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Adjusted TPS to 0.54, now idles at 1300

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Old 06-12-2018, 10:41 PM
  #81  
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Originally Posted by JasBass View Post
Checked for codes and throwing none. As much as I love these cars, these older computer systems really can be a pain when something isn't right. I'll hit the elbow with some RTV in the morning and try again after work. I swear, I feel like I can hear the IAC motor on when turning the car off. Re start and it idles high. I will not be defeated by a car!
It really is amazing to me how a computer system that was cutting edge ~30 years ago is dinosaur-ed nowadays.

Sealing the booster is a good idea, hopefully it is only leaking at the elbow, and the diaphragm is in good shape.

For what it's worth, girlfriend's IAC was loose by 1 turn from the TB housing. Don't know how, but it was. You could always check yours for snug-ness.

I don't know that I've ever heard my IAC after the car shuts off, but datalogging indicates that it does move. Maybe your IAC is acting up? You can take it out and clean/inspect it, mine was fairly carboned. You can replace the IAC gasket while you have it off as well. I just used rtv.
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Old 06-13-2018, 09:39 AM
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Originally Posted by TheBlaster9001 View Post
It really is amazing to me how a computer system that was cutting edge ~30 years ago is dinosaur-ed nowadays.

Sealing the booster is a good idea, hopefully it is only leaking at the elbow, and the diaphragm is in good shape.

For what it's worth, girlfriend's IAC was loose by 1 turn from the TB housing. Don't know how, but it was. You could always check yours for snug-ness.

I don't know that I've ever heard my IAC after the car shuts off, but datalogging indicates that it does move. Maybe your IAC is acting up? You can take it out and clean/inspect it, mine was fairly carboned. You can replace the IAC gasket while you have it off as well. I just used rtv.
I got out there this morning before clinic and started sealing the elbow and then realized, I don't know how I missed it, there is a small crack under the elbow, about 1.5cm long and a few or more mils thick that was leading into the elbow connection on the booster housing. Hit it with some RTV too. Fired it up real quick and it was holding its normal cold start idle of 1,000 and then it jumped up again but I realized it pulled the fresh RTV in. Resealed and it'll set up by the time I get back this evening. If anything, another learning point on this car...
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Old 06-13-2018, 09:46 AM
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Originally Posted by JasBass View Post
I'm confident the idle set screw and TPS are where they need to be. It worked well before tuning off. With IAC pintle fulled extended (A+B jumped, disconnected, etc.), it'll idle between 4-5. I know vac leaks can lead to a high idle, but I don't think 1500 would happen from a vac leak like that would it?
How did you know? Without knowing if it was leaking then, it would be hard to say what is happening. I'd get it sealed and check
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Old 06-13-2018, 10:42 AM
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I had a booster crack but before the crack I was checking for idle issues. When I replaced it I found a small crack on the bottom. Put a steel one in and much better overall.
I put tie straps on all of my vacuum connections to tighten them even more. Idles better than ever now. Right at 600.
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Old 06-13-2018, 09:40 PM
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Originally Posted by aklim View Post
How did you know? Without knowing if it was leaking then, it would be hard to say what is happening. I'd get it sealed and check
Originally Posted by xrav22 View Post
I had a booster crack but before the crack I was checking for idle issues. When I replaced it I found a small crack on the bottom. Put a steel one in and much better overall.
I put tie straps on all of my vacuum connections to tighten them even more. Idles better than ever now. Right at 600.
So i've had a frustrating but productive evening. Spent 2 hours going through the whole rest process again, playing with TPS settings, set screw settings, etc. No matter what I did, it would come back and idle at 1500. I exhausted the book of cusses, debated selling the car, and contemplated insurance fraud and burning the car down . So I said screw it, jumped A+B to extend the IAC pintle all the way and then unplugged it. Started it and used the set screw to set it at 700 and left the IAC unplugged. Ran it a few miles around the block and boom, it idled at 1400. I think this was pretty definitive proof that the culprit seems to be a vac leak... So now I have to start investigating. But something tells me this booster is going to be the culprit
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Old 06-13-2018, 10:05 PM
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Originally Posted by JasBass View Post
So i've had a frustrating but productive evening. Spent 2 hours going through the whole rest process again, playing with TPS settings, set screw settings, etc. No matter what I did, it would come back and idle at 1500. I exhausted the book of cusses, debated selling the car, and contemplated insurance fraud and burning the car down . So I said screw it, jumped A+B to extend the IAC pintle all the way and then unplugged it. Started it and used the set screw to set it at 700 and left the IAC unplugged. Ran it a few miles around the block and boom, it idled at 1400. I think this was pretty definitive proof that the culprit seems to be a vac leak... So now I have to start investigating. But something tells me this booster is going to be the culprit
If you set the idle to run at 700 and the ECM commands 650, there will be no adjustment the ECM can do.

