#1 |
I am working on an '88 Mustang that I swapped an '88 TC engine/ecu/VAM/sensors into. The car has a slightly rough and inconsistent idle, varies about 50 to 100 rpm intermittently. If the car is warm and I rev it up high (4000+ rpm) it will stumble for a minute or so then smooth out. Sometimes it will stall after reving. But it always revs crisp and fast. I have heard HLAs will do that but engine did not do it when it was in the donor car (bad frame). When everything was in the TC it idled so smooth you didn't even know the engine was running. But unfortuately TC was not savable due to frame damage. The Mustang seems to drive fine out on the road, pulls up hills easily, boost comes on smoothly, but it will stall if reved up and then clutch is pushed in within a short time after reving. If driven moderately it never stalls just has the rough inconsistent idle that was not there when engine was in the other car. Car starts easily all the time. Car does not smoke or run hot.
The KOEO and KOER tests come back with 81,82,83 which is the IRCM missing and should not cause problems.
Did boost leak check to 17 PSI on the in car guage, replaced throttle shaft seals, vacuum hoses, etc so it is leak free. VAM to turbo hose does not leak. All new felpro intake gaskets.
Replaced TFI, PIP, new Motorcraft wires, two sets of Motorcraft plugs, new cap/rotor, and it did not fix the problem.
All three temp sensors (VAT, ECT, ACT) have the correct resistence back at ECU connector in both hot and cold conditions.
All grounds zero ohms back to battery: pin 20, 40, and pin 60. Valve cover to negative battery zero ohms. Valve cover to shock tower bolt zero ohms. All engine compartment connectors (sensors, actuators, injectors) have been verified to be zero ohms back to their respective pins at the ECU connector. Full battery voltage (13.8 at idle) at distributor, coil, IAC, and EGR vent solonoid. VAM voltage is about .82 and looks steady. Headlights are nice and bright. Turbo housing grounded to Pin 49. O2 has good ground and full battery power. VREF is 5.2 volts at VAM and TPS.
Adjusted base idle to 750, TPS voltage set to .95. Base timing at 10 and with spout in it jumps to 25, looks stable, and increases when reved.
IAC is new (no change, old one worked fine on TC), throttle body clean, EGR is blocked off for now because it had a small air leak.
New 255 LPH fuel pump and pick up filter, new Wix fuel filter, new Kirban adjustable fuel pressure regulator. Pressure set at 39 vacuum hose off at idle, 30 with hose on, rises during boost, and goes back down once out of boost.
I tried unplugging the BAP sensor; no change, unplugging O2 sensor, no change, unplugging IAC and turning idle up, no change.
All plugs the same color, compression 140 PSI exactly on all cylinders, throttle body was held open and injectors unplugged during test.
With a timing light I sometimes see spark misses and replacing all the ignition components has not changed that. I see the misses when on the coil wire two but they are intermittent maybe one every 3-5 seconds or so. I can tough all ignition wires and never get shocked. No arcing visible when run at night.
If I pull the spout I do not see misses on the timing ligh. But turning distributor to increase timing with spout out does not smooth it out.
Here is a video that shows the problem. The idle is not smooth to begin with then after the moderate rev it gets really bad then smoother out over time. We have not seen the idle get really bad like that with just a moderate rev before or since but that is how it behaves with a high rev with engine warmed up:
http://www.youtube.com/watch?v=4cQ6uvsX-Rk
In this one you can see the air fuel ratio is in a pretty good range but not stable. The scope shows the TFI controlling the coil with the spout plugged in:
http://www.youtube.com/watch?v=i6s3ULxsBHw
Any advice greatly appreciated, thanks,
The KOEO and KOER tests come back with 81,82,83 which is the IRCM missing and should not cause problems.
Did boost leak check to 17 PSI on the in car guage, replaced throttle shaft seals, vacuum hoses, etc so it is leak free. VAM to turbo hose does not leak. All new felpro intake gaskets.
Replaced TFI, PIP, new Motorcraft wires, two sets of Motorcraft plugs, new cap/rotor, and it did not fix the problem.
All three temp sensors (VAT, ECT, ACT) have the correct resistence back at ECU connector in both hot and cold conditions.
All grounds zero ohms back to battery: pin 20, 40, and pin 60. Valve cover to negative battery zero ohms. Valve cover to shock tower bolt zero ohms. All engine compartment connectors (sensors, actuators, injectors) have been verified to be zero ohms back to their respective pins at the ECU connector. Full battery voltage (13.8 at idle) at distributor, coil, IAC, and EGR vent solonoid. VAM voltage is about .82 and looks steady. Headlights are nice and bright. Turbo housing grounded to Pin 49. O2 has good ground and full battery power. VREF is 5.2 volts at VAM and TPS.
Adjusted base idle to 750, TPS voltage set to .95. Base timing at 10 and with spout in it jumps to 25, looks stable, and increases when reved.
IAC is new (no change, old one worked fine on TC), throttle body clean, EGR is blocked off for now because it had a small air leak.
New 255 LPH fuel pump and pick up filter, new Wix fuel filter, new Kirban adjustable fuel pressure regulator. Pressure set at 39 vacuum hose off at idle, 30 with hose on, rises during boost, and goes back down once out of boost.
I tried unplugging the BAP sensor; no change, unplugging O2 sensor, no change, unplugging IAC and turning idle up, no change.
All plugs the same color, compression 140 PSI exactly on all cylinders, throttle body was held open and injectors unplugged during test.
With a timing light I sometimes see spark misses and replacing all the ignition components has not changed that. I see the misses when on the coil wire two but they are intermittent maybe one every 3-5 seconds or so. I can tough all ignition wires and never get shocked. No arcing visible when run at night.
If I pull the spout I do not see misses on the timing ligh. But turning distributor to increase timing with spout out does not smooth it out.
Here is a video that shows the problem. The idle is not smooth to begin with then after the moderate rev it gets really bad then smoother out over time. We have not seen the idle get really bad like that with just a moderate rev before or since but that is how it behaves with a high rev with engine warmed up:
http://www.youtube.com/watch?v=4cQ6uvsX-Rk
In this one you can see the air fuel ratio is in a pretty good range but not stable. The scope shows the TFI controlling the coil with the spout plugged in:
http://www.youtube.com/watch?v=i6s3ULxsBHw
Any advice greatly appreciated, thanks,
Bill
'88 Turbo Coupe
'88 Mustang LX 5.0L 5 spd Conv (one owner survivor)
'88 Mustang Hatchback 2.3 turbo 5 spd
'86 SVO ultra low mile survivor
'88 Turbo Coupe
'88 Mustang LX 5.0L 5 spd Conv (one owner survivor)
'88 Mustang Hatchback 2.3 turbo 5 spd
'86 SVO ultra low mile survivor