Hello to anyone who may help me!

I can not figure this out!

​​​I have a 90 Trofeo that idles anywhere from 1200-2100 rpms after "warming up".
I have chased and changed many sensors.
Has not solved the problem.
(Love throwing parts at a car)
I can't find any bad vacuum hoses that I can see or hear. Dont particularly know if it's the intake manifold either?Of the sensors changed I have not changed the temp sensor yet but am not sure if that would be the cause? Reason I say that is when it seems to get hot enough to turn the fan on, idle goes down to about 750 where it should be. I can't figure this one out.
Most likely would think some sort of vaccuum leak or unmetered air getting in there somewhere. But the fan thing throws off that thinking.
There may be an easy answer I am oblivious to and I am an idiot! I would love to get this thing running right so I can drive it again. She needs to be on the road!

Anyone have any ideas to fully troubleshoot this one top down?

I will give any details I can if a conversation gets started.
I do apologize if there is already a thread on this, I am not very good using forums!

Thanks

 

If you smoke you can pull the vacuum hose off of the brake booster and blow smoke into the engine. The smokier the better. This mimics a tool that professional technicians have to ID vacuum leaks.

 

Is the throttle body closed all the way?

 

if you can back off the idle stop screw till the plate seats and it still runs. You have an air leak. Intake gaskets bad pcv valve etc etc. start digging.

 

Yall Ready for a book?

Took it out of garage and ran it til it was around 220f. It was around a steady 1550rpm the whole time just sitting in the driveway. Fan kicked on, idle went down to normal steady 750ish. That is pretty much what it has been doing the last couple of months. Is that the temp sensor? Sprayed a whole can of carb cleaner every where I could, no noticable increase or drop of rpms due to the surge of carb cleaner. Took off one of the vac lines to the cruise control while running, only a slight surge in rpm, just to simulate a leak. Not 700+ over idle like it has been. I understand metal expands when hot and if it was a warped mani? or bad gasket? it might seal when getting up in temp? I will have to devise a smoke machine to see if it shows any leaks. I will admit it seems a but seepy in the areas surrounding the intake gasket and heads. This thing doesn't noticeably eat oil or coolant. Ln3 127k miles. I have never given the engine a proper cleaning since I bought the car a few years back but it had been running good after new plugs, wires, air filter at that time up until this spring, regular oil and filter changes every spring. Summer nice day car, not a year rounder. No salt! She garage queens over the winters on a trickle.
It is just odd to me and does not seem to be a coincidence that once the fans kick on, she idles normal. If at the point it cools down enough to turn off the fan, she jumps back up. What the hell is that? Has to be related.
What i have done:
A year or 2 ago I put in a new maf map sensor. Diagnosed that, that fixed that problem then.
Then this spring it started the high idle thing.
Cleaned the throtle body and around it. Nope.
New iac valve. Nope.
It developed a code for the cam sensor, changed that.
Did not fix that, turns out the magnet took a hike.
Did the Padgett interupter mod, installed new magnet.
That was fun with a mirror and needle nose and picks. That worked for the code.
Code gone.
New Bosch o2 sensor. Nope.

This thing has a working vic with service mode. If any of these numbers can indicate a diagnosis, I can get some numbers for you.

Thanks for the replies guys, I'm still digging to figure this out.

 

I don't know if you have access to a scan tool, but the first step is to see if the ecm WANTS it idling high or not. You need to monitor IAC counts, should be 25 ish at operating temp in gear. If it's at zero, the ecm is trying to lower the idle, if the counts are high, it wants the idle high.
Also, look at fuel trims, should be pretty close to 0%. If fuel trims are at +25% and IAC counts are at 0, you definitely have a vacuum leak somewhere.
Post data and I will help

 

The Series 2 3.8l v6 was more prone to vacuum leaks because it uses a plastic upper intake manifold that warps due to an EGR failure. It wasn't used until 95 though.

 

Later this afternoon I will grab a notebook and pen, check it's numbers as it sits not running, then while running high, then after it goes down and post that data. Using the vics numbers mind you, I do not have any sort of scanning tool. I think the vic if accurate may give just about as much info as a cheap scan tool? It definitely has some data.

 

When the EGR passageway melted the plastic, it was more likely to just pump a ton of coolant right into the intake. That was always exciting!

 

Unfortunately, the vehicle info center won't give any useful data

 

You'll need to get your hands on a factory service manual for your year Trofeo.
Beginning with the 1986 downsize, Toronado/Eldorado scan tool data could be displayed on the the driver information center. With the ignition key ON use the buttons on the climate control panel. Press and hold the "OFF" and "Warmer" buttons for about 5 seconds to access the data.
I'm unsure if this is the procedure for your vehicle; the service manual will talk you though it, and provide a description of the data available.
The system also provided the ability to actively test certain outputs of the ECM and other systems such as the compressor clutch, cooling fans, EGR solenoid, IAC etc. Once you're familiar with the system/data, you'll be 1/2 way to a solid diagnosis.
Good luck and keep us posted.

 

Check our IAC or Idle Air Control valve. If it's sticking, it will cause this condition.

Remove it from the throttle body and assure that the spring loaded plunger moves freely.

 

Data from vic and info center in service mode:

Ecm : no codes
b552 history
b671 current
B673 history
Crt and Sri : no codes

Ign on, service mode / "high idle" / 750 idle / in gear
(Cold Eng off) (after cold start) (idle 750 fan on)

Tps. .46 / .80-.94 / .40 / .48
8064 prom. . . .
mat. 23c / 24c / 33c / 45c
iac motor 150 / 64 / 24 / 26
air flow. 0.0 / 8.3-9.1/ 5.5/ 6.2
blm fuel. 128/ 131 / 121/ 128
Int fuel. 128/ 122-127/ 124/ 128
cross cts. 0 / 1-9 / . / 0
​​​​​old pa3. 0 / 9999 / . / 165
spark ang 0 / 0 / 0 / 0
rpm. 20?/ 1340/ 750/ 675
Batt volts. 11.6/13.9/13.5/13.5v
spark deg. 70/ 28-31/ 20 / 26
oxy sensor. .45/ .07-.87/ .07-.70/ .88 steady
Ms inj pw. 52.2 / 3.9-4.1 / 3.9-4.3 / 5-5.3
coolant temp. 23c/ 83c/ 96c/ 87c

(93c idle down to 750 , 96c fan came on)

Anything stick out?
Have not compared to the manual.
TBH not sure why I hadn't looked in there yet. I will if I have time tomorrow to see if it has any baselines and troubleshooting guides. It's not throwing any e codes.
I still intend on a smoke test at some point for any visible smoke leaks. I do not have a machine currently.

Thoughts?

 

Sure looks like your tps throttle position sensor was glitching during your high idle

 

Also while tps was .8-.94v, iac counts were at 65. That’s high so the ecm is commanding a high idle. I would make sure the throttle body is super clean especially around where the throttle blade closes. When carbon builds up, it can hang the blade open a little causing that high tps voltage.
You may need to remove the throttle body in order to clean properly in that area.
If it’s squeaky clean in there and it still gets an intermittent high tps and there’s no binding, I would be replacing that tps sensor