1991 Eldorado

[skyman]

Several weeks ago on my way home from the grocery store, my 91 Eldo started chug-a-lugging at a traffic light....like it was not running on all 8 cyl. I drove it that way for about 5 miles until I got to a long straight away. I slowly push the pedal down til it was all the way to the floor and it downshifted and took off like a rocket. No misses or chug-a-lugging. Then I backed off and it was fine. I'ts been ok until yesterday. I drove down to CT and back.About 500 miles round trip. I keep it at a steady 60-63. Coming back when I got off the highway, came to a stop at the end of the ramp, it started to do the same thing. I tried opening it up several times to see if it would clear up. My thought being that I might have gotten some bad gas. Did n't help. After doing some reading in the shop manuel, I'm leaning towards a bad EGR valve. From idle to 1/4- 1/3 throttle it chug-a-luggs. If I floor it, it takes off with no roughness.

The car has been always maintained. Recent spark-pluggs, both O-2 sensors , spark plugg wires, oil and filter, air filter but the EGR has not been replaced.

Thanks in advance

Sky

1991 eldorado

147,000 mostly highway miles.

[adallak]

Several weeks ago on my way home from the grocery store, my 91 Eldo started chug-a-lugging at a traffic light....like it was not running on all 8 cyl. I drove it that way for about 5 miles until I got to a long straight away. I slowly push the pedal down til it was all the way to the floor and it downshifted and took off like a rocket. No misses or chug-a-lugging. Then I backed off and it was fine. I'ts been ok until yesterday. I drove down to CT and back.About 500 miles round trip. I keep it at a steady 60-63. Coming back when I got off the highway, came to a stop at the end of the ramp, it started to do the same thing. I tried opening it up several times to see if it would clear up. My thought being that I might have gotten some bad gas. Did n't help. After doing some reading in the shop manuel, I'm leaning towards a bad EGR valve. From idle to 1/4- 1/3 throttle it chug-a-luggs. If I floor it, it takes off with no roughness.

The car has been always maintained. Recent spark-pluggs, both O-2 sensors , spark plugg wires, oil and filter, air filter but the EGR has not been replaced.

Thanks in advance

Sky

1991 eldorado

147,000 mostly highway miles.

Pull the codes (Warmer and OFF pressed simultaneously for a few seconds). Clean the throttle body bores and blades (back sides).

[Ranger]

Have you rodded out the EGR tubes in the TB?

[skyman]

Several weeks ago on my way home from the grocery store, my 91 Eldo started chug-a-lugging at a traffic light....like it was not running on all 8 cyl. I drove it that way for about 5 miles until I got to a long straight away. I slowly push the pedal down til it was all the way to the floor and it downshifted and took off like a rocket. No misses or chug-a-lugging. Then I backed off and it was fine. I'ts been ok until yesterday. I drove down to CT and back.About 500 miles round trip. I keep it at a steady 60-63. Coming back when I got off the highway, came to a stop at the end of the ramp, it started to do the same thing. I tried opening it up several times to see if it would clear up. My thought being that I might have gotten some bad gas. Did n't help. After doing some reading in the shop manuel, I'm leaning towards a bad EGR valve. From idle to 1/4- 1/3 throttle it chug-a-luggs. If I floor it, it takes off with no roughness.

The car has been always maintained. Recent spark-pluggs, both O-2 sensors , spark plugg wires, oil and filter, air filter but the EGR has not been replaced.

Thanks in advance

Sky

1991 eldorado

147,000 mostly highway miles.

Pull the codes (Warmer and OFF pressed simultaneously for a few seconds). Clean the throttle body bores and blades (back sides).

Thanks I'll give it a shot

[skyman]

Have you rodded out the EGR tubes in the TB?

No...but I'll give it a shot. Thanks

[Ed Hall]

Remove your EGR valve to clean it and to make sure it is closing properly. Use Carb cleaning to clean it. You can also make a blocker plate to block off the EGR if you still feel that it's the EGR valve.

[95SevilleSLS]

That exactly how my 92 chevy 350 is too and I know it's the EGR because it runs perfect when I by pass it (except it pings like a maniac!). Does it do it more when it's cold?

[Ed Hall]

That exactly how my 92 chevy 350 is too and I know it's the EGR because it runs perfect when I by pass it (except it pings like a maniac!). Does it do it more when it's cold?

