post office

This is the first real post for me; I've been reading yotatech as my #1 source for info on my 96 taco 5VZ FE @ 199k. By reading, i mean hours of reading/searching for any and all maintenance i think i can accomplish myself (Somewhat an automotive novice).

I will start with the long words version. For a short synopsis, scroll to the bottom.

First off, some background on how long i've had the truck and when problems first reared their ugly head. Let me start by saying i have pulled the EFI fuse to reset the computer a few times hoping i would get lucky. After a while of driving, i get CEL P0171 System too Lean (Bank 1). I am understanding that 'lean' doesnt mean lean fuel. Lean means low oxygen reported by the heated oxy sensor? Could be spark plugs not burning all the fuel?

I've had this truck for just short of 6 years. Its been pretty good to me. It had 156k when i got it. Timing belt done at 151k. I had free oil changes for 2 years from the stealership at which i purchased from. When they ran up i took that responsibility upon myself. Switched to full synthetic mobil 1 about 4 changes ago. Currently on 5k (really wanting to change oil after reading up on the sludge monster post here on yotatech).

I wish i had been reading these forums before i started having issues.

The first CEL i got was for the TPS, which i replaced and followed the FSM for calibration the best i could. CEL went away, milage was not noticeably any worse than before so i gave myself a pat on the back and started racking up more miles.

The second thing i did myself besides changing the oil was changing spark plugs. It was running kinda rough, loss of power so i pulled plugs to check em out. I wish i had done that when i first got it. The electrode on the old plugs were worn down rather low on one side. (the other side werent as bad). I immediately knew the plugs were robbing performance. HOWEVER, i did not know yotas and bosch plugs dont like one another. I'm still running the bosch equivalent to the dual electrode NKG's. This is high on my list of things to do. Money is super tight for me at the moment though, it being winter and all.
These new plugs restored the ˟˟˟˟ty performance i was experiencing. Not long after, the truck started this 'start up and die' thing. If it didn't fire right up on the 2nd/3rd crank, it would be hesitant to 'catch' and start. If it did fire up, it would idle momentarily and die. UNLESS i mashed the gas to the floor for a split second. If i did this it would idle normally without dieing. This problem got slightly worse over time. like, from once in a while to i expected it daily, if i did alot of short trip driving (shutting engine off.)

Fast forward to 3 weeks ago. I had one injector go bad (High resistance reading.) So i followed a guide on taking the intake plenum/throttlebody off to get down at the injectors. I had never pulled fuel injectors on an engine before but i managed with little or no difficulty. I just wish i could have replaced the gaskets, though i'm unsure if thats the issue.

With new injectors, it drives great. Lots of power. Feels like its new. However, it has trouble starting, idle is now higher. It used to be 730-750 right on the money. Before the injector completely went bad, i had no CEL, but cold idle would be at 2k. After changing the injectors cold idle went down a bit but it was a tad high. So i cleaned the throttlebody and the IAC valve.
Cleaning of the TB and iac did not help the starting issue, but the iac was really clogged up with crud and did not rotate freely. The guide i followed did not say removing the flat panel held on by 2 screws was not nessecary. But i did remove this. This metal panel is adjustable. Much like the TPS is, where it can be rotated, and doing so moves the spring inside. I put it on as best i could. The IAC is disgustingly espensive, so i would rather have to take it off and readjust it, rather pay the $250 for a new one.

I'm fairly certain the IAC is part of my starting problem. I information on this part is sparse, so i couldnt figure out if the valve should be fully closed, or if there should be a small gap. I think somewhere i read that fully closed should have a gap no bigger than 2mm. If someone can confirm this that would be great! I just cleaned it up and got the valve moving freely. and put it back together.

Now, i found contradicting info on the IAC. I found people saying that purging the air from the coolant side was not necessary. I also found people saying whatever air is trapped inside will be flushed out with just coolant pressure moving through the engine. Can someone confirm?


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tl;dr:

I am using Bosch plugs. (i didnt know yotas dont like them when i purchased these). I replaced a faulty fuel injector not long ago. Truck had 'start up/die' problem where it would fire up, idle momentarily, and die. UNLESS i pushed the gas to the floor for just a split second. THen it would continue running. I attribute this to the IAC not operating properly.

1: Currently, engine usually fires up strong 1st thing in the morning. After initial startup, it usually takes some cranking, and depressing the accelerator generally helps getting it started quicker.

2: Cold idle is between 1200/1300. Warm idle is between 900-1000. Lowest ive seen it is 850. I also get CEL P0171 System too Lean (Bank 1). Though

3: Besides poor MPG, drives runs great. No complaints there.

