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One thing that can happen with higher mileage cars with the original O2 sensors is that the O2 sensors can become lazy both front and rear. This can slightly lower the fuel economy (only with the front O2S) and sometimes cause a P0420 as well. Changing the O2 sensors with OEM brand/maker sensors can fix this problem.
Magna flow cats are well known to cause problems with false P0420 codes on many makes/models. There are a few tricks to fixing this problem on the internet and you should have seen some of these researching the Magna flow cats. Usually you use an “18mm spark plug non fouler” (google search for this quote), drill out the hole and reinstall the rear O2 sensor(s) with the problem fixed. There are better quality versions (ie chromed) of these online along with info on how they work.
Using an infrared thermometer (IR) and measuring the temperature at the front and rear weld rings on the catalytic converter (after the car has been warmed up and in closed loop for about ten minutes) should be used in step with the exhaust backpressure test, especially on pre-OBD2 vehicles. Simply put the rear of the cat will be warmer than the front of the cat (maybe 100F or so) because of fuel being burnt off.
You have to be careful about comparing apples to oranges such as the exhaust example. OEM exhausts usually are great and are better than most replacement components even from the dealer. Auto part stores mufflers can be very mickey mouse with a muffler company using a muffler with half a dozen different adapters, clamps, hangers, etc to replace an OEM muffler that was a one piece welded assembly. Not only will the one piece muffler last longer, many times it is much cheaper than the weaker mickey mouse assembly that have to pay more for as well as wait extra days for the “parts” to arrive! Chain muffler shops make a lot of money by selling a “lifetime” muffler and exhaust pipe at high premium prices, then come replacement time they will charge $10 each for the four clamps on the non OEM muffler assembly, plus all of the adapters and hangers, etc. Plus many times there is a labor fee for “installation” of all of these non OEM components.
Shocks and brake wise IMHO the better aftermarket components are as good if not better than the OEM equipment in many cases. OEM shocks/struts and brakes are designed to gave a soft ride and quite decent braking and be cheap, plus they are not designed to last much past the warranty period (which neither shocks or brakes are usually covered under). You have to pay good money and buy American/Canadian/Japanese/Euporean Union made components though, and this can be very hard to do nowadays.
Stock OEM electronics are the best for the most part although there are some exceptions. Even if the part cost more then price will be worth it if the car is not going to the junkyard sometime soon.
Legally the car should be able to crank and start after leaving the lights on for two hours so capacity is not an issue.
On any GM vehicle you must check and clean the side post battery cables as well as check and clean all the ground points that you can find. The side post bolts can come out of the battery cable end and you might be able to actually slip the rubber boot off of the battery cable then. You may have to replace a battery cable if it is too corroded. Use a brass brush on all corrosion that you find and dielectric gel on any connections.
Try using a nice digital battery charger if you have access to one. These newer chargers are able to desulfate batteries that otherwise would seem bad.
These are probably with is known as a GM OBD 1.5 setup which was terrible. No A-B jumper and sometimes the port was a OBD 2 port but used the older OBD I setup. Usually there is no way except with a professional scan tool to read the codes on these cars.
GM usually has a separate stop light brake switch and a TCC/cruise control/PCM release brake switch that tells the PCM/BCM that the brakes are being applied. You probably have either a stuck TCC brake switch or it needs to be readjusted.
Quoted From 3SheetsDiesel:
On a completely unrelated note, but still deep withing the realm of “What were they thinking?”, has anyone here ever done an oil change on a Mazda 3 with the 2.3L engine? it’s got a plastic skid plate mounted under the engine, which is not really a big deal, lots of cars have that. This car uses a canister-type oil filter, similar to the one used on the GM Ecotec engines, which is mounted near the bottom of the engine. Again, this isn’t a big deal as lots of cars use this setup as well. The stupid comes in when you actually look at the plastic skid plate. It’s got a hole cut into it, seemingly for oil filter access, except where the filter housing is mounted is right on the edge of the access hole, rather than directly above it. So, if you don’t remove the skid plate before you try and change the filter, you’re going to get oil all over the inside of the plate and make an even bigger mess that you normally would have simply by changing the filter.
