99 4-runner low idle help needed (1 Viewer)

[BioTex]

Just picked up a super clean 99 2wd 4 cyl. and 5 speed manual tran. 4-runner. Has 209k miles showing, and I have all the original receipts from day one. I read through them and nothing unusual. This car was driven only highway miles out in California since new.

The car is very hard to start when cold, and has a low idle (around 500 - 550). She wants to die out when coming to a stop when cold, but runs super smooth when warm, but still idles too low.

I read in the FSM and it says low idle check fuel system. So this weekend I figured I'd start with the tank/pump and see if it is clean inside. My thoughts were that perhaps the truck sat for a bit too long and had tarnish or sediment clogging the sock. I have a lift inside my shop so no big deal to drop the tank. I wanted to check the fuel pressure first but for the life of me I can't find a port to hook up a gauge. I did pinch off the return line and the idle got rougher, but still too low.

So I dropped the tank and pulled out the pump. To my surprise it was shiny clean inside. Not a speck of debris or any sign of tarnish. I put the tank back in and the engine fired up same as before. No change to idle.
My next thought was to run some sea foam thru the induction system via the brake hose. I did and could not tell any difference to the rough and low idle. I pulled the MAF and hit with some MAF cleaner. No change either.

This low idle isn't intermittent. It is a constant. I could use some direction as to what else to check. Crank sensor? EGR?
This engine is spotless BTW. It is 100% unmolested with new wires and plugs. According to the receipt it has iridium plugs IIRC. Could that be an issue? I didn't pull them to look since they were brand new.
I didn't have a CEL until I ran the seafoam thru. I'm going to put a code reader on it and see what I get but am thinking it will go away once reset.

 

[Kris]

I would be looking for some type of cold idle up vsv. Not extremely familiar with the 2/3RZ, but seems that if it runs well when at temp that some solenoid is not functioning properly.

 

[Jeremy9A]

Make sure the throttle body is clean. Sounds like there is a lot of carbon build up not allowing enough air flow at idle. I use carb cleaner on a rag to clean the bore while holding the throttle plate open.

 

[BioTex]

Make sure the throttle body is clean. Sounds like there is a lot of carbon build up not allowing enough air flow at idle. I use carb cleaner on a rag to clean the bore while holding the throttle plate open.

That sounds like an easy enough check to perform. I'll look and see and report back.

I would be looking for some type of cold idle up vsv. Not extremely familiar with the 2/3RZ, but seems that if it runs well when at temp that some solenoid is not functioning properly.

I was thinking something like the CTS (coolant temperature switch), but when I say it runs perfect at temperature, it still has the low idle issue and the hard starts. I just mean that it runs great when above idle. I hate to start replacing parts without a diagnosis. Just can't find anything specific in the FSM to fix a low idle issue. I guess I could check base timing for starters. Also isn't the TPS supposed to set idle (sort of)?

 

[Zoombyu]

Do a test on your IAC, idle air control valve. It's located on the underside of the throttle body.

 

[BioTex]

Do a test on your IAC, idle air control valve. It's located on the underside of the throttle body.

Will do. Thanks. Yesterday I took my mechanics stethoscope to each injector. They all 4 sound identical.

 

[Zoombyu]

Google symptoms of a bad IAC and I'm sure it'll match your symptoms exactly.
Id say make sure the thin wire inside of your MAF is clean too.

 

[vipergrhd]

Get a Vacuum Gauge and see how is the engine performing,it will tell you a lot from what your readings. A compression check is also a good idea and a leak down test on all cylinders.

 

[BioTex]

Changed out the fuel filter because It was an unknown. Didn't really expect it to cure anything, but changed it so I could rule it out mostly.
I took the throttle body off and cleaned her up real nice and shiny. To my delight, this totally cured the problem. Idle is smooth at 750 to 800 rpm now. Hot starts are much much better also. Not sure about a cold start yet. Will report back later on that one.

 

[Jeremy9A]

Awesome! Glad that worked so far.

Looking for carbon build up is the first thing I check for when I see low idle issues. It's getting to be very common on drive by wire vehicles too since they learn the throttle plate position for idle speed, but don't seem to compensate and relearn on their own for carobn build up over time.

