Dies right away after backfire/manifold change

[itsdaveman]

1997 Explorer 4.0, 4WD

About a month ago I went to start it and it backfired, blowing the plastic intake apart. I got another one from the junkyard, put it on, and now it does this:


http://youtu.be/SsSDjdvi6vE

(Sorry, I tried to embed it but it didn't work.)


It's obviously getting fuel. I'm almost certain I have the plugs wires correct. There's power going into the coil, but there doesn't seem to be power coming from any of the three signal wires from the computer. I'm not positive I had a good ground for those though, and it seems by the fact that it's firing that it's getting some spark.

Any ideas? Thanks in advance for any insight you may be able to offer.

 

[koda2000]

if you got a huge backfire out of the intake, you had a timing related issue. you say it's a 4.0L v6. is it an OHV or SOHC 4.0L? the SOHC is much more likely to have timing problems due to all the timing chains and related components. if you have a broken chain cassette, or if it's jumped time it's probably time to start looking for a new truck (or at least a new engine). do a compression test to see if you now have bent valves. a sure sign of serious timing problems.

 

[rb142]

Come on Koda ... not every problem on the SOHC is the chains... Besides, i'm pretty sure this is the OHC engine anyway.

There's a lot of things this could be, and it is going to take some checking to figure it out.

You are getting fuel, but are you getting enough volume, or is it not keeping up? Are you losing spark? Is the cam sensor working? Is the IAC working? MAF? Etc.

 

[koda2000]

Come on Koda ... not every problem on the SOHC is the chains... Besides, i'm pretty sure this is the OHC engine anyway.

There's a lot of things this could be, and it is going to take some checking to figure it out.

You are getting fuel, but are you getting enough volume, or is it not keeping up? Are you losing spark? Is the cam sensor working? Is the IAC working? MAF? Etc.

well, if you get a massive explosion in the intake manifold that tells me you got a spark when an intake valve was open. that's sure sounds like a probable camshaft timing problem to me. maybe a hung/broken intake valve. how would a MAF or IAC problem cause that? BTW, in my opinion the SOHC engine is that it is a time-bomb unless the cassettes have been replaced. the OP hasn't responded as to which engine he has, or how many miles are on it. even an OHV engine can jump time if the timing set has a million miles on it.

there was a thread a week ago, or so, where the OP couldn't figure out why his engine wouldn't start. it had good compression, fuel, air and spark. my second guess was that the engine jumped time. after many conversations, guess what? it turns out his SOHC had jumped time.

 

[itsdaveman]

Thanks for the responses! Sorry about taking a while to get back on here.

It's an OHV. Something I forgot to mention which is going to be really important - I thought it was in the video - is that every few times you try to start it there will be a pop that sounds kind of like a very mild backfire and is accompanied by the smell of unburnt fuel in the engine compartment.

I've tried not to give timing issues much consideration as I don't want that to be it. Ignoring problems works, right? Someone else tried starting it when it had the massive backfire so I was hoping that maybe they were depressing the gas pedal to get it to start which advanced the timing too much which caused the backfire and all my problems would go away after changing the manifold. No such luck, it would appear.

I'm unsure of the miles off the top off my head, but it's definitely 150K+ but under 200K I think. As far as I know nothing has been replaced/maintained in the timing system in all those miles.

I'll have video of an instance of what I believe to be that mild backfire that I mentioned, I'll have it up in a few minutes.

 

[itsdaveman]

Here it is:

http://youtu.be/XLXbmGa6mLY

I guess a backfire isn't what it sounds like. More like a valve opening in a cylinder under pressure maybe...

 

[itsdaveman]

Also, it's possible that it's the SOHC. I'm basing my saying that it's an OHV off that fact that the valve covers look normal-sized compared to OHC engines I've messed with, and that I vaguely remember seeing OHV molded into the manifold.

Is there a way to know for sure? I can post a good picture of the engine if that would help. I've also heard something about a character in the VIN denoting which it is, a V or X if I'm remembering correctly. Is that the case?

Again, thanks so much for the help.

 

[rb142]

well, if you get a massive explosion in the intake manifold that tells me you got a spark when an intake valve was open. that's sure sounds like a probable camshaft timing problem to me. maybe a hung/broken intake valve. how would a MAF or IAC problem cause that? BTW, in my opinion the SOHC engine is that it is a time-bomb unless the cassettes have been replaced. the OP hasn't responded as to which engine he has, or how many miles are on it. even an OHV engine can jump time if the timing set has a million miles on it.

there was a thread a week ago, or so, where the OP couldn't figure out why his engine wouldn't start. it had good compression, fuel, air and spark. my second guess was that the engine jumped time. after many conversations, guess what? it turns out his SOHC had jumped time.

I was just kidding ... thus the smiley. Not trying to give you a hard time.

I agree about having a timing issue to cause the backfire. I was suggesting that an alternative to a chain problem, it could be due to a problem with the spark timing (thus the comment about the cam signal). Yes, a chain problem is possible, but does not seem likely here.

In the video (where it looks like the OHV, but it is hard to tell), the engine starts fine and runs for a couple seconds before dying. It wouldn't likely run like that if a chain had jumped. So the question is what is making it die at that point? Running out of fuel? Losing the spark, or having the timing move? Having the throttle close too far because the idle valve isn't working, etc?

A compression test will answer the question of mechanical timing.

OP: Are there any codes set?

 

[koda2000]

I was just kidding ... thus the smiley. Not trying to give you a hard time.

I agree about having a timing issue to cause the backfire. I was suggesting that an alternative to a chain problem, it could be due to a problem with the spark timing (thus the comment about the cam signal). Yes, a chain problem is possible, but does not seem likely here.

In the video (where it looks like the OHV, but it is hard to tell), the engine starts fine and runs for a couple seconds before dying. It wouldn't likely run like that if a chain had jumped. So the question is what is making it die at that point? Running out of fuel? Losing the spark, or having the timing move? Having the throttle close too far because the idle valve isn't working, etc?

A compression test will answer the question of mechanical timing.

OP: Are there any codes set?

i saw the smiley face and i realized you were not trying to give me a hard time. i didn't watch the video (i usually don't) but you are correct that is the OHV 4.0 engine.

 

[itsdaveman]

I'll get a compression tester from Autozone and try that tomorrow. And I don't know if it has any codes but I'll pull them tomorrow if there are any.

I tested the IACV a few weeks ago as I've had one go bad and it reacted not unlike this. However, when I tested this one by putting 12v through it, it seemed to work fine. It should just click like a solenoid, right? Also, that's how you're supposed to test them, isn't it?

Thanks for the continued help, guys.

 

[itsdaveman]

Also, I don't think this has anything to do with it but it might:

After putting the manifold it did what it's doing now but then stopped firing all together after messing with a ground. No ignition power and no fuel. After fixing that ground the problem persisted and was finally traced to a blown fuse on the inside dashboard fuse box. It was a 25A fuse in slot 19 (I think) labeled ignition control something or another if I remember correctly.

Regardless, replaced the fuse and it returned to how it was prior to that happening. Which is what is happening right now.

Not sure if it affects this situation at all, just wanted to throw it out there.