45 to 50mph Issue, Feels Like TC is locking and Unlocking

[2seater]

In the interest of full disclosure, I tried the broken IAC actuator. The shaft is threaded for about 1/2 the length and the rest, extending to the actual head of the shaft is larger with a slot in the side to prevent it spinning. It could be rethreaded back into the housing until the slot engaged the housing and then tried electrically. It retracted fully just fine and appeared to extend fully as well, however when trying to retract a second time, it didn't appear to move, despite the override indicator on the dash changing counts. Hitting extend a second time caused the shaft to be ejected. It may be possible it is somehow broken and should not have done that, or, it can actually destroy itself if operated unrestrained. I was wrong and Ronnie and the manual know what they are talking about.

[Dashmaster]

Received a Delphi MAF yesterday. I will install it this evening and see what it does. One interesting thing is this one comes with a EMI cover to block outward signals. I did not see it on any picture of any brand sensor i looked at. 

[Dashmaster]

Will do, The Box also has a warning paper in it telling you to install the cover if not already on the unit. It on the sensor as shipped still sealed in the packaging.

[2seater]

Yes, interested to see what this cover may be and what it's purpose is.

[padgett]

Wow away for a day and see what happens (well two - left at Midnight Tuesday to take my Jeep with a friend to Atlanta, pick up a trailer and then a car. Drive back to his place outside Tampa, unload, back in Orlando a tad before 7 pm. About 950 miles & much of the return through construction on I-75 then a pileup on I-4. Then a day of cleanup and other things.

 

Sorry about the IAC/TPS mixup, IAC count itself does not mean much once it recalibrates, just the changes.

 

Some MAFS have an exposed coil that is covered until use.

Edited July 14, 2016 by padgett (see edit history)

[Dashmaster]

I will take pictures of it all. The Paper that explains the EMI cover. Box and both MAF's.  The picture on Rock Auto did not show the EMI cover. Looked like all the rest of the MAF's

[KDirk]

Ok, just to interject here, I don't suspect an EEPROM issue for two reasons:

1. This doesn't come off (to me anyway) as a symptom of an incorrect calibrator chip.

2. Unless I missed something, this problem came on out of nowhere. I'd hope if the ECM had been swapped (and with it - potentially - the EEPROM) that it would have been disclosed early on in this thread. 

 

Unless something damaged the EEPROM itself (possible but rather unlikely) and further only to a few bytes of the code therein, I don't see it being the root cause of this issue. I am following this thread with great interest, as I am wanting to see just what the magic bullet will end up being. At this point I haven't any great insights to offer.

 

[Machiner 55]

Don't want to argue (sure looks that way though) but I think this is where one gets the idea of manually adjusting the IAC. (see figure C2-9 below)

I couldn't find the text where it says to do this but I know I've read it in the FSM. Should I run across it, I"ll edit this post to include it.

It was my understanding that this was done to insure the pintle was fully retracted to prevent the mechanism from being damaged during installation. I am not suggesting anyone do this. I'm just pointing out that this is in fact something in the FSM and no one can be faulted for following it. I have, in the past, done this but I can't tell you if it is a good thing or a bad thing to do. I've had IAC's that retracted when pushed upon as shown figure C2-9 and others that have not. What that tells me... I don't know.

It was years ago and I don't remember the results exactly except that I figured that the ones that would not retract were defective.

Although they would retract when connected to the harness and the override function used.

 

(Image pulled from 1990 FSM)

Edited July 15, 2016 by Machiner 55 (see edit history)

[Ronnie]

Thanks for posting the photo John. The information written on it gave me what I needed to find it in the FSM.

 

It appears the FSM contradicts itself in different places concerning the IAC. Below is the text that goes with the photo John posted which seems to contradict what I quoted from the FSM earlier.  I apologize for not digging deeper into the FSM before making my post.and causing confusion. I'm sort of red faced on this but it's not the first time for that.

 

With that said, I won't recommend that anyone go against what is written in the FSM, but I will stick with what I have been taught over the years of not pushing in on the IAC pintle when you have it out. I will continue to clean it, clean the hole where it seats in the throttle body, and put it back in the way it came out..

 

When I read the text in the photo I take it to mean the adjustment is intended to be made only on a new IAC in order to install it properly. I don't think the adjustment was intended for resetting or adjusting the IAC to correct a problem with it's operation. I think what I quoted from the FSM earlier about resetting the IAC is more applicable for a used IAC. That is the section of the FSM that will guide me when I'm working on the IAC in my car..

 

 

[Ronnie]

OK

 

Have it your way

 

I will stop butting in when you are teaching class

 

I have a lot to do today and don't have time for a good argument

[2seater]

Crawled back out of my cave momentarily,  because I have had the same experience as stated by others, some will move with a little manual pressure and some that will not. It is confusing to be sure. I think I will dissect the one I have that is definitely broken to see what's what .