 

[BioTex]

Awesome! Glad that worked so far.

Looking for carbon build up is the first thing I check for when I see low idle issues. It's getting to be very common on drive by wire vehicles too since they learn the throttle plate position for idle speed, but don't seem to compensate and relearn on their own for carobn build up over time.

Thanks for the help so far Jeremy. Much appreciated.
Now for the hard start issue. I tried a cold start this AM and still have that problem. When I first crank her over, I get a very slight hit, but then cranks for like 20 seconds or more before it hits and starts. Sure feels like no fuel or injectors not firing. Warm starts are no problem, but are a tad bit longer than I think a fine tuned fuel injected engine should take. But not so much that it is a real problem, although i think the two are tied together.
When I let the key off from the start position, I can hear the fuel pump for a couple of seconds then it shuts off. I'm guessing that air flow through the MAF during cranking is completing the fuel pump relay circuit, so that part seems to be ok. I may try to jumper out the fuel pump so that I can energize it manually and try a cold start that way. I may be off track so feel free to jump in.

BTW, I hooked up a code reader and saw no codes during all this today.

 

[Jeremy9A]

Damn. I was really hoping your issues were linked to a problem with not enough air flow to idle.

If you crack the throttle open just a little bit, will it start any easier? Like maybe there is still an issue with the idle air control motor?

I know you mentioned the new iridium plugs, but maybe just pull one out and make sure they aren't Bosch plugs. You want NGK or Denso in there.

One easy thing to try would be giving it a small shot of starting fluid (while using the necessary precautions) to see if it fires right up implying a fuel delivery problem.

Something else just crossed my mind- does that motor have a cold start injector? If so you may have an issue with that or the temp sensor that would let the pcm know to use it. And also if it has one and is connected with a banjo fitting- thats is where you would hook a fuel pressure gauge (there are fittings that screw in like the banjo bolt and have a fitting to connect the gauge).

 

[Jeremy9A]

Actually, after googling I don't think you have a cold start injector. Don't mean to send you on a wild goose chase.

 

[BioTex]

Actually, after googling I don't think you have a cold start injector. Don't mean to send you on a wild goose chase.

I like the starting fluid idea. Will try it and report back. Will also pull a plug.

 

[BioTex]

Ok, so I sprayed a bit of starting fluid into a rubber hose that connects into the filter box. Reconnected the hose and she fire right up. I let her idle for five or six seconds and shut the engine off. Tried to restart and she cranked and cranked as before. I pulled a plug and they are new Autolites. So it seems this problem is fuel related after all. Since the engine runs so well at all speeds when warm, I'm going to say it is too lean at startup cold. Since I have a new temperature switch already, I might as well change it out huh? Could be a bad ECU I suppose...

 

[BioTex]

Update on replacing the CTS. No change to the hard cold starts. Still starts fine hot, but extremely long crank times cold. Anyone have any suggestions?
My next step is to look into the IAC as suggested a couple of times.

 

[BioTex]

After looking closer at the parts catalog, I believe I was sold a sender for the gauge and not the sensor for the ECU. I replaced a one wire sender, and it should have been the two wire sensor. I located the correct sensor at the back of the head. Am in the process of getting it out to take an ohm reading through the ranges.

Edit: I ordered a new sensor since I managed to drop it and broke it in two. Guess I'll never know if it was the sensor. I had it all ready to take some readings and knocked it off the table. What a bummer.

I don't think this is the problem, but will install a new sensor now anyways.

 

[ajax1]

On your hard cold start it usually means a injector is leaking down, or you are not holding pressure in the rail.

 

[vipergrhd]

If you could borrow a fuel pressure gauge and tap into the fuel rail,check your base fuel pressure and shut off engine rule of thumb is you can only loose about 5-10 psi with in 10-15 min and if you let it sit overnight you should still see a residual pressure around 20 psi. you may have some issue with how fast your pump is pumping fuel when the pressure drops you also need to check fuel volume even if your pressure is good but not enough volume your system could starve for fuel.

 

[BioTex]

On your hard cold start it usually means a injector is leaking down, or you are not holding pressure in the rail.

I haven't checked the rail pressure yet since my pressure gauge needs a Schroeder valve to hook to. Looks like the truck is a banjo style fitting.