Misfire above 2100 RPM. HELP!!

So I found a wrecked 1995 Riviera to get some exterior parts from. Went to the yard thinking "oh boy I just have to install these and the new HID lights I got and I'll be all set". WRONG. I pull out of the pick a part driveway and wouldn't you know it, a new problem pops up. It started to hesitate real bad above 2100RPM. Next thing I know the SES light starts flashing. I step on it again and the same thing happens. The whole car shudders and loses power. I went to autozone and they did a scan which came back with "cylinder 4 misfire condition". I bought a new coil pack thinking this would fix the problem. Nope. Same thing. I went ahead and bought new plugs and now I have wires on order that'll be here tomorrow (was planning on changing them anyway). Interesting thing is, after I replaced the coil pack for the number 1 and 4 cylinder the SES light went out. The car exhibits the problem when under any acceleration that brings the tach over 2100RPM. I also tried torque breaking it, it does the same thing. You can hear the misfire from the tailpipe.

My question is, what do you guys think is going on? Think new plugs and wires will solve it, or think it's something like a bad fuel injector on cylinder number 4? Seems I get one issues solved, and another one pops up. Meanwhile my HID light installation is being held off one more day. Any help or input would be appreciated. Thanks, Kyle.

start with what u said then look at injets and filter

Fuel filter was recently changed when the garage I used to bring it to decided to put a hole in the gas line. Hoping it's nothing major and it isn't the injector.

I can't resist paraphrasing the classic joke about the doctor & the patient:


Customer: My car misfires above 2100 RPM.

Mechanic: Don't rev it above 2100 RPM...


And to quote John Astin: I'm feeling muuuuch better now...

Eldo wrote:

I can't resist paraphrasing the classic joke about the doctor & the patient:


Customer: My car misfires above 2100 RPM.

Mechanic: Don't rev it above 2100 RPM...


And to quote John Astin: I'm feeling muuuuch better now...

I have to rev it! I can't live up to the typical Buick stereotype of being the old lady in the slow lane going along at 20. Everyone I know already thinks i'm an old fogey. Plus how am I supposed to race the ricers.

Most likely suspect is plugs and wires.

What did you change before this started happening?

deekster_caddy wrote:

Most likely suspect is plugs and wires.

What did you change before this started happening?

Not a thing. I had an oil change about 600 miles ago, that's about it. Everything I've done to the car has been cosmetic in the last week. Only thing I can think of is the fact that I've driven through some pretty harsh winter weather lately. Friday I drove 50 miles with about two inches of snow and slush on the road, and today I went through some pretty slushy areas before parking at the pick a part for a few hours.

The plugs and wires and coil packs are all original (except for the coil pack I just replaced).

A coil will generally only fail because of bad ignition wire and/or plugs.
If the wires and plugs are causing too high a resistance then the coil has to try and overcome that. After a period of time a coil can fail because of it.
Usually before the coil fails you will feel the loss of power and mis-fire from the bad wire(s) / plug(s)

I think the wires will fix. Too bad you spent money on a coil - I don't think that was the problem. One thing you can do is determine if it's actually happening above 2100 RPM - lock it in 2nd gear and see if you can ease it up (no heavy throttle) past that point with no hesitation. If so, it's probably boost, not RPM, that's causing the misfire (bad wires).

All wires look and feel good, not sure about the plugs. Getting up early, heading to advanced auto and getting the wires and will hopefully get everything done. That hopefully solves the issue.

AA wrote:

I think the wires will fix. Too bad you spent money on a coil - I don't think that was the problem. One thing you can do is determine if it's actually happening above 2100 RPM - lock it in 2nd gear and see if you can ease it up (no heavy throttle) past that point with no hesitation. If so, it's probably boost, not RPM, that's causing the misfire (bad wires).

I know I'm gonna need a coil eventually anyway. It's only a matter of time. I might put the stock one back on and keep the aftermarket as a spare. It was only $30 anyway. I did try second gear and it will go past 2100RPM, but it will eventually do it as the RPM increases either way. I think I made it to 2800 in second before it started doing it.

