5.0 idling at 800-1000, never been able to fix it October 07, 2017, 09:48:28 PM For as long as I’ve owned my ’87 5.0 TB, it’s idled at or just below 1000 RPM. I believe it should be closer to 600, no? I’ve replaced the IAC, EGR valve, and TPS. The only current error code is an intermittent KOER 44 (Thermactor system inoperative (cyl 1-4)). After replacing the above (while batter disconnected), it tried to idle down and seemed to be fine for several seconds at 400-600 according to the tach with a nice loping sound, but then fluctuated back up during a few drives and seems to have decided back on 800-1000 again. It’s not a huge issue but I imagine fixing it could improve performance and MPG slightly. Also, cold starts idle at 2200 for about 10-20 seconds; longer than I would like but I just deal with waiting before setitng off. Is this normal? Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #1 – October 07, 2017, 10:16:20 PM Quote from: SlaughterDog;463140For as long as I’ve owned my ’87 5.0 TB, it’s idled at or just below 1000 RPM. I believe it should be closer to 600, no? I’ve replaced the IAC, EGR valve, and TPS. The only current error code is an intermittent KOER 44 (Thermactor system inoperative (cyl 1-4)). After replacing the above (while batter disconnected), it tried to idle down and seemed to be fine for several seconds at 400-600 according to the tach with a nice loping sound, but then fluctuated back up during a few drives and seems to have decided back on 800-1000 again. It’s not a huge issue but I imagine fixing it could improve performance and MPG slightly. Also, cold starts idle at 2200 for about 10-20 seconds; longer than I would like but I just deal with waiting before setitng off. Is this normal?Have you replaced all the vacuum lines and grommets? Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #2 – October 08, 2017, 12:02:45 AM With throttle closed be sure TPS voltage is less than 1v... Once it's above 1v, the idle automatically increases... Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #3 – October 08, 2017, 01:46:07 AM Just check for vacuum leaks then do a base idle reset. Its a 15 minute thing if everything is working properly. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #4 – October 08, 2017, 08:11:52 AM Before all that, 800-1000rpm is based on what?My 88 has full digital cluster, including tach, and everybody here knows with absolute certainty that the digital tach in these cars would have to be MORE accurate than it is before you could even say it's inaccurate. It's the most disgracefully useless tachometer I've ever seen or heard of, and you can't consider engine speed based on it. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #5 – October 08, 2017, 08:07:42 PM Quote from: TheFoeYouKnow;463149Before all that, 800-1000rpm is based on what?My 88 has full digital cluster, including tach, and everybody here knows with absolute certainty that the digital tach in these cars would have to be MORE accurate than it is before you could even say it's inaccurate. It's the most disgracefully useless tachometer I've ever seen or heard of, and you can't consider engine speed based on it.This. At a 650 rpm hot idle on my Autometer tach the stock digital tach shows 800rpm. So if you're basing your high idle on the stock digital tach the idle is probably fine. The stock tach is lying to you. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #6 – October 09, 2017, 01:43:09 AM Only vacuum line I’ve replaced was the source line, but there appear to be no other leaks. As far as the tach goes, I do have the digital tach, that is what I’m basing this on, and now I feel like a dummy for being concerned since I’ve always known that period Fords have inaccurate induction tachs; makes me wonder how that affects timing advance and other ECU functions.If it’s reading high at low RPM, could it also be reading low at high RPM? When it reads 5k (all the redline bars from 5 to 6 light up at the same time) I let off the pedal to upshift, figuring the AOD is waiting too long. Waiting for the upshift at WOT feels like it’s left the power band and is slower. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #7 – October 09, 2017, 04:20:53 AM Stock motor is dead by 4k, probably more like 3.5k. Makes more noise, but not any faster. In the case you have about 10 minutes, you can do about 55, maybe 57 if you hate the car in 1st before rev limiter hits.If you can unplug the if sensor and get the motor to die by increasing the idle screw, the computer and iac are doing what they are supposed to do. How I set my idle after someone's messed with it...Key on engine off, test to a voltage. Anywhere around 1v is fine. I believe it to be okay from about .6 to 1.1v. Start it up and unplug iac. Back it off till engine starts to die then plug in iac and you are done.Now getting a silky smooth idle requires most stuff to be working exactly right and a decent tune up with not too many vacuum leaks. Low vacuum at idle with make the car run rich and mess with o2 readings.If you run a cylinder ballance test twice in a row and pass, you should be all set. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #8 – October 09, 2017, 04:21:34 AM Btw, idle should be about 850rpm in neutral snd 650 in gear with a aod. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #9 – October 09, 2017, 06:10:38 AM That tach is just a pretty light show. It means nothing. Interestingly, it's more accurate than the oil pressure gauge on a 6 cylinder Trailblazer. The TB OP gauge is displaying a calculated value based on temp and RPM. The sender is a simple on off switch. So our tach is more accurate than at least THAT. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #10 – October 09, 2017, 06:32:35 AM Quote from: SlaughterDog;463159As far as the tach goes, I do have the digital tach, that is what I’m basing this on, and now I feel like a dummy for being concerned since I’ve always known that period Fords have inaccurate induction tachs; makes me wonder how that affects timing advance and other ECU functions.The EEC has an accurate reading of RPM, you don't need to worry about that. These cars don't have any kind of multiplexing, which means that the different electronic modules don't communicate with one another. The cluster and EEC both know the engine speed, but it's because they both pick it up independently. It's like vehicle speed; the cluster, the EEC and the cruise all know the vehicle speed, but it's because they're all tapped into the VSS. They're not sharing info. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #11 – October 09, 2017, 03:43:54 PM Quote from: SlaughterDog;463159Only vacuum line I’ve replaced was the source line, but there appear to be no other leaks. As far as the tach goes, I do have the digital tach, that is what I’m basing this on, and now I feel like a dummy for being concerned since I’ve always known that period Fords have inaccurate induction tachs; makes me wonder how that affects timing advance and other ECU functions.If it’s reading high at low RPM, could it also be reading low at high RPM? When it reads 5k (all the redline bars from 5 to 6 light up at the same time) I let off the pedal to upshift, figuring the AOD is waiting too long. Waiting for the upshift at WOT feels like it’s left the power band and is slower.Yeah see here: http://www.foxtbirdcougarforums.com/showthread.php?38600-The-stock-digital-tach-is-apparently-very-inaccurate&highlight=tachometerIt's pretty much useless. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #12 – October 09, 2017, 04:08:39 PM What I'd like is for someone who knows electronics at an engineering level to look at it and find where pulse/rev is determined in the tach and to come up with a method to correct it for a V8. My research pretty much confirms what is in the linked thread, and that is that our V8 cars have a tach that is configured for a V6. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #13 – October 09, 2017, 04:56:46 PM Quote from: TheFoeYouKnow;463167What I'd like is for someone who knows electronics at an engineering level to look at it and find where pulse/rev is determined in the tach and to come up with a method to correct it for a V8. My research pretty much confirms what is in the linked thread, and that is that our V8 cars have a tach that is configured for a V6.That would be the ideal. Then I could ditch the Autometer tach. Until then it stays. Quote Selected
5.0 idling at 800-1000, never been able to fix it Reply #14 – March 29, 2018, 08:26:24 AM There's always THIS. Quote Selected
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