No power after 2.9 Rebuild

[kunar]

okay, so compression is consistently low on all 6 cyls. didnt change from before to after you replaced rings and honed the cylinders. not leaking from the valves. if all of this is true i have to assume theres an issue with the cam. i dont know if it's maybe a tooth off or what, but considering the fact that it's not a stock cam, im suspicious of it. not that aftermarket cam's are bad, but it's gotta be out of time or something, thats the only way i can explain all the symptoms

 

[adsm08]

Haaaa... Gaah!! I am embarrassed, since I had an 89 BII with the 2.9 motor for over 14 years!!!! I did say MAF...not MAP... I meant MAP sensor... Manifold Air Pressure. I do know that the only MAF sensors on the 2.9 were in California that was on the 90 model...sorry!!! I remember that when I lived out there. Thanks for correcting me, Bro!!!

I know you've had 2.9s before. That's why I had to call you on it.

I could see a failing MAP causing some of these issues. A failed MAP should make the engine not idle at all.

 

[Kadams87]

It is a stock cam that came in the truck from the factory. Cam timing would be a great idea but I double checked it when I pulled it down. Not to mention I did a leak down and compression test on a few cylinders that didn't even have the rocker shaft on the head. I have verified for a fact that the heads are good on this motor.

I changed the MAP and still no difference. Throttle linkage is free and clear.

 

[adsm08]

okay, so compression is consistently low on all 6 cyls. didnt change from before to after you replaced rings and honed the cylinders. not leaking from the valves. if all of this is true i have to assume theres an issue with the cam. i dont know if it's maybe a tooth off or what, but considering the fact that it's not a stock cam, im suspicious of it. not that aftermarket cam's are bad, but it's gotta be out of time or something, thats the only way i can explain all the symptoms

That's very much along the lines of what I was thinking too.

The fact that they are all low and all spot on to each other is just screaming that the issue has to be something that can affect all cylinders equally. It's a pretty simple engine. The cam is about the only thing that can drop the compression that much that perfectly. It almost has to be a tooth off. The intake valve is opening late and closing late.

 

[Kadams87]

That's very much along the lines of what I was thinking too.

The fact that they are all low and all spot on to each other is just screaming that the issue has to be something that can affect all cylinders equally. It's a pretty simple engine. The cam is about the only thing that can drop the compression that much that perfectly. It almost has to be a tooth off. The intake valve is opening late and closing late.

I guess I will be breaking out the degree wheel and see if this thing is ground wrong from the factory. When I had it torn apart last time the dots were at 12 on the crank and 6 on the cam

 

[Kadams87]

I know this is old but I figured I should post this. The 2.9 is gone in favor of a 4.0 Swap.

 

[kunar]

I know this is old but I figured I should post this. The 2.9 is gone in favor of a 4.0 Swap.

good idea, thats what i did.

 

[84bluebronco2]

4.0's are fun, but I like a good running 2.9 just as well. Best of luck with your swap.