The wires I have coming are OEM delphi or ACDELCO, can't remember now. Plugs I got were E3 iridium, which reading from the mod thread probably isn't the best when i do get into the mods, but that'll be later on down the road anyway.

As Rick indicated, coils should last a long time if you maintain the rest of your ignition system properly. I'm still on all three original coils at 198k miles. Nice to have a spare, but you may never need it.

What you're probably experiencing is a misfire when entering boost. The extra voltage required of the plugs is causing an arc at a weak point in one of the wires. A way to know for sure is to slip the SC belt off and secure out of the way around the engine mount bracket - the hesitation will go away.

But since you've got wires on the way, just drive the car easy for a few days and then it should get better once you swap them out.

The iridium plugs aren't ideal, but they'll work fine for a while. The plugs aren't causing your problem, imo.

AA wrote:

As Rick indicated, coils should last a long time if you maintain the rest of your ignition system properly. I'm still on all three original coils at 198k miles. Nice to have a spare, but you may never need it.

What you're probably experiencing is a misfire when entering boost. The extra voltage required of the plugs is causing an arc at a weak point in one of the wires. A way to know for sure is to slip the SC belt off and secure out of the way around the engine mount bracket - the hesitation will go away.

But since you've got wires on the way, just drive the car easy for a few days and then it should get better once you swap them out.

The iridium plugs aren't ideal, but they'll work fine for a while. The plugs aren't causing your problem, imo.

I'm just going from experience with the coil pack. Seems every 3.8 engine I've owned and those around me have owned go through coil packs. My last buick went through 4 of them in 250,000 miles.

OK so I woke up this morning to about four inches of snow, weather forecast called for a dusting. I've come to the conclusion that weather forecasters are highly overpaid guessers. Anyway, I said screw the plugs and putting a whole new set of wires on, I just replaced the wire for cylinder number 4. It fixed my issue. No more problems. I'll get the plugs changed and the other wires put in when I bring it to the body shop to get the door handle painted and fixed.

This may sound odd, but I think replacing the wire fixed my stereo too. I had an obnoxious buzz and squealing coming from my passenger door speaker along with some whining coming from the rest. That in my short test drive seems to have disappeared. Interesting how everything is so tied together.

Just took a close look at the old wire and there is a piece of insulation that is completely missing about an inch up from the boot near where it plugs into the spark plug. Not sure how that happened, but I can see how that could cause an issue.

Problems with hesitation under load fixed with new wires - 1,256

Problems with hesitation under load fixed by everything else - 7

Forum that knows these problems/solutions from hundreds of miles away across the internet - priceless


glad you got it fixed. As rick stated earlier most coil pack go out b/c of too much strain on them due to degraded plugs and wires. keep the plugs fresh and wires under 30k miles and i bet you will not have any more coil problems in your cars.

Kyle,
If you haven't already read the info available on ignition wires I recommend you do so by going to www.magnecor.com
They have an excellent write up on the make up of different types of wires and how the wires affect the coils and general operation of the ignition system.
It's not a bunch of hype, they are not trying to sell you their wires. I believe the information is good technical info that everyone should read that is interested.
At a minimum read "The truth about Ignition Wire Conductors" (first link.)

Try reading at least these two articles;

http://www.magnecor.com/magnecor1/truth.htm

http://www.magnecor.com/magnecor1/overview.htm

Then, when your ready for your next set of wires, I highly recommend their product.
I have a set and plan on them lasting a Lifetime. If there is a failure of a wire they will replace it free.
I am also going to have custom wire sets made by them per special order for one of my motorcycles that i have built a high compression engine for and added an additional spark plug per cylinder. With two plugs per cylinder and an additional coil necessary to make it all work I had to make my own coil mounting brackets and wires for it. I'm never comfortable crimping my own ignition wires, even with decent crimping tools, but that was the only choice I had at the time. Now I know i have another choice and a quality product that is guaranteed to boot.

Thanks for the rick.