Starting problem help

I have a 2000 V8 4WD with 305k miles on it. My issue is that when cold starting, the engine will crank over 1 or 2 times, act like it's gonna stall out or die, and then all of the sudden start. When hot starting, the engine will crank over like 5, 6, or 7 times (I don't know the exact number, I just know when it sounds right) and then start normally.

I was having a few issues like acceleration hesitation and the cold start issue, so I did some extensive repairs to try and fix the issues, as well as replaced parts from some long delayed maintenance.

Does anyone know why the problem with cold starts might be happening?

Things I recently replaced (all toyota OEM or denso parts):
-Fuel Pump
-Fuel Sending unit/fuel gauge
-Fuel pump filter screen
-Fuel Pressure Regulator
-Fuel Pulsation Damper
-Fuel injectors (Dirty Deeds 12 hold injectors)
-A couple fuel hoses that attach to the fuel rails and intake manifold.
-O2 upstream sensors
-Throttle body
-Throttle body gasket
-Intake manifold gaskets, upper and lower
-PCV Valve and PCV Valve gasket
-Valve Cover gaskets
-Spark plug tube gaskets
-Starter motor - 2.0 kW (cold package starter)

I'm at a total loss here. Any help will be much appreciated. I've got an appointment to take it in to the dealer to get diagnostics ran, but I don't want to get raked over the coals since I've already spent so much money on parts and my time replacing them.

Am I making too big of a deal and the ECM just hasn't reset itself? No CELs have come on since...

 

Did you do anything whatsoever to test the battery or its cabling? Like ...

• Have a local store test battery for CCA, not just voltage? (Batteries tend to exhibit less CCA performance in cold weather, and voltage verification is a bullshit, inadequate way to test a car battery)
• Loosen your terminals to verify their integrity, check for any cracks, loose shims, andclean them up? This is one reason why right here.
• Verify there isn't corrosion inside the cables? Here's why I bring it up.
• Verify all grounds in the engine bay are OK? (And maybe consider running a temporary ground direct from the battery to the block)

I had one case where I turned the key and everything went dead. Like, dead-dead. I posted about it once or twice. I'm convinced it was my terminals, which looked totally OK, but you see what was inside the cabling in that 2nd link. I'd consider doing the simple task of verifying or replacing your terminals. It's been almost 25 years running on those terminals. They've had a great life.

 

Thanks for your reply, shifty. How extensive of a task is it to replace the battery terminals and wires?

And I think I probably confused everyone by saying cold start when I really mean the engine isn't warmed up. It's about 65 degrees out the last few days.

 

I'd still go through that bulleted list. I'd ballpark 50% of the time starting issues are battery/cable/ground related. about 5% of the time it's starter, about 25% of the time it's relay/coolant temp sensor/other electrical, or related to a former or existing alarm install. probably 10% of the time it's one of the things from the megathread, note the last couple of sentences here:

• These trucks usually don't have a ton of other electrical issues. Hidden corrosion inside the battery/alt cables happens. Sometimes, a couple thousand miles after timing belt changes, people will have startup issues because the crank position sensor wasn't properly tucked away and gets rubbed by a belt (pic). There's also a similar problem with camshaft position sensor under the cam cover, where the belt will rub through (pics). There's the rodent issues mentioned earlier. Occasionally, water leaks can send water down into the ECM behind the glovebox (pics), or into the fusebox inside the cab/dash (pics & pics & pics, it happens a LOT). Many drain/vampire issues trace back to aftermarket add-ons whether the owner knows they exist or not - alarms as mentioned earlier, brake controllers, poorly installed trailer receptacles, those are some big ones.

The other percent of times, people don't figure it out, or don't bother to let us know. But because cabling/battery/grounds are so often the source of starting issues, that's where I would've started my hunt.

That said ... if you have cracks in your windshield, or have had water in your floorboard, I'd be suspicious of potential water intrusion.

 

I replaced the positive battery terminal, cleaned up the negative as best I could. Still having the cold start issue. Also took out the ECM and it was fine, no water intrusion on it or anything between the glove box and the firewall, that I could notice. Same with the fuse box on the driver's side.

Having replaced so many fuel components recently, is there any reason to believe that it is a fuel system delivery issue?

When you say run a temporary ground from the battery to the engine block, what does this do, just show that it could be a grounding issue?

Also, what is the likelihood it is the coolant temperature sensor?

Any chance it could be the fuel pump resistor?

 

Before I answer your other questions, have you had anyone hook a professional battery tester up to your current battery yet? Not a DMM/voltage meter, but an actual battery tester that will confirm CCA?

 

I have not. I guess I better go get that done today.

 

So I went to get the battery tested. Test came back that battery is fully charged and cranking amps match what is listed on the battery. Was close to the dealership and they said they had a coolant temperature sensor in stock, so went by to get one since it's probably never been replaced anyway.

