High RPM's? Idle air control opens?
This is a discussion on High RPM's? Idle air control opens? within the Computer & Tuning forums, part of the LSx Technical Help Section category; Hi everyone! I have a 2000 LS1 in a 33 Ford street rod. And I cannot get it to idle! ...
03-29-2009, 11:32 AM #1
High RPM's? Idle air control opens?
I have a 2000 LS1 in a 33 Ford street rod. And I cannot get it to idle!
It has a wiring harness and from Streeet and Performance. And NOW has a computer from them too.
For some reason the Idle Air Control Vavle opens?
OK! This is what I have done so far!
I have had 3 people look at it. 2 came to my shop with scan tools. Both did NOT get any codes that would tell them what was causing it. But we did find out that I didnt have a vacuum leak. Or anything worng with the enigine.
I can unplug the IACV and remove it. Pull it out by hand reinstall it. And the engine will idle as long as I leave it unpluged. As soon as I plug it back in the computer will open it.
We took it to a Chevy garage. And they pointed to a bad computer. Since the computer we were using (at that time) was a used on. And also found out that it was out of a 98 Firebird V6.
So we just spent $500.oo on a new one. From Street and Performance. That would be programed to our engine and transmission.
Just installed it! And it is still idling high!
So what do you guys think it could be????????????????
Hope someone on here can help me out!
Thanks Shannon Anderson
Last edited by Shannon2356; 03-29-2009 at 07:05 PM.
03-29-2009, 12:53 PM #2
I'm sorry that you had to go to S&P , I could get you a loaded PCM that was programmed custom for YOUR setup for under $200...
The IAC is supposed to open and operate in a feedback loop to provide the proper amount of idle airflow for the vehicle.
The scan tools of those shops are not very helpful, being in front of a tuner with real software would be a lifesaver if he is competent. He would be able to troubleshoot the IAC to ensure it is wired and functioning properly as well as set the base airflow requirements for the TB.
Last edited by Frost; 03-29-2009 at 02:10 PM.
03-29-2009, 03:08 PM #3
it would be nice to be able to log it and see what the IAC counts are. Just to clarify you have a pcm out of a 2000 f-body now? Are you running the MAF?
03-29-2009, 06:17 PM #4
Yes I am running a MAF. And I also have to add that the IACV is also new.
This is what I know.
Everything is from Street and Performance. But the engine and transmission are both from a GM dealer. The engine is a 2000 LS1 Corvette and the trany is a 4L60E. NOW everything else is for a 98. The IACV is from a Camaro. The computer and wiring harness is also from a 98. So it looks like the only thing that is a 2000 Corvette is the engine.
OK! What you were saying about the Throttle stop. I have NOT touched it. And it is not hanging open. And I don't think it is out of adjustment. Because I can get the engine up to running temp. Then remove the old IACV. Pull it out by hand. Reinstall it. Leave it unpluged from the harness. And the engine will idle VERY good.
What tells the comp. to open the IACV?
03-29-2009, 07:00 PM #5
frost will have to chime in on this one. The 98's were cable driven and the 2000 vette was a drive by wire. I think that's where your problem is. What throttle body do you have? Cable driven or drive by wire? If it's drive by wire I don't think you need the iac motor because it'll use the throttle body blade.
03-29-2009, 07:02 PM #6
NO! It does not have ANY of the emisson stuff on it. That is the only codes we were getting when we hooked the scan to it. We also got 2 fan codes and check engine light. Witch we dont have either.
03-29-2009, 07:24 PM #7
If the Vette motor is "fly by wire" wont he need the Vette harness? I would think the 98' Camaro harness would be different at the throttle plenum. Also would'nt he then need the Vette Comp too? Some things not addin' up here. If the comp is tuned for a cable thottle, it would seem to make sense that he could use the Camaro thottle body in place of the fly by wire one. Because there would'nt be plugs there for fly by wire on the 98' Camaro harness. Unless something else is totally different between the two motors and sensors besides the fly by wire setup. I dunno. Just seems something is missing. Probably something simple...
03-29-2009, 07:32 PM #8
OK! It is a cable. And I think that everything is from a 98. The only thing that is a 2000 is the engine itself. The throttle is from a Camaro. I just replaced the IACV. And the 98 Camaro matched it. So everything electrical is from a 98.