If you think the booster is a leak, it is very simple to determine. Get the motor hot, check the IAC counts and then plug the nipple at the manifold. Rev and recheck.
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Old 06-13-2018, 10:15 PM
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Originally Posted by JasBass View Post
So i've had a frustrating but productive evening. Spent 2 hours going through the whole rest process again, playing with TPS settings, set screw settings, etc. No matter what I did, it would come back and idle at 1500. I exhausted the book of cusses, debated selling the car, and contemplated insurance fraud and burning the car down . So I said screw it, jumped A+B to extend the IAC pintle all the way and then unplugged it. Started it and used the set screw to set it at 700 and left the IAC unplugged. Ran it a few miles around the block and boom, it idled at 1400. I think this was pretty definitive proof that the culprit seems to be a vac leak... So now I have to start investigating. But something tells me this booster is going to be the culprit

That seems to me like a leak somewhere. Likely heat related, since it took. A drive for the idle to get jacked up. Like the other guy said, you can easily check the booster by unplugging it at the plenum and capping the port, then revving.
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Old 06-13-2018, 11:53 PM
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Originally Posted by TheBlaster9001 View Post
That seems to me like a leak somewhere. Likely heat related, since it took. A drive for the idle to get jacked up. Like the other guy said, you can easily check the booster by unplugging it at the plenum and capping the port, then revving.
Yes plug the booster valve to engin(no driving of course) and eliminate the booster. When you set the idle do you get it down to 450 with the iac unplugged. The iac raises it up to 600 it cannot bring it down from 700. Now there are a lot of vacuum lines and intake leak is possible. Even the air box and the tube could be cracked. But the initial setting needs to be 450 as per the Idle adjust procedure.

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Old 06-14-2018, 07:46 AM
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AK: What scan setup are you running?


Originally Posted by TheBlaster9001 View Post
That seems to me like a leak somewhere. Likely heat related, since it took. A drive for the idle to get jacked up. Like the other guy said, you can easily check the booster by unplugging it at the plenum and capping the port, then revving.
We'll see what happens tonight. Talk about when it rains, it pours lol. All of this started with thinking the throttle response was a bit off and now we're here

Originally Posted by xrav22 View Post
Yes plug the booster valve to engin(no driving of course) and eliminate the booster. When you set the idle do you get it down to 450 with the iac unplugged. The iac raises it up to 600 it cannot bring it down from 700. Now there are a lot of vacuum lines and intake leak is possible. Even the air box and the tube could be cracked. But the initial setting needs to be 450 as per the Idle adjust procedure.
Yessir, I get it down as low as it'll run. Dash tach will show it bounces between 4-5. The only reason I did the test of setting it at 700 and leaving the IAC unplugged was to remove the IAC from the equation. I wanted to make sure the IAC wasn't acting up. For the car to be pushing up to 12-1400, there must be a substantial leak...
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Old 06-14-2018, 10:33 AM
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Originally Posted by JasBass View Post
AK: What scan setup are you running?.
Holley Stealth Ram, 42# injectors, AFR 190 heads, 1.6 intake RR and 1.5 exhaust RR, 230/236 - 110 lobe sep, 108 intake centerline (2 deg. advanced), TPIS Long Tube Headers, Random Tech Cat, Borla exhaust, Rossler Trans, HiTech Motorsport tuned ECM.
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Old 06-14-2018, 10:55 AM
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Originally Posted by aklim View Post
Holley Stealth Ram, 42# injectors, AFR 190 heads, 1.6 intake RR and 1.5 exhaust RR, 230/236 - 110 lobe sep, 108 intake centerline (2 deg. advanced), TPIS Long Tube Headers, Random Tech Cat, Borla exhaust, Rossler Trans, HiTech Motorsport tuned ECM.
My bad buddy, I meant your scan setup . But I like that setup too, very nice! Engine build is in the near-ish future. Just trying to decide direction at this point. 383 is a solid choice, part of me is wondering if it's worth it to push for over 400ci in a small block. Obviously I would go with a 4 bolt instead of the stock 2 bolt block. All part of the ongoing fun
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Old 06-14-2018, 03:52 PM
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Originally Posted by JasBass View Post
My bad buddy, I meant your scan setup . But I like that setup too, very nice! Engine build is in the near-ish future. Just trying to decide direction at this point. 383 is a solid choice, part of me is wondering if it's worth it to push for over 400ci in a small block. Obviously I would go with a 4 bolt instead of the stock 2 bolt block. All part of the ongoing fun
I have an Auto X-ray and an MT2500 and also testing out ALDL Scan
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Old 06-14-2018, 08:52 PM
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The nightly frustrating update lol. Brake booster is sealed and no longer hissing. Clamped off every vac hose connection, except for FPr (booster, HVAC-Cruise, evap off TB); turned it on and it idled at 6 until I gently revved it and bam, right back to 1500 when coming back down off rev. Went through the entire IAC reset process again, keyed the car back on and it stumbled for about half a second and then I heard the IAC rumble and bam, back to 1500. Removed the IAC and cleaned it up, it was pretty cruddy. Put it back in with the same result post cleaning.