When I tried taking off the sensor, coolant started leaking (which I expected but just wanted to test, and now I need to drain it a little) so I tightened it down again. When re-tightening it to stop the coolant from seeping out, the connector twisted off the sensor and this is what the internals look like. I'm assuming this is bad...

 

I would definitely say it's not good.

That should be the green one, which is what feeds the ECM - the one to the left of it feeds the gauge cluster on the non-VVTi 4.7L like you've got.

One guy on here a long time ago reported when he failed to hook his back up after timing belt swap, the truck wouldn't start. Wouldn't even turn over. So, since it's already fucked, may as well put in the new one and see if it turns over. If so ... lesson learned!

If that does solve it, let us know. I know I've seen this info once on here, maybe twice. Would be nice to have another confirmation.

 

Yeah, I can't tell if it's some sort of corrosion or if it's just the plastic from the mold when it was created that has slowly dried up. Good news is I have a new one to put in.

Good lesson learned about using a socket on that sensor, too. Don't use a socket because the connector sticks past the actual flat parts of the nut. I used an open ended wrench to put the new one on.

Started up fine when warm. Going to wait for the engine to cool down all the way and then start it up again and see if that fixed the issue. Fingers crossed.

 

So after waiting for it to cool down after replacing the coolant temperature sensor, it's still doing the same thing: cranks over two or three times, then acts like it's going to stall, then somehow manages to start, I'm guessing from the momentum that was generated by the first 2 or 3 cranks.

What else could be the problem? I'm at even more of a loss now than I was. I just don't get it...

 

When I think of cold vs. hot start issues, i.e. temperature is an issue, I almost always think resistor or similar component thing that's impacted by heat.

Without digging into the FSM, which is linked in the sticky megathread, I'd toss out a guess, have you tried bypassing the fuel pump resistor with a jumper? This is what allows the fuel pump to run in low-pressure mode, by reducing the voltage to the pump.

​

 

I see a whole list of things you tried but have you cleaned the MAF?

 

And to your point, that's another part that's impacted by heat/resistance. Good call.

 

I cleaned the MAF about a month ago pretty thoroughly to see if it would help the situation. I usually keep it pretty clean.

 

I took the resistor off to test the ohms with a Klein MM that I have. The 2M, 200k, 20k and 2k settings all seemed to big and yielded no results, so I set the MM at the 200 mark. The leads themselves have an ohms reading of 0.2-0.3 and the actual resistor has a ohms reading of 0.9 - 1.0. So Minus the 0.2 of the leads, the resistor should have an ohms reading of 0.7 - 0.8, which is in spec, based on the test procedure from the manual I found here:

https://www.tundras.com/threads/2006-double-cab-fuel-pump-no-power.36822/

Unless I'm a total idiot and didn't do the readings right, I think the resistor is fine.

 

Something I noticed that is interesting, don't know if this should be happening or not. When I turn the ignition but not crank it, I can hear a hum in the engine bay. If I press on the gas one time, the hum becomes louder and more intense. Does anyone know what this is and if it should be happening?

 

Question before I toss out a thought: Have you popped the hood to feel around on relays and such under ther hood, to pinpoint where it's coming from?

 

It's coming from the throttle body, somewhere. Can't pinpoint exactly what it is. Just replaced the throttle body.

 

I kind of doubt anyone is following this, but for future reference, I also took out the aftermarket alarm that has been in there for years. I don't know if this is gonna help or not, but we will see. This alarm was such a piece of junk and was installed so poorly. How and why they splice them like they do should be a crime.

 

That’s one of those things I almost always ask about. There’s just so many avenues to cover in these situations; it’s hard to remember suggesting to check them all…

 

My 2000 only makes a noise after pressing the gas pedal. Never noticed until now because I have never pressed the gas pedal before starting.

 

So after removing the aftermarket alarm and double checking the grounds around the truck/engine bay/etc, I'm still getting the weird start problem, where it will, when "cold" crank 1 or 2 times, act like it's gonna stall, and then all the sudden start up. I don't know if this is something that anyone else has had issues with, but if so, I would be more than grateful if you chimed in.

I actually bought the bluetooth OBDLinkMX+ scanner to look at fuel trims and the trims are mostly negative. The STFT on bank 1 and 2 both range anywhere from -4.0 to 4.0. LTFT as much as I could get a reading for, ranged from 0 to -2 on Bank 1 and stayed pretty close to 0 on Bank 2.

I'm thinking that there might be a MAF issue (which I tested resistance for and it came back in range) or a compression of the cylinders issue that isn't pulling enough vacuum. Or, since I've unhooked the negative battery terminal so many times, wondering if I also just need to leave it and drive it?

Honestly, I'm still banging my head around because of this and have an appointment for Thursday to take it into a reputable Toyota mechanic. Tomorrow I'm going to measure compression at each cylinder and I hope with everything in my body that compression is in range for each cylinder and across them all.

