Jump to content

91 Eldo STILL missing!


bschelle

Recommended Posts

Plugs are A/C, wires are Belden NAPA.]

Did you run the wires in the same path as before? Have you misted the wires at night to see if there is arcing? Any of the wires touching metal? The problem sounds similar to my coil problem, but you said you replaced the coil.

No Paul, he didn't replace the coil, I think that is next on his hit list. It is sounding to me that when demand is placed on the ignition system the coil is unable to accomodate the load. It will be interesting to see the outcome of this issue.

On another thread, I have to find it, a member tested the voltage output of a NS coil and found it only producing 20% of the other 3.... I never considered testing a coil that way but it makes sense. This of course is a 4.9 with HEI

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites


I just sprayed the wires and there are not any sparks flying. The part that has me baffled is that it runs OK for the first five minutes of cold start driving and then just like somebody is pushing a button it starts to do its stuttering. Also wnen I decelerate it feels like it loses power for a second and bucks a couple of times. This whole thing can be repeated over and over again. I am thinking that if it is electrical why only after getting warmed up? I put the pressure gauge on the rail and took it for a ride and there was no change in pressure when it falters. I got 40-42# cruising and 36-38 coasting.

Link to comment
Share on other sites

What happens with a WOT up to 75 to 80?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

I am thinking that if it is electrical why only after getting warmed up?

Remember that when things get hot they expand. Contacts seperate etc. I once had a starter do that. Would not start til it cooled down. A new solenoid fixed it. I am not quite sure how a coil would be affected by heat though.

Link to comment
Share on other sites

The part that has me baffled is that it runs OK for the first five minutes of cold start driving and then just like somebody is pushing a button it starts to do its stuttering.

Sounds like something associated with the shift from open to closed loop mode?

Regards,

Warren

Posted Image

There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

Link to comment
Share on other sites

While that is true, a closed loop problem should induce a code, no? Closed loop items include O2 sensors, ECM/PCM. He stated he has no codes.

The computer uses the oxygen sensor's input to regulate the fuel mixture, which is referred to as the fuel "feedback control loop." The computer takes its cues from the O2 sensor and responds by changing the fuel mixture. This produces a corresponding change in the O2 sensor reading. This is referred to as "closed loop" operation because the computer is using the O2 sensor's input to regulate the fuel mixture. The result is a constant flip-flop back and forth from rich to lean which allows the catalytic converter to operate at peak efficiency while keeping the average overall fuel mixture in proper balance to minimize emissions. It's a complicated setup but it works.

When no signal is received from the O2 sensor, as is the case when a cold engine is first started (or the 02 sensor fails), the computer orders a fixed (unchanging) rich fuel mixture. This is referred to as "open loop" operation because no input is used from the O2 sensor to regulate the fuel mixture. If the engine fails to go into closed loop when the O2 sensor reaches operating temperature, or drops out of closed loop because the O2 sensor's signal is lost, the engine will run too rich causing an increase in fuel consumption and emissions. A bad coolant sensor can also prevent the system from going into closed loop because the computer also considers engine coolant temperature when deciding whether or not to go into closed loop.

I believe that an ignition coil can short out internally when it is heated up..

Coil Diagnosis

Though coils are very reliable, they sometimes fail. Coils run hot because of the voltage that is constantly surging through them. Over time, the combination of heat and voltage may break down the insulation between the windings, coil housing or tower. If a coil problem is suspected, the coil’s primary and secondary resistance can be measured with an ohmmeter. If either is out of specifications, the coil needs to be replaced.

A short or lower-than-normal resistance in the primary windings allows excessive current to flow through the coil, which can quickly damage the ignition module. This also may reduce the coil’s voltage output resulting in a weak spark, hard starting and hesitation or misfire under load or when accelerating.

An open or high resistance in the coil primary windings will not usually damage the ignition module or PCM driver circuit right away, but it may cause the module to run hot and shorten its life. With this condition, coil output will be low or non-existent (weak spark or no spark).

