Cruise Control issues
Thread Starter
Burning Brakes
Joined: Jul 2014
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Cruise Control issues
I have a 1991 ZR-1. The car has 3.73 gears and has a Abbot ERA box to fix the speedometer. http://www.abbott-tach.com/era.htm
I have gone through everything in my cruise system. I have gone as far as replacing the Cruise Solenoid. Everything holds vacuum as it should. The cruise still pulsates when driving down the road. If I use the accelerate function it pulls without hiccup or issue. When I am just cruising along it will occasionally pulse the throttle. It will open the throttle then snap off, then come back on to hold speed, then snap off.
Abbot recommended hooking up the ERA box directly to the ground of my battery to make sure it doesn't get any "noise" from the chassis ground. I just did this today and the result was still the same. There was absolutely no change. Does anyone have suggestions on what it could be? Is it my brake switch, or cruise control stalk that need to be replaced?
I have gone through everything in my cruise system. I have gone as far as replacing the Cruise Solenoid. Everything holds vacuum as it should. The cruise still pulsates when driving down the road. If I use the accelerate function it pulls without hiccup or issue. When I am just cruising along it will occasionally pulse the throttle. It will open the throttle then snap off, then come back on to hold speed, then snap off.
Abbot recommended hooking up the ERA box directly to the ground of my battery to make sure it doesn't get any "noise" from the chassis ground. I just did this today and the result was still the same. There was absolutely no change. Does anyone have suggestions on what it could be? Is it my brake switch, or cruise control stalk that need to be replaced?
Race Director
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your switches on the brake or the clutch might just need ajusting. and did you replace the hose that goes to them? mine was like a dead night crawler where it went into the firewall. if you have not replaced that one yet I have a trick.
Last edited by antfarmer2; Nov 8, 2015 at 04:15 PM.
Thread Starter
Burning Brakes
Joined: Jul 2014
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Is there anyway to test the switches to see if they are out of adjustment?
BTW the cruise does not completely shutoff, it just pulsates.
Pro
Joined: Oct 2012
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From: Grapevine TX
Your symptoms make me think vacuum issue. Maybe try replacing the check valve if you haven't already. It may not be the issue but it's cheap enough to throw a few bucks at it on the off-chance it may be the culprit.
http://shop.advanceautoparts.com/p/d...m=vacuum+valve
http://shop.advanceautoparts.com/p/d...m=vacuum+valve
Thread Starter
Burning Brakes
Joined: Jul 2014
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Your symptoms make me think vacuum issue. Maybe try replacing the check valve if you haven't already. It may not be the issue but it's cheap enough to throw a few bucks at it on the off-chance it may be the culprit.
http://shop.advanceautoparts.com/p/d...m=vacuum+valve
http://shop.advanceautoparts.com/p/d...m=vacuum+valve
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did you replace the vacumme line the goes in the firewall that goes to the switches?
cut the line under the dash at a angle tape a wire to it lube up the hose and pull it. reverse it and put a connecter on it.
cut the line under the dash at a angle tape a wire to it lube up the hose and pull it. reverse it and put a connecter on it.
Last edited by antfarmer2; Nov 8, 2015 at 06:58 PM.
Team Owner
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You need to have the DRA connected correctly for it to function. For diagnostics I'd remove the DRA, put the wiring to stock and do the diagnostics for cruise connection. Once the cruise proves functional THEN you add the DRA to the system.
There's likely at least two and maybe three wiring schemes that will correct speedo/odo BUT they do NOT necessarily make all of the related functions operational.
That has always been an argument for a mechanical correction VS. a DRA, the related functions don't always function.
The 3.73 is a simple single driven gear for nearly perfect mechanical correction. There's actually no need for the DRA UNLESS you've done something with the tire RPM.
What size tires?
There's likely at least two and maybe three wiring schemes that will correct speedo/odo BUT they do NOT necessarily make all of the related functions operational.
That has always been an argument for a mechanical correction VS. a DRA, the related functions don't always function.
The 3.73 is a simple single driven gear for nearly perfect mechanical correction. There's actually no need for the DRA UNLESS you've done something with the tire RPM.
What size tires?
