HELP! Knock sensor r/r and now it won't start

[Lefty JD]

Edit: see post #12 for solution!

So I was getting a knock sensor code. 4R ran when I pulled it in to work on it, albeit down some power and MPG's. Replaced both sensors and the harness, took my time. 3.4 with a supercharger on it, I installed the s/c maybe a year ago-so I've had the intake off before. I changed nothing but the KS's, harness, and a new intake gasket. Didn't touch the coolant crossover, intake valley was nice and dry.



Now it cranks just fine but won't fire. Like it doesn't even try, starter just spins the motor.



Things I've checked:

-Pulled #1 coil pack and grounded a plug, it sparks

-Has fuel pressure to rails

-Get flashing test light when I hook up to the fuel injector leads (I assume thats

indicative of fuel injectors getting enough signal to flow?)

-Pulled plugs, they are wet. Brake cleaned them off, whirled motor over w/o

plugs to blow out the cylinders.

-Tried starting fluid, makes no change.



-OBD reader shows ~175rpm while rolling engine over with the starter, so

crank position sensor should be fine.

-Can't find any unhooked vacuum lines, ground wires etc.

-Checked the EFI/ECM fuses in the under hood box and under dash panel.

I swapped them out and no change.

-Tried both plugged in and unplugged MAF and Knock sensor harness. No

change



What am I missing? I need to get this thing running, it's over 100 out and it's kicking my butt being outside wrenching with zero progress. And yes I used search and read about a dozen posts, anything close I tried the solutions suggested.

 

[rideexileex]

Try checking other wire harnesses too - throttle body, etc. Some of those sensors prevent firing

 

[spartacus]

if every thing wss hooked up right and you have fuel ,spark and compression then make sure the shift lever is properly engaged in park or try starting in neutral.

 

[19963.4lsr5]

So you have no spark? Or fouled spark plugs.


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[Lefty JD]

I seem to have spark, as I pulled #1 plug out of the head and grounded it, definitely sparks as I roll engine over with the starter.
I changed passenger side plugs to fresh ones, still doesn’t even try to start...so if they were fouled I’d think having half new plugs would at least cough and sputter here and there?
Kinda at a loss....have spark, fuel, gotta be getting air in. What the hell?

I hate to just peel apart the whole top end without any known reason-these old wire harnesses get brittle after all these years, and gaskets add up.


Sent from my iPhone, so probably some stupid typos and autocorrects

 

[Lefty JD]

make sure the shift lever is properly engaged in park or try starting in neutral.

Wouldn’t it not turn over at all, if Park/neutral safety switch was malfunctioning? Or does it work differently on these than my old cars?


Sent from my iPhone, so probably some stupid typos and autocorrects

 

[19963.4lsr5]

I seem to have spark, as I pulled #1 plug out of the head and grounded it, definitely sparks as I roll engine over with the starter.
I changed passenger side plugs to fresh ones, still doesn’t even try to start...so if they were fouled I’d think having half new plugs would at least cough and sputter here and there?
Kinda at a loss....have spark, fuel, gotta be getting air in. What the hell?

I hate to just peel apart the whole top end without any known reason-these old wire harnesses get brittle after all these years, and gaskets add up.


Sent from my iPhone, so probably some stupid typos and autocorrects

The 3.4 uses wasted spark. It fires through two plugs. But I see what your saying. Lay a plug on the VC of the drivers side and see if the spark is blue-white in color. Your cam sensor is plugged in? My 4Runner won't start without the MAF sensor plugged in but you mentioned it already.


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[curryT4R]

Take a look at your crank position sensor wire. I did a timing belt on a 4.7 a couple years back and didn't route the crank sensor wire behind the fan bracket so it rubbed up against the drive belt and shorted it out. It would sit there and crank over but would never start.

 

[Lefty JD]

Today:

Pulled supercharger off to look for anything I missed. Didn't find anything unplugged or installed wrong. Vacuum lines are correct. Lower intake manifold looks to be bolted down without pinching anything or other bonehead moves.

All new spark plugs (IK22's, same as I've been running). Old ones were wet and funky when I pulled them. I Sprayed a bit of brake clean into each cylinder and whirled the motor over to clear out any funk in the chambers.

Cam sensor is plugged in, and Ohm tested good. I never disconnected it anyways, but rules that out at least.

Both sides of the engine give good spark to a grounded spark plug.

Per my OBD reader, while I turn motor over with the starter:
140rpms
.7 Liter/hour fuel consumption
5* ignition advance

Motor hasn't even sputtered with starting fluid, brake cleaner etc.
And ZERO progress :frusty:

 

[19963.4lsr5]

This is a dumb question.

You have fuel....you have spark.....your timing should not have changed. Air is the only thing left.

Here is the dumb question. Is the supercharger spinning the proper direction?

Is something messed up with your IAC that it's not getting enough air to start? Pull off the PCV line from the intake manifold and see if it will start.




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[Lefty JD]

Not a dumb question-all the reasonable ones I can think of are already off the table. Supercharger is spinning the correct direction. And while I haven't ever messed with the IAC, I have tried hitting the gas pedal while cranking, that would open the throttle body butterfly for plenty of air.

I gave up for the day. If an epiphany doesn't hit me -or get posted- I'll probably go get the tow dolly tomorrow and take it to a mechanic. I've wasted almost 3 days of free time, and frankly I'm out of patience for my version of uneducated guess and check in this heat.

Definitely have gas, have spark, have compression (hand over plug hole blows out as normal). What gives?

 

[Lefty JD]

Updating in case it helps somebody out in the future:
I was all setup to take it to a buddy’s shop. He knows I do my own work so he asked what was up to have me bringing it in. I told him the sequence of events (manifold off, sensors in, reinstalled everything and no start).
He immediately said “I know it doesn’t make sense, but pull timing cover and check belt/cam timing.”
He went on to explain years back at his shop a mechanic did that same job, followed by super rough running 3.4. After extensive diagnostic it turned out a missing bolt had ended up down in the timing cover and got under the belt, skipping a tooth or two. It threw them for a loop because cam timing isn’t normally touched during the process. Same reason why I didn’t pull the cover off to check it before this either.

As it turns out, that’s exactly what happened to mine. While lifting the back of the manifold, one of those front washers looks to have slid forward and dropped into the timing belt area. I could see where the belt teeth had some witness marks and the cam/belt marks no longer lined up quite right, off about 2 teeth on the passenger bank.

Belt was close to service time anyway-new belt and she starts right up! Yes I did the normal other stuff while I was at it.

Now I owe my buddy some beers for helping me out over the phone m, saving my wallet some cash.

 

[HiLife]

Thanks for taking the time to post what the problem was and how it was ultimately solved. This proves when a problem occurs, one should really double check/baseline all the areas that could possibly cause the issue.
Who would've thought the cam timing was thrown off by a washer/nut!!