Jump to content
Jay

Cold Brakes & High Idle?

Recommended Posts

Last night we had our first cold snap around 29 degrees.  When I came out this morning to drive the Reatta, the brake pedal was extremely hard to press.  When I was able to depress the pedal, the car pulled to the right.  I thought maybe since I still have a high idle issue that it was related to a vacuum leak causing a brake booster issue as exhibited by the brakes.  But to my surprise, the 89 brakes system does not have a vacuum line.  After a few miles, the brakes began to operate normally and have continued to do so throughout the day.  Why would my brakes be affected by the temperature so dramatically?

 

High Idles: 2,800-3,000 RPM in neutral while driving but eventually drops to 750-800 after several minutes in park. 

As for the high idle I have:

1) checked for leaks on all engine bay vacuum lines and connectors

2) cleaned IAC / IAC port (many times!)

3) cleaned MAF sensor (appropriately)

4) cleaned throttle valve area

5) replaced the IAC valve

6) set the TPS to .35v via adjustment screw on TPS

7) adjusted throttle stop screw

Share this post


Link to post
Share on other sites

When was the last time you flushed and put new fluid in the whole Brake system? Our Reatta's need to be flushed at least once every two years, some people on here do it more often.

Share this post


Link to post
Share on other sites

Brake fluid absorbs water over time.  I think water accumulated in the system freezing in the brake system might be the problem.  Flushing the brake system as Frogware suggested is good advice. That would get rid if any water that might be causing the problem.

 

46 minutes ago, Jay said:

But to my surprise, the 89 brakes system does not have a vacuum line.

This will explain that: 

About the Teves Brake System

  • Like 1

Share this post


Link to post
Share on other sites

I guess I am on the same wavelength on flushing the brakes. I have seen this more than once on cars that live in the humid south and then discover cold weather. I am curious about items #6 and #7. What was the TPS reading before adjustment? .35v is a little lower than the common standard and was the throttle stop screw loose or had it been moved prior to this time? 

Share this post


Link to post
Share on other sites

I have not flushed the system.  Good call.  Probably exactly what this is.  I will flush by the end of the week and report back.

 

Share this post


Link to post
Share on other sites

As for the high idle

#6 - voltage was at .4 but when I manually adjusted the TPS it read a little lower than what I see as the standard.  I was hoping it would help but I see no change which means it probably is not the TPS.

#7 - adjusting the throttle stop did lower the rpm but almost to the point of being too low.  I think I got it back to it's original setting.  This screw is very difficult to access btw.

I am going to keep looking for the vacuum leak.  My vents / heat / AC seem to open properly so I don't think it is leaking through the dash area.  

Share this post


Link to post
Share on other sites
38 minutes ago, Jay said:

#7 - adjusting the throttle stop did lower the rpm but almost to the point of being too low.  I think I got it back to it's original setting.  This screw is very difficult to access btw.

I'm not an expert on this and someone please correct me if I'm wrong. If adjusting the throttle stop lowered the idle I think something else must have caused it.  To my knowledge on modern fuel injected engines the purpose of the throttle stop is to keep the butterfly open just enough to keep it from sticking in the throttle bore. It's not intended to be used to control the idle speed.  The IAC routes air around the butterfly to keep the idle correct.  If you adjust the throttle stop enough to effect the idle speed the IAC is just going to compensate for any adjustment you make to keep the idle where the ECM thinks it should be. Adjusting the stop too much might cause the IAC to get out of the range it was designed to operate in and  actually cause problems with the ECM being able to control the idle speed.  I would make sure the throttle stop is adjusted correctly before moving on.

 

56 minutes ago, Jay said:

I am going to keep looking for the vacuum leak.  My vents / heat / AC seem to open properly so I don't think it is leaking through the dash area. 

I would plug off all the vacuum ports on the intake and see if the idle stabilizes.

Share this post


Link to post
Share on other sites

When looking for vacuum leaks, don't overlook the PCV which hides under hoses and wiring on the  back side of the intake plenum, passengers side. Thanks for the answer on the idle and TPS settings, makes perfect sense, but as Ronnie pointed out, unless adjusted way out of whack, the system is flexible enough to just override changes. Yes, that tiny throttle stop screw is a devil but usually doesn't require any adjustment unless the throttle body has been taken apart. 

Share this post


Link to post
Share on other sites

So using a flashlight in the dark I finally found the PCV.  It does seem loose and oily so I will try a replacement tomorrow. Looks like a lot of fun.  Thanks for the tip on this gentlemen!  I will let you know post installation results.  First the PCV replacement and then the brake flush.

Share this post


Link to post
Share on other sites

Don't forget the grommet

Share this post


Link to post
Share on other sites

Doh!

Share this post


Link to post
Share on other sites

Being an Old wrench, we used to spray carb cleaner around the intake, rubber grommets and hoses if the  idle speed smoothed out

it verified a possible vacuum leak. Not sure if it will define a leak today??

