Proud owner of a 2004 Mach1. My vehicle has been suffering for the longest time from this high idle and hanging rpms issue. I'm posting this just in case it will help others narrow down if not solve their high idle issues. After extensive research on many of the forums online, I've been able to solve my high idle issue. I'm not saying that it will solve anyone elses, but its another angle in which you can try to solve this annoyingly ridiculous issue. I know many other mustang owners have this issue.
My 2004 Mach1 has 19k miles and has been garage kept since I've been deployed for the last few years. initially my set-up included a BBK 65mm throttle, Long tube headers etc. I would start my Mach up and it would shoot up to 1500 Rpms, sometimes 2000rpms, the only way I could get the high idle to return to 700-800 rpms was either to shut the vehicle off and start it again or to kick the accelerator pedal. Once the vehicle achieved a decent idle, I would then drive it and in between shifting my rpms would shoot up again aproximately 1500-2000 rpms and would drop back to about 1000-1200 rpms once shifted. This would drive me crazy at a stoplight because the engine would sound like I was reving it and I'd have to kick the gas pedal raising the rpms even higher to get it to settle back at correct idle. Finally got fed up with this issue this past weekend and decided to dedicate it to solving the issue.
I tried Cleaning the IAC, the TPS, MAF, Throttle body, K&N filter. Vacuum lines seemed to be good and inserted properly. Made no adjustments to idle screw or anything else. Since the vehicle has very low mileage everything in the engine bay looks practically new, hoses and all. I found out through other forums that BBK throttle bodies are notorious for sticking closed and it says so on the the BBK FAQ at their site. the accelerator pedal didnt to seem to have a kink in the cable but I had to use alot of foot pressure to unstick the throttle, so I decided to manually rev up the engine at the throttle linkage it seemed not to bind as much, but it still it seemed to stick just slightly closed, especially with the vacuum created by the engine. Manually I could still rev the engine better than with the gas pedal, however the rpms would still shoot-up and hang. The Rpms wouldnt hang as long though.
Finally, I removed the BBK throttle body once again and decided to inspect it a bit closer. I had already cleaned it, so while it was unmounted and in my hands, I rotated the linkage, the shaft and the butterflies seemed to operate fine. I decided to see how much play the shaft (moving it in and out) had and I thought it had a little too much play, bearings in the TB could be off-center when the throttle cable tugs on the TB but what do I know?! Anyways, fortunately I still had the original Ford throttle body, so I compared the two. Ford throttle body seemed to have less play and did not stick in any position.
I decided to install the Ford throttle body. OMG, the comparison was like between night and day. Great throttle response, it idled like it did when I first purchase the vehicle, hanging rpms are GONE!!! High idle is also GONE!!
I had to relearn how to use my accelerator pedal since it was now light as a feather, as opposed to the pressure I had put on the BBK throttle body. I apologize for being longwinded and going on and on. I just want to share my findings with others that may be having the same symptoms as I. if it will help save anyone cash by preventing them from just part swapping like the IAC, TPS, etc. then my solution was well worth reading. Please share this with others that may be experiencing this. Thanks.
My 2004 Mach1 has 19k miles and has been garage kept since I've been deployed for the last few years. initially my set-up included a BBK 65mm throttle, Long tube headers etc. I would start my Mach up and it would shoot up to 1500 Rpms, sometimes 2000rpms, the only way I could get the high idle to return to 700-800 rpms was either to shut the vehicle off and start it again or to kick the accelerator pedal. Once the vehicle achieved a decent idle, I would then drive it and in between shifting my rpms would shoot up again aproximately 1500-2000 rpms and would drop back to about 1000-1200 rpms once shifted. This would drive me crazy at a stoplight because the engine would sound like I was reving it and I'd have to kick the gas pedal raising the rpms even higher to get it to settle back at correct idle. Finally got fed up with this issue this past weekend and decided to dedicate it to solving the issue.
I tried Cleaning the IAC, the TPS, MAF, Throttle body, K&N filter. Vacuum lines seemed to be good and inserted properly. Made no adjustments to idle screw or anything else. Since the vehicle has very low mileage everything in the engine bay looks practically new, hoses and all. I found out through other forums that BBK throttle bodies are notorious for sticking closed and it says so on the the BBK FAQ at their site. the accelerator pedal didnt to seem to have a kink in the cable but I had to use alot of foot pressure to unstick the throttle, so I decided to manually rev up the engine at the throttle linkage it seemed not to bind as much, but it still it seemed to stick just slightly closed, especially with the vacuum created by the engine. Manually I could still rev the engine better than with the gas pedal, however the rpms would still shoot-up and hang. The Rpms wouldnt hang as long though.
Finally, I removed the BBK throttle body once again and decided to inspect it a bit closer. I had already cleaned it, so while it was unmounted and in my hands, I rotated the linkage, the shaft and the butterflies seemed to operate fine. I decided to see how much play the shaft (moving it in and out) had and I thought it had a little too much play, bearings in the TB could be off-center when the throttle cable tugs on the TB but what do I know?! Anyways, fortunately I still had the original Ford throttle body, so I compared the two. Ford throttle body seemed to have less play and did not stick in any position.
I decided to install the Ford throttle body. OMG, the comparison was like between night and day. Great throttle response, it idled like it did when I first purchase the vehicle, hanging rpms are GONE!!! High idle is also GONE!!
I had to relearn how to use my accelerator pedal since it was now light as a feather, as opposed to the pressure I had put on the BBK throttle body. I apologize for being longwinded and going on and on. I just want to share my findings with others that may be having the same symptoms as I. if it will help save anyone cash by preventing them from just part swapping like the IAC, TPS, etc. then my solution was well worth reading. Please share this with others that may be experiencing this. Thanks.