Went through many articles on the forum with members who had a bad IAC that failed with high idles. Low idle and stumble was the inverse. I'm starting to question if the IAC is failing. Before all of this debacle started and I was basically daily driving the car, every so often when neutral coasting up to a light or when sitting at a light, it would sit at 1000 and sometimes settle down to 7. Other times it would hold 1000. I had noticed this was becoming more common. The IAC is the original 1989. Thoughts?

AK, I don't have a scanner so I can't give exact steps. Checking out the options you posted
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Old 06-14-2018, 09:07 PM
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Originally Posted by JasBass View Post
The nightly frustrating update lol. Brake booster is sealed and no longer hissing. Clamped off every vac hose connection, except for FPr (booster, HVAC-Cruise, evap off TB); turned it on and it idled at 6 until I gently revved it and bam, right back to 1500 when coming back down off rev. Went through the entire IAC reset process again, keyed the car back on and it stumbled for about half a second and then I heard the IAC rumble and bam, back to 1500. Removed the IAC and cleaned it up, it was pretty cruddy. Put it back in with the same result post cleaning.

Went through many articles on the forum with members who had a bad IAC that failed with high idles. Low idle and stumble was the inverse. I'm starting to question if the IAC is failing. Before all of this debacle started and I was basically daily driving the car, every so often when neutral coasting up to a light or when sitting at a light, it would sit at 1000 and sometimes settle down to 7. Other times it would hold 1000. I had noticed this was becoming more common. The IAC is the original 1989. Thoughts?

AK, I don't have a scanner so I can't give exact steps. Checking out the options you posted
I would also begin to suspect the IAC, given we can assume leaks are not a factor, you'd hear a leak if it was idling at 1500. I know my car is on it's second IAC, as I have the old one from PO. They look to be fairly expenisve, so it's good that we've narrowed it down before turning to the IAC.
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Old 06-14-2018, 09:46 PM
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Originally Posted by TheBlaster9001 View Post
I would also begin to suspect the IAC, given we can assume leaks are not a factor, you'd hear a leak if it was idling at 1500. I know my car is on it's second IAC, as I have the old one from PO. They look to be fairly expenisve, so it's good that we've narrowed it down before turning to the IAC.
Agreed. You can definitely hear the IAC hissing away when it does that. What a journey man. I'll pick up an IAC tomorrow, I'll be able to get it for like $30 after a discount I have. The ultimate fix for this, LS swap
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Old 06-14-2018, 09:51 PM
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Originally Posted by JasBass View Post
Agreed. You can definitely hear the IAC hissing away when it does that. What a journey man. I'll pick up an IAC tomorrow, I'll be able to get it for like $30 after a discount I have. The ultimate fix for this, LS swap
HA!
I thought about a swap at one point, but I think the L98 is the perfect engine for my understanding/disposition. A nice blend between the old (HEI spark, Gen 1 block), and new (EFI).

Pretty decent price. I'm crossing my fingers for ya. It's been a journey.

