M20 Idle and Rev Issue VIDEO

[ClayW]

Problem: M20 won't idle properly or rev past 2000 RPM.

History: The wife daily drives the E30 to work and tells me that it looses partial power at highway speeds then begins a rough idle. I get there and see a leak in the FPR and replace it. I drive it home, but the partial loss of power at highway speeds starts again intermittently, along with the rough idle. Here is what I've done so far:

Replaced fuel filter and a piece of the fuel line
Tested the fuel pump (good)
Replaced the AFM with a known good unit
Sprayed carb cleaner around intake (no change)
Tested spark at all cylinders (good)
Tested and cleaned the ICV (good)
Tested the TPS (bad idle circuit)
Replace the TPS with a tested good unit and adjusted

What next?

Here is a short list of stuff done in the last 5K miles:
M50 rebuilt injectors installed
New O2 sensor (could this have died prematurely?)
Adjusted valves
New cam seal and O-ring
New valve cover gasket
New fan clutch
New radiator
New thermostat
New gauge and ECU coolant temp sensors

As promised:

[ReSoP]

Does it have issues starting?

[ReSoP]

When you say tested fuel pump. Did you just test that its pushing fuel or did you get pressure readings? I would look at fuel pressure. And just as a process of elimination compression test, and check to the cam lobes and make sure it hasn't a flattened. From the video its kind of hard to tell be it sound like some clattering for sure.

[dnguyen1963]

It does sound like not all cylinders are firing, but more importantly, I think I have heard rod knocking.

[ClayW]

Since the problem is intermittent, I'm thinking that it's electrical (ignition or fuel related), instead of something mechanical, like a vacuum leak or a cam problem.

Thoughts?

[GDA]

That sounds like its running on three or four cylinders....

Pretty basic but have to ask - In your list you say you tested spark but what is condition of cap and rotor? Installed and not loose?

[ClayW]

That sounds like its running on three or four cylinders....

Pretty basic but have to ask - In your list you say you tested spark but what is condition of cap and rotor? Installed and not loose?

Got to the cap and rotor today. I was getting spark at each plug before, but I pulled the cap and found serious pitting on the contacts.

That's the next thing to replace.

Will report back.

[EatsHondas]

How did it run before with the stock injectors installed?

[ClayW]

FIXED: The issue was a dirty connection at the DME. Weird.


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