Seville 93 4.6 N* idle slow to come down

[BodybyFisher]

I have used the static method to adjust the ISC on both the 4.9 and NS.  Most recently the 95.

We will get this working, be patient.  

[floods]

Ok, so i will try the static method tomorrow and see what happen

Thanks a lot for help

[BodybyFisher]

Ill will try to find a description of this method for you  before my day is over.

It is 4:25 pm here, late afternoon, in New York, what time is it by you?

[floods]

Thanks a lot, if you don't have time don't worry, nothing urgent

It is 10:30 pm here in France

[BodybyFisher]

Ok here it is discussed by barczy01.  This is a good thread for you!

 

[floods]

Perfect, thanks a lot, i will try it tomorrow, just a question about the gap, so it is .030" not .060" or 0.045" ?

Thanks again

[BodybyFisher]

My memory told me .060, no one clarified my .030 or .045.  Start with .030 and see how she reacts.  Good luck

[floods]

Ok, will try it and let you know

Thanks again

[floods]

No luck with the static method, with the service manual method the gap it already about 0.030", so i try to go more and try 0.060", no change, i did a learning, but again same result, then i try to extract the plunger a lot more, i notice a little bit faster slow down, but really not better, (he go only up the 1000 RPM before slow down).

Look not to be the plunger adjustment who cause the issue, but clearly the ISC get a wrong information, because i leave the PD01 on the cluster (who is the throttle position), and i can see when the the ISC motor activate the angle of the throttle plate keep high and slowly go down, and that not the cable who keep it high, because when the ISC is manually frozen in retracted position, that don't happen, so that confirm there is not cable problem, and not vacuum leak, because it is the throttle plate who stay open too much because the ISC keep it too much open, so now, why he do that.

Maybe a little video can help to see better ?

Thanks a lot

Edited July 19, 2020 by floods

[BodybyFisher]

It is difficult to follow what you are trying to say when you start speaking about the angle of the throttle plate.  

If you push the plunger in while idling does it retract all the way?

What method did you use to retract the plunger?, via DIC or push the plunger to retract it?

The reason I say this is because, if the ISC isn't initially calibrated correct, if you fully retract it via the DIC, it might not be in fact fully retracted, so your starting point would be wrong.  

Retract the ISC plunger by pushing on the plunger (that will close the closed throttle contacts), once it fully retracts that way, then measure the gap.

[floods]

If i push it when idling he don't retract as i know, i have to manually rise RPM and in the same time push the plunger, then he retract, and he retract more than with the DIC method, so to be sure, i did the 2 method, first by pushing the plunger by hand and adjust the gap (that don't work better) so i retract it via DIC and did again the gap adjusting, and get exactly the same result on the idle issue.

Thanks for help.

 

Edited July 19, 2020 by floods

[Logan]

To back up some. Curious about the PCM / ECM replacement. Why was it replaced? 

What about the PROM? Was it moved over to the replacement PCM?  

Can you see the PROM ID with your scanner? 

Has anyone tampered with the idle speed screw on the throttle body? It should be blocked with a plug. 

[floods]

I replace the PCM because a really bad IDLE problem, after driving about 15min (sometime more or less) IDLE become crazy, go from 600 to 1500 rpm, i don't get error code, just some time in history i get a 24X signal error (don't remember the code sorry), i check all the wire, to be sure that not the ICM because this happen because a problem of communication between the ICM and PCM, so i check the wire, install my oscilloscope to the right wire and check the frequency and signal, who was right and according to many other thread i find on the web with the same problem, it was the PCM, and that was right, i replace it and since i don't get the big IDLE trouble, just this slow to get down issue, and as i remember i get the same problem with the old PCM.

The PROM is the original one as i know, i take it out from the old PCM and put it in the new one.

Yes, i think i can see the PROM ID if needed.

No plug on the throttle body idle speed screw (not on the old and not on the new) i am not sure there is one on this model, i don't see how it is possible to put a plug like it is made on my version.

Thanks a lot for help.

[BodybyFisher]

Before Logan's post regarding the ECM, because you began stating that the ISC was getting wrong info/ data, I began thinking about grounds, and ECM connectors.  Are you sure you have all grounds connected?

Is this a brand new ECM?  

If it is new, are you sure it is the correct ECM?

I wonder if the PROM could be damaged?

Just thinking here.  

[BodybyFisher]

These scans are from a 94 Eldo/Seville/Deville/Deville Concours factory service manual.  Have you done this ISC CHECK?

I have no doubt that you have this ISC Check in your 93 manual, but I find one of its conclusions to be thought provoking, see the conclusions to step 1 in the chart, specifically 'above 700 rpm' > inspect for intake manifold leaks if none replace the throttle body.  (You replaced yours) but Logan speaks about the idle screw above^^  <how is that set?

 However, this is complicated by the fact that your idle settles down at normal operating temp.  Again, I know we have explored this, but I want to specifically know,  does the idle settle down at closed loop or at normal operating temp?, and what is the P/N rpm?, what is the rpm in D?

The engine should go into closed loop as soon as the O2 sensors are hot enough to begin sending data << this needs thought, what conditions have to be met for the system to enter closed loop, I will explore that in my 94 manual tonight 

Can you check the coolant temperature you are going into closed loop?  

 

[BodybyFisher]

This is a long term thought >>>   Consider getting a new PROM flashed with the correct firmware for your vin #.  Do you have an original Tech 2?   You can get a flash I believe via the Tech 2, if you purchase a subscription (short term single vehicle).  

[floods]

As i know all ground is connected, but i will double check for sure, on the ECM yes all is connected, sure about that.