What's happening is the EGR is sticking slightly open.

[Ranger]

Rough idle or stall.

[skyman]

This is an update from my previous post.

Replaced the EGR valve. Same .Replaced the fuel filter filled up with Sunoco 93 and dry gas still the same. We did notice some noise comming from the distributer though so I ordered a GM coil and aftermarket cap and rotor. They should be in next week. Yestyerday I put in a can of fuel injector cleaner. Started it up a couple of times but let it sit. This morning I took it into town and could have sworn it was a little better but not right. When I pulled out of the drive, it took off fine but by the time I got into town about 6 miles, the roughness was back but I think maybe not quite so bad. before it would be rough to around 45 now I can push down the gas and it smooths out around thirty. I found it rough going uphill with moderate pressure on the gas. If I put the pedal to the florr it takes of very smoothly and with alot of thrust.????

[BodybyFisher]

Please keep your threads together so we can all benefit from your experience and its easier to search

I merged your two threads together here

[BodybyFisher]

This is an update from my previous post.

Replaced the EGR valve. Same .Replaced the fuel filter filled up with Sunoco 93 and dry gas still the same. We did notice some noise comming from the distributer though so I ordered a GM coil and aftermarket cap and rotor. They should be in next week. Yestyerday I put in a can of fuel injector cleaner. Started it up a couple of times but let it sit. This morning I took it into town and could have sworn it was a little better but not right. When I pulled out of the drive, it took off fine but by the time I got into town about 6 miles, the roughness was back but I think maybe not quite so bad. before it would be rough to around 45 now I can push down the gas and it smooths out around thirty. I found it rough going uphill with moderate pressure on the gas. If I put the pedal to the florr it takes of very smoothly and with alot of thrust.????

We did notice some noise comming from the distributer though so I ordered a GM coil and aftermarket cap and rotor (what kind of noise?, what does the cap look like, any cracks, carbon tracts, how are the metal contacts?)

Yestyerday I put in a can of fuel injector cleaner (NEVER use injector cleaner, drive it out as fast as possible, it will ruin the injector and fuel pump windings)

Try to discribe your symptoms clearly. Its rough around 45?

Why did you replace the EGR valve? Were you getting a code?

[skyman]

This is an update from my previous post.

Replaced the EGR valve. Same .Replaced the fuel filter filled up with Sunoco 93 and dry gas still the same. We did notice some noise comming from the distributer though so I ordered a GM coil and aftermarket cap and rotor. They should be in next week. Yestyerday I put in a can of fuel injector cleaner. Started it up a couple of times but let it sit. This morning I took it into town and could have sworn it was a little better but not right. When I pulled out of the drive, it took off fine but by the time I got into town about 6 miles, the roughness was back but I think maybe not quite so bad. before it would be rough to around 45 now I can push down the gas and it smooths out around thirty. I found it rough going uphill with moderate pressure on the gas. If I put the pedal to the florr it takes of very smoothly and with alot of thrust.????

We did notice some noise comming from the distributer though so I ordered a GM coil and aftermarket cap and rotor (what kind of noise?, what does the cap look like, any cracks, carbon tracts, how are the metal contacts?)

Yestyerday I put in a can of fuel injector cleaner (NEVER use injector cleaner, drive it out as fast as possible, it will ruin the injector and fuel pump windings)

Try to discribe your symptoms clearly. Its rough around 45?

Why did you replace the EGR valve? Were you getting a code?

When I first start it up it's ok and runs smooth. As soon as it warms up it acts as if it's not running on all 8 cylinders.Or stummbling.

Replaced the EGR because I read the symtoms of a bad EGR in the shop manual and they were similar. Guess not.

No codes that's what is so wierd.

The distributor noise is very low key but has a kind of rattely noise. It's hard to discribe. The guy at the garage listened to it with a scope and said it sounded like it was arcing?

I never heard of that with the fuel injector cleaner. Gee I ran several tanks of it last year when I was having some milage problems and it turned out to be a partially clogged CAT.I hope I didn't screw the injectors or fuel pump up.

The funny thing is that when this initially happend, It cleared up for a couple of weeks and now it's back and I can't seem to figure it out/

At higher speeds and not under a load, you don't really notice it, and like I said it doesn't normally start until it's warmed up.

