I've been fighting with a surge problem for all three days that I've owned this little 86 4x4. Well I couldn't repeat the surge while looking under the hood. Today I'm driving home and at a stop light the motor starts to surge and I zip into a parking lot and pull the hood....... nothing. I get back in and push the brake pedal so I can release the E-brake and the rpms drop to 700 from the 1400 or so that it was at. ?????????

So I let up and the idle was fine. Push the brake and it drops...... hold the brake and it surges.

I ran my butt home and pulled that little white diaphram piece out of the brake booster vacuum line and replaced it with a piece of tubing and the surge doesn't come back when the brakes are pressed and the idle is a lot more stable at 1000. I'll drive it tomorrow and see how things are (if you guys think I can run it without that baffle (I took a test drive and the brakes work fine) and then replace the baffle from one at NAPA. Now to open a beer.

 

Hey Junkers,

That Little white piece, in the booster vacum line, is a vacum line check valve.

It's job, is to keep vacum in the booster, in the event of vacum loss from the engine, ie; engine stalls while truck is still in motion.

This allows for 1 more power brake assist after vacum failure. If You ever drove a true manual brake system car, You would know why the d.o.t. mandates this.

If Your surge is related, to the brakes being applied, I would Guess that the booster itself is leaking vacum internally,(from Your description). However it may be a vacum line, check valve leak.

Now, You must become the Troubleshooter!

Thanks Kiwi

 

Kiwi I hate being that person. I will however take your advice and replace that little white demon. I had several of these over the years with old fords. When I replace it if the problem comes back then I'll replace the booster. Heck it's only 22 years old and been through 171,000 miles, it might be time for a replacement.

Thanks for the reply and the heads up!

 

Hey Junkers,

Please let us (can I say us with less then a 100 posts) know how this comes out, because You may help someone else.

Your welcome.

Thanks Kiwi

 

Just google "22RE idle surge" if that white part doesn't work. There are a lot of results that pretain to many different problems that can cause an idle surge. Including cutting the electrical brake wires that tell the computer that you're applying the brakes. There's WAY more than one cause to this problem.

 

Good point Helliphino!

Hey Junkers,

Is Your truck an Automatic Transmission?

 

I've had this exact problem before. As odd as it sounds, I'm willing to bet that it's because your throttle is not returning all the way back to the stop when you let off the gas. Stepping on the brake pedal is not the cause at all, it just magnifies the situation. I kind of found it by accident. When mine started acting up, I got my wife to hold the brake pedal while I looked under the hood. I started moving vacuum lines and then I noticed the throttle wasn't on the stop so I pushed it closed and problem solved! The brake booster is designed to work with the throttle closed as this is when max vacuum occurs. If it is slightly open, then essentially the booster becomes an open circuit and all kinds of funky stuff happens with the ecm, maf, and tps. Make sure the throttle cable/linkage is free and lubed up well so when you let off the pedal the throttle goes back to the stop and then your problem should be gone!

 

[QUOTE=Kiwipushrod;50778169]Good point Helliphino!

Hey Junkers,

Is Your truck an Automatic Transmission?[/QUOT

Kiwi,
It's a standard, 5 speed.

 

That's a really good point. I'll be cleaning the Throttle Body this weekend so I'll check the cable, linkage and be sure the throttle returns to closed.

Thanks for the heads up.

 

I know this is an old post, but the idle should only be 900. The ECU is cutting the fuel when you apply the brakes because you should not have the brakes and gas applied at the same time. Drop ping the idle is the right fix not playing with the vacuum system.

 

I'm have the idle drop surge but instead of the brakes it's the brake lights causing is. I figured this out by using a skrewdriver to hold the brake light switch down while pressing brakes and it didn't surge as soon as I flip on brake lights and have the rpm at 1000rpm or higher it surges. Anyone have this problem. I know it's electrical but Idk where to start.

 

That's strange. Has it been doing it ever since you bought the truck or did it start doing it some time after that?

 

Look a few posts up. Your ECU doesnt know that your brakes are being applied until the brake light switch tells the ECU to turn on the brake lights. Your idle should not be over 900. if you drop your idle it will not surge when you apply your brakes.

 

The trick with putting a bit of tape on also fixed my high/surging/brake cut idle. Has anyone been able to find the cause?

 

You put a tape where?
Every case of brake surge may have a different root cause. In my case, properly setting the idle fixed it; a simple as that.
You need to describe your own symptoms/problems in detail. A problem well-stated is a problem almost-solved.

 

I recently encountered this same problem on my pickup and it does have to do with the idle being too high, or rather, the throttle butterfly not seating all the way. At first I thought the throttle body was gunked up and so I removed the throttle body from my parts truck, cleaned it and lubed it, and installed it on my truck. I had to swap over the TPS sensor as they were differnt from 1990 to 1994. And the problem only got worse so I adjusted the idle down, but I noticed that I could physically turn the throttle counter clockwise just a hair, and the idle would settle down. The fault is in the throttle dampener, looks like a little diaphragm with a rod, holding it open slightly enough to raise the idle. I took mine off and it solved the issue

 

though it may have lowered your high idle, removing the throttle dampener was not the solution

 

On Mine

After some 200K, the throttle butterfly was "hanging up" a hair at the bottom.of the travel
I think the "pivot" bushings were worn out.

I replaced it with a "big bore" throttle body, and the problem is no more
I dunno if you can readily rebuild the throttle body shaft bushings...

 

apparently that's an often asked question upon a google search. seems difficult to impossible to finds parts or a kit to do so

 

A new throttle body sounds nice, but on a tight budget there's a workaround I just learned about here on yotatech somewhere.

As the bushings wear, the throttle plate will slightly contact one side of the bore as it closes. This causes the high-idle problem that some guys solve with a stronger return spring or removing the dash pot.

You can recreate the correct spacing by removing the throttle linkage springs and putting a very thin spacer on the shaft, then replace the spring and throttle linkage parts back over it. The poster machined down his spacer to get an exact fit. It was probably about 0.5 mm in the end.