Does anyone have any suggestions as to what would cause this. I have brand new ignition system, new cap and new rotor. The dist shaft was pulled and a new pick-up coil was installed as well as added a 2nd shim between the drive gear and the base of the dist shaft housing to make up any slack at all. But the damn timming still jitters a bit when checking it. I also have developed a slight miss that goes right though the entire rpm range when at zero load. I dont seem to notice it under WOT when I am in a gear on the road. But it does make the car jerky when in any gear trying to cruise around at really low rpms, (below 2000) I have replaced everything in the ignition from plugs to coil to wires, you name it. (with the execption of the actulle dist shaft itself, but that feels smooth with no slop)

How many miles are on the engine? Put a vacuum guage on the engine and see what it reads. I had a sloppy timing chain that caused erratic timing @ idle.

Motor has about 15,000 miles on it. It was professionally built by a local hot rod shop. It does mild cam in it, but has -12' overlap at .050 so that should not cause the problem. Compression is around 9.5-9.75 - 1

Capt, I have the same symptom and there are a few others... search for 'poot-poot'. My dist was replaced by the prev owner is like new. My car will intermittently miss with no load up to 2500 rpm. Under load there is no problem. I just bought new injectors & O2 sensor as it also runs rich, but I haven't put them in yet. If you put a vac gauge on it you will notice the timing jumping with the vac jumping but there is the chicken or egg scenario... A clue is that my timing jumps when in diag mode as well. I'll crosspost any results for these threads if I figure it out.
BTW I also had a very sloppy timing chain and the effect of the miss improved but it is still there.

Edited for the BTW

[This message has been edited by 87GTZ34 (edited 08-16-2001).]

I know that it has brand new timming gears and chain as well as chain guide, becuase I personally picked them up from the parts house and took them to the shop. When they returned me the longblock all wrapped in shrink-wrap you could see that it was all new. (this is kinda a funny thing) but to anyone that has held one brand new hyperutectic piston in there hand that is going into there motor. All new and shinny and feather light to hold. It is an awsome feeling. When I got my box of new pistons. And I took the first one out of the box to inspect it. I felt like a Dad holding a baby. (weep weep) ok sorry that was a little out of the original response but it popped into my head while I was typing this. But to answer that, the motor and all of its parts including injectors are new. (injectors had less than 20,000 miles on em, from a ford mustang 19#'ers)

I wasn't saying that your timing chain & gears are the culprit. I was mentioning that because I changed mine and still have the mis-fire although the chugging when cruising at 50 mph is much better due to alot less cam bounce.
I just went to the post office and had a major find... When I turn the AC on the fuel pump whine stops. Yes that's right the whine stops. So I got my multimeter out and checked the batt voltage with AC on and off. Only a slight drop, so I then checked the voltage up front let's say at the fusebox. There is almost a 1 volt drop on the fuel pump relay when the AC is turned on and only 100 mV at the battery... hmmmmmm I took Ogre's advice when he had his check your grounds post about 3 weeks ago with no change in behavior. I do think I have a ground or feed problem from the front to the back somewhere. When the car idles w/o the AC on, it does not miss, but when you turn it on it starts right away. Granted there is a little more load on the motor w/ the AC but there is also a 1 volt drop at some of the feeds & I assume all of them. This would mean the ignition also drops if that holds true. I will look further into it tomorrow and post my results with or w/o success.

Looks like she's gone rabid on you. Only thing to do is to lay her down.
Sorry guys, but I sure am having fun with these smilies.

Hey David,

These guys are on the right path. Did you find a Pre-Stretched timing chain, or did you just get a regular timing set?

The regular timing chains stretch within 10k miles, and will give you the jumping timing mark.

The price usually tells which chain you got, for example, a regular timing chain for a SBC costs about 15 dollars, and a pre-stretched chain will run over 100 dollars.