Jump to content



Cruise control wont't control above 50 mph

cruise control

  • Please log in to reply
13 replies to this topic

#1 madmanperez

madmanperez

    Member

  • Members
  • PipPipPip
  • 84 posts
  • Gender:Male
  • Location:Central Florida
  • Model:Starion

Posted 17 December 2018 - 03:08 PM

New problem, noticed it last time on I was on the highway. Around town, where speeds are in the 45 - 50 mph cruise control works (though a little sluggish to kick in). When I got on the highway (speeds upwards to 70 - 75 mph) when I tried to engage the cruise it didn't, or lets say it did but not I ended up slowing down to 50 mph. Luckily there weren't to many cars on the road. Just a couple who thought I was an old fart in the right lane. (the got the old part right)

Anyway, I realize the issue may be in the cruise control module in the engine bay. So basically any who could tell me if I need to replace or can it be rebuilt.

Thanks for the guys (or any girls that might be here) you all have never let me down.





#2 CaliConquestAlex

CaliConquestAlex

    The Wrench

  • Members
  • PipPipPip
  • 2,384 posts
  • Gender:Male
  • Location:Las Vegas, NV
  • Interests:BOOOST!
  • Model:Conquest

Posted 17 December 2018 - 05:06 PM

Check the vacuum line on the cruise actuator in the engine bay. Also check to ensure the cruise cable is properly connected to the gas pedal. Also, the cruise control requires the vacuum canister to work properly under boost.
2004 Infiniti FX35 Beryllium, Fully Loaded

2004 Lexus IS300 - Soon to be NA-T

1988 Conquest TSI - SOLD/Parted out
Magna Intake, MEGASQUIRT 2 (V3 Extra fw) Direct Coil Control - EDIS 4, 292m cam, Synapse Synchronic 40mm WG, Synapse Synchronic BOV, T3 TD06 20G turbo w/ .80 housing, 95 lb injectors, Treastone turbo manifold, ST springs, KYB GR2 shocks, MK1 front camber plates, Drilled/slotted rotors and braided brake lines, HD valve springs, SR20DET 3-row Radiator. MK1 Short Shifter, Da Funk Loc motor mount, Transmission Tuff-pan, Stedebani poly trans mount, Cusco front strut brace, TEP rear strut brace w/ battery tray, AEM UEGO wideband sensor.

Click the pictures for larger images:

Posted ImagePosted ImagePosted Image

#3 ucw458

ucw458

    This will mean the extinction of all life forms on this planet.

  • Moderators
  • PipPipPipPipPip
  • 11,467 posts
  • Gender:Male
  • Location:Colorado
  • Model:Conquest

Posted 17 December 2018 - 06:06 PM

View PostCaliConquestAlex, on 17 December 2018 - 05:06 PM, said:

Also, the cruise control requires the vacuum canister to work properly under boost.

The vacuum canister is for the HVAC controls only.  It doesn't store enough vacuum to operate cruise control.




3 things to check

The cruise control cable moves freely and doesn't bind in any way.

The filter on the actuator under the metal plate needs to be replaced if it's the stock one.  I used a cotton ball to replace mine.

Make sure the vacuum pump works and is connected.  There's a vacuum pump next to the radiator overflow bottle that is only for the cruise control actuator.  The relay for that pump is on the fender next to the wiper motor.  Vacuum line should go from pump to actuator then to a white check valve and finally to the intake.
My 87
Posted Image

#4 madmanperez

madmanperez

    Member

  • Members
  • PipPipPip
  • 84 posts
  • Gender:Male
  • Location:Central Florida
  • Model:Starion

Posted 18 December 2018 - 01:49 PM

Thanks for the info UCW458. I'll be working on replacing a busted/snapped speedometer cable today (12/18) I'll check under the hood for per your directions, though I'll have to check on the placement of some items. I've been under the hood plenty of times but vac pump, to actuator doesn't ring a bell. I know what the cruise control actuator is and I'll crack it open to check/replace filter. I'll check back and edit this post with my findings

#5 ucw458

ucw458

    This will mean the extinction of all life forms on this planet.

  • Moderators
  • PipPipPipPipPip
  • 11,467 posts
  • Gender:Male
  • Location:Colorado
  • Model:Conquest

Posted 18 December 2018 - 03:42 PM

Vacuum pump on the middle right, between the coolant resivour and the headlight.

Posted Image
My 87
Posted Image

#6 madmanperez

madmanperez

    Member

  • Members
  • PipPipPip
  • 84 posts
  • Gender:Male
  • Location:Central Florida
  • Model:Starion

Posted 25 December 2018 - 01:29 PM

Thanks for the ucw548. i did find the vac. pump it does run to the cruise control unit, but, the unit is tee'd into that vav. line I'll have to check again to see where the rest of that line goes to.
How would I check if the vac. pump is working?

