I am almost at my wits end.

[nmhenry]

On 9/16/2022 at 9:45 AM, padgett said:

"Would a bad EGR cause it to think it's lean?" any vacuum leak could. What is the manifold vacuum reading at idle ?

Here’s the vacuum reading at idle.

also I used a mechanic’s stethoscope on the injectors and only one gives a steady tapping. The rest seem intermittent and pause in time with the stumble.

 Vacuum is at 15 but decreases when the engine stumbled

[padgett]

Would expect 18-20 at idle and no leaks. A squirt gun full of water is good for finding leaks.

[2seater]

I see 18” of warm idle vacuum at 800-900ft if altitude.

[nmhenry]

13 hours ago, padgett said:

Would expect 18-20 at idle and no leaks. A squirt gun full of water is good for finding leaks.

I have sprayed carb cleaner all over the intake, on every gasket, vacuum line, grommet, and seal. Done the same with starting fluid. I have replaced every rubber vacuum line and even checked vacuum lines and components with a vacuum pump. I have found no leaks and every component except the line going to the purge solenoid hold vacuum. I plugged that port off with no change. I don't know how possible it is that the intake gaskets developed a leak on the bottom side of the intake but I would expect to hear it through the oil cap if that is the case and would expect to have water in the oil. No water in oil.

 

 

[Ronnie]

20 hours ago, nmhenry said:

 Vacuum is at 15 but decreases when the engine stumbled

I just wonder if the low vacuum could be explained by a plugged exhaust system? If you can't get air out you can't suck it in.

 

Even though the cat is what is turning red, I wouldn't rule out something restricting the exhaust on down the line. Like maybe a baffle rusted in the muffler and stopping it up or a mashed exhaust pipe. The cat just happens to be what has a honeycomb matrix inside that is designed to absorb heat to enable it to work properly. Even if it's not what is blocked it could still might be what would turn red first.

 

A restriction will cause the exhaust to turn red hot. I've saw it happen plenty of times on '60s and '70s model Cadillacs. GM came up with the bright idea of making the exhaust pipe before the muffler double wall to make the exhaust quieter. After they got old the inside wall of the pipe would collapse and partially block the flow of exhaust gases. The result was a red hot exhaust pipe where it made a bend and very poor performance. If you didn't know what to look for it was a very hard problem to figure out. I doubt a double wall pipe is causing the problem on the Reatta. I'm just giving an example of what a restricted exhaust can do.

[2seater]

Restricted exhaust should be least problematic at idle. With a vacuum gauge, it should steadily decrease at a high idle, say 2000 rpm or so.

Injectors being intermittent shouldn’t be normal but determining if it is the cause or symptom can be difficult. If it is the same injector that remains steady, I would try to switch connections with the neighbor if possible to see if the irregular operation follows the electrics. It may change the idle feel because of sequence change but we are looking for the cause of intermittent operation.

Did you disassemble the EGR to allow cleaning the moving pintle and the seating area in the lower housing? There can be no EGR flow at idle or it will affect the idle in a negative way.

[nmhenry]

8 hours ago, Ronnie said:

I just wonder if the low vacuum could be explained by a plugged exhaust system? If you can't get air out you can't suck it in.

 

Even though the cat is what is turning red, I wouldn't rule out something restricting the exhaust on down the line. Like maybe a baffle rusted in the muffler and stopping it up or a mashed exhaust pipe. The cat just happens to be what has a honeycomb matrix inside that is designed to absorb heat to enable it to work properly. Even if it's not what is blocked it could still might be what would turn red first.

 

A restriction will cause the exhaust to turn red hot. I've saw it happen plenty of times on '60s and '70s model Cadillacs. GM came up with the bright idea of making the exhaust pipe before the muffler double wall to make the exhaust quieter. After they got old the inside wall of the pipe would collapse and partially block the flow of exhaust gases. The result was a red hot exhaust pipe where it made a bend and very poor performance. If you didn't know what to look for it was a very hard problem to figure out. I doubt a double wall pipe is causing the problem on the Reatta. I'm just giving an example of what a restricted exhaust can do.

I removed the cat and ran it like that.
 No improvement so it now has a straight pipe to the muffler.

[nmhenry]

10 hours ago, 2seater said:

I see 18” of warm idle vacuum at 800-900ft if altitude.

I'm at 3510 ft altitude.

 

[nmhenry]

5 hours ago, 2seater said:

Restricted exhaust should be least problematic at idle. With a vacuum gauge, it should steadily decrease at a high idle, say 2000 rpm or so.

Injectors being intermittent shouldn’t be normal but determining if it is the cause or symptom can be difficult. If it is the same injector that remains steady, I would try to switch connections with the neighbor if possible to see if the irregular operation follows the electrics. It may change the idle feel because of sequence change but we are looking for the cause of intermittent operation.

Did you disassemble the EGR to allow cleaning the moving pintle and the seating area in the lower housing? There can be no EGR flow at idle or it will affect the idle in a negative way.

