Mass Air Flow / Hesitation Issue HELP

[acarlan]

Hey all. First timer here. I just recently picked up a project truck in my 1990 Power Ram 50.

It hasn't ran in a little over a 6 months. Initially it wouldn't start. I assumed it was fuel related so I replaced the fuel filter and flushed the lines.

Then, I discovered some slappy had swapped the vacuum lines on the EGR Control Solenoid and the purge solenoid. So, the EGR valve was staying open all the time. Once I fixed that, it actually started with a VERY rough idle.

So, I then checked the MAFS:

- When it's plugged in; rough idle and stall.
- Manually choke the two extra ports on the MAFS; it idles fine but hesitates badly when accelerating quickly and will eventually stall... but revs fine when accelerating slowly.
- Unplug it; Idles great but has the same hesitation but a little better. Still revs fine slowly.

Other notes:

- Pulled the plugs they are dry fouled, so I'm assuming it's actually running rich but they could have been fouled for a while. I'm replacing the plugs today.
- I haven't pulled the fuel rail and cleaned the injectors yet.
- Checked the TPS and it's fine
- Checked for vacuum leaks and cant find one anywhere
- I need to check timing but attempted to manually advance the spark. It seemed to help a little but not much

Any ideas? I'm leaning on a bad MAFS but those are hard to find and NOT cheap. Could it be anything else?

[camoit]

It sounds like it's off by 1 tooth on the belt timing. The mark is not the flat of the head like you would think. It's actually under the head by 1 tooth.
Has it ever run good for you?
The more info you give us the better we can help.

[acarlan]

It sounds like it's off by 1 tooth on the belt timing. The mark is not the flat of the head like you would think. It's actually under the head by 1 tooth.
Has it ever run good for you?
The more info you give us the better we can help.

So, it turns out it was actually the fuel pump. I replaced it and it runs amazingly well 🙂

[geezer101]

Nice work Always difficult to diagnose a fault without being able to see it in person.

[xboxrox]

Merry Christmas