Also, dam that's one clean engine bay. (NICE).

#7 ucw458

ucw458

    This will mean the extinction of all life forms on this planet.

  • Moderators
  • PipPipPipPipPip
  • 11,467 posts
  • Gender:Male
  • Location:Colorado
  • Model:Conquest

Posted 25 December 2018 - 10:09 PM

You can test the pump by putting 12v to it and holding your finger on the line.  Top line is in bottom is out.  Hose goes from pump to T for actuator.  Then to a check valve near the ABS then to the engine.  Between the check valve and engine the Vacuum canister and HVAC controls T in but they are not part of the cruise system.
My 87
Posted Image

#8 Turbo Cary

Turbo Cary

    Established Member

  • Members
  • PipPipPip
  • 1,583 posts
  • Gender:Male
  • Location:Charleston, South Carolina
  • Model:Conquest

Posted 25 December 2018 - 10:32 PM

Anyone ever though of adapting a GM vacuum pump? I had a factory Conquest pump go bad causing me to chase down a intermittent vacuum leak. When I smoke tested it the diaphragm had failed. A GM pump is cheap, easy to find, and would only require a little modification to the vacuum line.

You'd have to clip the quick disconnect with the pump if acquiring from a junk yard, then get some cheap vacuum adapters to shrink the tubing down. Splice in the new connector for the pump and you're good to go.

Edited by Turbo Cary, 25 December 2018 - 10:33 PM.


#9 ucw458

ucw458

    This will mean the extinction of all life forms on this planet.

  • Moderators
  • PipPipPipPipPip
  • 11,467 posts
  • Gender:Male
  • Location:Colorado
  • Model:Conquest

Posted 25 December 2018 - 11:32 PM

As long as it's a 12v pump with similar volume capability it will work.  But I'm sure people here have spare pumps to sell.  I have a spare for mine.  It's currently being used as a brake bleeder.


Off topic but a good size glass jar like a pickle jar and a vacuum pump it makes a great brake bleeder.  Glue 2 pieces of brake line or similar size tubing to the cap of the jar.  One tube connects to the vac pump.  The other to a brake bleed screw.  The tube that gets the bleed hose also gets a small hose for inside the jar running from the cap to the bottom of the jar.  That way you can see the bubbles coming out of the brake lines.  I've used this to bleed brakes, suck up engine oil, drain a power steering system.  I've even used it to remove gear oil from a diff that didn't have a drain plug.  It's a handy little tool you can make practically for free.
My 87
Posted Image

#10 Turbo Cary

Turbo Cary

    Established Member

  • Members
  • PipPipPip
  • 1,583 posts
  • Gender:Male
  • Location:Charleston, South Carolina
  • Model:Conquest

Posted 26 December 2018 - 01:01 PM

View Postucw458, on 25 December 2018 - 11:32 PM, said:

As long as it's a 12v pump with similar volume capability it will work.  But I'm sure people here have spare pumps to sell.  I have a spare for mine.  It's currently being used as a brake bleeder.

My main suggestion is due to the factory pump being 30+ year old plastic versus a newer aluminum bodied part readily found across the nation. Your idea for a cheap-o Mighty Vac is a good idea. MV's cost anywhere from 250-500 depending on capacity.

#11 vbrad511

vbrad511

    Advanced Member

  • Members
  • PipPipPipPip
  • 8,324 posts
  • Location:springfield, illinois
  • Interests:Keep the turbo spooled!

Posted 26 December 2018 - 10:08 PM

My '88 did this, until I changed all the vacuum lines.

#12 mikec

mikec

    not around much any more

  • Moderators
  • PipPipPipPip
  • 6,313 posts
  • Gender:Male
  • Location:Cypress California
  • Interests:Finish line at the Pikes Peak "Race to the Clouds"
  • Model:Starion

Posted 26 December 2018 - 10:48 PM

The cruise control actuator gets "working" vacuum from two sources.  The first is from the engine intake manifold via the larger port below the "row of three" - it's the same port that feeds the dash vents and the vacuum reservoir canister.  Follow the vac hose from that port, around behind the engine, and you'll see it "T" a couple of times and you'll also run into two little white gizmos in the vac hoses.  Those are check valves (=one-way valves) that let air flow TO the intake manifold when the engine is running with vacuum... and they block boost pressure FROM the intake manifold.  Eventually one of those vac hoses reaches a small cylinder shaped thing attached to the firewall near the wiper motor; this is a vacuum sensing switch.  When vacuum is low AND the cruise control power switch (on the steering column) is ON the relay turns ON to send power to the vacuum pump at the front of the car.  Thus the vacuum pump only runs when engine vacuum is low or when the engine is on-boost - the vacuum pump is the second source of vacuum for the cruise control system.  Those check valves isolate the vacuum pump from the rest of the under-hood vacuum hoses - the vacuum pump can't affect the engine nor does it supply vacuum to the dash vent actuators.

