Surge, skipping under load

[Eskareon]

1992 Buick Park Avenue.

When accelerating, the car will surge and "skip," which basically causes the entire car to shake. If from a stop I press the accelerator anymore than a half inch, it will surge and buck and sometimes backfire (or, at least I'm assuming that's what the popping sound coming from underneath is).

I've had the coil pack go out on me in the past, causing two cylinders not to fire. The lack of power I'm experiencing now is similar to that, but it's rapidly intermittent - the car will skip and buck but sort of "catch" in between. I'm assuming it is a fuel problem - the surging is very similar to that of when the car isn't getting fuel after a sharp turn, etc.

Things I've replaced recently enough that they should not be an issue:

Spark Plug Wires
Spark Plugs (about 3 years ago, Bosch Platinums. Tonight I replaced two of them that were looking a little botched from what seems to be a little bit of oil - no dice)
Crankshaft Position Sensor
Camshaft Sensor
Ignition Module
Coil Pack
Fuel Pump
Fuel Filter

There is no error code being thrown, so I really don't know where to start. I do know that a little bit of oil is being burned and when I took out the spark plugs to check them out, a few of them had wet oil in the threads. The spark plug firing heads, however, are completely dry, albeit a little dark.

Comments and Suggestions? I would really like to troubleshoot this problem on my own and save the money from shop poke-and-play, but this problem is dragging on too long.


Edit: A good example I left out. A few times when I've had to make a right turn and kind of "get on it," as soon as I push the accelerator and demand torque going into that turn, the whole car really does surge as if I just cut off its fuel supply. Then as I let off it'll shake and, sometimes, pop a backfire. Thinking about that, it sounds like a multi-cylinder problem. When I tested the fuel pressure before replacing the fuel pump, it was 1~2 psi below the acceptable range. Clearly, replacing the fuel pump did not solve it. There is, still, the fuel pressure regulator, but I figured that a -lack- of fuel wouldn't be causing a backfire. Then again, I don't know any better.

Edit #2: Forgot to add another thing. The car has a hard start with this problem. It'll crank over multiple times and then have this sort of skipping-start. Instead of a whirr-whirr-vroom, it's more like a whirr-whirr-whirr-whirr-whirr-vr-vrr-vrr-vroom, as if even when starting up it's choking a little bit. Idling, it is smooth. I think now I haven't left anything out.

[Loekee75]

You mention changing 2 plugs, but you really should replace all of them at the same time, and I'd use delco plugs because they are made for your engine in the factory.
Are you sure there isn't a code stored in the memory that isn't popping up? Since it's a 92' you can jump the data link connector underneath the steering column (A&B together, switch the ignition to power, not starting the engine). I've had codes come up in my 92' that didn't set off the light, so maybe you'll find something out that way? Good luck!

[Eskareon]

I've checked for error codes and received only the standard "1 2" reading.

I know it's good to change out all of the spark plugs, but the other ones are pretty much in good condition. I figured that if it was such a problem, changing those two would as least show some improvement. No dice, though.

The Hayne's mentions possible vacuum leaks as one cause of backfiring. I don't really know how the Fuel Pressure Regulator works (besides, you know, regulating fuel pressure), but I understand it does have some type of vacuum system. Could my problem be linked to the Regulator?

[Loekee75]

That pressure regulator sounds like the next component to look at! A vacuum leak is a possibility, the easiest way to check for a leak without any tools is the "hissing" noise. Good thing you got a "12", at least now you know it isn't a pesky sensor!

[maxwedge]

Get the "Botch" plugs out first, they are problematic in GM cars, at best!

[Eskareon]

So I've replaced the regulator and the problem is still very much there. A couple days ago, it felt like it was running pretty good - I could really get on the accelerator and it would respond like nothing was wrong. But after a while, and yesterday and today, it's doing the same thing again.

So, to recap, within the last 2~3 years or so I've changed the ignition module, coil pack, crankshaft sensor, camshaft sensor.

And most recently, within the last month or so, I've changed the fuel filter, fuel pump, the regulator, and the spark plugs. The spark plug wires were changed about a year ago.

Symptoms still persist: rough start, sometimes a rough idle, if I ask for power while driving I'll typically get a surge or a backfire or a rough reply. There's a "trouble zone" when accelerating, meaning I can push the accelerator so far and it'll run smoothly, but when I ask for more past that amount it'll surge and kinda 'even out.' By even out, I mean it doesn't matter how much I push after that point, the acceleration is very slow and it's shuddering or backfiring.

