The "Ask a Mechanic" Thread (merged)

[IONTOP]

I would think your o2 issues are a symptom rather than the problem,I'd suggest the BMW mechanic

or an exorcist

should be able to test the plate by spraying carb cleaner or starting fluid on it while running,if the idle changes you have a leak.....naturally this is flammable,so caution should be exercised

Yeah... I understand that... Although I'm concerned it might be the injectors... Therefore if I switch the 1-4 injectors with the 5-8 injectors I should be able to find definitive proof that it would be them if I drove for a few days with them in the opposite position right? And I'll suggest this to the guy that is changing my O2 Sensors ... Along with your Carb/TB cleaner suggestion

[twa]

I'm not familiar with this switching injectors and have never seen them cause the problems you describe...
maybe Springfields or one of the others can offer some suggestion

[IONTOP]

I'm not familiar with this switching injectors and have never seen them cause the problems you describe...
maybe Springfields or one of the others can offer some suggestion

My personal (cheapskate) theory is that the O2 sensors are telling the computer that the car's putting out too much air and to compensate to dump more fuel into the engine. Although your theory about a compound issue seems to be more valid, I asked Bank of America and they said that the cheapest solution was my idea, so that I could still pay their bills...

But it does make sense that the engine is taking in more air than it thought and the O2 sensors are seeing this and telling the CPU that it's happening and the CPU is saying to the ODB that the O2's are crazy, when it's actually the CPU that is crazy...

[twa]

more likely a leak is dumping fuel resulting in incomplete combustion which causes the o2 and smell

do the test thing

[DCsportsfan53]

If you have a scanner that will read value blocks there's probably one that monitors misfires and gives you a live misfire count. You could try swapping coils, plugs, injectors, ect and watching to see if the misfire moves with the part. Definitely should replace that O2 sensor as well, maybe try running it with the O2 unplugged and see what happens. In most cars the front O2 sensor is responsible for mixture readings and reports as such to the ECM, the rear O2 monitors the performance of the catalytic converter and doesn't play a part in fuel trim. Running as rich as it sounds like you are I would want to know that 1) the ignition system is in proper order (does the car have a single ignition coil and wires or individual coil on plugs? I'd imagine it's the second one) and that you don't have excessive fuel pressure and/or an injector stuck wide open.

As far as an air leak, if it's large enough to cause the car to run this poorly, in all likliehood, it's should be pretty easy to hear it and track it down. Modern cars are very adept at adjusting to conditions and in my experience, shouldn't throw an O2 sensor code like you are getting because of a vacuum leak, you'd more likely have a system too lean or too rich fault. A smaller air leak that isn't easily detectable would cause codes but the ECM should be able to compensate for it to where you won't notice much from a driving standpoint. Obviously my experience is primarily with VWs but Krautwagens tend to be similar enough. Also, while there is likely an issue with the O2 sensor, unless something is shorted in just the right way it shouldn't affect cold start running the way you're describing because the system should still be in open loop at the point as the O2 sensors won't be warm enough to read yet.

Edit: Looked back and saw you do have a fuel trim fault. Also, those O2 sensor faults are primarily heater circuit faults. The heater in the O2 sensor helps get the O2 up to operating temp quicker but doesn't play a part in detrmining fuel trim. Judging from the heater circuit faults for multiple O2 sensors a wiring harness issue such as shorted or broken wires between the O2s and the ECM are a possibility. For now, I would start by trying to address the fuel trim issue first, definitely worth finding the O2 harness connectors in the engine bay and unplugging them to see how it runs then. The ECM should be able to use an internal map and input from other sensors such as coolant temp, ambient air temp, mass air flow, ect to make the car run reasonably if the O2 sensors are the culprit. If that doesn't give you any discernable improvement (my suspicion is it won't) start audibly listening for wooshing air in the engine compartment and checking for broken vacuum lines. Continue with a fuel pressure test (pressure testers are cheap and a $13 Haynes manual will be able to guide you through using it) to check for the possiblility of a stuck open fuel pressure regulator or injectors.

[IONTOP]

But a question about all of this: Could my O2 sensors still be good? And would I be wasting my money possibly to fix this problem. Because up to this point right now, I was thinking that it wouldn't do any harm because I would eventually have to replace them in order to fix all my problems. Is there any way to differentiate ECM from O2 sensors without replacing the cheapest thing first?

[twa]

yes they can burn clean after a fault.....do the test for leak or the unplug the frt sensor as dc suggested

[DCsportsfan53]

Typically from my experience with German cars when O2 sensors throw range/performance faults they need to be replaced and usually they don't throw those faults due to other problems. The heater circuit faults, in particular, have nothing to do with fuel trim. There is a heater inside the sensor to heat the sensor up, the wires to the sensor and from the ECM are separate from the actual O2 signal ones and the circuit is simply being monitored for circuit integrity, ie the circuit is good, open or shorted. This is not going to affected by anything else with engine. Seeing as how you have many O2 faults for bank 2 and misfires on cylinders 4-8 a harness problem may be likely. One thing you can look for is check the routing of the harnesses underneath the car. They may have been poorly routed and allowed to make contact with the exhaust pipe and melt the wires and/or fuse them together. Given the faults I'm still going to say the first thing I would try is unplugging the O2s in the engine bay and seeing how it runs.

