Idle issues

apsmith49921 · Sep 23, 2020

So have 2 issues regarding my idle.

Issue 1: If I turn the heat or AC on the car idles high like 1500 rpm. It surges a touch, goes up then sometimes drops off back to about 700. 20 30 seconds goes by and pops back up.

Issue 2: was cruising about 55 in 4th or 5th and went to slow down so I popped it in neutral. Car dropped down to around 500rpm then died. I've had this happen once before. I noticed it does drop low in that situation but has only died on me twice.

I plan to check for vacuum leaks and maybe clean the IAC. Any other suggestions?

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evilcw311 · Sep 23, 2020

Clean the iac really good and put a couple drops of oil in it and manually work the spring a bit. Then put it back on.

Do a smoke test and I bet you’ll find a vacuum leak. Especially thinking it’s the plastic line that runs from the driver side fender to the firewall in the passenger side.

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apsmith49921 · Sep 23, 2020

Going to snag some cleaner on my lunch break today. Probably work on the smoke test and stuff this weekend and let you guys know what I find

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apsmith49921 · Sep 23, 2020

Iac was perfectly clean and functional I cleaned it anyway. Did a smoke test and found 0 leaks not even a pin hole

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ttocs · Sep 23, 2020

its time to get technical... Get the motor hot and if you notice its having problems even better. Pop the hood and lets try some technical taps on the IAC/TPS area. Just tap on the sensors and the harnesses that go to them while its running and see if you notice any difference. If nothing happens then take your knuckles and knock on them a little harder. If still no change try grabbing the harnesses and pull/tug/jiggle them around and see if they move, and if it makes any difference. Last year getting mine running again I discovered that the tps harness would get hot and start to loose contact and then start to drift and show 4-7% throttle when I was outside of the car. I replaced the sensor, same thing. Replaced the harness and it fixed it.

apsmith49921 · Sep 23, 2020

Will do. Should I have the heat or ac running when doing so? Will also add it was about 50 this morning but it continued to do this during cold start and after warm up. With the heat off at idle no matter the temp it idles 100% fine.

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ttocs · Sep 23, 2020

I would try with both the ac on and off if you can. It could be the tps, or the iac. IF the tps isn't reading correctly it can mess up the iac but then as well if the iac is not working correctly your tps could be perfect and its just not responding. Don't be afraid to get a little rough with the taps (back of a screw driver for example) and the harnesses should not be able to be pulled off. Mine had a broken clip and when it was hot I could barely tug on it and it would pop right off.

apsmith49921 · Sep 23, 2020

I should be able to do both no issue.

Another thing I'll check from reading a post on another forum. Low freon causing the ac compressor to surge thus causing idle surging issues. I did not realize that with the car in defrost (was this morning) it causes the ac compressor to run

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apsmith49921 · Sep 23, 2020

I was just able to confirm that the ac compressor is causing the surging idle issue. If you turn it to either of the settings directly next to "off" it's fine. If you turn to any other setting idle begins to hang and surge

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evilcw311 · Sep 24, 2020

My compressor caused a bit of an idle issue right before it burnt itself up. And by burning itself up I literally mean it caught on fire. Luckily I had just pulled up to my buddies building in the pitch dark and could see the glow coming from underneath. Put it out really fast before it could do any damage.

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apsmith49921 · Sep 24, 2020

so it died again on me today. Things I have observed....
1. only happens at higher speeds above 40mph
2. voltage gauge drops below its normal range (due to it low idle and almost dying I assume)
3. it does not die at lower speeds but I can see the idle get a bit low when putting it in neutral to coast to a stop.
4. It does this even with the heat/ac off at normal operating temp (has died a total of 3 times since I've owned it about 2 months)

Its done this a total of 3 times now. I have cleaned the IAC and checked connections. I have technical tapped on the TPS and checked its connection. Also a smoke test was done and no leaks were found. Only modifications I have done are a JLT intake and exhaust. if I remember correctly the dying while moving had not happened before the JLT install but I could be wrong.
Thinking clean the MAF and check its connection, Change Fuel filter as I'm sure its the 23 yr old original, Clean the TB.

I'm pretty certain the AC is causing the surging idle, it idles 100% good with AC off. When its away for the winter ill do a leak test and fix properly, not a huge issue to me at this moment. I can deal with it "bouncing from 800 to 1200 rpms"

edit: when i installed the JLT i used the MAF that was sent with it, bought used from a member on another site. I will probably clean and re install my old MAF that came with the car. This one is black plastic housing but the old one was the metal housing.

ttocs · Sep 24, 2020

what kind of maf?

apsmith49921 · Sep 24, 2020

Both are factory ford MAF. One is plastic(came with jlt) one is metal (came on vehicle) both are the same diameter

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ttocs · Sep 24, 2020

post a pic I am not aware of a factory maf that was plastic.

apsmith49921 · Sep 24, 2020

Here you go sir.

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ttocs · Sep 24, 2020

you might try doing a search on the model number on it I can't make it out. Some mafs are made to send different readings than it should to trick the ecu so you can run larger injectors. They are not the best way to go about it and if you do not have the larger injectors then it is absolutely not the way to go.

apsmith49921 · Sep 24, 2020

Injectors are stock. I tried to get it swapped back to the stock one tonight but ran out of time. I'll mess with it this weekend and report back. Guess I'll just have to down shift

it's actually perfectly fine at 40mph and under. Did a hard 2nd gear pull to 6500 and it ran great hit a nice backfire pop on the 2-3 shift too lol

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ttocs · Sep 24, 2020

apsmith49921 said:
Injectors are stock. I tried to get it swapped back to the stock one tonight but ran out of time. I'll mess with it this weekend and report back. Guess I'll just have to down shift it's actually perfectly fine at 40mph and under. Did a hard 2nd gear pull to 6500 and it ran great hit a nice backfire pop on the 2-3 shift too lol

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yea something is wrong then if its running a stock tune and backfiring.

apsmith49921 · Sep 24, 2020

I guess I cant 100% verify it's a stock tune. But I'm going to address the MAF. Also could have just been a pop or a cackle I guess. It has an slp lm1 exhaust which is pretty well a straight pipe

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apsmith49921 · Sep 25, 2020

So I have progress... swapped the original maf back in the car and took it to get dinner. No dying issues and car seemed to do much better. Went over 50 in 5th popped it in to neutral and 0 issues several times. It did seem to drop a bit low one time but no where near.

Now I did not clean this MAF before re install because I didnt have cleaner. So I'll clean it and should be good to go.

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