1990 3fe hesitation (1 Viewer)

[Smplybttr]

I've recently started getting some hesitation in my truck. It happens at all speeds and especially uphill. Feels like it isn't getting fuel, then all of a sudden will burst, then hesitate, then burst again. If I stomp on it, it'll level out until I let off.

1. I'm losing an overflow bottle's worth of coolant every three fill ups or about once a month. No "milkshake" in the oil.
2. I just changed the fuel filter under the hood.
3. It is NOT currently holding any codes, as I just replaced the alternator and the battery was disconnected for a couple of days, but about a month ago, it threw 25 and 26 consecutively, but then the CEL went out the next time I cranked her up.
4. I did a compression test yesterday and my numbers were 142, 122, 140, 120, 130, and 120. I'd like them to be more consistent, but they're not out of spec.
5. Injectors were recently sent out for cleaning, so I don't think those are the culprits.
6. I put a vacuum gauge on it and it hangs out right at 19, then misses and falls to 17, then comes back to 19 and stays. Revving the engine does all of the normal things that you'd expect from a good vacuum test. (I'll post video later)
7. Checked plugs and wires during compression test. All looked fine, although #3 had just a little oil on the threads. All were pretty close to correct gapping.
8. Cats are cored out.
9. Idles perfectly at 650, except for an intermittent miss.
10. I have an exhaust leak around both cats.

Any thoughts on what else to check?

 

[Alleycats]

You could try replacing your fuel sock in the gas tank and cleaning the contacts on the fuel pump harness connector (also apply dialectric grease), it worked for me and my 3FE.

 

[Smplybttr]

Does the tank have to be dropped to replace the sock?

...via IH8MUD app

 

[Alleycats]

Not sure on a fj62, maybe someone will chime in?

 

[Granite Grinder]

I've not had good luck accessing the the pump through the floor of the box. As much as it's a pia to drop the tank, it may also be a rust issue where the hoses run on top of the tank, the only visual your going to get of that is by dropping the tank.

 

[Spudman]

I could be way off as I only know diesels, but you did mention that you recently changed your fuel filter, do you need to bleed your fuel filter similar to the diesels. As that may cause fuel issues, it definitely would if it was a diesel.

 

[elripster]

I was losing coolant as well and get this, it was due to that short little pipe under the front right side of the engine rusting and allowing the system to suck in air under operation. Sounds crazy but that was the culprit. Replaced it and haven't had to add coolant since.

I would follow the FSM procedure and check that your O2 sensors are working. That will tell you if the engine is managing its mixture and if it is rich or lean. I had hesitation issues for a long time due to miss wired (flip flopped) O2 sensors due to way out of whack mixtures.

Frank