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Thread Starter
Burning Brakes
Joined: Jul 2014
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You need to have the DRA connected correctly for it to function. For diagnostics I'd remove the DRA, put the wiring to stock and do the diagnostics for cruise connection. Once the cruise proves functional THEN you add the DRA to the system.
There's likely at least two and maybe three wiring schemes that will correct speedo/odo BUT they do NOT necessarily make all of the related functions operational.
That has always been an argument for a mechanical correction VS. a DRA, the related functions don't always function.
The 3.73 is a simple single driven gear for nearly perfect mechanical correction. There's actually no need for the DRA UNLESS you've done something with the tire RPM.
What size tires?
There's likely at least two and maybe three wiring schemes that will correct speedo/odo BUT they do NOT necessarily make all of the related functions operational.
That has always been an argument for a mechanical correction VS. a DRA, the related functions don't always function.
The 3.73 is a simple single driven gear for nearly perfect mechanical correction. There's actually no need for the DRA UNLESS you've done something with the tire RPM.
What size tires?
BTW I did not do the rear end gears. That was done by the PO.
Team Owner
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A reference for the mechanical correction.
http://zr1specialist.com/HAT%20Web/p...on%20Gears.htm
I would put it back to known stock and do the cruise diagnostics by the diagnostic tree in the FSM, attempt to find a 45 tooth driven maybe OR once cruise diagnostics and repair is accomplished go back to the DRA. It would seem the DRA scheme is correct so maybe just do the diagnostics COMPLETE using the FSM.
The diagnostics for the switches involved is very straight forward and since you mention you've done the vacuum aspect and SEEM satisfied that it's not your issue do the electrical on the related switches.
Suggestions to cut, pull new vacuum are I'd think foolish. The diagnostics in 8A-33 of the FSM should give you solid diagnostics. You should need NOTHING else.
Last edited by WVZR-1; Nov 8, 2015 at 10:11 PM.
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Suggestions to cut, pull new vacuum are I'd think foolish. The diagnostics in 8A-33 of the FSM should give you solid diagnostics. You should need NOTHING else.
to change a degraded vacumme line foolish? to each thier own.
to change a degraded vacumme line foolish? to each thier own.
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OP - the diagnostics in the 8A-33 section are pretty straight forward even regarding the surge etc. I read you post a little more thoroughly and it certainly seems that the diagnostics are still pretty straight forward and the electronics are the "first order" of business for all diagnostics.
You mention solenoid. What are you calling the solenoid? There's a module in the car and a servo under the hood.
You mention solenoid. What are you calling the solenoid? There's a module in the car and a servo under the hood.
Thread Starter
Burning Brakes
Joined: Jul 2014
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OP - the diagnostics in the 8A-33 section are pretty straight forward even regarding the surge etc. I read you post a little more thoroughly and it certainly seems that the diagnostics are still pretty straight forward and the electronics are the "first order" of business for all diagnostics.
You mention solenoid. What are you calling the solenoid? There's a module in the car and a servo under the hood.
You mention solenoid. What are you calling the solenoid? There's a module in the car and a servo under the hood.
As far as the Speedometer goes, if I get rid of the ERA box, with the 3.73 gears my Speedometer should read just 1% off? That seems so small that I almost would rather delete it all together.
Is there a cruise control computer? I had a similar issue in my old 944 Turbo. I sent the computer off to have the cold solder joints fixed and it all went away.
Last edited by billy mild; Nov 10, 2015 at 07:33 AM.
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There is an electronic module "in the car" GM# 25140992 and it fits a multitude of GM cars. It's generally available inexpensively NOS on eBay.
I would think on a '91 it would be under/near the glove box under the dash. Look in the FSM 8A-34 and next page following diagram is component locations. It might even show an image of it's location in the 8A-201 section.
GOOGLE the GM# for an image.
The 1% error is after correction with the change of the present driven to the 45 tooth driven. Removing the DRA now and if your gear wasn't changed at all the error is something near 7 1/2%.
Here's the '90 location:
I'd think you can't complete diagnostics without having access to the module.
