New injectors = hunting idle
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Joined: Jul 2003
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From: Canada, B.C.
Car: 89 IROC t-tops
Engine: 5.7 (350 tpi)
Transmission: Auto (700R4)
Axle/Gears: 9 bolt disc with 3.73's
New injectors = hunting idle
Hey guys I had a "hot restart" issue with my stock 89 5.7 TPI, so after replacing a bunch of sensors and parts I decided to replace the injectors!
I got the yellow Bosch Type 3?
The car starts alot better but now it seems to hunt in idle?
Can anyone look at this log and see anything a "miss"
no pun intended...
I got the yellow Bosch Type 3?
The car starts alot better but now it seems to hunt in idle?
Can anyone look at this log and see anything a "miss"
no pun intended... 
Member
Joined: Sep 2007
Posts: 350
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Re: New injectors = hunting idle
Car is running 1,000 rpm on only 26-27 IAC counts. MAF readings are relatively low for 1,000 rpm with only 5-6 gm/sec airflow. BLM is pegged at 160.
All indications are that it is ingesting a significant amount of unmetered air and the ecm is adding as much fuel as possible to compensate.
Look for a big vacuum leak. Maybe brake booster hose or pcv valve port on the intake open to atmosphere to flow that much extra air.
All indications are that it is ingesting a significant amount of unmetered air and the ecm is adding as much fuel as possible to compensate.
Look for a big vacuum leak. Maybe brake booster hose or pcv valve port on the intake open to atmosphere to flow that much extra air.
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Re: New injectors = hunting idle
Good catch tequila. I'd have to agree. I would think you should be pulling 10 to 15 gms/sec at 7-800 rpm idle. I also think you have a vacuum leak somewhere. Could even be pulling air around the injector seals if they didn't seal up good. Thread Starter
Junior Member
Joined: Jul 2003
Posts: 62
Likes: 0
From: Canada, B.C.
Car: 89 IROC t-tops
Engine: 5.7 (350 tpi)
Transmission: Auto (700R4)
Axle/Gears: 9 bolt disc with 3.73's
Re: New injectors = hunting idle
Hey guys, thanks for the replies
I started to play with the values for the injector constant. I went down in size to 20 lbs and there seemed to be no difference. So I went and upped the MAF #1 table some. It starts like a hot damn, and it seems to idle higher and was smooth as a top, but after a good cruise she has a slight hunting still... (Vacuum leak as you suggested probably)
But I drove the car with the laptop hooked up and it seems that the only real issue with the High BLM's is at idle only
I am still getting used to tunerpro, I am not sure I even got the datalog from the drive... In tunerpro it says session 4, but I think it didn't save the datalog from the drive
The only other thing I noticed in tunerpro, is when I am connect to the ecm without the car running the MAF is already reading 5.0... Is that normal or is there an issue with the MAF?
I started to play with the values for the injector constant. I went down in size to 20 lbs and there seemed to be no difference. So I went and upped the MAF #1 table some. It starts like a hot damn, and it seems to idle higher and was smooth as a top, but after a good cruise she has a slight hunting still... (Vacuum leak as you suggested probably)
But I drove the car with the laptop hooked up and it seems that the only real issue with the High BLM's is at idle only
I am still getting used to tunerpro, I am not sure I even got the datalog from the drive... In tunerpro it says session 4, but I think it didn't save the datalog from the drive
The only other thing I noticed in tunerpro, is when I am connect to the ecm without the car running the MAF is already reading 5.0... Is that normal or is there an issue with the MAF?
Last edited by Grizzlee; Jul 18, 2010 at 06:36 PM. Reason: Attaching CSV file...
Joined: Sep 2003
Posts: 25,895
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From: Pittsburgh PA
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: New injectors = hunting idle
Yeah I'd look for a leak to be sure. high idle like that sounds like a leak with low MAF flow.
Sometimes different injectors will have different spray patterns and require a different tune. I had accel 24lb injectors on my car and it changed the way it idled so i had to tweak alittle to make it happy.
Sometimes different injectors will have different spray patterns and require a different tune. I had accel 24lb injectors on my car and it changed the way it idled so i had to tweak alittle to make it happy.
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Joined: Sep 2003
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Car: 2011 6.2 Silverado, 88/85 camaro
Re: New injectors = hunting idle
Stupid question possibly on my part but, after installing the new injectors, did you do the idle air adjust procedure resetting the IAC and adjusting? If not, I'm guessing your car is still adjusted according to your old injectors?