4: Cleaned throttlebody/IAC valve.
I'm fairly certain the IAC is part of but not all of my starting problem. I information on this part is sparse, so i couldnt figure out if the valve should be fully closed, or if there should be a small gap. I think somewhere i read that fully closed should have a gap no bigger than 2mm. If someone can confirm this that would be great! I just cleaned it up and got the valve moving freely. and put it back together. I also followed the FSM instruction on testing function by jumping at the diagnostics port (DLC1 ?)

Now, i found contradicting info on the IAC. I found people saying that purging the air from the coolant side was not necessary. I also found people saying whatever air is trapped inside will be flushed out with just coolant pressure moving through the engine. Can someone confirm?

I also found information on Fuel pressure regulators having a tear in the diaphram could affect starting. Though i'm slightly unsure if this would cause my problems, i have not attempted to troubleshoot this. If i'm not mistaken, pulling the vaccum hose on FPR and checking if fuel comes out is a definate indicator of this. Again this is a $150 fix so fingers crossed its ok. My scantool does report a negative reading on the ST(short term) reading. Which could indicate a problem if i'm not mistaken.

I'm mainly looking for suggestions and advice. I hopefully provided enough information to get some pointers. I know its a jumbled mess, but rather than go buy TB gaskets, spark plugs, sensors and replacing all; Id like some educated opinions.

Any questions?

post office

I forgot to mention, that the idle was perfectly normal immediately after replacing injectors (700ish) and my mileage wasn't as bad as it is now. Though this could be the winter gas blend and the increasingly cold weather here in Northwest WA. Nor did i get the Bank1 Lean CEL. I put a few hundred miles before i started getting the Lean CEL/High idle/poor MPG problems.

The high idle issue came a couple weeks after doing injectors, same as the bank 1 lean CEL.

I test drove it through the mountains after i made sure injectors werent leaking fuel on the engine or anything stupid of that nature.

Coolant temp sensor reports as it should. Hot engine, in the cold weather was 195 when i checked it today.
I'm 98% sure i do not have an airleak from any of the 2 dozen vacuum hoses. THough i do hear a loud noise that could be coming from the IAC valve. Its most likely the air rushing through the throttlebody but i cant be for sure. TB must be removed to check IAC valve vacuum hose. I know i connected this to the IAC valve though.

I did spray around all hoses (the ones i could access) and did not get any change in idle.

I cant think of much else that i didn't already cover in the OP.

I did notice the IAT temps just dont seem right. IAT temp should be pretty much the same as outdoor temps? While driving it says 45, almost all the time. After sitting (engine hot) IAT temp was 70 degrees. That was today, and it was 34 or 35 degrees outside. Could IAT sensor cause the issues i'm having? Research i've done says IAT sensor is a problem on these vehicles.

I will finish by saying, i've done all the no-brainer fixes. MAF cleaning being one of them, so dont ask! I'm not getting a CEL for the MAF but it could be part of the problem? though i highly doubt that.

I do have alot of miles. Some would call the engine 'tired.' Aside from just going balls out and replacing $2000 worth of sensors, i'd like to simply fix what the problem is

mynameistommy510

My 96 4runner 5vzfe is showing exactly the same symptoms. Rough starts, and same idle speeds as you posted. I have also narrowed it down to a bad IAC.

I am assuming that the sensor on the IAC, not sure what it is called, has gone bad over the years and is no longer functioning properly. Since I can't afford a new one, I mentioned it to my dad as a christmas present. Hopefully santa is good to me this year

Forgot to mention I recently cleaned the TB and MAF, and more recently changed the spark plugs the day before my problem started to occur. Just a coincidence. I also tried cleaning the IAC but didn't fix the problem.

broke1

Redo the TSP maybe the extra fuel from the new injector is throwing off the reading. The improved injector has changed the mixture or something. Im no machanic but seem to be the easiest solution. I took mine down to the smog pro place. I installed the new TSP and left the bottom screw out. Then I took it down and all he had to do was adjust it and tighten one screw. He charged me 40 buck to set idle, TSP and Timing.

post office

1. You guys are pretty good. I meant to post yesterday, but i found the air hose was connected to the iac, but somehow got disconnected on the other end (Back of the engine, easy to miss unless you get on a stool or lean way over and look down. It connects just below the injector circuit wiring which is encased in a plastic. Which is in a really bad spot to reconnect, if disconnected. My back is killing me from the ackward bending over positions performed over the last couple days.
   
