Ok- sorry if this is long, but I'm pulling my hair out trying to think of where to even begin on this. I have an '03 SSEi with just under 140,000 miles on it. It'* been going great, but I have this strange problem. Every once in a while I'll give it gas and the car will buck like you wouldn't believe. It'* hard, and very disturbing. Obviously the first thought is the transmission. The problem is, I've found that when this happens, I can shut the car off, wait about 2 minutes and start it up and it'* fine again. 90% or better of the time the car shifts perfectly- you wouldn't imagine anything would be wrong with the trans. When this starts happening, you would swear you just dropped the trans. Turn it off, wait, start and it is fine again.

I had a bad cat and thought it might have been due to the exhaust clogging temporarily. Replaced the cat and things ran great for about 3 weeks. Then it started happening again the other day and has happened a few times this week. At one point I put the car in park, lifted the hood, and tweaked the throttle body lever to see what happened. When I did this, the engine would start shaking violently under moderate throttle. I'm not talking very light throttle, but not near WOT either. Maybe about a quarter of the way open.

So, I was thinking- bad engine mount. But why would the engine only shake and the symptoms only come out so randomly and then go away with just a stop, rest, and restart of the car? Makes no more sense then the transmission would. I tried opening the throttle when the symptoms weren't occuring and it ran smooth...

So, I figure- start with the basics. I pulled the throttle body tonight to clean it. Maybe the door was sticking I figured. Well, I got it off and I can tell you that this is a distinct possibility- the door is black. However, I now have some other concerns.

1. On the interior of the engine where the throttle body attaches, there is a good layer of oil/dirt. I'm not sure this is normal- is it?

2. After clearning things out around the throttle body, I noticed moisture- a clear type fluid- seemed to be dripping down the engine from around the bottom of the throttle body and down over everything below it. With the accordion tube and throttle body on, I couldn't really see this- but now it'* clear as day. I can also see a lot more oil on the engine- particularly in the back of the engine. My oil is about 1/2 quart low. My anti-freeze is a little low also- but I haven't filled it in about a year. Could these be symptoms of a bad UIM or LIM?

3. If noa UIM/LIM, any other thoughts?

4. Any other thoughts on what could cause this to buck like this? I'm stumped.

I will try to get pictures tonight or in the morning....it'* dark out now and I didn't plan on doing much more than cleaning the throttle.....so I didn't do this in the garage. DOH!

Thanks in advance for any help/thoughts.

Do try to get pictures of your LIM area. You could very well have a leak there causing coolant to get into the cylinders causing a misfire. Brianj'* was bad enough to where it set a misfire code.

Revving the engine from under the hood won't tell us whether or not you hit the rev limiter, but the engine will run very rough if you free rev it above about 4,000 rpms. Have the plugs and wires ever been replaced? If so, when and with what?

Also, clean the battery cables under the back seat, paying close attention to where the grounding strap connects to the floor pan.

Sounds very similar to problem I had. Car would just cut out then back to normal then cut out. I changed the plugs and wires per this forum. No fix. Then I changed the maf sensor and it was back to running good. Not saying this maybe your problem but for some reason mine was bad but didnt through a code usually then it threw a maf low voltage code. So it might have just been the connector but oh well already changed.

OK, I have some pictures, I have to try to upload them today when I have more time. I figured the free rev would make it run rough at some point, but wasn't sure. Thanks for clarifying. If it explains it better- when the symptoms were occuring and I free rev'd it- it would buck almost as soon as I opened the throttle. When they weren't occuring, it would run smooth - unless I opened more which was probably around 4,000 RPM at that point.

I will check the battery cables- although I was in there about 4 months ago putting a new battery in and it was as clean and dry as could be and I was still having this problem. Can't hurt to look again.

I am not throwing any misfire codes- but I do have a 0420 lighting the dash- and since I just replaced the Cat, I'm thinking it'* an O2 that got gunked up after the cat and needs replacing.


Also, the plugs and wires have been well-maintained. I just changed the plugs and wires at around 125,000 (a few months ago). I have Autolite'* in there now- copper cores, not sure of the number....405 off the top of my head I think? I could be way off there. I also have 8 mm Taylor Ignition wires that I put in at the same time. This problem has gone on and off now for about 2 spark plug changes though. It'* just getting worse. I had the NGK'* in there before. It used to only seem to happen after the car was running on an hour long or more trip- like something was getting hot. Now it will happen 5 minutes into a ride.

