In what way can my brakes effect idle?

[Milt 92GT]

And just saying hi....I really like this website,looks like someone (heh,me?) could learn alot here...


Anyway,back to the question...

When I come to a stop and sit at idle,the RPMs will dip and then return...over and over,then slowly even out...almost to the point of stalling but not quite..It seems more likely to do the idle problem when the AC is on...I don't know if that could be a connection OR is it because when the AC is on the idle is lower and more easily falls into the idle problem?

Strangely I noticed that when it starts this idle problem,if I push fairly hard on the brake pedal,it immediately evens out???Then if I release the brake pedal it starts dipping again...The car drives great...plenty of power (all through the RPM range,no hesitations,pinging....so I kinda want to rule out a fuel problem BUT,I haven't been able to check the fuel pressure yet.

The car is all stock except for suspension stuff and exhaust...

All fairly new ignition parts,coil,plugs (gapped at 54) ,wires,IAB,TPS (.98),cap and rotor.New O2 sensors,fuel filter...etc...


Codes are as follow..

KOER system pass (11)

KOEO system pass (11)

KOEO memory (code 95)

That memory code is kinda recent because I went ahead and cleared the memory about a week ago.

Cylinder balance test passed as well.

If you have any ideas please,let me know and what and how to check for....

Thanks and I look foward to getting to know you guys ,and I hope you are looking foward to many strange little questions like this in the future from me!

Milt

[canukracer]

try and listen under the dash for a hissing sound as you push down the brake pedal it could be a bad power brake booster and/or a compressor starting to go bad causing a drag on the engine

[Milt 92GT]

Hey thanks for the reply!

Are those components difficult to replace?I'm not the greatest mechanic around but I know enough to get by most easy to moderate jobs...

Is there any way to test those components?


Thanks again-Milt

[PKRWUD]

The power booster is the big round can mounted on the firewall, right in front of the driver, in the engine compartment. The master cylinder is mounted to it. It will have a fat hose going to it. With the engine off, disconnect that hose from the booster, and plug it (the hose). Use a fat bolt, or a sharpie marker, etc., just make sure it's plugged. Don't worry about the hole left behind in the booster.

Start the engine, and compare the idle quality with the way it was before. Is it better? Has the unevenness that smoothed out when you applied the brakes gone away? If it has, you have a pinhole in the booster diaphram, and the entire booster will need to be replaced. DO NOT drive it with that hose disconnected and plugged. You will have virtually no brakes, so make sure you reattach the hose when you are done testing.

Personally, I don't think this is your problem because a vacuum leak will raise the idle 9 times out of 10, rather than lower it. Still, test it and see. Post your results.


Take care,
~Chris

[Milt 92GT]

PKRWUD:

Thanks for the info...I was wondering if I could do exacty that with the hose to check the booster...I'll check it out..

Thanks-Milt

[QuantumMotorsports]

Could be an electrical prob. From what I have seen, the majority of idle problems with these engines is something electrical. TPS not set right, dirty connectors, etc. But the only reason that the brakes would affect the idle if it is electrical is the brake light coming on and changine the voltage slightly. I doubt this is the problem, but who knows. I have come to really hate the 5.0 EEC. That is why my 306 is getting a carb and mechanical points ignition. At least at first, I may get an MSD setup later on or something. But the keep it simple stupid method is my favorite and usually works good. You might try cleaning the electrical connectors behind the upper intake. That seemed to solve a lot of my idle problems. My car would randomly idle up to like 1600 RPM and then back down to 800 and go back and forth between the two. Anyway, that's what I've got to say about that.

[crazypete]

In my humble experience, 90% of "idle issues" can be solved with a simple turning of a screw. On the trottle body plate lever, there is a screw that you can use to set the idle faster (through the simple mechanism of slightly opening the plate at idle). I go 1000-1200. This cures all kinds of issues caused by old alternators, power steering pumps and covers up a few engine issues. I know this is technically "ignoring the problem" but a stupid idea that works isnt stupid.....

[Milt 92GT]

Quantam Motorsports and crazypete:

Thanks for the tips!

