TobyDick

Howdy all.

Long time reader(Over a year for sure), first time poster. You guys seem to be a bright bunch and have answered hundreds of questions without
me even asking! I can't thank you enough for giving me the courage to tackle my Toyota by myself. (Google lead me to your forums many times)

My Rig:
1998 4runner 3.4L 2WD
145,000 Miles


My 4runner has been an awesome vehicle until March 31st when I tried to start it.
I was driving the 4runner earlier that day and it was running like a champ; then I went inside for a couple hours..came back out and had this problem:

When I turned the key, the engine severely hesitated before starting up. Only applying the gas would smooth it out and allow it to return to normal.
It stalls at what seems to be every other red light/stop. When it stalls it sort-of hesitates to start back up (again, gas pedal will help)
This does not happen at higher RPMs or on the freeway and it seems to pull good.

What I have done so far:

Replace Fuel Filter
Plugs/Wires
Seafoam in gas/vaccume lines
Replace vaccume hoses
Adjust the idle
Clean Throttle body
Removed IAC and cleaned it out well

Result:
It seems to be running allot smoother but it still stalls on idle.

Thoughts:

I hear/read that 95% of the time IAC is to blame. It seemed to help quite a bit when I cleaned the IAC..
I'm thinking about replacing the IAC all together but obveously I don't want to do that if it is not the problem.
If I disconnect a small vaccume hose that goes to the TB/IAC it keeps the truck from idling thus it won't stall..but I know this can't be healthy.


I try to be as complete as possible. Please let me know if I missed anything.

Is there anything else I should try?

Edit: There is no CE light.



-Toby

97ltd4x4

You are on the right track.The IAC gets really gummed up and it can take a good cleaning with pipe cleaners and carb clean to get all the gunk out of it..(Its spring loaded..so you have to move it on the bench while you clean it)

That being said when everything is working properly,the computer controls the IAC,which in-turn will control the idle speed.The ECM is looking for some inputs to control the IAC.....TPS idle contact,RPM,air flow,coolant temp.

After all your work,I would next do the following:First for kicks,pull the 15A efi fuse and see if the ECM needs a re-learn to set idle speed(if you have not done already)...next check the TPS idle contacts(ohm meter)If they are not making contact either the throttle body butterfly is out of adjustment,or your tps idle contacts are going intermittantly open...I do not believe there is a DTC for the idle contact in the TPS..there is a P0120,which is for the sweeping resistor in the TPS....So it is possible to have bad Idle contacts in the TPS and not throw a code.

Next I would make sure that the PCV Valve is not stuck closed,If it is it might make an idle speed lower than it should be.

If all still checks out good.I would pull the IAC again(get new O-ring/gasket) and really inspect it...making sure the valve does not have any burs on it.and really clean it good with very fine small brushes..might even want to soak it in carb cleaner overnight.....

It is possible that the IAC is not opening enough...since it has such a small stepper motor...But Its almost always a mechanical issue when they don't open,or open far enough causing stalling issues....also FYI there is a code for the IAC if it goes electrically open P0505...which is really quite a rare code for any Toyota.......

Hope that helps..

TobyDick

I did notice my rags got pretty dirty when I cleaned the IAC..allot of carbon buildup.

Is there a specific reading the TPS should give?

The PCV valve does seem like its a bit loose at the rubber gasket...It should be pretty snug right? Should I blow into it to test for a clog?

Its probably those damn muffler bearings again..


I can't thank you enough for the advice. One of these days I would love to be a valuable contributor.

97ltd4x4

The Repair manual is pretty vague on the readings...do a check on the outside wires/pins of TPS(should have 3) either back probe the wires or touch the terminals of the TPS with the leads of the meter...looking to test between E2(brown with a black stripe) and VTA(brown with a yellow stripe)...Basically with the throttle closed you should have a very low ohms reading and as you open the throttle the ohms will proportionally get higher in value...

Best way to see if the pcv is clogged/sticking is to remove the hose going to the manifold intake....block/cap the port on manifold..start enginge...air comming out of hose?...If just barely the pcv valve could be sticking..if none at all the pcv valve is blocked...do not remove the pcv valve.. unless you have another gromett...cause they get hard as a rock and will crack as soon as you remove it....always replace both the PCV valve and gromett at the same time.......been there done that!

TobyDick

Well...I can't locate my OHM meeter so I guess I'll replace the TPS and see what happens. I checked the PCV valve and it doesn't seem to be clogged at all.

Concern:
I can't find my OHM meeter to test the TPS so I think I'll try replacing it and see what happens. I'm tight on cash for a couple weeks (slammed with bills/birthdays) so I may have to get to that in a bit.

Side note:
When I disconnect the small vacuum hose going to the TB:
It doesn't stall..but I drove it down the street and at a red light the engine shuddered for a second (almost literally) then smoothed out again. Sometimes it drops down to ~850rpm..but mostly stays around 1k...It seems to start OK when its cold. I don't know if this helps.

I figure the more info the better.

Edit:
Temp gauge is in the middle where it usually is.
Hypothetically if I replace the TPS and that doesn't do the trick..should I replace the fuel pump?

Ironmike4x4

That's what I'm gearing towards. If you have a fuel pressure gauge then I would definitely check the pressure. Alldata is not pulling up for me so I cannot look up the pressure specification. If you have a haynes manual then check in there.

TobyDick

Before I start pulling things off...Is the TPS a plug and play part? Or do I have to dial it in :confused:

97ltd4x4

I would not think fuel pump...You would have many more drivability issues..not just when comming to a stop.

I would test things step by step..not just replace parts...Although the tps is a cheap try and they do go bad with higher milage...I would still be leary of the IAC cleaning..just because your problems seem to be a classic dirty IAC problem...

The TPS is two phillips screws...no adjustment...but you will have to set it in the throttle body housing..then turn the TPS to align the screws..don't for get to pull EFI fuse before and replace afterwards...

TobyDick

After cleaning the IAC again...extremely well..it starts great..drives..but It still stalls at red lights..just not NEAR as often as before. The TPS reads fine. My local Kragen Auto let me take home their ohm meeter to test it. The IAC does have 145k on it..Perhaps it needs to be replaced?

TobyDick

Ordered new IAC.....keeping my fingers crossed.

toy_tek

Be 100% certain you installed the (metal) TB to Intake plenum gasket correctly. Failure to do so will cause mixture and idle issues.

4runner4mark

I've had a similar problem once...it started happening after my battery drained when lights were on and I got a jump from someone. I got a new battery...no more problems.

TobyDick

the new IAC didn't fix the problem.....Is there anything else I should check? I noticed the flap that lets air in is completely closed in resting position..I thought I remember hearing it should always be open slightly...I don't hear vac leaks anywhere.

I don't want this to be the end of my 4runner! Any further advice would be appreciated

TobyDick

Its been running fine for the past 3 days. No stalling with or without A/C and seems to be running normally at 600-750rpms and if it starts to drop lower than 600 it bounces back to 750..I don't want to be too quick to call it victory... I'm going to replace the ground wires and see if it keeps on keepin' on.

When I deem this truck in working condition I'm going to reupholster the interior and do some upgrades. I pretty much bought my 4runner as a hobby (something big to tinker with/upgrade/wreck/rebuild)