i recently acquired a 68 xr7 j code (302/4 barrel). it runs fine for the most part and i haven’t gone completely through it yet but here is my issue. the car runs smooth when cold but after it gets to temperature it seems to start sputtering at lower rpms. at idle, just starting from a light, etc. on acceleration it doesn’t seem to sputter or hesitate but at cruising speed i can hear it sputtering as well. as i’ve said, i haven’t gone completely through the engine yet. i have replaced the fuel pump, plugs, and points with a Pertronix 1281. another note, the carb is an edelbrock and there is a mr gasket fuel regulator on the gas line.
Following. I’ve got a similar issue with the same year/engine. Mine always hesitates and it will sometimes stall if you aren’t really careful with the throttle. It seems worse when accelerating out of a turn.
Sounds like the timing is way off. What does the timing read at idle with all vacuum ports plugged and nothing connected to the distributor? What’s your idle RPM in neutral with headlights on and AC running?? What’s the timing read with all the vacuum vacuum hooked up at 3000 RPM?
Follow the good advice given.
Check the fuel lines, especially the one from the sender to the hard line." Out of sight and out of mind" is an old saying and if that line is old and collapsing on the inside it can cause all sorts of symptoms and you’ll chase all over. Happened to a friend of mine years ago to where he was damn near ready to pull the motor and a car buddy led him onto that line. Car ran fine when fixed.
ok, so i didn’t find a vacuum leak but as i was changing plugs, points, cap and wires, i found the firing order is completely out of whack.it appears to be 54263781. i tried to change it to 15426378 and the car would not start. i do not know if anything has been done to the engine and this seems pretty unusual. the attached picture is the firing sequence based on the plug wires to the distributor. the numbers inside the engine is the current cylinder order based on the wires connected to the distributor. the numbers outside the engine are what they are supposed to be. the numbers bottom left is the firing order on the distributor based on the cylinder numbers inside the engine (18627345) or 54263781 based on the real cylinder numbers. i know this seems like it can’t be but it is what it is. the car starts and runs but a little rough when at temperature. i assume the distributor may have been changed and was not put in correctly, maybe?
Going the wrong way 'round the distributor can cause some issues (been there done that one late night). Also be sure you have #1 located properly … the ones on the outside look right, which I think is what you’re saying. Looks like going the wrong way would get you : 18736245.
Obviously a good start would be to put #1 on the compression stroke, set the balancer on 0 or so and check where the rotor is pointing.
So, I just realized the sequence I posted, 54263781 is just 1 off the actual sequence of 15426378. Previous owner must have set the distributor and timing on the wrong cylinder. I’ll reset and see what happens
ok, i set the #1 cylinder to tdc and checked the timing mark as being 0 (picture just shows timing marks. white mark is 6 degrees) i pulled the distributor and reset it to point to the #1 plug on the cap. i plugged in all the plug wires in order 15426378 counterclockwise. now the car does not start. i’m confused.
ok, so i had #1 at tdc but not on the compression stroke. reset #1, reset distributor and now it runs. still have to put a timing gun on it but it is straight and does not have the rough and sputtering issues. thanks to everyone for the suggestions.
