New Swap New Problems (IAC And Timing Advance) (Page 1/1) AndrewTHG JUN 26, 08:05 PM So some of you may know, but I just recently finished my swap (L32 into 87 GT). I've been ironing out issues here and there as they come up, but just got a couple that have me a bit stumped for the time being. 1. I've had a high idle since the swap was done (~1500 RPM). I made sure the couplings around the MAF were tight and checked for vacuum leaks, and didn't find any. I also am getting a P0507 code which led me to think IAC. So I took it out, cleaned it, and tried to see of the pintle would move (this is LQ4 MAF with a N* throttle body by the way). The pintle did not budge, but it would twist (maybe I forced it a bit..I thought I was being gentle). I put it back in and now the idle is up to ~1900-2000 RPM. Could my IAC just be bad/broken? Did I break it more lol? Would high idle be a symptom? MAF is reading ~10.79g/sec. 2. Timing advance....when I checked it on my scanner it said 26*....AT IDLE! That does not seem right at all. Any clue as to why this is so high? 3. I just put my parking brake springs back in, and they seem to be working just fine now. I pull the parking brake lever and the rear wheels are locked right up nice and tight. However, when I spin the wheels on each side, it does sound like there is a slight rubbing still. Thoughts on how to maybe get rid of this? Thank you all for any help, this is by far the best forum out there. Wouldn't have done my swap without it. pmbrunelle JUN 26, 08:25 PM quote Originally posted by AndrewTHG: 2. Timing advance....when I checked it on my scanner it said 26*....AT IDLE! That does not seem right at all. Any clue as to why this is so high? That doesn't shock me, sounds OK. Vacuum advance cans connected to ported vacuum (hence no vacuum advance with closed throttle) fell out of a favor a while ago after they came into vogue for the 1970s emissions regulations. At low loads (as in idle), the air/fuel mixture is sparse, hence it takes a long time for the flame to propagate through the combustion chamber. The mixture is ignited early, to give the fire a "head start" in burning the mixture. Therefore, except for that 1970s emissions aberration, vacuum advance cans are connected to plenum vacuum. It is normal to have full vacuum advance at idle. The same principles apply to an engine that is computer-controlled. quote Originally posted by AndrewTHG: 3. I just put my parking brake springs back in, and they seem to be working just fine now. I pull the parking brake lever and the rear wheels are locked right up nice and tight. However, when I spin the wheels on each side, it does sound like there is a slight rubbing still. Thoughts on how to maybe get rid of this? If you are able to turn the wheels by hand, I wouldn't worry about the drag. AndrewTHG JUN 26, 10:01 PM Thanks for the reply pmbrunelle! I appreciate the explanation. I won't worry about the timing advance or slight brake rub then! Did a couple more tests to find my high idle now: 1. Unplugged IAC and removed valve from throttle body, then covered it with tape. Idle jumped to like 3000 RPM. Put it back in and it was back to 1500. This makes me think the IAC valve is actually working then... 2. Unhooked the PCV @ the throttle body. I have a rubber hose running from the supercharger port to the barb on the N* throttle body. When I unplugged it, nothing happened, same for when I capped it with my thumb. Thoughts here? Thanks! AndrewTHG JUL 01, 01:07 PM Bump bump! Still chasing this high idle. It sits 1t 1500 RPM and idles smoothly, but is just a bit high. phonedawgz JUL 01, 06:06 PM The IAC opens and closes the air passage around the throttle to adjust the idle. The pintle should be moving in and out. The farther it is extended, the more restricted the air passage and the slower the idle. No, removing the IAC totally and seeing the engine ran at 3K doesn't mean it's working. Note also - Putting an IAC in the throttle body with the pintle too extended can jam it and break it. Also note - the PCM adjusts the IAC in and out, but when it gets fully extended, the PCM might continue to try to extend it. That is fine. That is how it is supposed to work. And no, that doesn't burn out the IAC. How are you with your meter? Check for voltage first across the green pair of wires to the IAC and then across the blue pair. You can do this key on engine off and connector unplugged. You should find voltage on each pair. Don't worry about the polarity of the voltage. The PCM reverses the pairs in "steps" to move the IAC. Reverses and non-reversed voltage. Look for a youtube video on stepper motors if you want to see how it works. So, is your IAC working? Take it out, hold it in your hand and have someone start the car. Put one finger in the IAC hole in the throttle body to control the engine speed. The more you cover the hole inside the IAC hole, the slower the engine will idle. But the PCM should start right away moving the IAC. It should even move it when you first turn the key on and then off. The PCM should be moving the IAC pintle out when the engine is running too fast, and moving it in when the engine is running too slow. Watch out, if the ICM moves the pintle all the way out, it might release it along with the spring and it can go shooting across your garage. You can block the movement of the IAC with your hand to keep it from moving too far out. If it moves, it's working. Finally, have the engine run too slow for a bit so the PCM retracts the IAC at least as far as it was when you took it out. That way it won't jam when you reinstall it. If it doesn't move, since this is a new swap, I would expect the wiring to be bad and for it to fail the voltage test listed above. If the IAC is moving backwards, that is moving out when the engine is running too slow and in when it is running too fast, your IAC is wired wrong. Just swap one of the pairs (for example swap the green/white with the green/black) at the PCM and it's direction should change. OntarioKev JUL 01, 06:29 PM How did you check for vacuum leaks, did you use a pressurized smoke tester? If not you haven't really checked for leaks. The high idle could be a bad IAC, a vacuum leak, or a messed up tune/PCM. Who tuned your PCM for the swap? Are you running the 4t65e transmission, or a manual? You mentioned that its an L32 engine, but you also mentioned IAC valve. The L32 has drive by wire so there is no IAC on those. What throttle body are you running, and what PCM is controlling this? There is a good chance you have some mismatched parts on here that need to be corrected depending on what you are actually running. Can you give us a breakdown of the engine/transmission/PCM and any sensors you may have swapped? AndrewTHG JUL 10, 07:29 AM Kev/phonedawgz - thanks for the help. This is an L32, w/ the 5-speed Getrag, a N* TB, and LQ4 MAF. PCM was done by Ryan. So i took your advice phonedawgz and took my IAC out, blocking the throttle body hole varying amounts. It clicked a couple times but would not budge. It clicked the most at key off, as if it was trying to return to a position but could not do so. I will have to check the voltage next, I started with the IAC since that was easiest for me. Also - now I am throwing a P0102 code as well. Argh! I am hoping this is just related to the idle code...I am starting to go crazy lol! randy86 JUL 10, 04:48 PM Did you clean the IAC housing and passage way? Carbon will build up where the pintle meets the housing and the IAC cannot close off the airflow to the degree the PCM wants. randy86 JUL 10, 04:50 PM To clean the passage way, use a pipe cleaner. Just spray TB cleaner on it and run it through the passageway, use a new pipe cleaner each time till it comes out clean. AndrewTHG JUL 23, 06:39 AM Thanks for the help everyone! The problem is gone and it is idling at a nice steady 900-1000 RPM. It ended up being a bad IAC Valve. Per phonedawgz suggestions, I had someone start the car while i plugged the side of the TB to varying degrees and watched the pintle. No movement. But I could force it in and out by hand by screwing it in/out and vary the idle that way. Ordered a new one from ZZP (got the wrong one at first which is why it took me so long to update this thread) and the idle dropped right down. (Well actually, not at first. First it was at 2k RPM....then I realized I forgot to plug the new sensor in). Worked like a charm after that. Cleared the MAF and IAC codes and they have not been back. Thanks again!