Working out some bugs after a HG job

Ah, where to begin?

Saturday, Feb. 13th, I was doing doordash in my 2002 Limited. I got a few orders out and I was hyped because it was paying well due to the snow and how insanely cold it was out. I pulled up to a McDonalds and picked up the order, started the car, and it started running super rough and I started to smell coolant. Like, very strongly. I went outside to check it out and the thing was dumping white smoke out the exhaust. Keep in mind, the engine was definitely warm from the previous couple of hours of driving. I will mention, the 10-15 mins or so prior, I did notice the engine sputter a few times, and just during normal driving. I wasn't accelerating and it wasn't under crazy load or anything.
So that night, I arranged to have a tow truck take it to a local mechanic. The next morning, I decided to bring it back to my house because I figured a mechanic would charge me at least a couple grand for a HG job, since I thought that's what the problem was. So I got the car back to my house on the 14th, and the work began the following week. Fast forward just over two months. I've replaced the headgaskets, resurfaced the heads, replaced a few odds and ends, and finally gotten the motor back together. And now it won't start.

It won't start. It'll crank and sometimes it will sound like it's about to start and whatnot, but it won't. Occasionally I'll get a pop in the intake or the exhaust, which I've heard is a possible symptom of incorrect valve timing? So I checked and with the crank at the 0 mark (top dead center cylinder 1, right?) both cams line up. And yes, I do have both my intake and exhaust cams on both banks aligned with that little dot lining up on the teeth. Fun fact to note before I forget: I have the 3.4L V6. I also checked my spark plug wires and those are all in the correct places. Help.

ps sorry my writing is awful

Usually when I see a post like this it’s a cam or crank sensor not plugged in after the repair. Also make sure your MAF is plugged in. It will not start with that unplugged.


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I hope you ensured correct bore and compressed thickness with the gaskets, failing to nail both can lead to your engine running radically different. Can even drastically effect compression ratio. Just something to think about, never done the HGs myself but this is VERY commonly overlooked across all cars (though it typically only becomes an issue when straying from OEM).

Like the other poster said, probably an unplugged sensor.

Also, careful not to mix up these hoses on the throttle body, or you'll puke coolant into the intake, engine won't start and will sputter sometimes like you (happened to me)

As for your valve timing, which I doubt it would be, you could do a compression test on one cylinder on each side.

Your symptoms really sounds like a sensor unplugged or something miss fitted somewhere. Go back and look at everything you touched with a strong flashlight.

19963.4lsr5 said:

Usually when I see a post like this it’s a cam or crank sensor not plugged in after the repair. Also make sure your MAF is plugged in. It will not start with that unplugged.


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Click to expand...

I have started mine with the MAF unplugged and it ran for about 1-2 seconds and would immediately die, but it ran normal for that brief period. Sounds like some may not start at all though.

Another thing to think about, did you take apart the engine harness wiring at all?
I had a harness part when doing a 5vz swap and mixed up coil pack connectors, the longest wire in the loom goes to the middle coil pack, not the front as seemed logical to me at the time, one has a red and one has an orange wire and they are easy to mix up. I can't remember which one is which but I could look in my EWD tomorrow, it is for a 97 though so I am not sure colors would be the same.

It acted like you describe, timing WAY off. It would fire sometimes, kickback the starter occasionally, just general ugliness.

I agree that it sounds like a missed sensor or ground wire.

When I did my head gaskets, I followed a youtuber's videos names "worsethanchiggers". He literally has every step documented perfectly in the multi video series. I would go back through his videos and see if anything sparks your memory of what you may have forgotten/missed.

Good luck. Its a good feeling when you get it fired back up after a job like that.

19963.4lsr5 said:

Usually when I see a post like this it’s a cam or crank sensor not plugged in after the repair. Also make sure your MAF is plugged in. It will not start with that unplugged.


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Click to expand...

MAF is plugged in and doesn't look dirty or anything. I can go back and check to make sure the crank sensor is plugged in. It was kind of difficult to find the right plugs for everything on the harness. I think I'll go back and see if I can figure out if I mixed up any of the plugs, though I'm not sure whether or not that would be possible. The cam sensor plug is in, though there is a 3rd black wire that is stripped and not plugged into anything. I've seen other threads where people have had this happen and there doesn't seem to be a conclusion as to the cause. I may end up just ordering a new one.

Devbot said:

I hope you ensured correct bore and compressed thickness with the gaskets, failing to nail both can lead to your engine running radically different. Can even drastically effect compression ratio. Just something to think about, never done the HGs myself but this is VERY commonly overlooked across all cars (though it typically only becomes an issue when straying from OEM).

Click to expand...

Yikes... ummmmm I just bought (Felpro I believe) a couple of gaskets and slapped them on there after cleaning up the block mating surface..... And when you say it typically only becomes an issue when straying from OEM, do you mean straying from using OEM gaskets??

diverscale said:

Like the other poster said, probably an unplugged sensor.

Also, careful not to mix up these hoses on the throttle body, or you'll puke coolant into the intake, engine won't start and will sputter sometimes like you (happened to me)

As for your valve timing, which I doubt it would be, you could do a compression test on one cylinder on each side.