A short or low resistance in the coil’s secondary windings will result in a weak spark, but will not damage the module or PCM driver circuit. An open or high resistance in the coil’s secondary windings will also cause a weak spark or no spark, and it may also damage the ignition module due to feedback induction through the primary circuit.

An important point to keep in mind with respect to all types of ignition coils is that when the magnetic field collapses, the high-voltage surge has to go someplace. If it can’t go to the spark plug, it will find another path to ground - which may be back through the ignition module, PCM driver circuit or through the insulation inside the coil itself. This can be very damaging to these parts. So never disconnect a plug wire or COP coil while the engine is running. It can be very damaging as well as dangerous to you should you become the path to ground. When a coil failure occurs on a distributor ignition system, it affects all of the cylinders. The engine may not start, or it may misfire badly when under load. But with multi-coil ignition systems, a single coil failure will only affect one cylinder (or paired cylinders in the case of waste spark DIS systems).

http://www.babcox.com/editorial/us/us20406.htm

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

WOT is terrible! It will hardly get out of its own way. I never do WOT on my commute to work and back. But I did it this morning and it would not get up to 70 MPH and was laboring all of the time. I apologize to the forum for not doing this basic test. I am sure it will change the thought process on my problem. <_< I am going to bang on the converter tonight and see if it rattles. I replaced the fuel filter when I put in the new fuel pump.

Link to comment
Share on other sites

WOT can tell you a lot, I always do one when I am diagnosing engine performance. Sometimes you can determine if its fuel or ignition related by how it behaves when the engine is labored.

You have replaced so much already. Did you do those replacements chasing this MISS? Check that COIL...

When you replaced the rotor, did you replace the carbon center electrode? There is a plug on the distributor, check the knife contacts for tightness.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

WOT can tell you a lot, I always do one when I am diagnosing engine performance.

Mike,

I'd guess you do WOT when you're diagnosing just about anything. :lol::lol::lol:

Seriously though, it's hard to do long distance troubleshooting, but it's starting to sound more and more like bschelles's problem might be CAT related. That's seat-o-the pants of course.

Regards,

Warren

Posted Image

There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

Link to comment
Share on other sites

All of the parts I replaced before where for another problem but I have replaced the TPS,Cap,Rotor,Module & Coil trying to resolve this miss. I did replace the carbon button & wire when I did the coil. The plugs on the cap are good and tight. The way it performed at WOT has the symptoms of a plugged exhaust. It just groans and acts like it has an anchor on the bumper. I have a rattle when it idles and I bet it's the cat! This whole process has been enjoyable and I really like to do my own work on my car. Although I replaced some parts that are probably not needed i know that most of them are near lifes end with 127k on the clock!

Link to comment
Share on other sites

All of the parts I replaced before where for another problem but I have replaced the TPS,Cap,Rotor,Module & Coil trying to resolve this miss. I did replace the carbon button & wire when I did the coil. The plugs on the cap are good and tight. The way it performed at WOT has the symptoms of a plugged exhaust. It just groans and acts like it has an anchor on the bumper. I have a rattle when it idles and I bet it's the cat! This whole process has been enjoyable and I really like to do my own work on my car. Although I replaced some parts that are probably not needed i know that most of them are near lifes end with 127k on the clock!

An idle "rattle" is a prime time symptom of a bad CAT. Just the same, don't jump to conclusions. Investigate. Clang it with a rubber mallet. If you hear anything loose, you've found your problem.

Regards,

Warren

Posted Image

There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

Link to comment
Share on other sites

All of the parts I replaced before where for another problem but I have replaced the TPS,Cap,Rotor,Module & Coil trying to resolve this miss. I did replace the carbon button & wire when I did the coil. The plugs on the cap are good and tight. The way it performed at WOT has the symptoms of a plugged exhaust. It just groans and acts like it has an anchor on the bumper. I have a rattle when it idles and I bet it's the cat! This whole process has been enjoyable and I really like to do my own work on my car. Although I replaced some parts that are probably not needed i know that most of them are near lifes end with 127k on the clock!