2000Boostedbonnie- I am glad you said that. I was hoping it was the throttle body sticking or the MAF being gunked up. When I took the TB out, it was very black. To quote the tech article, I sprayed the living snot out of it and let it dry. I sprayed it actually about 3-4 times.

Thanks for the input guys. I will get those pics up today.

Taylor?

Let'* try to rule that one out. Inspect them CAREFULLY for carbon tracing arcing through the insulation, and check the resistance of each wire and report the number back here in order from 1-6.

Here'* my pile of failed Taylors (most warranty replacements) in ONE YEAR:


I'd also encourage you to keep a sharp eye on your coolant level and consider changing your LIM gaskets as a preventive measure.

As Bill mentioned, Taylor wires have been a problem. I believe that he had some bad ones right out of the box! The autolites are fine, and probably 605s.

When you replaced the battery, did you check the grounding strap to floor pan connection and bolt - not just the connections to the battery? That connection has been known to be an issue, also.

This topic is a few weeks old, but I haven't had much time lately and I am going take advantage of this long weekend and get *some* of the work I need to done. I had some pictures, but I think they got deleted before I could post them (not my camera!!). Doh.

So far I have cleaned out the throttle body, checked to make sure none of the wires are touching the O2 sensor (it was- I moved it), changed my transmission fluid and filter (the pan was clean as I can imagine- hardly even any grey fine shavings. It was way cleaner than the first time I cleaned it- but the fluid was toast), changed the engine oil, cleaned off some of the burnt oil around the engine, and refilled the coolant.

This weekend I am replacing both O2 sensors, checking the coil packs and wires (resistance and arching). I have not noticed any coolant missing since I refilled it, and my oil did not appear any different than normal- knock on wood.

So, now my questions are, and the first one may be stupid on my part since I am barely able to accomplish most of this myself- does the 2003 Supercharged 3800 have an Upper Intake Manifold? Or would it just be a lower intake manifold that needs replacement? If so, can you give me specific part numbers? I have read and re-read the Techinfo, and searched the forum, and can't get what I feel is a definitive answer on my own. It appears I do not have a UIM but I should replace the LIM?

Also, I found another thread talking about valve cover gaskets, which appear to cost $50, are readily available, easy to replace, and commonly bad on our cars? I am thinking thi * is what'* causing my oil seepage, and would like to replace. However, if I'm tearing into the engine, I'd like to do the LIM at the same time. Is there any info or a how-to available on this procedure?

The supercharger takes the place of the upper intake manifold on the supercharged engine. Get the Felpro gasket for that. It will include the coolant o-rings. Also pick up the Dorman coolant elbows hanging on the "Help" cards. The Felpro valve cover gaskets are also recommended. These should all be available at most auto parts stores. Advance does not carry the elbows, but Autozone and PepBoys do.

Get the aluminum framed lower intake manifold gaskets from the dealer. Below is a link to the demo vehicle at AllData. It is the non-supercharged engine so it will not have any information on how to remove and reinstall the supercharger. If you are going to do serious work on your car, you should either purchase a subscription that covers your car, or buy a factory service manual.
Intake Manifold Replacement - Lower

My lumina did this to me before, try the 02 Sensor

Archon, JBMark- thanks for the input.

I replaced the O2 after the cat last night, which was the one throwing the codes- and the car runs WAY better now. I knew it would cause problems, but I'm surprised at how bad it was running and I did not notice because I hadn't had it run well in so long. The old O2 was completely black and carbon fouled and actually had dents in the tip- probably from crud getting sent down the pipe when the CAT went bad. I am going to grab an O2 removal tool and do the one behind the engine today- my wrenches just wouldn't pull it off.

While I was under the car I noticed oil on the bottom of the back of the engine and on the side of the transmission casing. I think the valve covers are probably the problem for the black oil, and will be picking those up today. However, the oil on the side of the transmission casing is yellow-ish brown. I tried to follow it up, and couldn't see anything on the top of the transmission. However, it is just below the brake master cylinder. I did not see a leak, but when I checked that fluid, it had a bunch of "crud" floating in it. I'm going to suck that out and refill with fresh (do you think I'll need to bleed if I don't suck it all out and just kind of replace say, half of it at a time over the next few weeks?). Ok I'm being lazy, maybe I should just bleed it. I bled them maybe 6 months ago and put new fluid in throughout with Valvoline Dot 4 Synthetic. I think this is weird.

Sorry to keep bringing up new problems, but your help and input is much appreciated. Thanks guys!