I would think on a '91 it would be under/near the glove box under the dash. Look in the FSM 8A-34 and next page following diagram is component locations. It might even show an image of it's location in the 8A-201 section.
GOOGLE the GM# for an image.
The 1% error is after correction with the change of the present driven to the 45 tooth driven. Removing the DRA now and if your gear wasn't changed at all the error is something near 7 1/2%.
Here's the '90 location:
I'd think you can't complete diagnostics without having access to the module.
Last edited by WVZR-1; Nov 10, 2015 at 08:15 AM.
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Sorry I should have said the Cruise Control servo. All vacuum appears to hold just fine. I have tested that multiple times.
As far as the Speedometer goes, if I get rid of the ERA box, with the 3.73 gears my Speedometer should read just 1% off? That seems so small that I almost would rather delete it all together.
Is there a cruise control computer? I had a similar issue in my old 944 Turbo. I sent the computer off to have the cold solder joints fixed and it all went away.
As far as the Speedometer goes, if I get rid of the ERA box, with the 3.73 gears my Speedometer should read just 1% off? That seems so small that I almost would rather delete it all together.
Is there a cruise control computer? I had a similar issue in my old 944 Turbo. I sent the computer off to have the cold solder joints fixed and it all went away.
with WV but just want to point out what mine did once again. my line that went in the fire wall looked good and held vacumme. but was so degraded just a the outside of the firewall it was collapsing when pulling vacumme so it held it just fine. the I way told you will save you tearing your car apart and standing on your head also getting the hose off the switches is not much fun. it cost a couple bucks and took ten min and fixed my hit and miss cc. just my 2 cents
Last edited by antfarmer2; Nov 10, 2015 at 08:46 AM.
Thread Starter
Burning Brakes
Joined: Jul 2014
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with WV but just want to point out what mine did once again. my line that went in the fire wall looked good and held vacumme. but was so degraded just a the outside of the firewall it was collapsing when pulling vacumme so it held it just fine. the I way told you will save you tearing your car apart and standing on your head also getting the hose off the switches is not much fun. it cost a couple bucks and took ten min and fixed my hit and miss cc. just my 2 cents
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mine was leaking very small cracks. but when I put the vacumme test on it tested good. the night crawler hose would collapse and hold vacumme.
Last edited by antfarmer2; Nov 11, 2015 at 11:33 AM.
Melting Slicks
Joined: Aug 2008
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From: Palmdale CA
Take a look at this article, it breaks down the various components in pretty good detail, along with some good trouble shooting.. and yes there are [2] solenoids located inside of the servo housing.. I'm guessing they could possibly be your problem..
http://www.superchevy.com/how-to/82001/
http://www.superchevy.com/how-to/82001/
Thread Starter
Burning Brakes
Joined: Jul 2014
Posts: 801
Likes: 31
Take a look at this article, it breaks down the various components in pretty good detail, along with some good trouble shooting.. and yes there are [2] solenoids located inside of the servo housing.. I'm guessing they could possibly be your problem..
http://www.superchevy.com/how-to/82001/
http://www.superchevy.com/how-to/82001/
So either my vacuum hose is collapsing, my cruise control controls wiring is flaky or lastly the module/brain is bad.
Is the module going bad ever an issue? I know my old 944 Turbo it was common for the solder joints to fail. People would re solder them and it would be perfect after.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
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From: Palmdale CA
This is a good article and I have read both of the Super Chevy ones. My car thus far has been fine on both of those tests.
So either my vacuum hose is collapsing, my cruise control controls wiring is flaky or lastly the module/brain is bad.
Is the module going bad ever an issue? I know my old 944 Turbo it was common for the solder joints to fail. People would re solder them and it would be perfect after.
So either my vacuum hose is collapsing, my cruise control controls wiring is flaky or lastly the module/brain is bad.
Is the module going bad ever an issue? I know my old 944 Turbo it was common for the solder joints to fail. People would re solder them and it would be perfect after.
Did you check the coil resistance of the servo's solenoids, as well as the internal plungers for freedom of movement. I have read; were it has been said that the solenoid's plunger's inside of the Servo, can "Hang" up
Last edited by desertmike1; Nov 12, 2015 at 10:39 PM.