Okay, I have read through a lot of the boards here and I am still struggling with this problem...


I just replaced the lower intake manifold on my 1986 2.8L MPFI motor.
Now that I have her back together, she idles fine, but bogs down and has NO power under load. In fact, she tries to stall out once in gear.


I replaced the manifold, all gaskets, valve covers, distributor cap, rotor, plugs and wires while I was at it. I also replaced the o rings on the fuel injectors.


The motor is timed at 10 degrees BTDC.


The engine is not giving any trouble codes.


I checked all of my vacuum lines and have not found any leaks.


Does anyone have any suggestions on what I might be able to try next??


Is it possible that the distributor is bad? It was functioning properly when I removed it.


I really appreciate any advice.


Thanks!!!

 

A Couple of notes to add on that may help.
While it does not shoe a CEL when running, when I check the codes it gives Code 42, EST Signal Did not change. Could this be from when I set the timing or a symptom of the current problem?
Also, when I start the car there is a fairly strong fuel scent from the exhaust.


It almost seems like a timing problem, but I know it is set correctly.


I am sure I connected all of the connectors on the fuel injectors correctly but find myself second guessing my work. would connecting the fuel injectors in the wrong order cause this?


I did not replace the injectors, just the O-rings. could the injectors be faulty?


Sorry to ask so many questions just reaching a very high frustration level with this project at the moment.


Thanks again!!

 

You are correct about code 42, it was set while the EST/BYPASS connector was open on a running engine.

The injector connectors doesn't matter, they all fire together (batch mode).

With changing the cap and plug wires, that could be an issue. #1 on these engines is the front passenger side cylinder. Firing order is easy: 1-2-3-4-5-6

This is where I would start (firing order). If you find it incorrect double check the base timing once OK.

RBob.

P.S. Welcome to TGO!

 

Thanks for the welcome!
Firing order is correct. Double checked timing.
It runs well with the EST disconnected and holds 10 deg BTDC. It stubles just a bit occasionally.
When I start it with the EST connected, it seems to have difficulty maintaining timing. Idles a bit rough, and I noticed last night will sometimes be fine under load (backed out of the driveway great) but stumble and bog down under load. to the point where she almost stalls. By the time I got her turned around, power picked up again somewhat but with a fair amount of stumble.
I rechecked the timing light after unplugging EST again, still at -10 deg. (the distributor did not shift)


Now I am thinking about when I pulled the distributor... the distributor base (including electrical) had fairly heavy corrosion. It did not spin freely, there was resistance when turning the distributor.


I did not think much about it while I was working on it, since it was working before I took it out, but looking back on it, could the distributor or onboard electronics need replaced?


When I think to shortly before I completed the work, I can remember a couple of times the engine lost power when under heavier load, but didn't think much of it since I was about to start the current work.


I am wondering if the EST was going out before I removed the distributor and the manual adjusting/manipulating crapped out the distributor or EST electrical in the distributor.


I am either on the right track or grasping at straws at this point lol not sure just getting frustrated chasing gremlins...

 

Check the spark timing with the EST/BYPASS connected. Should be up in the 18* - 22* BTDC range.

RBob.

 

Fought with the timing for 2 hours yesterday. Set at -10 with EST disconnected, ran fine, after connecting EST, timing mark jumps so bad, impossible to check and runs rough and stalls.


Ended up replacing the distributor, Timed her spot on, -10. Runs smooth as silk, even with EST plugged back in. Drives out fine. Actually she feels like she has more pickup on acceleration than she did before I started any of this work as well.


Thanks for the advice RBob!

 

Good job!

RBob.