Those were a terrible design from all that I have read about them. There was a guy that did videos and a nice picture walkthough about how the Mazda 3 were a nicer version of the Ford Focus but the cartridge oil filter was expensive, very messy to change, sometimes one of both o rings leak on the then dealer only filter (which cost $7-8 back then instead of $3 canister), and that you had to remove the skid plate shield to access everything. He actually found out that you could go to a Ford dealer, buy the oil filter mount adapter for about $40, and simply unbolt 4 screws and install the oil filter mount adapter using a normal canister filter. This car was under warranty at the time so he threw the OE oil filter mount adapter in the truck and could swap it back in if the car broke down in about ten minutes.
If the car hit the curb hard enough to blow a tire then it hit hard enough to bend something in the steering. It might be a bad/bent tie rod end, damaged rack and pinion, loose or damaged rack and pinion mount, some other suspension part, or even something in the steering column. Have this looked at by a professional as soon as possible.
First thing to do in this case for any GM FWD vehicle is to follow all of the battery cables and remove and clean all connectors. Very common problem, especially on a car that old.
You can find cheap ODB 2 code readers with CAN abilities starting around $30. For $75 or so you can get a nice ODB 2 USB adapter that workings on a laptop and does real time data. Otherwise you are just guessing at the problem.
Check the fuel pressure regulator for leaking gas from the vacuum diaphragm. Use a Mity Vac tool or a long piece of clear tubing so if you start to suck out gas then you will have a bit of warning. The FPR should hold vacuum and not leak any gas if good.
Ditto on what Johnzcarz has said about doing an used oil analysis (UOA). If you do this make sure to get the total base number (TBN) and the total acid number (TAN) if possible. The best place to find out about UOA is the Bob is the Oil Guy forum. An UOA will detect some problems such as coolant leaking into the engine oil which is a very common problem in GM 3100/3400 engines such as RichWhitehead Montana minivan and several OLM intervals before the engine destroys itself. And you can detect poor air filtering problems, blowby problems, engine wear, etc.
Honorable Grasshopper, one thing that you do when buying a decent car from a dealer is to read usedcartips.org. This is a plain website written by a retired car salesman about all of the cons that new and used car salesmen will use on people during a car purchase. My father and step mother read the site and not very closely because it said used and not new car tips. They ended up having half the crappy cons that salesmen pull on customers at the last minute happen to them.
Tri9SS has nice points and I would like to add Autocheck to his list. This company is like Carfax, but may be able to check dealer records as well as auto auction data such as “Sold at auction – announced as frame damage” which was a real car that I came across. Autocheck can be used to double check Carfax and vice versa.
Most cars brands and models have similar issues that causes problems or break down time and time again. GM 3100/3400 have lower intake manifold gaskets that need replacing by 150k miles. Most Kia/Hyundai cars all seem to use timing belts on interference engines that really need to be changed on schedule if not earlier. VW DSG transaxles have had so many problems that the recent resale values of VW with DSG transaxles are $1-2k less than manual transaxles cars that cost $1k less in the first place.
Do not screw around with the engine computer on a GM unless you have troubleshooted everything else possible and really know what you are doing because one thing that GM does correctly on all their cars is their engine computer.
What you want to check is the ignition control module, or ICM. This is a small heat sinked board under the coil packs. Check the various resistances of each of the coil packs per the manual as well when everything is apart. No spark can be caused by a bad “bypass mode” in the ICM. Also check for any wiring problems to the camshaft position behind the power steering pump as well as the crankshaft position sensor behind the harmonic balancer. Note that the harmonic balancers that GM used are a steel over rubber sleeve over steel center construction that will over time go bad becoming wobbly and then destroying the crank position sensor as well as causing belt drive problems.
I have been listening to a lot of symphonic power metal lately. Original Nightwish, Epica, Delain, Tarja (original singer for Nightwish), Within Temptation, After Forever, We are the Fallen, etc. If you like Pat Benatar and Heart then you probably will like some of those bands because the lead singers are all women.
Many times self adjusting drums do not self adjust properly if at all so you might want to try what the GM service manual says to do. Measure the inside diameter of the drum and then adjust the shoes outward until the widest part of the shoes is the same as the inside diameter. Hopefully the drums will adjust better. My ’04 Grand AM SE has about the same rear drum setup and brake adjustment is lacking.
By the way most GM cars stopped using adjustable parking brake cables several generations ago. I know that the final N Bodies do not have adjustable cables and am pretty sure that the final N Bodies did not as well.