reading about brakes here on MM I came across this thread. Curious from it's title I began to read it. Seafoam was mentioned and I figured that 8 or 10 bucks was worth the risk.

I looked Seafoam up on the internet, viewed their video, bought a can, followed the instructions, and NOTHING!!! No smoke. Yes, I poured it into the PCV vacume line. MY wife kept the engine running. I turned it off and let it set for about 12 minutes while I did some other stuff. I turned on the engine and nothing. No smoke. I thought, what could I have done wrong? It looks simple enough. I viewed the video again. And one more time. Then my wife went back out and started the engine. SMOKE!!!! And lot's of it!!! Yeah!!!

I have to guess that it simply needed more time to do it's job. After the smoke cleared I took it for a ride. WHAT A DIFFERENCE!!! No more hesitation! It runs great. The engine tachs right through the 3K, 4K, 5k rpms as smooth as silk. Very pleased. Thank for the information!!!