The ECM is a remanufactured  unit from Rockauto, yes it is the right, same OEM number on it, about the PROM i don't see any problem (i mean nothing visible), so hard to say, other than that the cur run just perfect, no issue, MPG look right.....

Yes, that the method from the manual i use to adjust the plunger of the ISC motor, and i did this check, in my case, here the result :

- PO7 make the plunger extend and retract : Yes

- PS03 + cooler button then check PD11 : Engine stall after 5 to 10 sec. and RPM is below 700 RPM.

- Then i did the adjustment of the plunger with PS03 to retract and extend then check difference on PD01 i get exactly 10.3 at the last time i did it (value of PD01 with plung retracted what -2.2 and extracted 8.1, by the way is that normal that value is negative when retracted ? ) and what i notice is that he retract low slowly than he extract when using PS03 override, but with PO07 extract and retract is the same speed.

About the adjusting screw on the throttle body, i can see the throttle plate just a bit open, really not much, and engine stall, so that way lower than IDLE, service manual say that this adjustment is ok when engine stall and i can't adjust it without removing the throttle body.

Yes IDLE settle down at closed loop or at normal operating temp, IDLE is just higher when engine is cold and slowly get lower with engine temp increasing.

When engine hot IDLE in P/N is about 650-675 RPM and in D about 600-625 RPM.

About the coolant temperature when switching to closed loop, it was about 40°C, just let the time to the O2 sensor to get hot (less than a min. after starting the engine as i recall), according to the manual it is only after 80°C (this information is on the starting of the Fuel and Air control system section), but that was not the case.

About the PROM, i don't think my TECH II is a original, i know i already use it to program a ECU for a Cadillac CTS 2003 and it was working.

Thanks a lot for help.

[floods]

I see on the diagram on the service manual ISC Check on the page you just send, there is the power steering switch, so look like he is in the IDLE circuit, maybe he can make some trouble, i will check it, i know he work when i check on the Tech II but was not looking in detail.

I am know 99.99% sure that not a vacuum problem of calble.... because it is the ISC motor who keep the throttle plate too much open and then slowly close it, can really see it when i look the plunger in action, so he receive a wrong information or something like that.

Maybe i should try to put the old ECM back in just to see how the IDLE is and see if the problem is the same or not, because that maybe the new ECM who as a problem....

Edited July 20, 2020 by floods

[BodybyFisher]

21 minutes ago, floods said:

I see on the diagram on the service manual ISC Check on the page you just send, there is the power steering switch, so look like he is in the IDLE circuit, maybe he can make some trouble, i will check it, i know he work when i check on the Tech II but was not looking in detail.

I am know 99.99% sure that not a vacuum problem of calble.... because it is the ISC motor who keep the throttle plate too much open and then slowly close it, can really see it when i look the plunger in action, so he receive a wrong information or something like that.

Maybe i should try to put the old ECM back in just to see how the IDLE is and see if the problem is the same or not, because that maybe the new ECM who as a problem....

Good idea, the info we receive from that would be helpful

[BodybyFisher]

Good, if you reprogrammed a CTS, it may be in your Tech 2s capability to flash your ECM, lets keep that in mind.

[Logan]

No way to program a '94 PCM with a Tech 2. 

The '94 used PROMs for the PCM calibration. 

I'm sure finding a replacement PROM would be difficult.....the PROM ID # might give a clue of what calibration is in there (California, US, Export?). 

 

[BodybyFisher]

2 hours ago, Logan said:

No way to program a '94 PCM with a Tech 2. 

The '94 used PROMs for the PCM calibration. 

I'm sure finding a replacement PROM would be difficult.....the PROM ID # might give a clue of what calibration is in there (California, US, Export?). 

 

@Logan I trust that is the same with a 93?

This is before my time, how were PROM's flashed or programmed?   I was under the impression a Tech 2 was backward compatible.  

[Logan]

Actually.....the Chart 6C-6 is in the 1993 manual. The procedure is the same.....but the schematic IS different.

It is on page 6C-40 1993 service manual. 

 

PROMs / Memcals were around before PCs and the internet. 

The same car may have have 25 different PROMs available for different options or markets (California, Canada, US FED emissions) manual or automatic trans or gear ratios or even different engines (Think Pontiac Grand Am...2 different 4 cylinder engines and a 6 cylinder engine available) etc.

There may be a new PROM issued to fix a transmission chuggle issue kind of thing (technical service bulletin). 

So a PROM was really the software for the ECM......you would buy it using a part number and insert it in the ECM as a whole unit as shown. 

[cdgrinci]

I don't want to get off target, and previously content stated no vacuum leaks, however has this engine ever been smoke tested; it wouldn't require a major leak for this to occur.  And again, yielding to the more experienced but it seems a lot of parts swapping has occurred with no success, so trying to stop going down the "rabbit hole".   Best of luck in getting this fixed.

[floods]

About the PROM i can agree, look difficult to find, i am in France and the car is a export version sell in Germany in 93.

Logan is right, there is no programming option on the Tech II for this car.

So today i will try putting back the old PCM, this PCM only get wrong after 15-20min. that let me time to see how the IDLE is.

I check the power steering pressure switch, an no problem there, working like it should.

@cdgrinci yes in France we have a technical control all 2 year, my control was about 2 month ago, and the smoke test was good, and it can not be a vacuum leak, because i see the ISC motor plunger pushing the throttle plate, if i keep the plunger retracted manually, then no issue, the RPM go down fast and normal, so if there was a vacuum leak, the RPM would no drop faster when ISC is retracted, would be the same, that really the ISC motor who keep the throttle plate too much open and then slowly close it to get the right IDLE.

Thanks to all for help.