SOLVED! Post 2853 Leaking Injectors, Dealer Techs Rock! Extended Cranking after Engine Swap 3.4L 5vz

Well, I think you have enough experience to go ahead and change that sensor. No sense waiting for your mechanic.

 

http://www.obd-codes.com/p0120

WTF should we do? try changing the throttle position sensor if they're cheap enough? This is what the article says:

Potential causes of the P0120 code include:
Sticking throttle return spring
MAP or TPS connector corrosion
Misrouted harness causing chafing
Bad TPS
Bad PCM

Potential symptoms include:
MIL (Malfunction Indicator Lamp) illumination
Misfiring at idle or at highway speed
Poor idle quality
Possibly won't idle
Possibly starts and stalls

Koditten, how's the whole TB assembly on your 98? is it by chance for sale right now? if it's that "sticking throttle return spring" that's the problem, to me that sounds like replace the whole assembly. I know those engine dudes cleaned the TB, and considering the evidence of how "careful and gentle" they were with all else on our truck, sure seems possible that the spring got messed up, especially with it being 17 years old.

 

I haven't seen one, but I would just clean it up really well and lubricate any spots that might need it to see if things will move more freely. The fact that it roars to life with the throttle wide open kind of points to the butterfly/blade not being where it is supposed to be all the time, so that may be the issue. The TPS is only 35 bucks, so maybe worth swapping that out if it has not already been done.

 

Thanks TenBeers, that's a really good point about the roaring to life thing. Calling around for TPS now to find best price/brand/convenience now. Printed FSM pages about this whole topic, will review those in detail now too.

It has GOT to have something to do with the position of the hood. The number of hard starts we've had and we've NEVER gotten a code until now, when the hood was just barely up, maybe 1/4-1/2" above the side body panels. Still puzzling over that part...........thoughts? Seems like the key to knowing EXACTLY what is wrong (bad sensor, bad wire, bad TB, etc) is in that piece of info....

Attached is the FSM file on what it means/what to do when you get this code....I'm gonna devour every word of it NOW

FSM diagnostic trouble code chart says when you get a P0120, the 3 most common "trouble areas" to check are:

1) open or short in throttle position sensor circuit
2) throttle position sensor
3) ECM

But it seems to me if our ECM was smart enough to adjust the timing, and smart enough to throw a code when started while MAF was off, and smart enough to throw a code for this, it can't be totally idiotic, right?

It does make me very nervous that the other article I linked in my previous post listed a "Misrouted harness causing chafing" as a possible cause for getting this code. Do you guys think that means the worst, like replace all the wiring to the entire truck, all new wiring harness period type thing, or is this more like, tweak/replace some wires that run between TPS and ECM type easy/cheap stuff?

Promise won't freak out, chime in with thoughts, please!! We finally have some solid data to work off of guys!!!!

 

Let's step back a second. You said that with hood open the truck tended to start good. Is there a chance when you slam hood closed, you jar some wired and the sensor looses communication?

You may have a wire that is cut and is randomly reconnecting. The mechanics had to move the wire harnesses to pull the engine, there may be cracked wire under it's insulation.

Put your scan gauge on the dash facing the engine compartmente, have is set to TPS, start truck and start wiggling wired. Watch to see if the number on the gauge stays static.

 

I wouldn't think the hood would have anything to do with it. Even if it was way out of adjustment, I don't think it would come in contact with anything that is in its normal position.

Check the wiring harness for chafing or damage, check the connectors, and check your chassis grounds. I cannot stress this enough, especially on an older vehicle that has had a lot of work done -- even a ground that appears tight may have corrosion. Just make sure you have good wiring first, and that mechanically the throttle body is operating properly.

 

Thank you so much for chiming in guys!!

K, rereading your post again after I finish this post, but at first glance what you said it sounds like something husband and I can do this evening. Just glanced at your post again, and I think I see what you're getting at......

Ten Beers, the hood has got to have something to do with it! It just has to, at least in my mind! We've had probably at least 100 hard starts in past 1.5 months, and no codes. But popping hood up just a hair above it's "new normal" closed position then having a hard start while it hood was positioned like that set a code? Gotta be related somehow....

Calling around for that sensor now, have instructed hubby to read the FSM file I attached above to understand steps a Toyota tech would take if this code came up, then we can decide whether to start with swapping sensor vs testing, based on costs, difficulty of testing, etc.

But K, I like your advice - that sounds easy enough, and it's free!

I am so excited you guys, we might be really close to ending this misery!!!!

EDIT: K, if we do what you said:

Help me understand here - are you thinking the TPS number on Scan Gauge should move or should not move if the wire is bad?

 

I think you are over thinking the hood a bit. How many times has that +10 year old piece of metal been opened and slammed in the last 2 months? I'm guessing things are just coming a bit out of alignment with all the stress of being opened and closed hard so many times in such a short period of time.