[BodybyFisher]

You are not answering my questions, we need more details, when you are asked a question please reply to it or said you don't know, if you don't know and we will instruct you as to what to do. This method of communication is difficult. Without your cooperation we are not going to figure this out.

You are not getting codes? Sometimes the PCM will not provide codes and need to be reset. Disconnect the negative cable off of your battery for about a minute, and reattach it, to reinitialize your PCM, this kind of problem should throw codes, unless its the FPR. When you try to pull codes nothing happens? Do ANY codes come up at all?, I can't believe that a 91 shows NO codes, not even suspension codes?

When you say scope, was he was using a listening device? or can you hear it standing there? HEI ignitions make no noise to speak of, I don't know what using a listening device would do, did he pull the cap off?

Pull the vacuum hose off of your fuel pressure regulator and see if it smells like fuel. Leave the hose off, start the car and see if it spits fuel.

Please try to answer these questions:

What does the cap look like, what do the 8 contacts inside the cap look like?

If you grap the rotor and shake it back and forth is there any play?

Do you see arching or cracks inside the cap between any of the towers, or carbon tracks?

This can be a vacuum leak

A cracked cap

A cap with carbon tracks

A bad coil

A bad fuel pressure regulator

A bad PCM

Slow O2 sensors

Injector problems

A vacuum leak

A bad bushing in the distributor

A bad pick up or ignition module

[BodybyFisher]

I hate to sound like I am being picky but this is a difficult statement

At higher speeds and not under a load, you don't really notice it, and like I said it doesn't normally start until it's warmed up

Either its missing or its NOT missing, LOAD OR NO LOAD, what do you mean NOT UNDER A LOAD YOU DON'T NOTICE IT? That is an insignificant, it either misses or it doesn't miss. The ONLY way I personally test engines is to LOAD them, open it wide open in all ranges if something is WRONG, you find it quickly. WHAT does it do when you accelerate hard from 40 to 70, floored? If it hesitates, bucks, misses, I need to know specifically what it does.

Have you changed the wires and plugs?

[BodybyFisher]

The method we solve problems here is through the INVERTED CONE METHOD

Think of an INVERTED CONE

At the beginning of a problem it can be SO MANY things, the top of the cone

But, based upon what you tell us, we discard things one at a time based on how the engine responds under certain conditions and we determine what is wrong by process of elimination and come down to the CONES POINT.... the answer

[BodybyFisher]

Remove your EGR valve to clean it and to make sure it is closing properly. Use Carb cleaning to clean it. You can also make a blocker plate to block off the EGR if you still feel that it's the EGR valve.

What purpose does the blocker plate serve?

[Ranger]

Here's my take. Miss under load. Arcing sound in the distributor. My guess is that the distributor cap contacts are spark eroded, thus too large of a gap and a new cap will solve the problem.

[Ed Hall]

Remove your EGR valve to clean it and to make sure it is closing properly. Use Carb cleaning to clean it. You can also make a blocker plate to block off the EGR if you still feel that it's the EGR valve.

What purpose does the blocker plate serve?

Well, he already put in a new EGR valve so there's no need to put in the blocker plate. The idea behind the blocker plate was to test whether or not the EGR was faulty. If the EGR never completely shut, the installation of the blocker plate would eliminated any flow of EGR and would have resulted in better idle quality.

You might want to open the hood late at night when it is completely dark and inspect for stray sparks. I also had poor idle quality on my 93 Allante and I found stray sparks coming from brand new looking spark plugs wires.

[KHE]

Here's my take. Miss under load. Arcing sound in the distributor. My guess is that the distributor cap contacts are spark eroded, thus too large of a gap and a new cap will solve the problem.

I second that - also, a new rotor would be in order.

[BodybyFisher]

Remove your EGR valve to clean it and to make sure it is closing properly. Use Carb cleaning to clean it. You can also make a blocker plate to block off the EGR if you still feel that it's the EGR valve.

What purpose does the blocker plate serve?

Well, he already put in a new EGR valve so there's no need to put in the blocker plate. The idea behind the blocker plate was to test whether or not the EGR was faulty. If the EGR never completely shut, the installation of the blocker plate would eliminated any flow of EGR and would have resulted in better idle quality.

You might want to open the hood late at night when it is completely dark and inspect for stray sparks. I also had poor idle quality on my 93 Allante and I found stray sparks coming from brand new looking spark plugs wires.

