Bigport 4AGE FWD->RWD (Hunting idle)

[Pimpin_1JZ]

Hi, I have an AE82 bigport 4AGE, I have done the old cut and shut for the inlet manifold. Iv'e got it wired up and running but am having a little trouble with it. Now when I start it, the engine constantly revs to say 2000rpm drops to 1000rpm and keeps doing the same thing, Have I blocked off a hole I shouldn't have when I did the cut and shut? I tried to look at the thread which the witzl did but all of the photo's are not working. Does anyone have any photo's or any info that could help me?

Thanks Adam

[Hiro]

Hi, I have an AE82 bigport 4AGE, I have done the old cut and shut for the inlet manifold. Iv'e got it wired up and running but am having a little trouble with it. Now when I start it, the engine constantly revs to say 2000rpm drops to 1000rpm and keeps doing the same thing, Have I blocked off a hole I shouldn't have when I did the cut and shut? I tried to look at the thread which the witzl did but all of the photo's are not working. Does anyone have any photo's or any info that could help me?

Thanks Adam

Sounds like an air-bubble in the cold-idle valve. Cold-idle is usually around the 2000rpm mark. Coolant runs through the valve, and when it warms up there's a wax pellet inside that melts and expands, closing the valve. If there's no coolant, or an air-bubble or erratic coolant flow, the pellet won't stay expanded and the valve will keep cutting in.

I remember having the exact same problem when I was changing the thermostat in my 82 earlier this year. Fixed it by jacking the front of the car up and taping a soft-drink bottle over the radiator cap-hole (with the cap off obviously) so that the bubble would find it's way to the top of the system and out through the bubble.

Of course, first thing to do would be to check that the coolant plumbing to the throttle body is hooked up right.

[Mr*Beach]

The 2 things i've come across that cause what you have described are an air lock in the cooling system or an incorrect inlet manifold gasket. And since you've had everything apart, either of these could be your problem. I can't remember what it was about the gasket that caused the hunting, but it stopped after I replaced it. Good luck.

~Josh

[Pimpin_1JZ]

Ah yep like you would for the commodore's. Great, I will give this a go when I get home tonight.

[Pimpin_1JZ]

Hmm an air leak from the inlet gasket, I will try this also. Now that I remember (as it was last week since I touched it) there was a hissing sound soming from the inlet manifold area, which also constatly went psssssssssss stop psssssss stop pssssssss. That's why I was kind of thinking I may have blocked something I shouldn't have.

[Hiro]

Hmm an air leak from the inlet gasket, I will try this also. Now that I remember (as it was last week since I touched it) there was a hissing sound soming from the inlet manifold area, which also constatly went psssssssssss stop psssssss stop pssssssss. That's why I was kind of thinking I may have blocked something I shouldn't have.

Was the intake piping taken off at the same time? The cold-idle valve makes a very loud and distinctive hissing when it's open. Take the piping off up until the throttle (keep vacuum lines connected though) and block the large hole in the rim of the throttle body (the little hole will be the warm-idle valve), and note the change in noise and revs. This'll determine absolutely whether the problem is in the cold-idle valve or not too.

[LeeRoy]

Leaking intake gasket will cause a high idle but not a hunting one.

+1 for either air in system or not enough coolant.

[oldeskewltoy]

I have done the old cut and shut for the inlet manifold.

Problem right there............. (imho)


here is why

(small port manifold)



note the horizontal tube.... look all the way on the inside and you should see a small hole. This is the idle circuit! A cut and shut uses the hole diameter at the throttle body to try and keep an idle......

Since it is a bigport.... I'd spend a few $$ on a rwd intake and you'll likely fix your problem


btw... this is the intake I'll be using on my rwd smallport

[The Real Roadrunner]

how was it cut and shut? if it was just modified at both ends chances are you havn't blocked off the PCV correctly (the hose from the cam cover) and this will give you a large vac leak, it will come in thru 2 sections 1 being the TB and the second being the nipple in the middle of the mani that runs to the cam cover.

post a pic of it and it will make it easier to figure out what you have done.

the hunting is caused by the ECU seeing the TPS at idle but the engine reving harder than 2K thus hitting a rev limit.

cheers
linden

[Pimpin_1JZ]

Cool, when I get home tonight, I will see if I can get some pics of the cut and shut.

Cheers for the replies.

OT - Linden, any word on those inlet manifolds for the non VVTI 1JZ?

[adam-__-]

The hunting idle could also be caused by the TPS. Just unplug it and the revs should pick up and stop hunting, if it continues going then the TPS wouldn't be it.

If the hunting stops while TPS is unplugged, plug back in then just adjust it until the hunting stops pretty much. The Toyota manual tells you to use a multimeter and measure the resistance, but the range they give you is too wide.

[sammyp]

+1 for the air in the coolant idea.

A mate and I had the same problem with our rwd inlet 4age when we first got it going and then had the same problem after replacing the radiator until the bubbles worked their way out.

All we had to do was take the radiator cap off and run the engine for a couple of minutes and it went away

[Golberg]

What some don't realise is that radiator caps usually have 2 stopping points for a reason. If you turn it to the first stopping place run the engine and wait until coolant comes out of the cap its bled the system. Turn it all the way and its locked off.

[jono]

i know this is an oldish thread now, i ran a smallport in my ke20 for years without the support bracket between the manifold and the engine block. I finally decided to put one in and then the engine started hunting as it was pushing the manifold, causing a leak. I ended up having to pack out one end of the bracket with a fat washer so it could be snug but not putting pressure on the underside of the manifold.
I just thought i'd chuck this up here in case anyone searches for this problem to give them a different idea.

[DTrain]

id put my money on tps as well. adjust it as per the toyota manual