 

Exactly!! That's my point! I'm sure they are! Not trying to blame anyone for hood being weird, and definitely agree, not normal to open/close a hood that many times in such a short period, and of course it's logical that things will misalign after all that's been done on such an old truck!! For sure.

But I'm hammering that point because how can having it raised a hair not have something to do with a code finally being set for that thing, after all those times of hard starts with it closed and NO CODES? I don't know, maybe it doesn't mean anything, I will definitely admit my mind is RACING right now because this is the first piece of solid data that could actually explain our problem!!!!

 

I still think the hood thing is a coincidence, but I looked up some photos and the throttle cable is the highest part of the engine and probably most likely to be interfered with by the hood. But there should be PLENTY of room between that and the hood. And not sure that would throw the code you are seeing. Shine a flashlight under there and see how much clearance you have.

Anyway, at the very least you have something to chase now. Make sure that assembly that the throttle cable attaches to moves and returns freely.

 

Just remembered we took a photo of our TB back on 1/18, right after we brought it home for the 3rd and final time from engine guys. They'd just swapped the IAC valve, and also cleaned the TB. They'd told me our TB only had mild residue, whereas normally they are coated in gunk, so initially they hadn't cleaned it. But when I took it back that time, I asked them to clean it anyway, for lack of a better plan on their part or ours. This is a photo of what it looked like after they cleaned it, FWIW.

EDIT: where the heck is the TPS anyway? is it visible in this photo? And where's the wire to wiggle, is it visible in this photo?

 

TPS should be connected to that 3-wire connector on the left in the pic. Inside looks good, but the spring on the right on the outside looks pretty dirty. That butterfly needs to move and return freely.

 

OK, attached is the same photo of our TB as the one I posted earlier, but this one has markings.

Is the red circled area the TPS? Are the wires coming off of that the wires we'd be possibly questioning?

Is the blue circled area the butterfly valve? More specifically, is it that black rectangle bar going across the throttle plate with 2 screws in it, which I'm guessing allows the plate to open and close?

Is the spring you mentioned attached to it? I know you said it's on the outside - can you help me understand where exactly?

 

Husband's been reading the attached FSM document, which is the file about how to proceed with testing/troubleshooting when you get this code (P0120). This was his email to me after reading it, does it sound like he's on the right track?

"we are hoping for condition 3 of DI-179. also, it states that we would have gotten three codes if it was a loose ground wire, so we know it is not that. i will use steves multimeter tonight to check voltages. also, i should pick up a new sensor someplace anyway, because i can always return it. good job honey!"

 

Yes, exactly.

Yes, the valve rotates on the rod going through the center. The throttle cable attaches on the right, and there is a spring to return the valve to the closed position. Have your husband press the throttle to the floor while you watch under the hood, you will see what I mean as the cable moves. The TPS mounts to the opposite end of the rod and measures the position of the valve.

Do that test with your husband and you should see what I mean.

 

Gen, as per our PM, the calibration I was referring to applies to much later models.

P0120 is more likely to be a loose connection than a problem with the sensor itself. Nothing hard and fast here, just more likely than if you had a P0121. Check that plug on the rear of the t-body.

Senior day, heading to the liquor store. More on the TPS when I get back.

 

Thanks DP!

 

Shit! I was just at the booze store, never even thought to check for that Buffalo stuff

 

Man, is it me, or do a lot of us on this thread seem to frequent our local liquor stores A LOT??!?!?

Makes me feel better though - sometimes I'm wondering if it's bad that they recognize me so easily there. Good to know I'm not the only one who is there once a week........errr, I mean, once a month, um yeah that's it!!

 

Kinda like what Koditten said here, is why I still feel like the position the hood rests in when closed somehow has something to do with this. Not that it's the sole cause of the issue, but it's gotta play a part somehow because why else would it have taken THIS LONG to set a code, and the only diff this time was the hood being just a teensy bit elevated from a closed position? We did start it at least 2x (maybe more, not sure) back in mid January with hood up all the way, and one of those times it started right up, but the other time it was excessive cranking. Just looked it up on a post I made way back from that time, that's how I know for sure on that.

But since then, our mechanic reset the ECM. Which means right now, the ECM is supposed to be in a mode where it's relearning all of the sensors. So I feel like that, coupled with cracking the hood a bit while starting this time - that somehow all of those factors play a part in this. Don't know how, but they gotta be related. We've literally started that thing AT LEAST 100 times with hood down, and probably at least 20-30 times or more since ECM was reset - always with hood closed all the way (which now means closed more than it should be since it's not situated right).

Somehow that HAS to be playing a part here, dontcha think? Again, not saying it's the root of the issue at all, but that something (like K is saying above) could possibly be getting pinched or something, and maybe that something is already faulty.........I don't know............anybody care to attempt to complete this half assed thought I'm having?