Anybody have other ideas?

Also low key suspecting the Throttle position sensor might not be adjusted correclty from factory? I bought a brand new throttle body assembly and the TPS came with it already installed...

 

How did you re-attach the wiring after removing the alarm? If you did it properly and either butt-spliced or solder/wrapped, did you tug test each wire?

Usually folks report odd running issues when neg batt cable is off for a period of time. Not latent starts. And you could potentially see everything all-over-the-place, because the ECM is relearning.

On the TPS, you could always toss back on the old one... right?

 

I used butt splices since soldering and wrapping were out of the question since the wires weren't long enough to connect/solder/shrink wrap. Butt splices gave me a little extra length. I tugged on all the connections and made sure that they were shored up.

I could try tossing the old TPS on, though I am a little worried about how some folks have had issues when just replacing the TPS and not the entire throttle body with TPS already installed. They have reported a range of issues when trying to get it turned to just the right angle. Maybe I'm missing something about the install they're doing.

 

Wanted to bump this thread back up to the top.

After weeks of diagnosing and trying things, I still haven't fixed the issue. As it stands, the starting problem issue has actually gotten worse in hot weather.

To revisit, these are things I have tried to do in order to fix the issue:

-Replaced starter (twice)
-New Intake Manifold Gaskets (twice)
-Swapped back my old ignition coils
-Swapped back the old fuel pressure regulator
-Swapped back the old fuel pulsation damper
-New Fuel Filter
-New fuel rail washers
-All new fuel supply hoses from tank to fuel rail
-Cleaned up fuel rails really well
-New injector o-rings, seals, grommets (replacing the new ones that came with the 12 hole set, as advised by Keith from Dirty Deeds)
-Removed the aftermarket alarm.
-Replaced Coolant Temperature Sensor
-Replaced Crank Position Sensor
-Replaced MAF
-Replaced PCV and hose
-Tried swapping VSV valve and charcoal canister with ones found at a pick n pull to see if it is a strange vapor lock issue
-Cleaned up all grounds around engine and battery terminals
-Vacuum gauge test - Reads at 18, no flickering. Assuming engine is in good health.


The only thing that I didn't change was the injectors themselves, which I ended up changing out with a new set that I re-purchased from Dirty Deeds (now I'm in over 700 bucks on fuel injectors), to see if maybe the set I got from them to start was bad. I put in the new set, same thing.

After taking it to the dealer for a second time and them telling me nothing is wrong, again, the only thing left to try is to swap back in the old 4 hole injectors (which I just got professionally cleaned and rebuilt).

Has anybody had issues with the 12 hole injectors? I'm wondering if there is some sort of vapor lock issue with the 12 holes that doesn't exist with the 4 holes, like the fuel system is building up heat and then the 12 holes atomize too much, and not enough "liquid" gas is getting to the intake...

 

When heat is a factor in making things worse, it's usually an electrical problem, i.e. there's a resistor involved somewhere that's not working as expected.

Like ...

The temp sensor the ECU uses (there are two, side-by-side on passenger side of TB on the early models) is faulty, and it can't get a signal - ECU won't allow start if it can't sense if it's overheating, supposedly. But you replaced that.

Fuel pump resistor, if the truck starts with the fuel pump in low-flow mode, it's passing signal thru the fuel pump resistor; if hot/not working, resistor may over-restrict or stop flow of power entirely, i.e. pump no energized.

Don't disregard that it's possible it's corrosion inside wiring.

 

Yeah, that all makes sense. I definitely don't think it couldn't be a wiring problem. I just find it very "coincidental" that it started to happen after I put in the 12 hole injectors. Of course, if that is a crazy coincidence, it wouldn't be the first time someone experienced strange timing in failures.

I forgot to add that I replaced the fuel pump resistor, too.

 

It is weird that it started after the injectors, unless...

Again, HEAT, connections tend to expand/shrink with heat/cold. So when you said this started right after the injector install, I'm just spitballing here... but what if you popped off a connector and bent/cracked a pin during that process? Or broke plastics, in a way that, when the engine is hot, either the connection lifts off (because a tab broke for that connector), or a bent/broken pin which is difficult to see is the issue? We've also seen cases where people have gone to check connections on things (crank position sensor, coolant temp sensor), either the connector has disintegrated the next time it was taken off, OR the sensor body snaps in half, especially with those two sensors I just mentioned, specifically.

Maybe think long and hard about every connector you needed to pop off or remove when doing the injectors. Maybe recheck, try pulling the connector without unfastening to see if it comes up, and if not, pop it up, tug on each pin, look inside the connector for bent pins, etc.

 

Great advice, I appreciate your input on this as car problems can get pretty lonely at times. I will re-check every connector and pin when installing the old 4 hole injectors. If checking all connectors and pins and installing the old injectors doesn't solve the issue, then I might be SOL and will need to go back to the drawing board.