Help Please - Engine Hesitates (Bogs) Under Load
 

1980 SC. At first I thought that my clutch was slipping. I did the 5th gear pull from 25 mph and there's no slipping. Clutch is a Sachs with less than 25,000 miles.

Perfect idle. Revs in neutral are clean and crisp. But when driving (in any gear) the engine seems to bog and hesitate and stumble under load.

It's been raining a lot. Could be a bad tank of gas. Could be bad timing. Could be clogged fuel filter. Could be poor spark. I have a "tired" fuel pressure regulator that causes rev surge in cold temps, and I haven't put the pressure gauge on to confirm pressures, but other than idle, the engine runs strong when when ambient temps are > 50 degrees.

Have an 8 month old rebuilt Bosch ignition box, 18,000 mile Bosch plugs, 120,000 mile+ ignition (shielded) wires. Cap and rotor look "ok" but not fresh.

Where's a good place to start?

This is a daily driver with 250,000 miles on the motor.

Bump for any suggestions?

Wires, cap and rotor for a quick, less expensive start?

Plus spark plugs
Ignition timing
Then check air/fuel ratio

CIS? First check is fuel pressure. Then fuel flow......filters.......then vacuum leaks.

Check Timing with a timing light to see if you're getting full advance.

Well... congratulations. All of you were right. Which is kind of bad for me.

1. Lean running condition from vacuum leaks at injector seals. Seals now fixed.
2. Stuck fuel injector - cleaned and put injector cleaner in the tank.
3. Lean-run plugs "white frosted" needed to be replaced
4. One spark plug boot not making solid contact - replaced
5. Timing too far advanced

Now it's possible to see if the Lamda is doing it's job. Power to the unit and relay works. Need a test unit to compare.