I know that there are lots of other threads floating around out there on this topic, I just couldn't find any that were recent. If there is a better place for this post, I would ask the mods to move it there.

So my car is a nice 2000 SSEi with 71k miles on it. I bought it back in late may and (one of?) the previous owners kept pretty good records as to what kinds of work was done on the car. Anyhow, about 4-6 weeks ago my car started doing this shuddering, stuttering thing going uphill, about 40ish mph, under light acceleration (rpms about 1500 - 2000).

The transmission fluid had been changed by the previous owner around 55,000 miles and I did it again at about 70,000 to eliminate that as a possible cause. The mechanic I took it too said that it'* the cleanest transmission fluid he'* seen in car. I had him replace the filter and tear into the old one and there was only one little fleck of clutch pad in it, no other little bits of shrapnel were found, so the presumption is that everything is ok in that respect. He mentioned that somewhere along the line GM had updated a few of the tranny parts and said that mine had the updated bits installed.

On a drive, the mechanic couldn't find anything wrong. When I went out with him he hooked the scanner up to monitor everything with no obvious faults or errors, but then of course I couldn't get it to do it'* thing.

I have noticed that when this happens, more often than not, the tach jumps around a little bit, so I'm at a loss as to what it could be. I say more often than not because I sometimes forget to check and when it happens it doesn't last long, despite my efforts to learn to control and prolong it to help with the diagnosis. Doing a torque brake (pressing gas and brake at the same time) does not make the tach jump or give the engine any problems. On my previous car which had a similar problem I could reproduce it by doing this....that ended up being a plug wire that was shorting out.

If any one has any ideas please let me know. The problem is gradually getting worse in that it'* happening more often. I'm going to try a place for gas on the next fill up (place I've been buying from is 10c less per gallon) and see if that helps like some people suggest. I can do new plugs and wires too if anyone thinks that would help.

I will mention that the problem became more noticeable after I put on the CAI. Not really sure what the relation is there, if any, just something I noticed.

Thanks, and please post with any ideas you have!!!!

**EDIT** Since I posted this the tach has only bounced around once, so I'm going to call it unrelated. Without the tach component that removes the possibility of an engine problem doesn't it?

Typical symptoms under load, light throttle, particularly going uphill:

Intermittent ignition miss. I suggest changing your plugs and wires. 95% of the time, this is the problem with those symptoms. It'* more apparent at the low-rpm speeds under load.

I'll give it a try as soon I get my service manuals from the ebay guy. I haven't spent enough time in the engine compartment to know how to get to the rear plugs.

Any recommendations on plugs/wires to use?

Anyone else have any ideas?

Belden Premium 8mm wires from NAPA are quite popular here.

AC Delco or NGK plugs. NKG makes the Delco'*. I prefer the NGK V-Power TR55 in both my L67'*.

Plug wires and plugs are straightforward, but somewhat tight in the rear. Front three cylinders from left to right facing the engine are 1, 3, 5. Rear are 2, 4, 6. Have at it, you don't need a manual for this.

I want to bring up my Service Stability System thread.

Anyhow, with that Steering sensor out, mine was shuddering going up hills. Some hills, I actually got to see the Low Trac light come on. Anyhow, point being, the traction control was applying the brakes while going up hills.

Let'* see if you don't just have a bad plug or plug wire and so forth, but in most cases, I thought you would set a Service Engine Soon code for misfiring. This one'* interesting..

I'm the proud recipient of 3 bad sets of Taylors.

A lot of people seem to like the NGK- TR55'* and the Belden Premium wires, so that'* what I'm picking up tonight. Do the plugs come pre-gapped or will I need to regap them?

I tried gas from a different station yesterday, a little higher octane (93 vs 92) than the one I usually go to, but it made no difference.

I picked up my plugs and wires and will be putting those on this weekend. I got the plugs from Napa who says that the TR5'* are a direct replacement for the TR55'*. Just got off the phone with NGK to verify this and that is not correct, the TR5'* aren't designed for the .060 gap that our cars take. I'll be returning mine today but wanted to mention it so that no one else would be fed the same line.

I finally found some time when it wasn't too incredibly hot out and replaced my plugs and wires. I found a place that had the NGK TR55'* (Napa insisted the TR5'* are the same..NGK disagreed) and grabbed some Belden premuims too. I had been hoping that replacing these (which looked rather old) would take care of my problem, but no luck. It'* still there, same as always.

While I was under the hood I also replaced my PCV valve. I forget what they do but it is a maintenance item.

Anybody have any other ideas? Today it occured to me that sometimes the car feels like it'* being held back, much like a manual thats trying to go faster than the gear it'* in would allow.