Can anyone tell me what the spec range is for primary resistance on coil packs on a 1998 3.4L V6 5vzfe Taco, ideally tell me both hot and cold ranges, from a FSM?

Thanks!

 

Cold Primary 0.67 Ohms - 1.05 Ohms

Hot Primary 0.85 Ohms - 1.23Ohms

Just remember some times Meter probes make a much better connection .

When things are plugged back together the resistance can be higher.

*** With the MAF sensor unplugged the ECM does not see the signal telling it the engine is drawing in air .

So if it is all working like it should it turns off the COR*** shutting off your fuel pump.

*** The ECM just no longer sends the voltage to the COR

 

If your coils are on the way out the first thing that most often happens is loss of spark.

So once these got hot and failed it would no longer start at all if it was allof them.

Be interesting to check for spark at the time it will not start.

 

Thanks Wyoming. All 3 coils had primary reading of 1.3 when intake air temp was up high enough to cause ˟˟˟˟ starts (~75-80F), and ECT was ~120-130F. Assuming the hot spec range is based on ECT, not IAT, so if that's correct, ours tested pretty far above spec, as top end of cold range is 1.05, and top end of hot is 1.23, so I assume if ECT is ~125F, our top end of spec range would be ~1.1, 1.2, right? But the crazy part is that all 3 were exact same out of spec reading. That makes it seem more like a symptom of a bigger problem, rather than the root cause of the problem, ya think? Pretty sure those coil packs are many years old. I know #3 was replaced in '07 when we had the funky carbon tracking on all the stuff there, but other 2 are probably lots older than that. Are they something you replace periodically, even if they're testing fine (not that ours did, just curious though)? You don't think our whole issue could be those damn coil packs, do you?

Checking for spark when it struggles to start, how would we do that?

I'll be honest, some of the stuff in your last 2 posts was over my head. But husband will read tonight, so I suspect it will all make sense to him.

Our good news update for today is our neighbor has a mechanic buddy that lives close by, and he wants us to bring our Taco to his house tonight. And check this out -

HE HAS ALL THE CRITICAL DIAGNOSTIC TOOLS THAT WE DON'T!!! And I'm sure he's got the skill/knowledge and garage to go with them, cuz neighbor said the guy has the nice stuff! He has a fuel pressure gauge, so he can double check that for us, he's got some kind of fancy scan tool that neighbor thinks is Toyota factory one (sounds too good to be true, but maybe it'll give more info than our scan gauge at least), and some kind of fancy sounding spark tool/tester. Neighbor said he's seen the guy work miracles on other Toyota trucks having electrical/sensor/fuel issues, so I have more hope now than I have in a long time. We get so discouraged spinning our wheels (bad pun!) on this that we start talking about selling it, then get even more depressed. We were going to a dealer for a diagnostic inspection tomorrow as our last ditch hope, but then this came up, and I'm sure this guy's prices will be a lot cheaper than the dealer - maybe even free!!

But please, if you think of anything, keep telling us your thoughts. You've already helped us a ton, just to be able to cross easy stuff that we can do ourselves off the suspect list, then for stuff that we're too chicken to do, we keep referring back to your posts and they help us talk to/give ideas to the people who take it from there.

Thanks Wyoming!

Will post end results no matter what!

 

One thing that may or may not impact your starting issue .

I never really took notice but it does happen to me sometimes where the engine just will not start the first time.

I always cycle the key to off turn to on wait till the radio powers up then crank that always seem to do the trick.

 

Hey there Wyoming! Good news! Our neighbor hooked us up w/his buddy who's a Master Mechanic that used to work for Toyota! Not giving up his name, he's mine! Seriously though, this guy knows what he's doing. 100%. He's got all the proper tools and experience to diagnose things correctly, and he's fairly certain it's our fuel pump. He tried to hook into our fuel system at the rail where the gauge would normally go, but said he found that the bolt was stripped from whoever handled it last (hmm, I know who), so he was starting to go at it w/vice grips, then realized that would create an additional problem, so he aborted that mission and tapped in near the filter. He closed the valve and started it at the ˟˟˟˟ starts interval (~30 min) and it started right up. He wanted to repeat that test before having us order a new pump though, cuz he wants to be certain he's not wasting our money - I LOVE THIS GUY!! In retrospect, it's likely we didn't even need a FPR, but I'm not going to get too ruffled about that, because at least now we'll have a brand new fuel system head to toe, and more importantly, we're finally in the hands of someone that won't let it go til he PROPERLY DIAGNOSES all the issues. We are happier than we've been in a loooooooooooooooong time, as it looks like our frustrating issue will be resolved very soon, for a very reasonable cost!