[padgett]

Note that the illustration is of a screw-in IAC like an 84 Fiero and not the later one that uses screws. Could be a design change.

[2seater]

I know this may not be actually related to the problem the OP started with but is a follow on the IAC question. From dissecting the one I have that cam apart, as stated, there is no feedback mechanism, it is simply a slave. When I reinstalled the moving shaft from the one that had disassembled itself, I was able to press the shaft back into the assembly a small amount. In no case can it be pulled back out. Without totally destroying the rotating portion, it "appears" there is a small range where the threaded portion inside the rotator can travel, but I am unable to determine why? I surmise, if this is fully seated, the shaft cannot be pushed in, but if not bottomed, it will be movable. As to why it could be in more than one position is unclear until I disassemble further.  Perhaps it is for assembly tolerance? In any case, there is nothing to prevent the shaft from unthreading itself if fully extended electrically in the open. This is a poor photo of the basic assembly. The actual moving part, aside from the extension shaft, is the rotator, third from the left in the bottom row. It has a ball bearing on the left end and the small ring to the left is just the metal seat for the bearing in the cap at the far left. The spring for the shaft is missing as it went walkabout when the shaft left the assembly

 

[2seater]

I did split the rotating actuator and the threaded portion inside is solid and part of the assembly, no movement is possible. The only place I could see where possibly 1/8" of movement could exist is where the ball bearing inserts into the cap. Even with a third of the side of the rotator removed the threads capture the shaft more firmly than a firm push will dislodge. Somewhat baffled.

[Dashmaster]

PROBLEM RESOLVED

The MAF solved this problem

Here are pictures of the old and new Delphi MAF with EMI Shield

 

[Dashmaster]

Have slight new issue, High RPM stumble or miss. Only when you give its lots of throttle, Example,kick down to pass, its over 3K RPM when it does it very briefly. Car may still be learning the MAF. 

[Ronnie]

On 7/2/2016 at 6:23 PM, Dashmaster said:

Interesting Update

Ronnie, I unhooked the MAF, Car did not run as good. Drove it about a mile did not notice the issue but not running as good. Stopped and plugged in the MAF, Car Stalled, I turned off the key and restarted. Drove wonderfully, No issue at all, drove about 10 miles. On my way back I thought I should stop and turn it off for a minute or two and see if the problem is still solved, Nope Nada. Problem returned.

 

Here is some new information, The unplugged MAF did not set a code, I unplugged the EGR earlier today, Did not set a code and EGR light was flashing notmally in the ECM data screen.  The only think the ECM complain about is the Cruise, even though it plugged into a new unit.

 

I am starting to think the ECM may be bad. What do you think??

The ECM I have, I bought 2 years ago from the Reatta store when the original would not fire the injectors.

 

Thanks for letting us know you got it fixed. This was the post (#50) that should have resulted in the problem being fixed but I can't blame you for not spending the money on a MAF until you knew for sure..

[Dashmaster]

I am very Thankful for all the help and suggestions on this problem, I can say I learned a lot more about the engine on the car and what the CRT can and can't do.

All the work I have done was worth it. It run so good except for the high RPM stumble. Best it ever has. If not having this problem I would still be running around on vary bad timing chain and tensioner. I now also have a good selection of spare parts for backup.

 

Since the old MAF would give ECM reading from about 6.2 at idle and into the 20 driving. I suspect it had no square wave data. The ECM won't show that. I am surprised it did not act up when tapped on.

 

Edited July 17, 2016 by Dashmaster (see edit history)

[2seater]

Thank you for sharing the fix with us. I too have found failures that do not follow the typical symptoms and resolution so this one will be filed away in the memory bank. The shield is a curious item to be needed after this style MAF was used for decades, on a LOT of vehicles?  The typical idle reading I see is in the 4-6 gm/sec range with a typical maximum reading of around 125, a really good running one will be in the mid-upper 130's. The scale is at maximum at 170gm/sec but requires some form of boost to get there.

 

The MAF learning will likely take a little while to get all the BLM cells filled but if running at a high accel. rate, and rpm, you are may have a misfire, running out of fuel pressure or other possibilities? Did you start the ECM from scratch with the new MAF? 

[Dashmaster]

I did not start out with fresh ECM but did unhook battery so I could re-mount ECM. So it did start fresh. The Miss was more

pronounced at first. The I decided to change a couple of things back. put my Rapid Fire #14 plugs back in and put the old fuel

regulator on. I get better pressure reading with the old one. After the plug change it was much better, Drove it to where I catch the commuter train a 25 mile run on the highway pulling some good hills at speed. I had it miss maybe 2 times right after I got on the highway pulling the first large hill, Nothing after that. I had to slow down once due to a slow driver, to get back up to speed it kicked down and went. Nothing else rest of the trip. I will be driving it daily to make sure the bugs are out of it.