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Re: New injectors = hunting idle
What is that procedure? I may need to do that as well. I've been trying to find the right BPW for my injectors, and my engine is idling pretty high (1000rpm) and the iac was sitting at about 95 while idling cold.
I don't know if that's normal, or if that needs to be adjusted, or what.
I don't know if that's normal, or if that needs to be adjusted, or what.
Member
Joined: Sep 2003
Posts: 232
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Car: 2011 6.2 Silverado, 88/85 camaro
Re: New injectors = hunting idle
LOL I feel stupid now, sorry about that, thought you had TPI, maybe these links might help ----
http://forums.chevyhiperformance.com...lem/index.html
Best link for adjustment --- http://www.texastruckscene.com/showthread.php?p=120282
Info on cleaning it looks like --- http://www.chevytalk.org/fusionbb/sh...hp?tid/189758/
http://forums.chevyhiperformance.com...lem/index.html
Best link for adjustment --- http://www.texastruckscene.com/showthread.php?p=120282
Info on cleaning it looks like --- http://www.chevytalk.org/fusionbb/sh...hp?tid/189758/
Last edited by resinlake; Jul 27, 2010 at 04:40 PM.
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Re: New injectors = hunting idle
"Tom Keliher Mar 31 2006 - 4:07pm
Idle Air Control
Tools needed:
1. Torx bit # T-20
2. Paper Clip
3. Small Punch
Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.
Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.
Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.
Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).
If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style."
Idle Air Control
Tools needed:
1. Torx bit # T-20
2. Paper Clip
3. Small Punch
Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.
Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.
Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.
Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).
If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style."
I can post a picture of my IAC valve, if need be. This idle is at 1000 RPM, and it's really annoying. I'd like to get it down around 650-700. Changing the target idle speed in my PROM didn't do anything.
Re: New injectors = hunting idle
Hello, Got a question for ya and need some assistance since I can not find it anywhere. I have to replace injectors on my 89 pontiac formula 350 5.7 liter. can you talk me thru how to do it.
I know you have to release fuel pressure which i was told the fuel cap can be removed to accomplish this.
I know the fuel rail has to be removed but don't know how to do that.
Also know the exhaust manifold has to be removed and also not really too sure as to do that. I have a shop that wants to charge me 300 to do the job but I do not have the money to get 6 more injectors and to have the job done.
I am pretty mechanically inclined as well as my friend who will be helping me. Once we hear or see how to do the job, It is as good as done.
Any assistance would be most appreciated. Would you mind helping?
Thanks in advance.
Tom
I know you have to release fuel pressure which i was told the fuel cap can be removed to accomplish this.
I know the fuel rail has to be removed but don't know how to do that.
Also know the exhaust manifold has to be removed and also not really too sure as to do that. I have a shop that wants to charge me 300 to do the job but I do not have the money to get 6 more injectors and to have the job done.
I am pretty mechanically inclined as well as my friend who will be helping me. Once we hear or see how to do the job, It is as good as done.
Any assistance would be most appreciated. Would you mind helping?
Thanks in advance.
Tom
Thread Starter
Junior Member
Joined: Jul 2003
Posts: 62
Likes: 0
From: Canada, B.C.
Car: 89 IROC t-tops
Engine: 5.7 (350 tpi)
Transmission: Auto (700R4)
Axle/Gears: 9 bolt disc with 3.73's
Re: New injectors = hunting idle
Ok, so do I have to adjust the IAC then? Its great off idle and I got it running well by enriching the MAF 1 table... To much so, i could smell the fuel but it started like a hot damn. So I reburnt a factory tuned chip. It's harder to start but it will run. So do i adjust the IAC?
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Joined: Sep 2003
Posts: 232
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Car: 2011 6.2 Silverado, 88/85 camaro
Re: New injectors = hunting idle
Was hoping someone could back me up here as I have not worked with TBI before but it looks like the same deal between TPI/TBI. When you change the amount of fuel being delivered, if you did say your old injectors were putting out less fuel or inconsistent, and now your new injectors are being more efficient or something, you may need to adjust your IAC. My car was having an issue at idle, hunting. If I would get the car off idle, raise the rpm it would stop hunting. Now that I've adjusted the IAC, cleaned it out, old one was shot, bought a new one it runs great. For as easy as the process looks, might be worth it to check it out. 
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