On Thursday afternoon, my '97 850 GLT began to make a "funny sound." (Yes, I'm a non-mechanically-inclined female. I'm sorry. Please indulge me!) When idle, it would sound almost as if it were backfiring. It wasn't as loud as a backfire, more like a "putt...putt...putt..." with a very slight accompanying jerk forward. I drove it home and parked it, hoping that if it cooled off, it would be okay. The next day, I drove it a few miles and it started making the same noise. Then the check engine light came on. I am going to take it to be checked out today. I'm just wondering what it could be. I really don't want to go into the mechanic's sounding like a complete damsel in distress and get ripped off.

Thanks for reading. I would appreciate any suggestions.

You really should try to vocalize the sound and attached it as an audio file to your message. It probably wouldn't help, but is usually quite entertaining ;-)

Joking aside, the real mechanics would be able to help more than me, but since they haven't yet....

First, from your post it could be one of many things, some not so harmful to the car and others quite harmful. Since you are already bringing it to a shop this afternoon, it sound like you're on top of it. If you don't trust the shop to which you are bring the car (and you don't have other options), tell them you want a record of all the codes the car's computer has stored.

If they don't have a Volvo Scanning Tool (VST) or satellite based diagnostic system (forgot the name???), you should be hesitant to bring it to them. If they don't have any OBDII scanning tool at all, or they don't plan on using one, you should bring it to another shop. Whatever scanning tool they use, have them write down the codes read from the OBDII connector and give tell them to you when they call you with an estimate. Then report back to this board with the codes before authorizing the repairs.

A note about OBDII scanning tools: I work on only my own car (1998 V70) and I only have a generic OBDII scanning tools. I don't have the Volvo Scanning Tools because it costs about $3500, but I don't charge other people to fix their cars either. In other words, by far the best diagnosis of you problem willl be done by a good mechanic who has a VST in hand. The second best job will be done by a good mechanic with a scanning tool which cannot read Volvo's proprietary codes generated by the cars computer. (Yes, it has gotten that high tech!) The difference in properly diagnosing your problem can be a $1000.









When was the timing belt last replaced and how many miles are on the car?

I got the car back today. The mechanic said that the reading they got was a "misfire." Or at least, I think that's what he said. Anyway, he replaced the spark plugs, the distributor cap and did something else that I can't remember right now... (Sorry... it's late and I've had a long day.) The light is gone and the car is running fine now.

Thanks for your help!

I'm glad it's running well again. Hopefully he did write down the exact code or codes he read before clearing. The generic OBDII codes (the minimum codes mandated by the EPA) will still tell you plenty. P0300 through P0316 are the ones in misfire. For example, P0304 tells you that cylinder four is misfiring, and P0313 says you have misfire with low fuel. So if the car's computer only stored a P0304, the mechanic can switch the number four and five wires and then see if P0305 is generated.

It is important to record the codes before he clears the codes out of the computer. If the engine light comes on again tomorrow and there are different codes, then he has two pieces of a puzzle: the earlier codes and the later codes. The second one is important for you. Say the mechanic tells you that he read P0172 (too rich) and P0304 (misfire on cylinder four). He changes the wires, cap, and rotor and clears the codes. Tomorrow, the light comes on again and you bring it back in. Same codes, so he now tracks down a vacuum leak and charges you another $150. At that point, I would tell him to put the old wires, cap, and rotor back on because he misdiagnosed the problem yesterday AND he had enough information to look for a vacuum leak first.

I'm not asking you to understand all of this. The point is that keeping a record of these codes can be an excellent way to reduce your costs on subsequent visits and a way to legitimately question a mechanic--even if you don't know much! So, if not this time, make certain taht in the future he writes down any OBDII codes (or DTCs) on your receipts.

Optimist

Thanks!!

Thanks for the help. The shop where I'm taking it says they "specialize in European cars" and has a big Volvo sign outside, so I hope they have the proper equipment. I haven't heard anything negative about them, but usually when a relatively young female comes into an auto shop and doesn't possess a great deal of mechanical knowledge, her bill mysteriously goes up! I just wanted to be able to have an idea of something that it *could* be and what to expect when I take it in. The closest dealership is 50+ miles from here.

The timing belt was replaced at 69000 miles. It has 88,700 miles now.

You would LAUGH so hard if I were to attach my vocalization to the message!! Imagine a combination of a southern accent and "putt...putt...putt..."

And I wonder why a mechanic wouldn't take me seriously...

Well, what did they say was the matter with the car? What was the estimate? Did they read the codes and did they write them down for you? Just curious.


Optimist

We had a storm this afternoon that knocked out power in part of the city, so I ended up having to leave it overnight. They are going to call me in the morning. I'll post when I find out more.

They can check for this code at the dealer and maybe some auto parts supply stores. If it is an O2 sensor, it could be very expensive if done at the dealer - $150 just for the part in some cases!!

If you need to change one or both I'd take it to an independent shop (reputable): They might be able to give you a better price. While you're at it, go ahead and change plugs, rotor, cap, distributor, plug wires. I did and the car ran much better (better mileage, too). Also check for any vacuum leaks that might be causing the 02 sensor to fail. There's a hose near the manifold (looks like an elbow) that goes bad over time. Since it's in the shop anyway, go ahead and have minor stuff fixed - like the thermostat if it's never been done and flush the transmission fluid.

Good luck

My understanding is that if the check engine light comes on you should NOT drive the car!

I didn't drive it after the light came on except to bring it home. I am going to drive it to the shop in about half an hour.