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Backfire when quick throttle


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Hi All ..
I am new to the group and did a search and really couldn't find any posts about a specific problem I had yesterday when driving my caddy.
It is a 1999 Eldorado with about 80K on it and I don't drive it much but recently I have put about 500 miles on it or so with no issues.
Yesterday when going up a small hill it seemed like it had less power than normal and almost seemed to be missing..
Anyway when I got it home in the driveway I was giving it throttle and noticed when I gave it a quick full throttle "pump" it was not smooth at all and was even popping through the intake.
Would this just be a tune up needed or map sensor issue or could there maybe more of a major issue of the head gasket or something?
I don't smell any gas or antifreeze out of the exhaust and it doesn't use any fluids except a little oil once in a while which I believe is normal for these engines.
I haven't done any tune up on it since I've owned it and the car does sit a lot for months at a time inside a garage but this came on all of a sudden and I have no check engine light at the moment.
I did have a "knock sensor" code a few weeks ago but it reset and I haven't had any problems since...
Any help would be appreciated
Thanks

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Any other codes stored in diagnostics?

One possibility is the platinum pads have come off the ground electroded on one or more of the plugs, increasing the plug gap and causing a loss of power. I had a '96 Seville that did that and it acted like it was starving for fuel or there was water in the fuel.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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welcome to caddyinfo.

Is the SES light on?

How is the gas quality?
Very possibly due for a tuneup.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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  • 2 weeks later...

Well I finally had a chance to check codes...There are none.

I'm not sure about the gas but I got it at a place I have always gotten it.

I also sprayed carb cleaner around all the vacuum hoses I could see and got no change in idle.

car seems to idle ok in park. But when you are in drive and come up to a stop sign the car seems to jerk a little every so often and the tach moves a little each time you feel the movement.

I pulled the front plugs just to see and none of them were black or wet. Just a light brown color. I also pulled the wires on the front of the engine while running in park and I could hear and see spark from all of them but 2 of them didn't seem to arc as much as the other 2....

Just wondering if it could be a coil pack going bad or does this sound like a fuel problem since it came on all of a sudden????

Any ideas?

Thanks

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What you describe sounds like a weak(failing coil). Pop the plug wires off of the towers one at a time and look at the tower. If it is all rusty then it is likely bad.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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What you describe sounds like a weak(failing coil). Pop the plug wires off of the towers one at a time and look at the tower. If it is all rusty then it is likely bad.

Thanks..

I actually "looked" at all the coil connections and didn't see anything like corrosion or rust. All the contacts looked good on all the wires/coils.

is there a way to test a coil?

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Does your car have a quick surge at cold startup? I had this, and i had the fuel injectors cleaned, and it went away. Dealer told me it looked like an injector(s) was leaking

No surge at start up...I actually think the "miss" is a little less noticeable when the car is cold. Seems to bog more when warmed up.

I also checked all the bolts on the intake manifold and they were loose. I thought I had the problem fixed because after I tightened these and started it up it seemed OK for a little while and got worse shortly after it heated up...

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A sticking egr valve can cause stumbling when warming up. Does not always throw a code either.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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  • 4 weeks later...

What you describe sounds like a weak(failing coil). Pop the plug wires off of the towers one at a time and look at the tower. If it is all rusty then it is likely bad.

Well you were right! I actually changed the plugs and wires first with no success and bought 1 coil to try one at a time and when I got to the third one that I tried (from right to left) The 1 - 4 coil pack was bad. It looked fine too no signs of rust or corrosion or anything...

What a difference!

Running like a champ now...

Thanks again!

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