To tell you the truth, the car has had a idle problem for about two months now...I have tried just about everything except changing the fuel pump and relay..If you REALLY like to read, try this thread from another board on for size to get more backround on it..

I can't believe that I had never noticed it before but,when I push the brake pedal very hard,the idle dip goes away...so,I thought I was on to something with that but,I tried disconnectiong the hose for the booster and pluggin it but,the problem is still there..

I did try bumping the idle up to 900 RPM and it did help quite a bit but...it still will do it but,there aren't any more codes 41 and 91 that I was getting.Besdies the car use to idle great at 750 with no problems at all...so I will continue to try to find the problem instead of just bumping the idle..

Again thanks for the help and keep the ideas coming!-Milt

[canukracer]

try using some air intake cleaner on the maf meter it may have some crud on the wire, !!!!DON"T touch the wire!!!!!!!!! just spray it with the cleaner,it won't hurt it and most are dirty if ya use a K&N filter and use to much oil it will stick to the wire and insulate it giving a wrong reading to the comp.

[Milt 92GT]

Originally posted by canukracer
try using some air intake cleaner on the maf meter it may have some crud on the wire, !!!!DON"T touch the wire!!!!!!!!! just spray it with the cleaner,it won't hurt it and most are dirty if ya use a K&N filter and use to much oil it will stick to the wire and insulate it giving a wrong reading to the comp.

I was wondering about the MAF,I just bought a multi meter to try testing it although...it's RAINING!LOL...

Now what do you mean intake cleaner?Like TB/carb cleaner?Or should I maybe try electronics cleaner...BTW,I'm probably one of the few who don't use a K&N filter so...I don't think it's oil...BUT I do have the silencer removed so,just plain old dirt and grime could be the problem..or age and it's just failing...would the multi meter show if it is failing?Which wires do I test and how exactly?(yes I know.stupid question but...you gotta ask if you don't know right?)


Thanks for the tips guys...really apprrciated,keep them coming-Milt

[canukracer]

it's in a spray can, think carb cleaner is to strong to clean the maf meter try and find a air intake cleaner, most say will not harm o2sensor, to test the maf you need a very good meter that has frequency hz on it most are upwards of 3or4 hundred dollars I use my snapon vantage meter just clean it first, probably a $6 can of cleaner u can also use it to clean the throttle plate too

[Milt 92GT]

So I guess my little "Radio Shack special" multimeter won't cut it...

I'll go ahead and clean it out....would a 95GT MAF be the same as one meant for a Fox Chassis GT?If it is the same,I can try just swapping it out..I had tried doing this a while back with my brother-inlaw's 93GT MAF but,then I realized that his MAF was calibrated for 24# injectors so that idea was a bust....

Thanks you very much for all the help-Milt

[Milt 92GT]

Well..............

My brother and I figured to go ahead and just eliminate what has been our BIGGEST suspect since this all started...The fuel pump.

We changed it out earlier tonight and when we were done,I started the car.First thing I noticed as I turned the key was that the pump priming was considerably quieter...I never really though it was loud to begin with but,there was a noticable difference.

I started the car and she turned right on....She kinda acted funny at first,like stumbling a bit and then it smoothed out after a couple of minutes. ( I have heard that these cars have to kinda re-learn tier idle after being cut from power for a while)...I waited for the car to get fully warmed up (this is when it usually will start with the idle problem).It didn't dip what so ever.....I kept playing around with the throttle,trying to induce it and it would hold the idle steady...

I took the car out for a drive and stopped softly and hard...held fine...I drove it hard and soft...and still fine....drove it for about 30 minutes,then came back home and let it sit in the driveway idling for about another 20 minutes and it never dipped...Air on and off,and playing around with the brake pedal and nothing seems to induce it...

Hopefully we fixed the problem this time...I'm still uneasy about it...I won't consider it fixed untill there has been no problems for at least a week or two...I'm going to run the self tests tomorrow and see what I get....If this turns out to be "the fix",I am going to kick myself SOO hard for not going with my gut when this all started in the first place!!