Your symptoms really sounds like a sensor unplugged or something miss fitted somewhere. Go back and look at everything you touched with a strong flashlight.

Click to expand...

May be an unplugged sensor. An I did mix up the hoses at first, but I think I've fixed them so it should be good now. Do you know if there is any way to make 100% sure I have the right hoses plugged into the right locations? I can try to get a good picture of how I have them currently plugged in. Also, I haven't put any coolant back in since reassembling.

swapped_mini said:

Another thing to think about, did you take apart the engine harness wiring at all?
I had a harness part when doing a 5vz swap and mixed up coil pack connectors, the longest wire in the loom goes to the middle coil pack, not the front as seemed logical to me at the time, one has a red and one has an orange wire and they are easy to mix up. I can't remember which one is which but I could look in my EWD tomorrow, it is for a 97 though so I am not sure colors would be the same.

It acted like you describe, timing WAY off. It would fire sometimes, kickback the starter occasionally, just general ugliness.

Click to expand...

Oh shoooot.... I'm pretty sure I did that. The plastic harness casing that sits on top of the engine basically disintegrated in my hand like many other people have experienced, so I spent a good hour or so removing it all and wrapping the harness with some of that German high-temp high-tensile-strength indestructible goodness. But that will absolutely be the first thing I check when I get home. Thank you

Vansnxtweek said:

I agree that it sounds like a missed sensor or ground wire.

When I did my head gaskets, I followed a youtuber's videos names "worsethanchiggers". He literally has every step documented perfectly in the multi video series. I would go back through his videos and see if anything sparks your memory of what you may have forgotten/missed.

Good luck. Its a good feeling when you get it fired back up after a job like that.

Click to expand...

Worsethanchiggers' videos have been a life-saver for me. If he ever takes them down I think I'll cry. The thing I noticed though, is that there are a few extra vacuum hoses and such on his truck than on mine

sean.turner.1238 said:

Oh shoooot.... I'm pretty sure I did that. The plastic harness casing that sits on top of the engine basically disintegrated in my hand like many other people have experienced, so I spent a good hour or so removing it all and wrapping the harness with some of that German high-temp high-tensile-strength indestructible goodness. But that will absolutely be the first thing I check when I get home. Thank you

Click to expand...

I will check my wiring colors for you today but I can't be sure they are the same as your 2002. But I am guessing the harness length will be the same, longest wires to middle coil pack. Good luck, hope it works!

While Cranking, take a look at the coolant inside the radiator (DO IT WHEN COLD). If coolant is bubbling, compression is escaping into the cooling system. I saw that in my corolla after doing my first HG job. Then went and re-torqued all head bolts and no issues ever since. I am at 50K miles since the HG job.

swapped_mini said:

I will check my wiring colors for you today but I can't be sure they are the same as your 2002. But I am guessing the harness length will be the same, longest wires to middle coil pack. Good luck, hope it works!

Click to expand...

Thank you. By the way, did this occur with just one side? Or was it both sides

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sean.turner.1238 said:

Thank you. By the way, did this occur with just one side? Or was it both sides

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harness and coils are only on one side, the pass side, the coils feed both sides. It sure sonds , like others have said, that something is not plugged in correctly. would be nice if its just the order of the coils and plugging them in correct.
Otherise, i I remeber correct, many of the parts have plugs that only fit that part, so its pretty hard to plug the worng plug to a sensor....the coils, all take the same kind of plug, so yuo could mess up the order I guess.

3bears said:

harness and coils are only on one side, the pass side, the coils feed both sides. It sure sonds , like others have said, that something is not plugged in correctly. would be nice if its just the order of the coils and plugging them in correct.
Otherise, i I remeber correct, many of the parts have plugs that only fit that part, so its pretty hard to plug the worng plug to a sensor....the coils, all take the same kind of plug, so yuo could mess up the order I guess.

Click to expand...

Agreed. And since each coil pack fires two cylinders if they are switched 4 will be firing at the wrong time.
Only likely to happen if the wiring harness is pulled apart. The wire for the middle pack goes all the way to the front of the factory plastic loom and exits at the same place as the wire for the front coil pack. Then has to go back to the middle plug, hence why it is longest.

3bears said:

harness and coils are only on one side, the pass side, the coils feed both sides. It sure sonds , like others have said, that something is not plugged in correctly. would be nice if its just the order of the coils and plugging them in correct.
Otherise, i I remeber correct, many of the parts have plugs that only fit that part, so its pretty hard to plug the worng plug to a sensor....the coils, all take the same kind of plug, so yuo could mess up the order I guess.

Click to expand...

Lol duh nvm

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swapped_mini said:

Agreed. And since each coil pack fires two cylinders if they are switched 4 will be firing at the wrong time.

Only likely to happen if the wiring harness is pulled apart. The wire for the middle pack goes all the way to the front of the factory plastic loom and exits at the same place as the wire for the front coil pack. Then has to go back to the middle plug, hence why it is longest.

Click to expand...

May have happened actually since I unwrapped a lot of the factory tape to wrap it with my new stuff.

Moment of truth in 15 mins when I get home!

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Well boys she fired up. It was the backwards coil pack connectors.

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