Another note, if I'm sitting in park, sometimes it'll idle a little rough. If I rev it to about 1000 rpm or so it'll smoothen out. Of course, when I'm driving, it seems to be the reverse.

Ideas? I'm not too keen on much of the real technical stuff, so if it's something to do with vacuums or valves, please go into detail. Thanks!

Edit: Most of the parts I've swapped over the years have been for other problems which were resolved. This problem is fairly new, happening since about the end of December.

[auto trainy]

I'll second the idea of getting rid of the botch plugs then put the car in the dark and see if the wires are any good by letting it idle and watching for leaking voltage.the next thing I would do is putting the car in gear and while holding the brake down put a load on the engine(2 seconds max),post back with results.

[Eskareon]

Ah, forgot to add that I replaced all the plugs shortly after I purchased those Bosch ones. All six spark plugs are new Delcos, the same that come factory with the car. They are also gapped to spec. When you say to put the car in the dark and look for "leaking voltage," what exactly am I looking for? Literal sparks?

I just did the brake + accelerator and got interesting results. I know that the Buick already has a limiter on it so that if the brake is depressed it will not rev past 2000 RPM, even if you floor it (don't ask me how I know that, heh). However, now when I do it, it gets up to roughly 1500, 1600 RPM and won't go any farther and I can definitely hear/feel the problem - the shaking, vibrating, struggling.

Hope that helps. I'll do the "dark" process as soon as I know exactly what I'm looking for. Another note to add: it sometimes seems to run better in really cold weather when it's been sitting for awhile (i.e., cold engine). I wouldn't say this is 100% everytime, but often enough to where I know if it's cold, I'll get a few miles out of it performing pretty well.

[HotZ28]

You could have spark scatter as described above. Also, you should investigate the timing set. I.e. cam gear & magnet, chain & crank gear. If your magnet is broken or missing, the injectors will fire out of time. You can inspect the magnet by pulling the cam sensor out and use a mirror to see what it looks like. (You may have to turn the engine over some to see it) It should look like the projectile of a 22 caliber bullet.

[Loekee75]

Also, by "leaking voltage" they did mean actual sparks escaping from the plug wires. You need to be in a pitch black area to see if the spark plug wires are leaking any spark. Don't forget to inspect the wires at every spark plug! Good luck!

[Eskareon]

Well, got the car to a really dark place. I don't have a garage so I had to drive to this little cul de sac with no street lamps anywhere. Let my eyes adjust to the darkness and idled the car. From the front three spark plug boots, I could see, barely, a little bit of blueish spark. Now, these sparks weren't arc'ing to the engine block, but they appeared to be emitting from the inside of the boot, where the spark plug head is, sorta. It was really dark so I couldn't see much more than just the spark, but the front three had a little bit of spark each. I had my roommate rev it to 2000 RPM and hold it and two of the sparks faded to invisible. The first spark plug still had a little bit of spark. I had him take it to 2500RPM and I couldn't see any spark whatsoever.

It's good to note here that while the car was idling and I could see the sparks, it was idling slightly rough. I had him put the car in drive, press the brake with all his strength (I'm in front of the dang car, after all), and rev it as high as it will go. As I expected, it only reached about 1600 RPM (instead of 2000 as it used to) and ran rough and the sparks were clearly flickering.

Interestingly enough, the spark flickering reflects the driving: when I'm idle, it's slightly rough at times. When I give it a little gas, it smoothens out. When I ask for too much, it goes back to problematic.

Could it be that my spark plug wires are already faulty after less than a year? I saw sparks at the three spark plugs I could see - even with a mirror, I really couldn't get a clear vision on the back plugs.

[imidazol97]

Originally Posted by Eskareon

Another note to add: it sometimes seems to run better in really cold weather when it's been sitting for awhile (i.e., cold engine). I wouldn't say this is 100% everytime, but often enough to where I know if it's cold, I'll get a few miles out of it performing pretty well.

When the motor is cold, the mixture is richer. A leaner mixture lets some problems show up more, like bad plugs/wires.

[Eskareon]

Well, I've replaced the spark plug wires. No dice. I'm at a dead-end here. Tonight I'll take it out again to see if I see the same spark pattern when it's dark, but with new spark plug wires not fixing the problem, I really don't know what to look at next.

Help.

[Loekee75]

If you see spark scatter again (with the new wires) take off one of your new plugs and inspect it for tiny cracks. I've had a few cases of new plugs being damaged from the start. Look carefully, because cracks won't be easy to see against the white porcelain.

[HotZ28]

Disconnect the 02 sensor and see if it runs better.