Thanks for all of your help Wyoming!

I do have two wacky questions for you to puzzle over though -

1) Any thoughts as to why no CEL when piston hole occurred? Haven't asked our new mechanic that yet, but I suspect he'll find the answer one way or another. Curious what you think though too.

2) Any theories on why good cold starts if pump is at fault? I did ask mechanic that, as well as the Taco World guys, and honestly our new mechanic was stumped on that one, but I could tell he wasn't gonna let it go. I suspect he may have an answer to it tomorrow. One of the Taco World guys said this (the one that called fuel pump first, and is basking in the glory of being right tonight!):

"On a cold start the pcm cycles the fuel pump for an extended period when cranking to deliver more fuel to prime the system for the extended cranking a cold start can cause.
If the pcm knows via the coolant temp that the vehicle is warm it will start the vehicle in closed loop ( which means when the truck is warm its uses feedback from all of your sensors to make your engine run at peak efficency) while warm its not triggering the fuel pump to cycle longer and having a bad pump thats allowing the pressure to bleed back into the tank is causing your engine to crank until the pump cycles enough to pressurize the lines and feed the injectors."

Sounds logical, although parts of it are somewhat over my head. You have any theories? What's the PCM; how does that relate to the ECM?

Thanks Wyoming! Have a good night!

 

The minute the spark plug broke the MIL should have tripped.

The fuel pump is either on or off

Turn the key it should be at full pressure in theory if there is nothing wrong your fuel system should always maintain pressure.

This is why you have a fuel return line to allow excess fuel to be returned to the tank

I am waiting to see the end results I don`t think it is the fuel pump although it could be in the control circuit.

We will see best of luck!!

 

Wyoming, thanks! You do have me worried though, with your doubts about the pump and still not resolving the big nasty burning question of why no CEL during piston hole. Plus, some of the sharper tools in the shed on Taco World have repeatedly echoed your thoughts on these issues from the start, and even our fabulous new mechanic repeatedly said to me, "that's a really good question" when I asked why good cold starts if fuel pump is culprit. However, I take comfort in knowing that this guy doesn't seem like one to just take a stab, leave questions unanswered, replace parts, and send us on our way. I think he'll insist on truly getting to the bottom of it first, which is how it should be handled.

OK, here's my wacky thoughts on why no CEL, so get out your crystal ball and tell me whatcha think:

1) Got CEL on 8/6/14 (I know this from combing back over Visa statements - went to Petsmart that day!) - perhaps that was the first misfire at #3? Got some gas while it was on, asked attendant to tighten cap really good, CEL went away.

2) Husband got CEL on 8/28/14 (good ol' Visa, it's like a diary) on his way to work in AM. ~9 hours later, drove home, light came on again. Bought a new gas cap on his way home, CEL went away. Maybe that was the second misfire at #3?

3) 11/30/14 - I was driving on the interstate, Taco started lurching/hesitating, got to my exit within 2-3 min of this, heard the nightmare knock/tap noise, parked - NO CEL immediately before, during, or after this event. Maybe the lurching was the center electrode finally giving up and taking off to spark plug heaven, and maybe the knock/tap noise was the plug (with no center electrode by this point) literally drilling a hole into the piston? By the way, I've always been convinced that the VERY SUDDEN/UNUSUAL temp drop to freezing cold temps that day somehow played a hand; coupled with, that was probably the first time Taco had driven at interstate speeds in quite a while, at least days, maybe weeks. And I basically floored it out of the driveway the second I started it - you know, cuz that's what you're supposed to do, especially when it's unusually freezing cold, right? Why warm it up, it's just an engine?!

4) First week of Dec - started Taco a handful of time for seconds each time, to see if awful noise magically fixed itself, or helped us determine something helpful about WTF was happening under the hood. NO CEL each time - but it's not like there's a compression sensor (right?), so why would it?

IF either/both CELs in August were related to piston hole/plug electrode, that is really remarkable and scary at the same time - because we drove A LOT during those 3 months between August & December. We did a Labor Day trip of ~800 miles round trip, most of which was in a remote area! Not to mention 3 months worth of daily errands, park w/the dog, etc.