I did not disassemble since the gasket between the two halves is unobtanium.
 I will have a new EGR next week.
 I did listen to injectors with a mechanic's stethoscope and the only one that had a steady click was #4. The others quit clicking in time with the stumble. I don't know if that would be normal, if the injectors are sticking, or if this is the computer trying to compensate.
 

 

[2seater]

51 minutes ago, nmhenry said:

I'm at 3510 ft altitude.

 

That likely would account for the lower vacuum reading. The key is if it is steady or has a regular variation, which might indicate a mechanical issue.

[2seater]

55 minutes ago, nmhenry said:

I did not disassemble since the gasket between the two halves is unobtanium.
 I will have a new EGR next week.
 I did listen to injectors with a mechanic's stethoscope and the only one that had a steady click was #4. The others quit clicking in time with the stumble. I don't know if that would be normal, if the injectors are sticking, or if this is the computer trying to compensate.
 

 

You should be able to switch #4 & #6 harness connections, they are right next to each other. It may give a hint if the problem is electrical if #6 becomes the steady one or if mechanical if #4 remains the only one with rhythm. 

[nmhenry]

1 hour ago, 2seater said:

That likely would account for the lower vacuum reading. The key is if it is steady or has a regular variation, which might indicate a mechanical issue.

It is not a regular fluctuation like I would expect if I had a bad valve. Compression is 150 PSI on all cylinders except #6 which is 140 or so.
 Vacuum only fluctuates when the engine stumbles.

 

[nmhenry]

54 minutes ago, 2seater said:

You should be able to switch #4 & #6 harness connections, they are right next to each other. It may give a hint if the problem is electrical if #6 becomes the steady one or if mechanical if #4 remains the only one with rhythm. 

I'll try that.

 

[2seater]

On 9/18/2022 at 8:04 PM, nmhenry said:

I'll try that.

 

While chasing a different issue on my car, I had the opportunity to listen to my injectors with a stethoscope today. All injectors click at a steady rate with no deviation. This confirms that irregular operation is not normal. They should operate continuously and track right along with 50% of engine rpm, the only difference being how long they stay open, per the pulse width on ED06. 

[padgett]

Personally think a leakdown test tells more than compression.

BTW can shut down individual injectors with the ECM scream. ES10. One that has no effect is culprit.

[nmhenry]

On 9/21/2022 at 2:49 PM, 2seater said:

While chasing a different issue on my car, I had the opportunity to listen to my injectors with a stethoscope today. All injectors click at a steady rate with no deviation. This confirms that irregular operation is not normal. They should operate continuously and track right along with 50% of engine rpm, the only difference being how long they stay open, per the pulse width on ED06. 

The mystery deepens. I have spark on all cylinders. Replaced the MAF still no joy. The car starts intermittently and when it does it runs rough and eventually stalls.
It will run on starting fluid. This time when it wouldn't start I got the noid light out. #5 which is the only one consistently clicking when I listen with a stethoscope is the only one getting any signal now. Have replaced crank sensor, cam sensor, coolant temperature sensor, MAF, EGR valve,O2 sensor, timing chain and gears, timing chain tensioner, trigger magnet, PCV valve and grommets, spark plugs, wires, coil and ICM. I have cleaned all grounds also.
 Possibly bad ECM? What am I missing?

 

[Ronnie]

26 minutes ago, nmhenry said:

Possibly bad ECM?

That's what I would try next.

[2seater]

Did the consistent injector change? Previously was listed as #4? In any case, injectors are a constant 12v+ with a switched ground to activate. If memory serves, it is a brown wire at each connector. In any case, it is the wire that is present in all six connections at the injector. The ECM does the switching of the ground, so it is possible to have a bad connection or, the ECM itself.

 

This sounds somewhat like a problem I have been chasing that may be a bad ECM in my case too. Too soon to tell if that is the case, but if I would disconnect the battery ground to change the Memcal, the engine would run fine, but only for a period of time and it would act up again, rough idle, stalling, black smoke etc.. In other words, the behavior would change if I reset the ECM. I am not suggesting this is the same case, but it costs nothing to reset the ECM so it starts from scratch to see if things change.

[nmhenry]

14 hours ago, 2seater said:

Did the consistent injector change? Previously was listed as #4? In any case, injectors are a constant 12v+ with a switched ground to activate. If memory serves, it is a brown wire at each connector. In any case, it is the wire that is present in all six connections at the injector. The ECM does the switching of the ground, so it is possible to have a bad connection or, the ECM itself.

 

This sounds somewhat like a problem I have been chasing that may be a bad ECM in my case too. Too soon to tell if that is the case, but if I would disconnect the battery ground to change the Memcal, the engine would run fine, but only for a period of time and it would act up again, rough idle, stalling, black smoke etc.. In other words, the behavior would change if I reset the ECM. I am not suggesting this is the same case, but it costs nothing to reset the ECM so it starts from scratch to see if things change.

Sorry about that. It was always #3. I got a bit confused I guess on cylinder numbering. The only one working now is the second one on the front bank. That one was always the consistent one. Had my head in my 4th point of contact previously.

