co4rnr

When I press and hold the brake pedal, the idle goes up and down. When I release the brake pedal at idle, the idle jumps up to 1300 RPM's. Why does my engine do this?

NOTE:
The truck is an 87 4Runner with the 22RE

TORTIS

iTrader: (1)

adjust your idle. it is too high. this is the very problem that brought me to Y/T. i don't remember why it does this , but the adjustment generally fixes it.

co4rnr

My truck has never done this before. How would turning down the idle fix it?

TORTIS

iTrader: (1)

i don't remember why, and i didn,t have to turn mine down much either. idles great now . somebody on here can tell you.

fredtheturd

Mine did that a few years ago & the idle was too high. The reason it does it is because of the engine brake system. When the brakes are pressed the engine senses that it must slow down too during normal driving. If the idle is too high, say 1200-1500, and the brakes are pressed, the engine will think that it must slow itself down. If you have a 3.0, set the idle to 800 when the engine is nice & warm. I have to fiddle with mine every now & again depending on the grade of fuel & the time of year it is. Hope this helps...

co4rnr

Before today, my truck was idling at around 800. It has never idled so high before. I don't know what would have caused this. This is very strange. Can the idle just jump that high by itself?

fredtheturd

My idle varies quite a bit during 30-40 degrees air temperature changes or if I buy gas with ethanol on a tank, then not on the next. Not sure why but I have to stay on top of it. If the idle isn't the answer, double check your TPS...that's the expert's fall back on idle problems.

TORTIS

iTrader: (1)

have you checked all your vacuum lines?

4Crawler

iTrader: (3)

Explanation why high idle speed causes the problem:
- http://www.4crawler.com/4x4/TLCA_Tru...ech.04.09.html

thook

I've read this before. Though I'm not experiencing the same problem (and apologies if I step on toes by piggybacking here), I recently adjusted the TPS ('86 4rnr...MT) and timing. Which in turn, raised the idle higher....higher than I thought it should be. The sticker under my hood says 750rpm. What's the discrepancy here?

4Crawler

iTrader: (3)

Assuming the timing was not correct before, then setting it correctly can increase or decrease the idle speed. Increasing speed would be the result of advancing the timing from what it was before. How could that happen and how could the TPS affect that? Well, the TPS IDLe contact tells the ECU the engine is at idle and when the timing jumper is installed, tells the ECU to go to the base timing (typically retards timing about 7 degrees in doing so). Well, if the TPS IDL is not set right, or the test jumper not installed, the ECU won't retard the timing and if you then set the timing to 5 BTDC and then pull the jumper, the timing won't advance to where it normally is. So you are running with retarded timing, and correcting that condition is like advancing timing, which will bump up the idle speed.

thook

Thank you much for the explanation, but I should've been clearer. I meant that on your linked page you stated the idle was to be set at 850-900rpm while the sticker on my hood says 750. <<That disrepancy.

EDIT: Maybe I should add that I was experiencing a low idle problem and thought to check the TPS. It was out of adjustment and so I reset it by following the procedure on your 4crawler page. I checked for proper operation by jumping the terminals. It went to base timing and I proceded to check the timing. It was retarded by 2 deg's. So I then it set it at 5 and have noticed a definite improvement. It's still acting weird at initial idle on start up and the vehicle now has a hestitation at times when the throttle is released and at times when engaged. While engaged, it feels like I'm moving through a head wind. This is all intermittent, though. Most times she runs great climbing hills with no prob's in 5th....and that's with a stock set up.... aside from 31" tires.

4Crawler

iTrader: (3)

Yes, I think 750 in the manual, I find my engine idles better in the 850-900 range, so that is what I use. I find at 750, it is OK, but every once in a while, the idle will drop below that and then it is not very smooth. Also, I live near sea level and find out that at higher elevations, especially on wheeling trips, the idle drops, so another reason I set mine a little higher.

Also, I think trucks with automatics use a higher idle RPM. Point being that it should not be any higher than that or the idle cut in the ECU kicks in.

Shoua

Another explanation is that your throttle body is just too worn out, and you need to replace it. That is what I was told by numerous Toyota mechanics when I had that problem. But I still haven't.

jmcbmx

http://www.geocities.com/toyotashawn/bizzareidle.html

co4rnr

Last night when I drove my truck home from work, the problem went away. This is so weird. Has anyone else experinced this? To add some more background on my truck I have the engnbldr torkr cam. I have advanced the timing by 6 degrees to try and gain a little more power for running at high elevation (I live at 6000 feet).

I just recently re-adjusted the valves, could I have made them to tight?

I have no engine codes, and my TPS was just replaced and adjusted according to the 4crawler link.

My last question, if in fact my throtle body is worn out, were do you get a new one from?

4Crawler

iTrader: (3)

Might be your RPMs are right on the edge of the fuel cut RPM limit. So at night, cooler air and additional load of lights on may have lowered the idle RPM enough to stay under the cut out value.

Note that advacing timing will increase the idle speed, to the point that you can't lower it via the throttle body screw. I know on my '85/TRD cam, I can't bump my timing up much past 5 BTDC without my idle speed going too high. If you need to run that advanced, you can always cut the brake line to the ECU.

thook

Are you using a tachometer to set the idle?

Yes, you could have adjusted the valves too tight, but that depends on what the recommended setting is for the engnbldr cam and what you actually set them at.

Have you tried cleaning your throttle body?

*And thanks, Roger. I'll play around with it. I do live in slightly high elevation, so I'll take that into consideration. It's good to know the idle setting is not necessarily a "set thing".

co4rnr

I set the valves per engblders spec. .007 and .009. I sprayed around all the vacum lines with brake cleaner to check for leaks and found none.

I did check my air filter and to my surprise I found a piece of plastic on the lower side. I am sure that did not help anything out at all.

I checked all the electrical plugs and they all seem to be tight.

Yes, my truck is the SR5 and when it is hot I set the idle a little uner a 1000 rpm. Probally right around 800 rpm.

I cleaned the throttle body when I rebuilt the engine. It has about 3500 miles on it since the rebuild. It has always idled a little funny. I had a Japanses auto mechanic look at it and he said that the 22RE idles a little rough any ways and with the lumpier cam it makes it more pronounced.

Any feedback?

co4rnr

Alright, I think it is an idle issue. How do I go about setting the idle? I know that it has to be at operating temp, but my question is how do you set the a/c idle in conjunction with the screw on top of the throtle body? I konw there is a white plastic screw with a spring under it for adjusting the a/c. If someone could give me a link to an FSM that says how to do it that would be awesome! I looked at the 93 service manual uner A/C but I could not find it.