!!!Help with Heads and cam install!!!
PM me if you would want to borrow it.
Thanks for all the help guys, joecar..that pic helped alot, I was thinking I was just suppose to remove the brass part and not the black part as well. Squirts, I can return the kent moore tool next wk (made it alot easier).
I got it all finished everything up tonight. The car wanted to die at first, but after giving it some gas the car stayed on for ~5min with a rough idle while I refilled the radiator. I turned off the car and also deleted the p0300 code and now the car won't stay on without me staying on the gas...I am going to get a dyno tune next wk, but was trying to figure out why it won't idle now...could it be due to me deleting that code? Just trying to figure out if I can make it to the shop or if I need to get it towed there.
I got it all finished everything up tonight. The car wanted to die at first, but after giving it some gas the car stayed on for ~5min with a rough idle while I refilled the radiator. I turned off the car and also deleted the p0300 code and now the car won't stay on without me staying on the gas...I am going to get a dyno tune next wk, but was trying to figure out why it won't idle now...could it be due to me deleting that code? Just trying to figure out if I can make it to the shop or if I need to get it towed there.
DTCs(either setting them or resetting them) do NOT control idle speed. Idle speed is controlled by the IAC based on data from a bunch of sensors. MAF,IAT,MAP,RPM,ECT, open or closed loop and more give input to the PCM or ECM which controls pintle duty cycle which I guess is determined by the GM engineers or maybe even the EPA.
DTCs(either setting them or resetting them) do NOT control idle speed. Idle speed is controlled by the IAC based on data from a bunch of sensors. MAF,IAT,MAP,RPM,ECT, open or closed loop and more give input to the PCM or ECM which controls pintle duty cycle which I guess is determined by the GM engineers or maybe even the EPA.
Ok, that's the classic symptom of a faulty IAC. Two things can happen with a IAC. It might be stuck closed(carbon buildup or a real defect). It might not start at all(no air bypassing the throttlebody and if does it may kill immediately unless you crack the throttle a little(the job of the IAC). If it dies as soon as you remove your foot(while idling) you've narrowed down the problem. You can try cleaning it and checking the voltage at the connector. I believe it is PWM on the LS series so you might need a GMM, Labscope or Oscope to see the pulse. It could also stick open, but that's not your symptom.
Might be a dumb question but how to I check the IAC and clean it (can I just use MAF cleaner)? Like I said, it was running for 5 min and I turned the car off to recap the radiator and now it won't stay on..
Could it be due to a faulty O2 sensor as well? When I was removing the passenger front one, it might have gotten some fluids on it (coolant dripping down the headers)...just remembered that and forgot to clean it when I reinstalled it.
Could it be due to a faulty O2 sensor as well? When I was removing the passenger front one, it might have gotten some fluids on it (coolant dripping down the headers)...just remembered that and forgot to clean it when I reinstalled it.
Last edited by peterlawl84; Apr 18, 2010 at 09:23 PM.
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Verdad Gallardo Don't start fishing for answers. Stick to your symptom first before you turn yourself into a parts swapper. That gets expensive real fast. What is the job of the pre cat O2s? Could that kill the engine only at idle? When are the O2 outputs used and when are the ignored? Does it makes sense that a faulty O2 would give this symptom or is it more likely something else(IAC)? What do your STFTs and LTFTs look like? Are the within the acceptable range? If so you know fuel trims are being controlled and the O2s must be working. There are two screws holding the IAC in(usually torx). Remove the IAC and clean it and also clean the pintle seat on the throttlebody. You can also monitor the PID for the IAC to see if the counts are correct at idle. That way at least you'll know if the IAC is being "commanded" to operate. It may be defective, but at least you can tell from the PID if the command is being given. The IAC is a stepper motor so it isn't cheap. I'd try the cleaning route first unless money is no object. Remember the IAC only does it's job at idle. The rest of the time it is coasting along. If you can do the job of the IAC with your foot you're half way home.
Don't start fishing for answers. Stick to your symptom first before you turn yourself into a parts swapper. That gets expensive real fast. What is the job of the pre cat O2s? Could that kill the engine only at idle? When are the O2 outputs used and when are the ignored? Does it makes sense that a faulty O2 would give this symptom or is it more likely something else(IAC)? What do your STFTs and LTFTs look like? Are the within the acceptable range? If so you know fuel trims are being controlled and the O2s must be working. There are two screws holding the IAC in(usually torx). Remove the IAC and clean it and also clean the pintle seat on the throttlebody. You can also monitor the PID for the IAC to see if the counts are correct at idle. That way at least you'll know if the IAC is being "commanded" to operate. It may be defective, but at least you can tell from the PID if the command is being given. The IAC is a stepper motor so it isn't cheap. I'd try the cleaning route first unless money is no object. Remember the IAC only does it's job at idle. The rest of the time it is coasting along. If you can do the job of the IAC with your foot you're half way home.