[MissU28]

Ok so my car has recently hit 100k miles. I have yet to take it in for its 100k inspection and a new timing belt. Spark Plugs are only a few months old (and yes, they are the good platinum or whatever ones that are supposed to be in there).

I have an '03 Acura TL Type-S, and I am aware of a transmission recall my car had and the previous owner took care of (documented on Acura website with the VIN). My car still has an issue when driving from 1st to 2nd gear (around 30-40mph). It will buck if I am pressing down lightly on the accelerator at these speeds, but I can pick up speed and drive through it. Just an FYI, as I don't know if this issue (or the transmission) has anything to do with what I am experiencing.

In the past month or so, my car has started to shudder or vibrate a little bit at idle. It doesn't shudder every single time I drive, and not every single time I am at idle. When my car DOES shudder, it shudders on and off. The lights on my dashboard dim in and out with the shuddering. My RPMs stay between 0 and 1, but the gauge thing moves a little bit (pardon my not knowing official car words).

The shuddering is not horrible, but it's definitely annoying. It goes away when I start driving again and only sometimes returns when I am at idle again.

Any ideas of what is happening to my precious Acura? I just paid it off, too

p.s. my maintenance light is on, but I think that's because I hit 100k miles

[twa]

probably need to have it scanned,could be the plug wires or one of the sensors....or 1/2 a dozen things

about the only thing I can suggest for DIY is check and make sure the plug wires are firmly connected..or if you see arcing from them when it is running.

[Predicto]

More simple question.

I've got a 1991 VW Cabriolet. It still has the original shocks and struts, so I feel every bump in the road and it rattles like a mofo.

Do I need to go to a VW specialist to get that stuff swapped out, or can I just go to someplace generic like Big O Tires or Midas?

[zoony]

Predicto, I'm no mechanic, but I did stay at a holiday inn express last night.

First of all, I think your car is front wheel drive so it probably has struts in front and shocks in the rear. But I don't know, ask DCSportsfan53, he is an expert on VW's. You might have struts on all 4 wheels, or you might have shocks/suspension combo.

A strut is a combination of the car's suspension and a shock absorber.

A shock is what dampens your car's suspension (spring). Bad shocks are usually characterized by your car bouncing up and down for some-time after hitting a bump. You can test this by stepping on your rear bumper. The car should rise back up and basically stop in place (the action of the shock dampening the spring). If it keeps bouncing, the shock is bad and needs to be changed asap.

Bad struts, otoh, can fail in a couple different ways, but most likely will be characterized by excessive bouncing or swaying, or bottoming out.

Yes, you can do this anywhere, you do not need to take it to a VW dealer. Shocks are relatively simple to replace. Struts, a little more to it. I would suggest buying a quality shock or strut, however. You get what you pay for, and if you're looking to save money, there are better places to do it than on your suspension, tires, or brakes. They're kind of important

...

---------- Post added September-21st-2011 at 01:41 PM ----------

I have a question for DCSportsfan53, do you work on older air cooled porsches?

[skinfan2k]

wow the dealer was charging 70 dollars to replace a cabin filter! thats crazy!

[DCsportsfan53]

Predicto, strut and shock replacement on a 91 Cabriolet is straight forward and relatively simple. http://www.germanautoparts.com/Volkswagen/Cabriolet is a good place for parts, good prices and a stand up small business that does things the right way, been using them for over a decade. Your car may be fitted with rebuildable shocks (inserts that go into a housing), the $38 OE option or with one piece units, the $67 OE option on that site. If you wind up getting aftermarket struts/shocks at a shop, see if they can get you KYB GR2s, I find them to be very reasonably priced, durable and better riding than similar options.

Whatever option you choose for parts, make sure the repair includes all the associated hardware, ie the strut mounts/bearings, the bump stops and dust boots. Probably also a good idea to have the front suspension components checked before/while doing this, in particular the front suspension. The tie rods and ball joints should be checked for any play and check the integrity of their rubber boots, which hold grease in the moveable joints. Secondarily, control arm bushings would be a good thing to check, particularly if you hear that clunk while backing out of a parking space.

As far as shops to go to, definitely doesn't need to be a dealer but, and this is just in general, stay away from large chain repair shops. Find yourself a trusworthy, small independent shop, for something like this they don't need to be VW specialists or anything, I just find the quality of technician and work at the chain tire/lube type stores to be spotty at best.

Zoony, can't say I've had much experience with aircooled engines in general, what'd you have in mind?

[Predicto]

Thank you both.