 

I think the EMI shield is there because this MAF is used on other GM cars that have the coil pack on the same side as the MAF. Truly just my speculation. 

[2seater]

Sounds sweet to me. A happy car is such a pleasure Your conjecture about the shield sounds as good as any I can think of.

[KDirk]

Glad to see a resolution. This is the type of situation where the OBD falls short. As good as the diagnostics system was - for it's time - it has some major limitations. Most notably in catching ignition problems, but this is yet another where old school seat-of-the pants troubleshooting was needed.

[Dashmaster]

Guest, See page 5 of this there are several pictures, They did not turn out as good as i thought. Hope to see you in Allentown.

[DAVES89]

39 minutes ago, Dashmaster said:

Guest, See page 5 of this there are several pictures, They did not turn out as good as i thought. Hope to see you in Allentown.

  Good running car... clear tail light... what could be better?

[Dashmaster]

TPS is new, Set to .4, sometimes settles to .38. It looks good from ECM, My old one is good to and was set to .4

My miss or stumble happened again this morning pulling the fist Mountain. 73 mph needing to accelerate a bit more, 4th gear locked misses a couple of times randomly, give it more pedal it kicks down to 3rd no missing up into the 3K rpm range at all.

My fuel pump is 3 years old, Delphi unit I think. Its just running in the lower spec range. After Allentown I plan to replace it and then

install some Bosch 3 injectors. I could have an injector going bad at specific frequency. RPMs in 4th are just above 2k rpm range. If it was fuel pressure I would think it would miss during the kickdown the running higher RPM's  

[Dashmaster]

Its is running very good with this minor exception. Hope to meet lots of you in Allentown. Good  Looking Taillight, Still has bad paint though. 

[Ronnie]

It's been my experience that the miss under load as you describe is caused by the secondary ignition system. Spark plugs, bad plug wires, burned wires or torn spark plug boot is what I would be looking for. Fuel pressure drop because of a dirty filter or bad pump or regulator is a less likely possibility.

[Dashmaster]

Ronnie, Wires are New from Reatta Store, Plugs my old Rapid Fire #14 all good. Coils checked Primary/Secondary with Meter, They are 6 months old Standard Motor Product brand.. ICM is Airtex one week old. I did try to swap back in the old Delco, But it quit working car would not start.

Before the Lock and Unlock issue car was running perfect. Only new parts that are in place now are. TPS, ICM, Wires, OX sensor, MAF.

I did not check the wires since they are new. They are AC Delco Brand but made in china.

 

[Ronnie]

Don't take for granted that new parts are always good. I worked for three weeks trying to find a miss in my brother-in-law's car the ended up being a new ACDelco spark plug that he purchased.

 

This is old school but the way I would test for your problem is to get the car in a dark garage and have a friend start the engine, put the transmission in Drive and while holding the brake tightly, apply the gas to load up the engine. It should miss under those conditions like it would if you were accelerating up a hill Look for any spark flashing around the coils, plug wires, etc.

[padgett]

Night works well also. When I open both doors, my garage is flow through. 4th lockup/low rpm/grade is the biggest strain you can put on an ignition system and missing in lockup is much more noticeable than unlocked. Secondary ignition (plugs/wires/coils) will not set codes. Primary ignition (crank sensor/ICM/ECM/cables) may set codes and cause an unstable tach.

[Dashmaster]

I agree it could be a bad wire. I will have to swap my old ones in after meter check. When I leave in the morning for work its plenty Dark. 4am. Since it does not do this anywhere but the hill pull might not show up but will see. 

[Dashmaster]

No water. Guest, I have had the whole rear out of my car to fix rust issues, Bad gas and broken brake and fuel lines 2 years ago. Tank was removed, cleaned , POR15 painted and new pump installed. I also tried some fuel treatment for the last problem. car gets driven often,  Gas usually no older than 2 weeks or so. 

This is a pretty good grade coming out of Hagerstown, Md. heading to Frederick, MD.

Yes would be very nice to have fuel rail pressure and trans. temp gauges for the CRT. 

 

[Dashmaster]

I have swapped back all my old wires. Load miss still there.

[padgett]

OK TPS at idle sounds good, is it over 4.0v at WOT ? Never heard of switches in a GM TPS.

 

Is just possible a dirty injector could cause this, low rpm high load is dad for a number of things.

 

Must admit at this point I'd use Tuner Pro RT to whip up a dashboard of just about every parameter and record a run. Back when I was designing flight controls we had rolls of Brush records and would unroll on a long corridor and just walk the roll looking for outliers.

 

Better would be fast temp sensors on each exhaust  and look for one that is different when it stutters to find which cyl it is but am not equipped for that.