 

Edited September 27, 2022 by nmhenry (see edit history)

[nmhenry]

9 hours ago, 2seater said:

Did the consistent injector change? Previously was listed as #4? In any case, injectors are a constant 12v+ with a switched ground to activate. If memory serves, it is a brown wire at each connector. In any case, it is the wire that is present in all six connections at the injector. The ECM does the switching of the ground, so it is possible to have a bad connection or, the ECM itself.

 

This sounds somewhat like a problem I have been chasing that may be a bad ECM in my case too. Too soon to tell if that is the case, but if I would disconnect the battery ground to change the Memcal, the engine would run fine, but only for a period of time and it would act up again, rough idle, stalling, black smoke etc.. In other words, the behavior would change if I reset the ECM. I am not suggesting this is the same case, but it costs nothing to reset the ECM so it starts from scratch to see if things change.

I've had the battery disconnected a few times throughout this ordeal. It hasn't helped.

 

[Ronnie]

With the ignition key on, check each injector connector to see all of them have 12 volts anytime the key is turned to the RUN position..

[nmhenry]

43 minutes ago, Ronnie said:

With the ignition key on, check each injector connector to see all of them have 12 volts anytime the key is turned to the RUN position..

I have done so and they do.

 

[Ronnie]

21 minutes ago, nmhenry said:

I have done so and they do.

 

If the injector isn't firing about the only thing left is a bad connection between the ECM and the ECM or a bad ECM. I don't know of anything that would tell the ECM to only fire one injector. If you have a spare ECM, swap it out to rule the ECM out as the problem. 

[nmhenry]

34 minutes ago, Ronnie said:

If the injector isn't firing about the only thing left is a bad connection between the ECM and the ECM or a bad ECM. I don't know of anything that would tell the ECM to only fire one injector. If you have a spare ECM, swap it out to rule the ECM out as the problem. 

I'm going to order one from Rockauto once I get the number off of my old one

[padgett]

One injector won't make the engine stall. About the only thing left is water in the gas ?

[nmhenry]

38 minutes ago, padgett said:

One injector won't make the engine stall. About the only thing left is water in the gas ?

 Only one injector is firing. #3 is the only one receiving a signal.

Edited September 27, 2022 by nmhenry (see edit history)

[2seater]

2 hours ago, nmhenry said:

 Only one injector is firing. #3 is the only one receiving a signal.

I saw the injector number was edited so it is still possible to swap #1 & #3 to help verify the ECM is likely the problem. It may be a stretch to get the connectors to snap on but the injectors can be rotated in place to facilitate the connection. Pretty sure the stock ECM for the LN3 engines is service number 01228253.

[nmhenry]

2 hours ago, 2seater said:

I saw the injector number was edited so it is still possible to swap #1 & #3 to help verify the ECM is likely the problem. It may be a stretch to get the connectors to snap on but the injectors can be rotated in place to facilitate the connection. Pretty sure the stock ECM for the LN3 engines is service number 01228253.

Rockauto is listing three different ones.
 I worked GM parts from 1991-1996 so I wouldn't doubt that there would be three different ones. Best to get the number off of the old one.
 I am pretty confident it hasn't been changed. The car only has 60,000 miles on it and everything but filters that I have run across has been original.

[bikemikey]

One thing to consider is a stuck TCC solenoid valve which can cause a rough idle and possibly stall when coming to a stop. From what I understand they are not suppose to kick in until they reach about 45 mph. In fact I'm having trouble with mine on my  89. I got it unstuck the other day by putting it in reverse and then drive , back and forth a few times and then luckily it unstuck.  Some people change the fluid and add an additive to get it to release, sometimes that works. Just a thought.

[padgett]

Seafoam Transtune works for me. With a stuck TCC is more likely it would not idle atol.

[nmhenry]

Well I got the ECM in today and changed it out. Problem seems to be solved though I had to put the old MAF back on it.
Thanks for all the suggestions and help. I have learned a lot about troubleshooting this what I call an in between car. It is between the old stuff that was simple to troubleshoot and not new enough to tell you what's wrong.
 This whole time I was not getting any codes and yet it wasn't telling the injectors to fire.
 No I gotta clean everything up and put it all back together as it is supposed to be.

 

[Ronnie]

1 hour ago, nmhenry said:

Well I got the ECM in today and changed it out. Problem seems to be solved

Glad to hear it. Thanks for letting us know. Hope the ECM fixed it permanently.

[nmhenry]

23 minutes ago, Ronnie said:

Glad to hear it. Thanks for letting us know. Hope the ECM fixed it permanently.

 We all know that nothing is fixed permanently.
 Like the old saying goes, " If it has t*ts or tires it's gonna give you problems."

 

[nmhenry]

One thing I neglected to mention. Amazon had the ECM for $85. Cardone has a rebate program on this one for about $65 so the ECM is only $20 after you send it back and get the rebate.

 

[EmTee]

11 hours ago, nmhenry said:

Well I got the ECM in today and changed it out. Problem seems to be solved...

I came to the same conclusion with my father's '84 Corvette years ago.  Wouldn't start; ECM wasn't firing the injectors (at all).  Rebuilt ECM fixed it - and other issues, including a fuel pump power issue that the PO had 'rigged' using some lamp cord...