Share this post


Link to post
Share on other sites

Welcome to the forum Duckster!  I've used carb leaner to find vacuum leaks on cars with carburetors. Never tried it on a fuel injected engine but don't see why it wouldn't work.

Share this post


Link to post
Share on other sites
2 hours ago, Ronnie said:

Welcome to the forum Duckster!  I've used carb leaner to find vacuum leaks on cars with carburetors. Never tried it on a fuel injected engine but don't see why it wouldn't work.

Vacuum is vacuum, no matter the system, so I agree absolutely, it is still useful😎 For reference, mine idles with 16"-18"Hg vacuum, warm, in and out of gear.

  • Like 1

Share this post


Link to post
Share on other sites

So I replaced the PCV valve and grommet.  I sprayed the PCV after installation with no change in engine characteristics.  High idles is still present.  It starts correctly, after it warms up it drops to 625-700.  After I drive down the road several miles, it will idle as high as 3,200 rpm.  Needless to say it makes for interesting stops at red lights.  Once I stop, it will eventually lower to 625 rpm but this might take as long as a minute or longer.  I checked the main vacuum tank with vehicle off.  When I pulled the line it immediately sucked in air so it is working and when I pulled a vacuum with a brake bleeder it held the vacuum.  I did find that the small plastic hose on the firewall that supplies vacuum to the HVAC controls was not holding a vacuum.  I pulled the bottom of the dash cover off below the glove box and found it disconnected.  It must have been pulled while I replaced ECM.  I thought this must be the culprit.  However, no change.  I have sprayed the engine many times looking for the leak.  The vehicle runs very smooth, just running extremely high.  My mileage has gone from 24 mpg to 19 mpg on average.  I checked the cruise control but it works perfectly so not sure how that might apply.  I understand that age is an issue, but the motor only has 32K.  Is my next step to replace the intake manifold gaskets?  Replace the TPS?

 

As for the brakes, I flushed them and I did have a similar experience yesterday morning when I first started the vehicle and drove down the road.  It has not been as cold the last few days so I can say for sure that the issue is resolved.  This morning they seemed normal.  I am going to call the brakes complete pending until it gets cold again.

Share this post


Link to post
Share on other sites
On 11/13/2019 at 9:36 PM, Ronnie said:

I would plug off all the vacuum ports on the intake and see if the idle stabilizes.

Have you tried this yet? 

 

Go into diagnostics while the engine is idling at 3000 rpm and see if you can bring it down by using the IAC override ES09. If you can use the override buttons to get it to idle at the correct RPM that will tell you that the ECM is commanding the idle to be high for some reason.  If you can't get it down with override ES09 that probably means there is a vacuum leak.

 

Share this post


Link to post
Share on other sites

So I am able to raise and lower the rpm through the ECM Override at ES09.  However, once I start rolling the idle goes to 2,800-3,200 rpm.  If I sit in the driveway idle is rock steady at 725.  I put it in drive with foot on the brake and revved the engine to 1800 rpm.  Engine rpm smoothly drops to 725.  So this only happens when I am rolling.  Is there some type of speed sensor on the tranny?

Share this post


Link to post
Share on other sites

I know this is not helpful but I am very interested in this symptom. My somewhat derelict '89 has a similar issue. The idle will go very high for no apparent reason but after manually reducing the idle through IAC override, it will stay there. I have not driven it after one of these occasions but I suspect it might do as you experience. I know you have made every effort to ferret out vacuum leaks so it seems at this point that something is driving the high idle via the ECM command. I can only think of a few sensors that can be disconnected and still allow the engine to run which may help narrow the possible culprits. The MAF sensor, cam sensor, air temp. sensor in the airbox, coolant temp sensor and even the O2 sensor and possibly the tps. In theory, all of the above can be disconnected and then start the engine and see how it behaves. It won't be responsive to the throttle so I am not suggesting driving it, but just gradually reconnect them if the idle remains stable.

Share this post


Link to post
Share on other sites
38 minutes ago, Jay said:

So I am able to raise and lower the rpm through the ECM Override at ES09.  However, once I start rolling the idle goes to 2,800-3,200 rpm.  If I sit in the driveway idle is rock steady at 725.  I put it in drive with foot on the brake and revved the engine to 1800 rpm.  Engine rpm smoothly drops to 725.  So this only happens when I am rolling.  Is there some type of speed sensor on the tranny?

Yes there is a speed sensor in the transaxle. Now that you mention it, if you watch IAC counts, they will generally increase when the engine is running following an increase in throttle so it can smooth the transition back to idle when the throttle is released. In other words, it acts like a dashpot on a carburetor to keep the throttle from snapping shut.  

Share this post


Link to post
Share on other sites

I can certainly try those.  I am beginning to think it is my ECM.  I did buy a used ECM from another Reatta forum member and maybe it is causing the issue.  I will try those tomorrow and let you know.

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...