Typical issues with the cruise control are:
1: obviously leaks in the vacuum hoses to/from the cruise actuator itself.

2: leaks at the vacuum pump.  I've seen the hose split/leak underneath the rubber cover piece of the pump.

3: that little vacuum sensing switch fails.  When this happens, the cruise will work fine when the engine is not loaded too heavily (i.e. when engine vacuum is high).

4: the relay controlled by the vacuum sensing switch fails.  So the switch can't trigger the relay to send electrical power to the vacuum pump.

5: air filters in the cruise actuator are clogged as ucw458 posted.

6: where the cable exists the cruise actuator you'll see a small plastic square-shaped thing... sometimes the cable gets frayed inside this two-piece plastic gizmo.  The cable passes through the firewall and makes a U-turn underneath the dash to grab the linkage above the throttle pedal.  Kinks and binding in the cable, or wires/air ducting under the dash that are hanging low can get in the way of this linkage.

7: Underneath the dash the end of the cruise control actuator cable is clipped to the dash metal structure... via a rectangular shaped piece of metal with a slot cut in it.  That clip fits over the metal part of the cable sheathing to anchor it to the dash/chassis structure.  If the clip is missing, or is in the wrong part of the sheathing, then the whole cable flops about when the cruise control actuator tries to pull on the throttle linkage.  With the engine OFF and the throttle pedal "relaxed" to the idle position, ideally there is very little slop between the cruise cable sheathing and the throttle pedal linkage.  The closer the clip is to the end of the sheathing the better - until you go one slot (you'll see slots in the end of the sheathing) too far and there is NO slack at all... you need some slack to make sure the cruise control cable doesn't keep the throttle pedal from relaxing to the idle position.

8: an incorrect replacement cruise control cable was installed - basically if the ends of the cable (the parts sticking out beyond the protective sheathing) are too long then most of the cruise control actuator's in/out travel range is wasted absorbing this slop.  This is not too likely; consider it a last resort once you've ruled out the other possibilities.

I think you can test the vacuum pump and the vacuum sensing switch by unplugging the hose at the base of the throttle body.  Cap the port but not the hose.  This should force the cruise control system into using the vacuum pump only.  So go for a drive and try using the cruise control... if it works at all then the vacuum switch and pump are at least trying to work... the bug is elsewhere.  (hoses, jammed cable, etc.)  You'll notice during this test drive that your dash vent controls may not work either because we've disconnected their vacuum source.  (they may work for a little while based on the vacuum trapped in the reservoir/canister unit)

mike c.

#13 Indiana

Indiana

    Addicted Starquester

  • Members
  • PipPipPipPipPip
  • 14,748 posts
  • Gender:Male
  • Location:Bloomington, IN
  • Model:Other

Posted 29 December 2018 - 10:11 PM

Yes dead filters.
Check valves are rubber flappers.
Break down the actuator to get to the check valves and clean the goo (that used to be a filter but now is not) off.

#14 madmanperez

madmanperez

    Member

  • Members
  • PipPipPip
  • 84 posts
  • Gender:Male
  • Location:Central Florida
  • Model:Starion

Posted 10 January 2019 - 05:34 PM

I want to thank everyone for their input. Believe it or not, it took all this time to take care of the speedometer cable problem. RockAuto has always had the parts I needed but this time, though the part picture was right, the part was not. Not once but twice. My local Autozone only had a "universal" cable, but it didn't have the right type of end to fit into the transmission. In the end leave it to Amazon to have the right part. Same image that was found on RockAuto, same part number, but the RIGHT part.

Mid you all I do is strip out the cable core and fish it through the existing sheath. Works well when you got the right part to start with. So, make note that RockAuto does not carry the right part for our speedometers. Regardless of the image and part number ATP Y-861. Amazon has the same part number but actually has the right part.

I've pretty much lost daylight as of this writing, but I have made note of all of the info and will endeavor to start figuring out the source of the fault. I'll check back hopefully with good news, if not with more questions.

Edited by madmanperez, 10 January 2019 - 05:36 PM.






Also tagged with one or more of these keywords: cruise control

1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users