Loping with the brakes?

RiftRider · 11-14-2009, 06:00 PM

Help please,

I had this same issue with my 22re, but my 3.slow 4 runner now is loping when I step ion the braskes. Also the brake light on dash glows dim and occasionally gets brighter and dimmer. I thought maybe I had a vacuum leak but cant seem to find one. Any ideas? All input is aweesome. Thanks.

Rift

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**DeathCougar** · 11-14-2009, 06:46 PM

You posted this in the for sale section.

Moved to 86-95 section

turboboost · 11-14-2009, 06:49 PM

Check your fluid level.

wd21_sr5 · 11-14-2009, 06:53 PM

Loping? You mean pulsing? If so does it feel more in the floor or steering wheel? If wheel, I'd say get your rotors trimmed. If floor (or I like to use the e-brake trick) get the drums trimmed.

Matt16 · 11-14-2009, 08:45 PM

No, the engine idle is loping.

Try adjusting your idle and reseting it to the proper speed.

aerocorey · 11-15-2009, 01:46 AM

Loping engine when stepping on brake pedal is brake booster issue. Not real sure about Yotas, but on Full Sized Jeeps there's a check valve that can be replaced. My Grand Wag's idle would increase when I hit the brakes. I couldn't find a leak, but I replaced the booster anyway. I hadn't realized how bad my brakes sucked until I drove it with the new booster, and my idle smoothed out. I'd download the FSM that's available on this site, get into the brake section, and troubleshoot the booster. Or just replace it.

Junkers88 · 11-15-2009, 08:38 AM

What is the engine idle speed set to. I'll bet you money it's too high and that is causing the loping idle.

RiftRider · 11-15-2009, 08:58 PM

I am not sure what the idle is set at, it idles about 1200 even after its warm.
It should idle about 900-1000. When I swap the booster Ill post my results.
Thanks

abecedarian · 11-15-2009, 09:29 PM

Umm... if it idles at about 1200 after warm, that's where the idle is set at. If you think it should be 900-1000, you already know the idle isn't where it's supposed to be, right?

For the record, it should be around 850. 800 is too low, 900 is too high.

Set the idle and ignition timing before you change the booster. You might be pleasantly surprised.

aerocorey · 11-16-2009, 08:08 AM

I'm sorry, how does a high idle result in a loping loping? I can't make mine lope by adjusting the idle. I must be missing a fact here...

Junkers88 · 11-16-2009, 10:53 AM

Quote:

Originally Posted by aerocorey

I'm sorry, how does a high idle result in a loping loping? I can't make mine lope by adjusting the idle. I must be missing a fact here...

I'd love to get into it but the answer has been posted dozens of times, by me on several of those. Do a quick search and I'm sure you'll find it.

aerocorey · 11-16-2009, 01:36 PM

Here's the reference Junkers is talking about:

"Assuming there are no vacuum leaks, such as in the brake booster, it’s likely because your idle speed is set too high. I can exactly duplicate this “problem” in my ‘85 by bumping up the idle speed to a bit over 1000 RPM and it’ll act as described. Turn the idle speed back to normal, and it works fine. It’s really not a problem, its supposed to work this way and if everything is set properly, and you won’t have the “problem”.

Why is this the case? Because the ECU has logic built in that says if you hit the brakes and the engine is turning over 1000-1100 RPM, it’ll cut the fuel to the injectors in an attempt to help you stop faster. After all, no sense pumping gas into the engine when you are braking to a stop. So idle rises, fuel is cut, idle falls, fuel restored, idle rises, etc. Turn the idle back to 850-900 RPM where it’s supposed to be and it’ll get back to normal. Idle speed is adjusted with the large slotted screw atop the throttle body. Turn it in to lower the amount of air passing through the throttle body at idle (and thus lower the idle speed)."