Is it possible the initial misfires (the key events that SHOULD have set a CEL in all of this, right?) happened way back in August, but that piston was still moving up and down correctly all that time til November? Is it possible that cylinder was still firing with only the two side electrodes intact all that time?

It raises the questions of "how exactly does a spark plug work?" and "define misfire" (those will be the google mission of today! but assistance from you guys is always a helpful lesson supplement too!) Does it need both side electrodes AND the center electrode to properly create spark? Or can it still fire/create enough spark to keep that cylinder functioning with only the side electrodes to rely on?

Today I plan on asking our new mechanic what he thinks about why no CEL during the knarly event, but in the meantime it's driving me a bit batty, considering it's the last MAJOR stone that hasn't been turned over yet. I am determined to prove to myself that my Taco doesn't have some kind of brain damage!

EDIT: Update from new mechanic. He repeated his test to check the pump. Closed the gauge, started at 30 min, it started right up. Opened the gauge, started at 30 min, it started right up. He doesn't think it's the pump. But, while we were on the phone, he found a fuel leak! Said it's in the return hose off the FPR, and is a fuel line that's about ~1/4" diameter above the driver's side valve something or other. He's going to replace that hose, which he said would be like $3! But not getting my hopes up just yet, after the false alarm w/the pump. Others have said that hose "is kinda in a position that could be damaged by the removal/insertion of engine. It is also kind of hard to see when engine is installed." They also said that would explain why good cold starts, good starts after sitting just a few minutes, but bad starts when hot, at the 1/2 hr mark.

Do you agree, that this could possibly explain all of our fuel issues?

But still doesn't explain why no CEL during piston hole. The only possible explanation for that is ECU problem, isn't it? If a $3 hose fixes fuel issue, pending this mechanic's comfort level w/diagnosing ECU stuff, perhaps it'd be worth getting the dealer diagnosis on that one for $110. Guessing an ECU is not something you'd want to get from anywhere but brand new at a dealer, right? That could be our tipping point of giving up if so.......would love to know your thoughts on that.......

 

Not sure about the fuel hose.

You never smelled gas?? If it was allowing the pressure to bleed off perhaps??

Spark Plugs the center electrode is what carries the High voltage it jumps to the other electrode that is grounded via the spark plug threads .

without the center electrode it should have tripped a misfire code like P0303 also when the idle was wonky it should have tripped as well

ECM depot Grand Paririe TX rebuilds them for what I think is a decent price I can only go by my experience would buy again

I was having water issues taking out the ECM went through 3 till I found the cause.

It is very hard to find someone I think you lucked out

 

Hey there, thanks for the reply!

So, our new mechanic replaced that hose section that had the leak, then repeated his pressure test, and based on those results, he said we need a new fuel pump. Which I was fine with, but at that moment I was super hung up on whether our ECU was OK, because you and some of the sharper tools in the shed on Taco World have been very concerned from the start that we didn't get CEL during piston hole.

Mechanic said on an older truck like ours, it can take 3 ignition cycles for ECU to kick a code that something is wrong. So he thinks it's likely that the plug giving up/hole in piston event occurred within seconds, after which I parked and turned the truck off within 5 minutes, so his theory is it just never had a chance to register in the ECU. He said on older trucks like ours, the ECU doesn't monitor what the injectors are doing, and we know that we had 2 failing injectors that were the likely culprit creating the lean condition. He said he's rarely seen ECUs fail on Toyotas and Hondas - that it takes disastrous stuff for that to happen usually (like what you experienced I suppose!). He also said if ECU was failing, there'd be a whole lotta wacky ˟˟˟˟ going on w/the truck, and there's not. So I'm putting that worry to rest - he convinced me that our ECU is fine, and lucky me, a Taco World guy offered us his old one out of his 98 Taco should we find out different down the road.....these forums are truly awesome in times of need for Toyota folks!

There's still this semi unanswered question about why good cold starts if fuel pump is failing. Honestly, I didn't even go there again w/mechanic today, after pestering him w/a billion versions of "prove to me that my ECU is OK before I order a fuel pump!" Some of the Taco World guys have said maybe because metal expands and contracts when hot and cold, so the pump COULD function better when cold and worse when hot. For now, I'm going with it, spending the couple hundred to have this mechanic (who seems like he actually cares about doing things right, and will not rest til that happens) swap the damn pump, and will hopefully find out for SURE by this weekend when we finally finally finally get our Taco back!