Your FIRST post did not state that you replaced the COIL. When did you replace the COIL, I saw you said this "but I will replace them and the coil is old and next on my hit list". I just went back to see if I lost my mind.

You are giving a different description here saying ANCHOR ON BUMPER.... A miss is ONE thing and its normally ignition related (could be injector related also), an ANCHOR ON BUMPER is quite another. The rattle is a clear indication that your CAT has died, this is the first time I think I heard that you had a rattle at idle and saw previously that you planned to hit the CAT with a mallet to SEE if it was bad. My CAT rattled on my 91 4.9 but never caused a restriction. Let us know how this turns out. Here is a link to my 02 Monte Carlo CAT problem along with the symptoms:

http://caddyinfo.ipbhost.com/index.php?sho...;hl=monte+carlo

WOT can tell you a lot, I always do one when I am diagnosing engine performance.

Mike,

I'd guess you do WOT when you're diagnosing just about anything. :lol::lol::lol:

Seriously though, it's hard to do long distance troubleshooting, but it's starting to sound more and more like bschelles's problem might be CAT related. That's seat-o-the pants of course.

Regards,

Warren

Since I was a kid, a WOT is a great was to uncover performance problems as it stresses the ignition system and fuel system. The first thing I do is wind the engine out to see if it is capable of laboring hard without negative symptoms. You are right.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

Mike,

When I wrote: "I'd guess you do WOT when you're diagnosing just about anything. :lol::lol::lol:,"

I should have added "Me too!"

Regards,

Warren :)

Posted Image

There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

Link to comment
Share on other sites

I did mention the new coil in Post #16. I just got back from a test run with the new cat I installed and all is good! It was the converter. The old one was all in peices on the inside. I had also thought my gas mileage was bad but I never payed any attention to it. I couldn't see the forest through the trees. A simple WOT diagnosed the problem. Thanks for all of the great impute you guys contributed!! I was a NAPA jobber for 28 years and I spent many a day with customers trying to fix their cars by telling them to have it diagnosed before they go throwing parts at it. I should have followed my own advice. Go figure!

Link to comment
Share on other sites

Glad you got it fixed. I think the hardest problem to diagnose is a clogged CAT. They actually sell a backpressure gage that screws into the O2 sensor in front of the CAT to help diagnose it. Glad you got it running.. Mike

What threw me off was the MISS, clogged CATs don't typically cause a miss, they sap power badly.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

Glad you got it fixed. I think the hardest problem to diagnose is a clogged CAT. They actually sell a backpressure gage that screws into the O2 sensor in front of the CAT to help diagnose it. Glad you got it running.. Mike

What threw me off was the MISS, clogged CATs don't typically cause a miss, they sap power badly.

You guys were NEVER off or wrong. If I had done the WOT right away, I would have told you the correct symptoms and you guys would have the solutuion!

Thanks Again,

Bill.

Link to comment
Share on other sites

bschelle,

Thanks for reporting back!

A lot of folk don't do that and the people here are left wondering what eventually happened. Without a follow-up the learning experience we all seek just doesn't happen for us.

Glad you're running good again.

Regards,

Warren

Posted Image

There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

Link to comment
Share on other sites

Glad you got it fixed. I think the hardest problem to diagnose is a clogged CAT. They actually sell a backpressure gage that screws into the O2 sensor in front of the CAT to help diagnose it. Glad you got it running.. Mike

What threw me off was the MISS, clogged CATs don't typically cause a miss, they sap power badly.

You guys were NEVER off or wrong. If I had done the WOT right away, I would have told you the correct symptoms and you guys would have the solutuion!

Thanks Again,

Bill.

Thanks, you have a great car there in the 91 Seville, I miss mine.. very special car if you ask me. Glad you got it going again, don't consider all the parts replacing a waste, she is probably running terrific now.... As Warren said, thanks for letting us know how this turned out, Mike

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

  • 1 month later...

Sorry for the late update!! I replaced the catalytic converter and all is well. I should have tried the WOT ! I did that and I could tell the converter was plugged.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...