11-14-2009, 06:49 PM	#3 (permalink)
turboboost Registered User Join Date: Aug 2008 Location: Winnipeg, Manitoba, Canada Posts: 377	Check your fluid level. __________________ 1990 Toyota 4Runner - SR5, 22RE, 5 speed, 35" Mud King XT, a bunch of mods. 1986 Mazda B2000 - 5 speed, carb'd 2.0, the winter beater. 1979 Datsun 280zx - 2 seater, 5 speed, stripped interior, etc. 1998 Nissan Altima - 5 speed, 1981 280zx turbo snowflake rims. 1985 Toyota Pickup - SR5, 22RE, 5 speed, Xtra cab, lifted 2", 35" boggers, etc - Sold 1983 Datsun 280zx - Turbo Intercooled L28ET - Crushed. 1985 Nissan 300zx - 5 speed, race prepped, etc - Crushed. IFS Club #7

11-15-2009, 01:46 AM	#6 (permalink)
aerocorey Registered User Join Date: Aug 2008 Location: Fanna, Italy / Springfield, VT Posts: 68	Loping engine when stepping on brake pedal is brake booster issue. Not real sure about Yotas, but on Full Sized Jeeps there's a check valve that can be replaced. My Grand Wag's idle would increase when I hit the brakes. I couldn't find a leak, but I replaced the booster anyway. I hadn't realized how bad my brakes sucked until I drove it with the new booster, and my idle smoothed out. I'd download the FSM that's available on this site, get into the brake section, and troubleshoot the booster. Or just replace it. __________________ Corey '94 3.0 5 speed Last edited by aerocorey; 11-15-2009 at 01:48 AM.

11-15-2009, 08:38 AM	#7 (permalink)
Junkers88 Registered User Join Date: Mar 2008 Location: Albuquerque NM Posts: 2,776	What is the engine idle speed set to. I'll bet you money it's too high and that is causing the loping idle. __________________ RB4R Life Member. 1989 SR5 4runner. Tread Wright 31/10.50/15's. 4.56 thirds, an Aussie in the @$$, Budbuilt plate, Marlin Crawler front, modified MC rear, Supra MAF conversion, ZUK coils in the rear and 4crawler BJ's in the front, LCE header.

11-15-2009, 08:58 PM	#8 (permalink)
RiftRider Registered User Join Date: Nov 2009 Posts: 4	Thanks I am not sure what the idle is set at, it idles about 1200 even after its warm. It should idle about 900-1000. When I swap the booster Ill post my results. Thanks

11-16-2009, 08:08 AM	#10 (permalink)
aerocorey Registered User Join Date: Aug 2008 Location: Fanna, Italy / Springfield, VT Posts: 68	I'm sorry, how does a high idle result in a loping loping? I can't make mine lope by adjusting the idle. I must be missing a fact here... __________________ Corey '94 3.0 5 speed

11-14-2009, 06:53 PM	#4 (permalink)
wd21_sr5 Registered User Join Date: Oct 2009 Posts: 11	Loping? You mean pulsing? If so does it feel more in the floor or steering wheel? If wheel, I'd say get your rotors trimmed. If floor (or I like to use the e-brake trick) get the drums trimmed.

11-16-2009, 01:36 PM	#12 (permalink)
aerocorey Registered User Join Date: Aug 2008 Location: Fanna, Italy / Springfield, VT Posts: 68	Here's the reference Junkers is talking about: "Assuming there are no vacuum leaks, such as in the brake booster, it’s likely because your idle speed is set too high. I can exactly duplicate this “problem” in my ‘85 by bumping up the idle speed to a bit over 1000 RPM and it’ll act as described. Turn the idle speed back to normal, and it works fine. It’s really not a problem, its supposed to work this way and if everything is set properly, and you won’t have the “problem”. Why is this the case? Because the ECU has logic built in that says if you hit the brakes and the engine is turning over 1000-1100 RPM, it’ll cut the fuel to the injectors in an attempt to help you stop faster. After all, no sense pumping gas into the engine when you are braking to a stop. So idle rises, fuel is cut, idle falls, fuel restored, idle rises, etc. Turn the idle back to 850-900 RPM where it’s supposed to be and it’ll get back to normal. Idle speed is adjusted with the large slotted screw atop the throttle body. Turn it in to lower the amount of air passing through the throttle body at idle (and thus lower the idle speed)." __________________ Corey '94 3.0 5 speed Last edited by aerocorey; 11-16-2009 at 01:38 PM.

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