Eta motor misfiring and low on power

[lolcantturn]

My M20B27 sounds like it has two step. Any rpm between 1000-2500 is a very harsh misfire that results in exhaust backfire. This causes significant drivability issues on the highway. If I keep my foot planted WOT through the entire RPM range, I can kind of "get around" these harsh misfires, but I still feel very slight ones happening as i'm climbing through the RPM's. The video will explain more of this.

Here's what I've replaced:
TPS- nothing
coolant temp sensor- nothing
crank position sensors, one was out of spec and replaced it- nothing


Distributor cap and rotor, plugs, and O2 are new from 7 months ago. The backfire has only gotten gradually worse.

I don't believe it's the fuel pump because the car pulls kind of hard after 3k RPM.


What are your thoughts?

[lolcantturn]

It also gets pretty bad whenever the engine is cold

[lolcantturn]

Anyone?

[YosemiteSam]

Try your AFM. Your resistor strip may be worn out in the normal driving area causing the engine to not give enough fuel. Being at WOT would help with this because the TPS would indicate WOT to the PCM and you would get a bit more fuel. See if you can borrow a known good from someone and see if that fixes it. If that does fix it BavRest sells refurbished units for a good price.

[squidmaster]

AFM or injectors. Checking the AFM is a bit easier than injectors, so try starting with that. Make sure it reads a smooth transition from close to open with no dead spots or gaps (a *small* dead spot can be okay)

If you need a tutorial I have one bookmarked somewhere

[MrBurgundy]

Maybe you swapped two ignition wires. Backfire usually points to ignition problems.

I would pull the plugs and check to see if they have fouled too

[lolcantturn]

Spark plugs appeared foul - replaced, no change in issue.
AFM was replaced with "known working one" - no change in issue.

Now I'm going to look into the distributor and cap, and start to look into the fuel delivery.

Issue appears to be getting worse as the car won't really hold an idle anymore. Giving it WOT now appears to bog it down significantly at low RPM's.

[lolcantturn]

Mechanic tracked down the issue- reference pin on the flywheel has gone kaput. $1450 for flywheel replacement, clutch and labor. Yikes.

[Sasquatch440]

sounds like time for a swap

[lolcantturn]

sounds like time for a swap

At this point yep. The car's all original, but M20B27's are garbage. Luckily all these new parts he's installing will transfer over to a 24V.

[lolcantturn]

Lean conditions caused the bottom end to fail - need to source a new motor aka time for 24V! Don't continue to drive your car on a really bad misfire kids