Then the other goodies start - we need to fix a driver's side wheel bearing, address a bellow boot seep (or maybe replace whole rack & pinion - what's your opinion?), and replace shocks & struts. So still an uphill battle at this point, but with a new engine, a new fuel system head to toe, and all that other crap replaced, SURELY at that point (hopefully by summer!) we'll be able to finally finally finally just start 'er up, crank some tunes, and head out to the middle of nowhere with not a care in the world! Will be a damn good day when that happens again!

Thanks Wyoming! Really appreciate your continued input!

PS - Do you have any theories on why good cold starts if pump is dying?

 

Wow with all the money you spent you could have bought something newer !!

One of those things now your in to deep to not keep this one for another 1/2 a million miles or so..

Good cold starts means to me that fuel pressure is not dropping over the long term..

this is a different problem to be sure.

just a thought if the bearings in the fuel pump are starting to wear after sitting for 30 minutes they might be tighter then normal reducing pump rpm and hence pressure. Plus the reduced voltage from cranking as well.

This is just a thought nice when things fail and are easy to find.

I for one am waiting eagerly for a good outcome to this problem.

 

Hi Wyoming!

We are eagerly awaiting a call from our new mechanic. He put the new fuel pump in yesterday morning, and as of last night when we talked to him, no more hard warm starts. No rust found in the tank, and wires looked good (I'd read about a guy who's lead wire, or maybe his sender gauge, were totally charred/melted when he opened his up). He wanted to keep it overnight, said he wanted to drive today some, to be sure pump is truly the cure to the hard warm starts.

He also inspected all of our front end stuff (R & P, shocks/struts, wheel bearings) and that was good news. He said we could put all of that off for at least a year/12,000 miles, and was surprised someone else had told us they needed to be done now. And, we just realized today that we've got a lifetime warranty on our shocks, so that will pretty much eliminate that expense, because my husband (the real Oregon Taco) can do all of the labor on that stuff.

We're expecting to hear from him anytime now, to tell us to either pick up and finally be done with repair mode (at least til we deal w/front end stuff this fall), OR to tell us pump wasn't the fix.

Guess which one I am nervously hoping and praying he says???? : )

Will post end results when we know, thanks for your help! Happy Saturday night!

 

Well ??

Is it back to the drawing board ??

Or the partying from a ordeal now over is still going strong??

Then your trying to stay ahead of the hangovers.

 

Pump was replaced, but still hard warm starts. Then our mechanic found 2 bad injectors. So, those are being replaced, and the other 4 are being rebuilt again. Meaning, the engine guys SAID they sent all 6 out to be cleaned/tested, then 2 came back bad, so those were SUPPOSEDLY replaced, and the other 4 were reinstalled. So we are now paying for a second time for a service that was already SUPPOSEDLY done. We will be having a conversation with them about that. In the meantime, we wait til the injectors are ready and put back in, then we shall see if we have actually finally found the cause of the hard warm starts. The good times continue.......

 

Wyoming, I hope you're still looking in on this thread.

New info - injectors were all freshly cleaned/tested/2 bad ones replaced/reinstalled.

Hard warm starts still present.

Then our mechanic found, using a noid light, that all 6 injectors are not receiving pulse during hard warm starts, but they are all receiving pulse at other times.

He was going to check the cam and crank sensors next, and also the MAF (even though these are things that we've been assured were checked by engine guys). No word on the results of checking these yet.

Does the new info trigger any light bulbs for you?

 

ECM!!!

Either the ECM or the igniter is being effected by heat soak it seems.

If it is The ECM it could explain the MIL not always tripping.

Your in far to deep to quit now

 

WYOMING!!! Uploading photos now, we're pretty sure we found the culprit......

 

Our new mechanic found this and said it looked like someone took a chisel too it. He's replacing it as we speak and we're bringing her home tonight, after 2 months of PURE HELL. Those wonderful engine mechanics will be hearing from us.......

 

I hope this does it .

I will keep my fingers crossed .

We will see.

 

At least some parts got replaced that were actually bad and it'll probably run better when you get it back. Like mentioned the older our vehicles get the less the expensive certified dealership mechanics actually know about them. If that's the way it is we might as well just throw parts at the problem ourselves, at least ya get some new parts instead of nothing but excuses.