Engine Engine Running Rough After Reinstalling Timing Chains

[cjcoburn]

Hello again all,

Man...this project (1999 GT 5-speed NA) is going to keep me always posting for help with issues.

So I got the engine and tranny back in and all together. When the engine runs it's rather rough - way down on power. I can tell it's missing. It will also backfire through the intake every so often. I'm rather certain I was quite particular when I installed the timing chains.

The chains slipped when I replaced the guides. So I pulled all the followers, put timing marks on the chains (by folding chain in half and marking each end), and installed the chains with the cams at 12 o'clock (driver's side) and ~11 o'clock (passenger side) and aligning with all timings marks. Then I put the followers back in where I could. I rotated the crank (CW as I looked at it from the front) to give me more room to install the remaining followers.

The thing I'm wondering is if I have a chain off by 1 link would it run like this?

I also replaced intake manifold gaskets - could that cause backfires?

Looking forward to sage advise...again.

 

[1987stangman]

Yes, if I was off by just one link it could cause a miss, on whichever affected bank, or both if both sides are off. Check to see if there are any codes. I once had one that skipped a tooth on the drivers side from a broken guide and I got no miss fire codes but was getting a rich bank code, but it was missing. Actually scratched my head on the issue at first until I pulled the ds cam cover and discovered the broken guide. Engine only had 78k on it. Installing new timing components and retiming made it all better.

 

[cjcoburn]

Yes, if I was off by just one link it could cause a miss, on whichever affected bank, or both if both sides are off. ...

Glad to hear that. I'd hate to pull the timing covers only to find the problem isn't in there. Once I get back in there I'm sure to have more questions and pics.

Thanks!

 

[1987stangman]

Good luck

 

[cjcoburn]

Good luck

Thanks!

So far things are going okay. Got the engine at TDC and timed everything up. Even sprung for putting some fresh white-out on the timing marks and chain links - big spender that I am; next is a KB (I wish). The big thrill so far is that I don't seem to have bent any valves. The shade-tree-leak-down test was good on all cylinders. But as we all know, the real test will be when I fire it up.

So now I just need to put the timing cover on, valve covers, and other front engine stuff.

 

[cjcoburn]

And it lives!

Fired right up and ran smooth. Now on to the next project - the suspension. Finally putting in some lowering springs and all that entails - new shocks and struts, bushings, stabilizers bars, and CC plates. Woo-hoo.

 

[1987stangman]

Great, glad to see you up and running. Timing those engines is really simple. Once you have done it once it's no big deal.

 

[Gearbanger 101]

And it lives!

Fired right up and ran smooth. Now on to the next project - the suspension. Finally putting in some lowering springs and all that entails - new shocks and struts, bushings, stabilizers bars, and CC plates. Woo-hoo.

So no idea what was causing the rough idle?

 

[cjcoburn]

So no idea what was causing the rough idle?

Oh the cause was crystal clear. When I first installed the timing chains I ended-up having the driver's side cam off by 180°. This can happen if #1 is not at TDC when lining-up all the timing marks - not one of my brighter moments. Fortunately no PTV issues.