OH I mis-understood, I thought you were suggesting to remove the EGR altogether like we used to do in the 70s to improve performance, you were just testing. I was going to say that when the 4.9 does not have good EGR flow it detonates badly.

[skyman]

You are not answering my questions, we need more details, when you are asked a question please reply to it or said you don't know, if you don't know and we will instruct you as to what to do. This method of communication is difficult. Without your cooperation we are not going to figure this out.

You are not getting codes? Sometimes the PCM will not provide codes and need to be reset. Disconnect the negative cable off of your battery for about a minute, and reattach it, to reinitialize your PCM, this kind of problem should throw codes, unless its the FPR. When you try to pull codes nothing happens? Do ANY codes come up at all?, I can't believe that a 91 shows NO codes, not even suspension codes?

When you say scope, was he was using a listening device? or can you hear it standing there? HEI ignitions make no noise to speak of, I don't know what using a listening device would do, did he pull the cap off?

Pull the vacuum hose off of your fuel pressure regulator and see if it smells like fuel. Leave the hose off, start the car and see if it spits fuel.

Please try to answer these questions:

What does the cap look like, what do the 8 contacts inside the cap look like?

If you grap the rotor and shake it back and forth is there any play?

Do you see arching or cracks inside the cap between any of the towers, or carbon tracks?

This can be a vacuum leak

A cracked cap

A cap with carbon tracks

A bad coil

A bad fuel pressure regulator

A bad PCM

Slow O2 sensors

Injector problems

A vacuum leak

A bad bushing in the distributor

A bad pick up or ignition module

The inside of the cap does not look that bad for 147,000 miles. Some minor corosion on the posts and rotor but no cracks. I took care or that with some very fine emory cloth. There is no play in the rotor.O2 sensors are less than 3 month old. Can't hear any vacuum leak all hoses look and feel tight none dried out. Have a coil on order from GM. Also a new rotor and cap.

Will see about the fuel pressure regulator when the engine cools of.

When I say dist noise I mean there is a noise just as the alternator oe power steering pump or tentioner...anything mechanical and moving makes some sort of noise.

After I cleaned the dist. I took it out on the road and it drove off fine and smooth...I thought I had solved the problem with cleaning the dist posts. But after being driven for about 12 miles and everything warmed up fully, it started again. Best way to describe it is like it's running on 7 cylinders.

[skyman]

I hate to sound like I am being picky but this is a difficult statement

At higher speeds and not under a load, you don't really notice it, and like I said it doesn't normally start until it's warmed up

Either its missing or its NOT missing, LOAD OR NO LOAD, what do you mean NOT UNDER A LOAD YOU DON'T NOTICE IT? That is an insignificant, it either misses or it doesn't miss. The ONLY way I personally test engines is to LOAD them, open it wide open in all ranges if something is WRONG, you find it quickly. WHAT does it do when you accelerate hard from 40 to 70, floored? If it hesitates, bucks, misses, I need to know specifically what it does.

Have you changed the wires and plugs?

I mean once I have reached crusing speed what ever that might be , as long as I'm not going up a hill or starting out from a stop sign it's not as noticable. If I floor it, it downshifts and takes off from 40 to 70 smoothly and quickly.

Wires and pluges are not quite a year old and used the good platinum plugs.

[BodybyFisher]

QUOTE: But after being driven for about 12 miles and everything warmed up fully, it started again

So starting off and laboring the engine you feel it. This could be the coil shorting when it gets hot, or an ignition module or PCM messing up hot.

Cleaning the contacts in the cap, won't help that much if at all, maybe as the guys stated a new cap and rotor will solve this problem, maybe the carbon anode bit in the center is worn down, cracked or shorting out. I would REALLY hope you don't have 147,000 on that cap and rotor, they need changing much more often than that, its not likely that is the original cap unless you have owned the car since 91 and know that for a fact. A cap, rotor, plugs and wires are part of a tune up for any distributor engine. .

If you change the cap and coil together you will never know what your problem was. I would change the cap and rotor first and NOT change the coil at first.

[Texas Jim]

Just a thought here.......

It runs good till it warms up......

WHAT CHANGES when it goes from open loop to closed loop???? I am not sure.

He has mentioned sever times that it runs fine when COLD... then acts up AFTER it WARMS UP.