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Old 06-14-2018, 10:04 PM
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Originally Posted by JasBass View Post
Agreed. You can definitely hear the IAC hissing away when it does that. What a journey man. I'll pick up an IAC tomorrow, I'll be able to get it for like $30 after a discount I have. The ultimate fix for this, LS swap
Sure but it will cost more
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Old 06-16-2018, 10:01 AM
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Y'all, I think we have a winner here. Took out the TB and cleaned everything up, installed new IAC and gasket. Even went through and used some nice RTV on the IAC/coolant housing and the gasket on the top of the TB for the CCV "chamber". Went through the entire TPI runner setup and made sure the bolts were tight, all the vac lines are routed properly and have tight fittings, etc. Installed the TB back on this morning and cranked it up, ran nice for like a minute and then went right into the 1500 idle. I pulled the connector for the MAF and it immediately idled perfect. Like so perfect, I couldn't believe how perfect the car idled. It's never idled that good. Settled right down to 7-8 and sounded stronger than it ever has. Plugged it back in and it went right back to 1500. This was a new Bosch unit that is literally a year old two weeks ago. So we can eliminate vacuum leaks since the car idles amazing with MAF disconnected and the IAC and set screw setting seem to be spot on.

I had thrown a code 36 for a while, but when I had the tune built for the car, PCM widened the Voltage table for the burnoff circuit and the 36 went away. MAF would explain many things about how the car has been behaving. Feeling lower on power, some crummy throttle response, the weird high idle issue that was variable, and feeling like the car was running a little lean. Thankfully I have the receipts and the thing is in warranty.

Thoughts?
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Old 06-16-2018, 10:56 AM
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Originally Posted by JasBass View Post
Y'all, I think we have a winner here. Took out the TB and cleaned everything up, installed new IAC and gasket. Even went through and used some nice RTV on the IAC/coolant housing and the gasket on the top of the TB for the CCV "chamber". Went through the entire TPI runner setup and made sure the bolts were tight, all the vac lines are routed properly and have tight fittings, etc. Installed the TB back on this morning and cranked it up, ran nice for like a minute and then went right into the 1500 idle. I pulled the connector for the MAF and it immediately idled perfect. Like so perfect, I couldn't believe how perfect the car idled. It's never idled that good. Settled right down to 7-8 and sounded stronger than it ever has. Plugged it back in and it went right back to 1500. This was a new Bosch unit that is literally a year old two weeks ago. So we can eliminate vacuum leaks since the car idles amazing with MAF disconnected and the IAC and set screw setting seem to be spot on.

I had thrown a code 36 for a while, but when I had the tune built for the car, PCM widened the Voltage table for the burnoff circuit and the 36 went away. MAF would explain many things about how the car has been behaving. Feeling lower on power, some crummy throttle response, the weird high idle issue that was variable, and feeling like the car was running a little lean. Thankfully I have the receipts and the thing is in warranty.

Thoughts?
Do you have a K&N air filter? Or any other oil type filter? They can kill MAF sensors. Luckily it's under warranty, they are not cheap. A bad MAF could definently cause a whole host of issues. Setting a high idle would not make me suspect the MAF straight away, but I can see how it may be at fault.
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Old 06-16-2018, 01:27 PM
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Originally Posted by TheBlaster9001 View Post
Do you have a K&N air filter? Or any other oil type filter? They can kill MAF sensors. Luckily it's under warranty, they are not cheap. A bad MAF could definently cause a whole host of issues. Setting a high idle would not make me suspect the MAF straight away, but I can see how it may be at fault.
Just a standard regular filter. So apparently Advance no longer stocks Bosch MAFs for this car. So I have a store credit and need to choose between a Spectra, Cardone, and Carquest. Spectra/Carquest are new units and Cardone is remanu. It kinda seems like the forum feedback on these varies case by case. I could always keep the store credit and source elsewhere. Any feedback on brands?

I can't think of any other reason other than the MAF being bad that would cause it to idle high like that. I know pulling the MAF kicks it into a standard fueling map that guesstimates engine needs. But I'm curious if the issue is going to be a closed loop issue where one of the inputs could be bad. But the only two that come to mind would be 02 and MAF (with 02, MAF, IAT, CTS being the main players). I'm assuming the MAF is showing more air flow than what is actually flowing so the ECM is adding more fuel to compensate and leading to higher RPM. Journey, what a journey
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