I recently fixed a head gasket blow on my 2000 4.0 Sport, it was the first time I have ever done it and everything seemed to go back together fine. I tried starting it up, and it takes a little bit of effort, if I press the gas it helps. When it actually starts though it redlines instantly even though the gas pedal isn't pressed. I have no idea what is causing it and any help would be great.

 

Sounds like a fuel delivery problem. First not enough, then too much.

 

Do you know what would cause that?
And you don't think it's a throttle body problem? Like something wrong with the IAC or something?

 

Welcome Bouwenca Weekends can be pretty slow here, and I myself am not so good with the new Jeeps (Ha Ha). Tomorrow more people familiar with yours will be around.

Something needs to let air into the manifold for it to redline. Is the throttle plate in the TB closing? Some other big leak..like the hose to the brake booster. You sure the intake manifold fit up nice?

 

I'm pretty sure the plate is closing, I wd40 it and cleaned it before I put it on the new manifold and it opens and closes without sticking. And as far as I know it's seated properly.

 

And what brake booster hose are you talking about?

 

On one of mine it's a large hose that comes off the intake, below the TB and runs to the brake booster. On my other 90 with ABS that just has a cap on that pipe nipple.

 

What kind of new manifold?

 

It looks like this but cleaner.

 

Kinda sounds like a massive intake leak. Maybe when you put the intake manifold back on it didn't seal up right. Just a thought...

 

I'm probably going to try to take it off and put it back on, see if that helps. After I'm going to put my new brake booster cable on, and if it's still bad after that I'm going to replace stuff on the throttle body such as the iac sensor and motor

 

Also, if you look at my intake manifold picture, at the bottom you can see three shiny little prongs where hoses hook up. The one on the left doesn't hook up to anything and it's just a hole into the manifold, could that cause it? Should I seal that or am I missing something?

 

1) The brake booster is the larger of the two hoses on the intake manifold.
2) Were the intake manifold ports the same size?

 

Ya think?????

Plug it.

 

I edited post #7. Agreed with all/ massive vacuum leak from somewhere. IIRC there ARE aftermarket headers that have a thicker flange than the intake, so the bolts don't pull the intake in tight.....