Help! Low idle, No power, Running Hot, out of ideas

[turbocoupe5.0]

Hi All,

I need some fresh minds, cause I've tried everything I can think of, I've gotten nowhere, and I'm burning out!

Megasquirt II
Megatune 2.25
3.0 board
2.872 firmware
EDIS-8 ignition
eight 36lb low impedance "brown top" Ford Turbocoupe injectors
302ci/5.0L Ford
GT40P heads
Explorer (GT40ish) Intake & throttle body
Shorty Headers
Trick Flow Stage 1 Cam 221int/225exh .499"int/.510"exh
9.4:1 compression
88 Ford Turbocoupe
T-5 trans
3.55 rear gear

I assembled and installed this system roughly 4 years and 20,000 miles ago and up until a couple months ago, it has been running great. Then it started going down hill.

The problems started with the idle being a couple hundred rpm low. I was too busy at the time (buying a house) to look into it so I just gave the throttle stop screw a half a turn and it was back to normal. This process repeated itself a few times. Idle would get too low and I would turn it up. Yes, I realise this was a band-aid, not a fix, but I just didn't have the time then.

Current Symptoms:

Now, it has gotten to the point where the car is really not drivable. It will go, but it's running so bad I don't want to risk damaging the engine.

The throttle is now open about 10% from its original 0% idle position to maintain the same 800 rpm idle speed.

The idle vacuum is down to about 5 in-hg. It used to be about 15-16 in-hg. I have checked for vacuum leaks, etc. But, I think the low vacuum is because the throttle is so far open at low rpm. If the problem was a vacuum leak the idle should have gone up, not down right?

The headers glow after idling for a few minutes if you look under the hood at night.

The last few times I drove it, the coolant was running about 20-30 degrees hotter than normal.

Its backfiring through the intake when opening the throttle.

Extremely slow throttle response.

Significant power loss across the entire rpm range, but especially at low rpm. This car used to fly, now I have to down shift to get up hills.

When slowly opening the throttle in neutral, the motor has a significant change in tone around 2500-2700 rpm. It quickly jumps to about 3000 rpm and sounds like it's running significantly better (almost like its old self, but that may be just wishful thinking).

What I've Tested:

Fuel pressure - 39psi with no vacuum. This is what it was originally set to. When connected to manifold vacuum, the regulator adjusts accordingly. I even taped the gage to the windshield and went for a ride. Pressure is ok even under load.

Compression Test - 170-190psi

Leak Down Test - 6-13% I heard no air at the throttle body or exhaust on any cylinder, only at the valve cover breather

Ignition Timing is right on at idle (10 deg BTDC) and advances with rpm. I can't measure actual advance with my timing light but it appears to be advancing ok.

Valve Timing - I removed the rocker arm from the #1 exhaust valve, put a dial indicator on the push rod, and compared the readings from the balancer and dial indicator against the cam card. It's dead on. The distributor is still in place to drive the oil pump so I checked for chain slack by moving the crank back and forth watching the rotor. No noticable backlash.

The engine is not missing and responds the same when you pull 1 plug wire at a time from each cylinder so I don't think the problem is isolated to any one cylinder.

Throttle position sensor, MAP sensor, coolant temp sensor, and intake air temp sensor all appear to be functioning ok per the Megatune display.

I had not made any tuning, firmware, or hardware changes since 10/07. I have played with some tuning settings recently trying to diagnose the problem with no success, but I have always reverted back to my original program from 10/07.

I put an oscilloscope on the injector outputs at the ECU with the engine idling to verify the pulse width on the screen was really being sent to the injectors. This looked ok too.

I've been banging my head against a wall with this for 2 months and I'm about 2 weeks away from putting a 4bbl on it, but I know it is just something I'm overlooking. I had it running great for thousands of miles.

PLEASE HELP!!!

Brian

[trakkies]

Headers glowing red hot is a classic sign of retarded ignition. I'd first check it actually is following the MS ignition map.
And /or a weak mixture - you don't appear of have an O2 sensor? Your local emission testing place should be able to measure the AF ratio for you.