Possible timing issues

Victim: 91 Civic 1.5 /w AC Hatch back
Problem: Runs rough at idle and it seems to be starting likes it's out of time.

I bought the car last fall and did a tune up: Plugs, wires, cap, rotor, oil, all the filters, and O2. Car ran great winter (Average 39-43mpg). Then one day when I got off the express way it seemed to run rough. It has always used oil and smokes a little when I first take off but it's fine after that. Most of oil leaks on the ground. Is it possible that the timing belt slipped a tooth? I have not check my mpg but it's got to be around 20-25mpg. If that's the case, do I have to take the upper dust cover off the timing belt to check the timing? Also, if I have to replace the timing belt, how do you get the crank bolt off? I tried to hold it on the ring gear with no luck. Thanks in advance

Yup, possible it jumped a tooth.

Rotate the motor to TDC and see if all the marks line up, not too complicated but best to get a Haynes or Chilton's for all the details.

Best way to get the crank bolt off is using the biggest impact wrench you can find. IMO

If you decide to replace the belt make sure you replace the water pump and consider replacing the belt tensioner too. BTW also check your ignition timing. GL

My current problem is getting the crank bolt off..I've tried an impact wrench at 150psi and a 1/2 in. drive breaker bar. I tried locking the ring gear and still can not get bolt off. I can't hold the engine enough to break the bolt. Im basing the direction of the bolt by the engine rotation as CCW to loosen. I can't see the (bottom) timing marks until I get the covers off. To get the covers off I have to get the crank pulley off (bottom cover). Which brings me back to getting the crank bolt off. I have a water pump to replace along with the belt..I will take your advice and replace the tensioner also..thanks for the help.

John: I don't see how I can change the ignition timing, how is that done? I have changed it in the past by rotating the distributer. I don't think I can rotate this one or is it done electronically?

You are using the right tools, what was the foot pound capacity of your impact wrench? When I did mine our wrench was rated at like 450ft/lbs and it still took a few tries.....

You are also correct about the bolt, it does come off CCW or left.

You can verify TCD without taking the crank pulley off. There are four marks on the rim of the crank pulley. The one by itself is the mark for TDC you have to look down at it and line it up with a pointer on the timing cover, they are near the hole for the inspect/adjust the tensioner. There are also TDC ref marks on the upper cam pulley and they should be level with the valve cover sealing surface. It's kinda hard to explain, the service manual will have a better explanation and pics.

You are correct there too, with this car I guess you set the base ignition timing the same way and then the computer fine tunes it based on conditions. There are three distributer mounting bolts you have to loosen to get this dizzy to rotate. GL

I finally found a shop manual...I see the three bolts that are loosened to adjust timing. I appears you do not have to remove the bottom timing belt cover to check the marks. The way I see it:
1. remove the top timing belt cover
2. set 1 cyl to TDC
3. top pulley two marks should line up with top edge of head
4. white timing mark on crank pulley should line up with pointer
on lower timing cover
Here's where I can see if my belt slipped and maybe even slide it back where it should be. I'm still planning to replace the belt, pump, and adj but, I can't take my car down for long right now.

Also, it looks like I have to bypass the computer with a jumper to see the correct timing with a light. Thanks for you help John.

Your welcome and BTW welcome to the forum! :)

Good luck to you with that crank bolt!