Well I didn't think it would be an O2, but I was reading through other posts and ppl were mentioning that. Just trying to cover all bases, since this was the first time I have taken apart the motor and figured there are alot more knowledgeable ppl on this forum. I was going to start by looking at the IAC tomorrow and hopefully it will be an easy fix...I am assuming I can clean it with MAF cleaner?
Don't forget to clean the pintle seat on the throttlebody. You may have to raise your idle speed through tuning if you have a big cam. Look at Top Fuel and the Alcohol class. Those engines idle at 2500 RPM just to keep them running because of the cam profile. You don't won't to have to idle too high or it becomes a PITA to drive especially in traffic.
Last edited by eallanboggs; Apr 19, 2010 at 07:37 AM.
I was following LS1howto.com for the H&C swap, but I don't recall seeing anything about IAC issues on it, and I realized that the idle would be poor after the install and will probably be higher after the tune than it was before. The cam is 228/232. I had seen ppl talk about drilling a small hole in the throttle body plate, but I wanted to first get the tune done before going to that step. I'll let you guys know how cleaning the IAC/throttle body and MAF turns out.
I don't think people drill the blade much anymore. In the early years of OBDII that was a common thing, but they came to realize the IAC has a job to do and that is to provide air(bypassing the TB at closed throttle) to the engine at idle. All drilling a hole does is allows the IAC to work less(less counts). I guess if you drilled a big enough hole you could remove the IAC all together since sufficient air would get in through the hole, but then you would loose the precise speed control the IAC is designed to provide. With TBs before drive by wire you could rig your TB blade with the throttle adjuster screw or throttle cable and accomplish the same thing. You could modify them so that the throttle never fully closed. Who needs an IAC anyway when there are so many ways to get along without it.
Ok, so I tried cleaning the IAC off and the car did idle for several minutes with occasional surges. Then when I put it into gear, it died promptly and now I can't get it to idle (back to the same symptoms as yesterday). I tried starting the car with the IAC pulled out to see if it was moving like I had seen in other threads, but the car didn't like that (made a loud noise and didn't start). I am able to keep the car running if I am pushing on the gas.
My question is, do you guys think its still the IAC or something else? I was not sure if I should replace the IAC and see what happens?
My question is, do you guys think its still the IAC or something else? I was not sure if I should replace the IAC and see what happens?
The questions is: Do YOU think it is the IAC? Think about your post. Do you trust your own troubleshooting ability? It doesn't sound like it. If it didn't idle UNTIL you put your foot on the pedal to crack the throttle a little(the job of the IAC) what does that tell you? When you removed the IAC and ran the engine you created a giant vacuum leak. It might run with a small leak, but not one that big. Don't forget the IAC has to COMMANDED to operate. Is the PWM signal present? Is the pintle sluggish or not moving at all? You have to answer these questions BEFORE you pull the trigger.
Sorry I am a novice when it comes to this stuff and my questions may seem ridiculous to some, thats why I have been asking questions. I am just trying to determine if the tune will solve the issue or if there is something else going on. I don't want to get to the tune to find out something else is going on and then not get the tune done that day since my schedule is pretty tight over the next few months.
I am not sure how to check the PWM signal, nor am I sure if I have the equipment at my house to check it.
...Well I just went to remove it again and plug the hole, the car ran with a high idle. The IAC was not moving at all, but when I shut the car off, the black plunger piece sprung off. I'll replace that and just wait til the tune then.
I am not sure how to check the PWM signal, nor am I sure if I have the equipment at my house to check it.
...Well I just went to remove it again and plug the hole, the car ran with a high idle. The IAC was not moving at all, but when I shut the car off, the black plunger piece sprung off. I'll replace that and just wait til the tune then.
Last edited by peterlawl84; Apr 20, 2010 at 09:30 AM.
It's called a pintle and no it's not supposed to take a flying leap. You should have already been convinced through the tests you did previously that the IAC had a problem. To see IAC counts you need a good scan tool or a GMM, Labscope or Oscope to see the commanded PWM signal to the IAC. Sometimes you have to get creative when you troubleshoot and you did when you removed the IAC and blocked off the hole so you could observe the pintle while the engine is running. You can't always use substitution because you might not have an extra part to try out to prove the existing one is faulty. That's when trying other things like what you did with the IAC comes in handy. When you observed the results of the test you did by using your foot as an IAC you should have realized then that you were onto something. Some parts are cheap. The IAC which is a stepper motor is not so don't be a parts swapper. Prove a part to be defective even if you don't always have the most sophisticated equipment to do the testing. Do you know you can use a dollar bill to check for misfires? If you think you have a misfire you can put a dollar bill over the end of the tailpipe. If there is one the bill will be momentarily sucked up against the pipe end. Simple test, but effective. The dollare bill becomes a pressure transducer.
