Hey guys, any thoughts? I have an 85 T-Bird with 5.0L 5-speed. I just swapped in a new Holley Systemax kit with heads, upper intake, lower intake, throttle body and a C&L mass air meter. I've gone though adjusting the idle and TPS. Here's how the car behaves... warm or cold it will hold a nice 900RPM idle for 5 minutes sitting right in my driveway, then it starts oscillatting slowly until the motor begins swinging from 500RPM to 1500 RPM, eventually it dies. Start it up, and immediately I have a smooth idle again.... 5 minutes later the oscillation starts again lasting for about 30 seconds until it dies. Otherwise everything is cool. Any ideas? Thanks in advance.
Don't let it idle... LOL
What cam???
Funny ;)... It's got the Ford Motorsport E303. That's the same cam that was in it before the swap.
Probably doesn't have enough base idle speed...
With motor warm, disconnect the IAB and set it for the RPMs you want(do not adj the idle with the IAB connected)... Then set the TPS to .9 -.95v, reconnect IAB... Would be a good idea to disconnect the battery for a few minutes after the voltage adjustment, so the EEC will start a fresh learning cycle...... If you still have problems, try rotating the MAF slightly, often this helps...
Another trick that works, is create a vacuum leak after the MAF meter... If you're looking for 900 RPM, use the above method to set idle about 750 and "leak in" the difference...
Thanks TC50. Yeah, been through that process a few times with no luck. I have no problem getting any idle speed I want and my TPS is set to .95. It just keeps foolin me. I take it for a drive, idles great, accelerates great... then suddenly it starts the oscillation, I feather the throttle to keep it alive for about 30 seconds, then the issue passes and it's back to normal driving.
I did notice the idle oscillation can be induced by heavy accelleration. Whatever, thanks... I know it's a weird one but it's keepin me from taking the car out of my neighborhood!
Check your vaccum lines and try cleaning out your IAC.
Does it throw any codes? Sounds like an IAC issue to me.
didn't notice you were in nevada. If you ever feel like going for a really long road trip, let me know. My birds nothing to look at though.
Big time shot in the dark put your original mass air meter back
Thanks guys for the suggestions. I haven't had time to get back in the garage but will in the next day or two to try some out some of these possible solutions.
I did notice that if I unplug the MAF, the car just idles rough but there is no oscillation. When I plug the MAF in, it starts oscillating and I hear a noticeable whistle in sync with the oscillation.
Like said try the old mass air if you can. Try codes to.
My 3.8 did this when it was cold out. I know your is substantially more built than mine. I dumped 4 cans of fuel injector cleaner in it, and it did it once more, then never again. I'm not saying it was the injectors, but it was something. I don't recomend that, it says 1 can for 20 gallons, I was just frustrated.
Thanks. Ok, I got the hint guys :)... hold on for an update.
Update. I put the 19lb injectors back in (had 24's) and also put the stock MAF in as well. Problem went away.
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.
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 ;)
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 :)
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 ;)
2.7v indicates a engine temp of approx 80*...
ahhh TC50. You're right. Thanks.
Hey I knew that chart was somewhere. Can you get the car up to temp and check the ECT sensor?
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.
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.
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?
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.