03-29-2009, 07:49 PM #9
I dont think I can remove it all together. The engine idles very low. And does not ilde at all if its cold. And I also think that the IACV work like a choke when the engine is cold.
03-29-2009, 07:58 PM #10
I'd be tossing guesses to help you with much past just making sure there's no unmetered air getting into the car ie. vac leaks, throttle body set screw backed off, or one thing is since it's from a 98 do you know the history of the throttle body? Perhaps it's been drilled out for a cam or something like that. There should be a hole in the center of the throttle blade but it's popular for people to drill that out larger when doing a cam. You're really going to need to get it in front of a tuner that can log the car and see exactly what the airflow is doing.
03-29-2009, 08:16 PM #11
The throttle body is stock. And is untouched. Everything on this engine is NEW. And has 0 miles on it. Just run time only.
Let me ask you guys something alse. Sincfe we are talking about the throttle body.
There is a water bypass tube. That runs under and through the throttle body.
Now since I installed this engine in a 33. I had to drill and tap the flat area of the water pump (beside the throttle cable) for a water outlet. NOW instead of running the water throught the throttle bady. I ran a hose behind it and over to the water bypass tube outlet.
So there is NO water running throught the throttle body.
03-29-2009, 08:18 PM #12
Yeah sorry doing ten things at once,LOL. I totally forgot the function of the IAC.
03-29-2009, 08:25 PM #13
What intake is on the engine? Does it have the open port for the EGR just behind the TB? If so how did you block that off? You went over all the lines and checked for vac leaks right? If those tables are stock and you have no unmetered air entering the engine I'd probably take a hard look at that throttle body. Like I said before though, I'm guessing at this point.
03-29-2009, 08:40 PM #14
There is a line comming out of the intake behind the TBS. And goes to a sensor on the pass. side head. It is between the first two injectors. There is a wire pluged into it. And the vacuum is pluged off at that point.
The reason I dont think its a vacuum leak. Is because it idles to good and smooth. If you pull out the IACV and leave it unpluged. When you unplug it. The engine will run at what looks like 800 rpm's. And sounds great. But when you plug it back in. The rpm's go up.
03-29-2009, 08:40 PM #15
03-29-2009, 08:52 PM #16
Trust me I know! I wish it had a carb on it. LOL!
And I have been saying that since the beginning! Its something stupid! Once I find out what it is. I will be kicking myself in the A**!
03-29-2009, 08:53 PM #17
I'm begining to wonder when you bought the new IACV if they gave you the wrong one at this point. Just dont make sense why it's doing what it's doing.
03-29-2009, 08:59 PM #18
NO! LOL The reason I bought a new one is because the first guy I talked to and had look at it. Told me that it mnaybe sticking. I bought a new one. It is only about 3 weeks old. And the new computor I just installed yesterday. Really thought it would fix it. LOL!
I want to thank all of you for all the help so far!
03-29-2009, 09:34 PM #19
03-29-2009, 09:52 PM #20
This is not true. I don't even log desired position, I log actual...
You know when it's right because the IAC will be at 60-80 counts at hot idle. You need a scan tool to see this. I'd start by looking at TPS with a scan-tool and key-on, and adjust that screw in the TB untilt he blade is open to about 2%. Now turn the key to off, unplug the TPS, turn the key to on and wait a few seconds and turn it back off. Plug the TPS back in and turn the key back to on. Verify with a scan tool that the TPS is reading 0%. Start the motor up and get it as warm as you can; keep the fans forced off. At hot idle you want 60-80 counts on the IAC, and you know that you have it in a proper place in it's operating range.
Are you sure that your PCM was flashed for a CABLE operated TB? If you told them vette, they may have assumed DBW instead of cable...
Users Browsing this Thread
There are currently 1 users browsing this thread. (0 members and 1 guests)
By ssweet99ss in forum Computer & TuningReplies: 60Last Post: 11-03-2009, 03:18 PM
By Ed Blown Vert in forum CorvetteReplies: 0Last Post: 05-30-2008, 08:50 PM
By T/Aboo in forum General HelpReplies: 3Last Post: 04-26-2006, 02:20 PM
By jwn407 in forum General HelpReplies: 1Last Post: 01-05-2006, 06:39 PM
By flynlow32 in forum Computer & TuningReplies: 7Last Post: 01-01-2006, 09:21 PM