5.0L idle oscillating then dies

Topic: 5.0L idle oscillating then dies (Read 1770 times) previous topic - next topic

5.0L idle oscillating then dies

Reply #15 – June 22, 2009, 03:40:28 PM

OK, guys. Update on this issue. Installing the old MAF and 19lbs injectors seemed to only decrease the oscillation. So, it's still there. It just came on later. I pulled the codes and got a 21 and 44.

21 ECT out of range

44 Thermactor bypass inactive

Anyhow, during the Holley Systemax swap I relocated the ECT to the rear of the lower intake and extended the wiring harness to get it there. Since my engine oscillation is certainly a "warm condition" problem, I think the EEC might be tripping on the bad ECT readings.

I'll let you know. If it works out, I'll feel good about getting the 24lb injectors and 75mm MAF back in to complete the upgrade as originally intended.

5.0L idle oscillating then dies

Reply #16 – June 23, 2009, 11:08:58 AM

So the ECT (engine coolant temp) sensor is not int he heater core rail but instead mounted in the intake manifold? I know that it can be mounted in the heater rail or in the fitting near the thermostate housing with out problems but I don't know about putting it in the fitting on the rear of the intake manifold. It *could* be your problem.

Oh and ignore the code 44 if the thermactor system is gone ;)

5.0L idle oscillating then dies

Reply #17 – June 25, 2009, 12:53:11 PM

Thunderjet, Thanks. The ECT was in the heater core rail but I removed that stuff because the heater core was shot and inoperable anyway. So, I first located it in the rear of the intake. Since the oscillation occured I moved it to the front of the intake. Oscillation still there.

Last night I back probed and tested voltage to the ECT with the harness connected to the ECT... result... 2.7 volts.

With the harness disconnected from the ECT I got 5 volts. So, I'm gonna try a new ECT sensor tonight. Sorry, it's slow going between work and putting in new irrigation and a lawn.... you know, family-man priorities :)

5.0L idle oscillating then dies

Reply #18 – June 25, 2009, 12:57:39 PM

If the ECT doesn't fix it check the wires going to the ECT. You could have damaged insulation as the car is, you know, old

5.0L idle oscillating then dies

Reply #19 – June 25, 2009, 01:27:46 PM

2.7v indicates a engine temp of approx 80*...

5.0L idle oscillating then dies

Reply #20 – June 25, 2009, 02:38:25 PM

ahhh TC50. You're right. Thanks.

5.0L idle oscillating then dies

Reply #21 – June 25, 2009, 02:45:21 PM

Hey I knew that chart was somewhere. Can you get the car up to temp and check the ECT sensor?

5.0L idle oscillating then dies

Reply #22 – July 10, 2009, 02:44:30 PM

Update guys. My ECT tested ok all through the range. I was able to eliminate the "21" code (ECT out of range) after I bought a new radiator cap. During my testing, I noticed the cooling system was not pressurized. I switched caps, the system was now pressurized and after running codes... no more "21".

I still need to take her for a run to see if the idle oscillation is gone. Next update.

5.0L idle oscillating then dies

Reply #23 – July 14, 2009, 12:48:59 PM

Well, this is embarrassing but I cured the problem and have been driving the car to work and back which is the ultimate test IMO. Good thing is, this ordeal gave me a chance to get familiar with EFI and EEC-IV which was all new to me.

All this time, I had the fuel pressure set to 50 psi. Neglected to check it because I was positive I had it set to 40 psi. Once I lowered it, the oscillation is 99% gone. At times, after hard acceleration the idle will drop to 500 RPM but it easily recovers to 800 RPM and quickly. The big undriveable RPM swing and shut-off is gone.

I baselined the car on a chassis dyno just before the Systemax upgrade and I'm going in for the "after" test next week. Will share the results.

5.0L idle oscillating then dies

Reply #24 – July 14, 2009, 03:09:07 PM

Yeah the 50 psi thing would be a problem. The EEC likes about 40 PSI. If you turn it past that it just re-learns the pressure and tries to compensate for it.

Did you pop the 24lb injectors back in yet?

5.0L idle oscillating then dies

Reply #25 – July 14, 2009, 03:14:06 PM

Good question, that's the only item I haven't put back. I think I'm gonna enjoy the car for a while and then try those out in a few weeks.