   What confuses me is why it let me put many miles with little symptoms with this hose disconnected. After connecting the hose, CEL went away, mileage seems better, though i haven't done much driving. Idle is back to normal (same crap spark plugs)
   
   Today, I went and got some NGK plugs, and put those in, along with dielectric grease and very little anti seize on the threads. While changing the coil pack side plugs, i noticed a small bit of what looked like coolant on the airhose on the bottom of IAC. After pulling off the TB (2nd time) and inspecting the IAC (again) I noticed the valve was again stuck, not moving freely. I guess the first clean i did wasn't good enough. I just put it all together though have yet to start it. Am giving the RTV some time to harden before i see if the plugs made a difference. While cleaning, i noticed, you can spray cleaner in there, get it rotating freely, and when the cleaner evaporates it will become sticky again. If cleaning IAC, make dam sure you got it good before putting it back together . I found that using cue-tips are the best method to get down in the valve. I didn't have the balls to rip the whole mechanism out. I can't afford $250 for a new Iac. I also attempted locating a gasket for this. Autozone didn't have it. Shucks/o'reilly was utterly confused by my phone call. I think the girl was new. I settled for some RTV and the same old gasket. It worked last time!@
   
   The Throttle Body is still pretty squeaky (clean) from when i went through it, following the injector adventure. I re-did the TPS while it was on my table. Much easier to OCD out getting it just right when its on the kitchen table! Though i lack feeler guages, i used a razorblade/credit card. FSM says to apply vacuum, insert .43 guage, and rotate until deflection. It also says with .53mm guage, meter should be 'open'. While .35(i think) is less than .5k. I tried for 30 min or so trying to get this scenario. I found it impossible to have continuity at .34mm, and open at .53mm. I almost believe this is a typo in the FSM. All other resistances check out perfectly within spec. Never threw a CEL before, i doubt this minor inconsistency will affect much, if at all.
   
   The bosch plugs were REALLY ugly. Only one of the plugs threads were clean of oil/wet carbon or whatever was on them. I'm thinking they were semi-fouled, some providing spark, others not so much. Not properly burning the fuel as well. The TB also had some of this 'wet carbon' crap. I noticed the electrode on the Bosch is a very small conductor, encased in ceramic. The NGK electrode is a solid conductor mounted on top of a ceramic bell thing (technical terms?)
   
   am excited to see how it starts in the morning. I will never touch bosch plugs again. Fairly confident it will be a strong performer after this round.

rworegon

post office, as you found vacuum leaks can cause very noticeable problems with idle and performance. Given the age of your rig, carefully inspect all vacuum hoses for cracks including the air intake tube and replace as necessary.

post office

I did go over hoses, but at startup vac leaks would be less of an issue? The only hose that had real cracks at the end was the passenger side hose from pcv to TB.

Fired right up this morning, cold idle was around 1600. Still having start problems after its been sitting. Except first thing in the morning.

With new plugs, exhaust definately smells less like unburned fuel, and more like exhaust. Absolutely no qualms while driving. Now takes less pedal to reach speed limits. Engine also warms up noticeably faster.

Just this starting problem...

post office

I'm going out on a limb here, but i'm thinking its fuel pump related/ or just the wires. Looking around the internet, Same symptoms as me, and this person found wiring to fuel pump were getting hot/corroded. Which would explain why it only likes to start when its been sitting cold for 12 hours+. Checking out the fuel pump wiring will be my next educated guess. I have only let the fuel level go below 1/4 a few times for as long as i've owned this vehicle. Hate having to see it below 1/4 but i guess i will have to

http://www.ttora.com/forum/showthread.php?t=85565
http://forum.ih8mud.com/79-95-toyota...lp-please.html

If the iac resistance is ok, and you can verify that it can adjust idle with A/C on then i would say replacing a $250 sensor would be like throwing tools at the windshield to open the glove box.
I'm not replacing such an expensive sensor without a CEL. I will drive it till it explodes before i start throwing money in the toilet . Or go to the junkyard and pull off the "electrical part" of the IAC and offer them $30.

The 2nd time i cleaned the IAC, it brought my cold idle back to factory setting. I'd be more suspect of any other part. The IAC is on the bottom of my list due to the price. Stubborn like that

Pictures Below:
1: This is what the bosch plugs looked like when i pulled them. The bottom middle is the only one not covered in wet carbon from unburned fuel. The guy at autozone knew nothing of bosch platinums and waste spark ignition problems. Apparently he runs bosch platinums in toyota without problems. The clean thread plug came from cylinder 3. Which was the same cyilder that had a faulty injector. Not sure if that means anything.

2: Because posts are always better with pictures. The + and = indicate where the hose is supposed to connect. Easily overlooked, atleast in my case. TPS labelled for reference. Its filthy, i know. If the city would pave my F'in street i would probably care to clean it.