Thank you guys for all the help...wish my Stang luck!

-Milt

[Milt 92GT]

Ok...here is a twist...

The Mustang started doing the idle problem again,so obviously it wasn't the fuel pump..Although the old pump looked terrible...real old looking..

When it started doing the idle problem,I ran the codes and was getting a code 45 KOER...Thermactor air diverter...I had gotten this code before Off and on...so,I found the air diverter and disconnected the hoses from it and plugged them with a couple of screws..The idle problem almost instantly stopped!

I figured to just block them off (let me know if I am harming the car by doing this) since the hoses from the diverter are only (from what I have read) for emissions and are routed from the air pump to the diverter,and then out to the exhaust...

I don't know how exactly, but this seemed to cure the problem.For now..I'm thinking that the excessive air being diverted all the time to the exhaust was causing the O2 sensors to incorrectly read a lean condition.This then causes the computer to unnecessarily richen the mixture which probably was causing the idle problem and the small pops I kept hearing in the exhaust....

Of course this is ALL just theory and for all I know,the problem might come right back just like before...so,I won't call it "solved" until it hasn't done the idle problem for a few days at least......

Anyway,I thought I would update this post with the latest on this problem..if I did find the culprit,maybe it might help someone else down the road..

Thanks for all your help again guys-Milt

[PKRWUD]

The purpose of sending the air to the exhaust is to make sure your cats are hot enough to work. Without that added air, the cats won't work properly, and they will start to fuse together internally, clogging your exhaust. If you have removed your cats, or intend to, then this won't be an issue. If you are keeping cats in your exhaust, though, then you need to determine what the cause of the problem was, and repair it correctly.

Good luck either way.

Take care,
~Chris

[Milt 92GT]

Originally posted by PKRWUD
The purpose of sending the air to the exhaust is to make sure your cats are hot enough to work. Without that added air, the cats won't work properly, and they will start to fuse together internally, clogging your exhaust. If you have removed your cats, or intend to, then this won't be an issue. If you are keeping cats in your exhaust, though, then you need to determine what the cause of the problem was, and repair it correctly.

Good luck either way.

Take care,
~Chris

Well...I don't have Cats at the moment so that isn't an issue I guess...I had someone tell me that disconnecting the TAD solenoid from the hoses can effect the combustion process in the heads?Is this true?And something to worry about?

Don't people delete thier emissions stuff all the time and just block off the old connections?That's whyI figured that there wouldn't be any negative effects other than being able to pass emissions...

I still plan on replacing the TAD as soon as I can because I plan on getting a catted mid-pipe later on..and I just like to tie up loose ends..BUT!Am I hurting anything in the meantime till I get a new TAD?(besides the environment..)

Thanks for your advice man-Milt

PS...day 2 and no idle problem..Out of curiousity,I re-connected the hoses to the TAD and sure enough,it started dipping the idle again...Pulled them off the diverter and capped them...steady as a rock again..

[PKRWUD]

In the 60's, you could pull off all the "smog" stuff, and the car ran fine. Since about 1973, the engines have been designed to run with them, and there is very little, if anything to be gained by removing them. If you tamper with your EGR system, for example, your engine is likely to overheat. I would replace the defective parts as soon as you can, but that's just me.

[richd]

Does that apply to the smog pump as well?

[PKRWUD]

It's pretty much a giant package. All the components are designed to work together. If you pull your smog pump, for example, you'll clog up your cats.

[USMC302]

would a 95GT MAF be the same as one meant for a Fox Chassis GT?If it is the same,I can try just swapping it out..I had tried doing this a while back with my brother-inlaw's 93GT MAF but,then I realized that his MAF was calibrated for 24# injectors so that idea was a bust....

I would like to point this very important fact out at this time. Even if you do have a 95 MAF calibrated for 24lbers and a 87-93 MAF calibrated for 24lbers, THEY ARE DIFFERENT, the tubes may both be calibrated for 24lb injectors but they are still different sizes due to the make of that years meter. Do not swap them unless you order or have the correct tube for the correct year. Good luck