1987 3.0 extremely high idle

[Projectmudfinder]

First I want to start with saying this is my first time posting in a forum and i apologize if i do something wrong. But to get to the point of this post i just bought a 1987 pathfinder with the 3.0 last Saturday. My problem is once it starts it shoots straight to somewhere between 3-4k and holds idle there. I've talked to a mechanic over the phone and the best he could tell me was the idle air control valve. But for the life of me i cant find any information on one for my pathfinder nor can i find a replacement for my year and engine online. Last night i decided to pull the throttle body to clean it and in the process discovered that the plug for the idle switch on the tps was not there. it just had to wires sticking out of the harness. with electrical tape on the ends. Could this be what is causing my idle problem? I know it is a problem and have ordered and new tps and plug for it so i can wire it in but if that isn't the problem i don't know what to look to next. Any help would be greatly appreciated.

[JackStraw1]

Did it do the high idle from the minute you first drove it? or is this something new ?

[Projectmudfinder]

^{it has the high idle from the beginning when I bought it. I drove 4 hours to get it and got a great deal and thought it would be a simple fix. the previous owner said that the first time it ever did it was when I came to look at it. I find that hard to believe but I do believe someone has had it running and driving recently.}

[NWT87PATHY]

Unhook your cruise control cable,If its not the throttle body opening up letting more air in, you have a leaky injector dumping more fuel in.

Edited April 27, 2016 by NWT87PATHY

[Projectmudfinder]

no cruise control but ill check injectors tomorrow. i re wired the tps correctly today and still have the same problem. it also only revs to about 4500 then start sputtering and when the engine is under load it has no throttle response. is this possibly a timing problem? i have new plugs and wires coming in the mail next week.

[PathyAndTheJets]

Have you checked codes on the PCM?

Here's a write up on it.

http://www.nissanpathfinders.net/forum/topic/21-ecu-self-diagnostics-for-87-95-pathfinder/page-4?do=findComment&comment=770992

[NWT87PATHY]

I dont think timing can be a issue. The dizzy cant be adjusted as far as i know.. And if its off a tooth it wont run. Could be a botched timing belt job but it would be un driveable and you would have bent valves. I wonder if the idle set screw has been monkey'd with? If it shows signs of it start backing off the screws on the TB and trial and error untill you get a stable idle. Also a nasty vacuum leak could cause idle problems bit not WOT at start up...check if the hose on the back of the frying pan (filter housing) is hooked up and all the vac lines are in good shape. Electro port engines are pretty basic fuel/air operations like chevy TBI only so manythings to go wrong.. Generaly if its not a Air issue its a fuel problem.

[Slartibartfast]

Unless the TBI dizzy is very different from the MPFI, it can be adjusted, you just loosen the hold-down bolt and turn the whole dizzy to change timing. I can't imagine bad timing making it rev high, though, much less that high.

 

I think you're thinking of a diesel with the leaky injector, more fuel won't make a gasser run any faster unless there's more air to burn it.

+1 on checking for codes.

 

The first thing I would check, though, is the throttle body. Just make sure the throttle is actually closing. The throttle cable could've frayed and bound up in its sheath, or something could've fallen in and jammed the throttle open (saw a guy on Youtube pull part of his airbox out of his Subaru's throttle body).

 

Could be the idle air control but I'd be amazed if it could pass enough air to rev the motor that high.

[Projectmudfinder]

I plan on checking codes today. I've pulled the throttle body and looking at it from the bottom there is a post that sticks out it looks like the butterfly valve should rest on it but my throttle doesn't close that far. Even closed to its farthest point it's still open a decent amount. I will try to take pictures and post tonight. I'm not sure how much the throttle should be open at idle if any

[NWT87PATHY]

 

I think you're thinking of a diesel with the leaky injector, more fuel won't make a gasser run any faster unless there's more air to burn

 

Ive seen chevy tbi's that were pouring gas in insted of a spray mixed with vac leak caused higher idel (

[Slartibartfast]

I don't know the TBI throttle body too well but every TB I've seen closes more or less completely unless it's held open by an adjuster screw or a fast idle cam or something.

[NWT87PATHY]

Exactly. and the IAC is for the warm up and in the 80's it was a mercury thermo switch for kick down or in the fashion of a electric choke. My suggestion is to back all the screws off and get a base line idle then dial it in to smooth 6-700 rpm. TBI is basicly a carburetor that uses the O2,water temp and MAP to adjust it's own A/F ratio. Easy stuff compared to the 2bar speed density VE tables i tune LS1's with..lol

[byob]

As mentioned throttle body's are a very simple set up. There are three manuel adjustments-cold start idle cam, base idle screw and the fast idle air screw. Check the adjustments and make sure there is slack in the throttle cable. Then check for a/f ratio and pulse at the injectors

[Projectmudfinder]

I think my fast idle cam (I believe that's what it's called it the device with the 2 coolant hoses going to it) needs to be replaced I also think that whatever lever that is pushes on that is connected to the throttle body is stuck open. My reason for thinking this is I took the fast idle cam off the throttle body and that lever fell then started the engine and grabbed the lever and moved it as far as it would go each way and there was no adjustment in engine rpm

[NWT87PATHY]

Try unhooking or disabling it..

 

Fast Idle Control Device (FICD)-

This device actuates a fast idle cam based on coolant temperature flowing thru it. The temperature at which the fast idle cam eases off can be set by the FICD Adjuster. The fast idle cam pushes on the fast idle lever and how much this lever adjusts the idle is controlled by the Fast Idle Screw.

 

Fast Idle Screw-

Head points skyward and is often mistaken for the normal Idle Screw. When the engine is cold the âfast Idle Camâ increases the idle for faster warm-up. This screw sets the fast idle speed which should be between 1,000-1,200 rpm set depending on how cold your climate is.

[Projectmudfinder]

This sounds like my problem the fast idle lever does not adjust anything upon start up. I disconnected it from the fast idle control Device and moved it by hand while it was running and there was no change. Is it possible it stuck in the open position inside the throttle body.

[NWT87PATHY]

Yup maybe you have seized parts in the tb. Just take it apart and find out why your tb is not in the idle position