Hi Everyone,

I have a 1999 MC Z34 3.8 96K miles. I bought this car in March and it needed a bunch of little things, but overall is seemed sound. I had my neighbor (a mechanic) come with me when we test drove it. So before I even brought the car home I let my mechanic keep it for a few weeks to fix all the little things... Here's the list of what he did: Front Rotors and pads, serpentine belt, thermostat, lighter receptacle, spark plugs, Upper and Lower radiator hoses. Both horns are dead, but I can live with that for now. It was making a clicking noise on right turns and turned out to be the starter. So that has since been replaced. Car was running great!

However, in the last 2 months I've been having more troubles.
- It started when the cigarette lighter didn't work again. My mechanic friend popped it open and it had just come unplugged underneath.
- A few days later it wouldn't start at all. Almost like the battery was dead, but I wasn't hearing any clicking and the dash was lighting up. After a few tries it started. That happened once or twice and now it doesn't happen.
- I was then getting a low coolant sensor light and the coolant was full. My mech friend looked at it, reseated some connection to the coolant tank and the light went away.
- Then the "Service Engine Soon" light started coming on intermittently.
- I noticed that the car would make a sound as if steam was building up and not being released. The engine would rev a little by itself then idle normally.
- Then I noticed that when I back out of my driveway which is on an incline, I will hear a popping sort of sound and the brake pedal releases further to the floor. I feel it in the pedal and it seems like it's coming from the steering column. I am not sure if this was always the case, but I think it may have been and I'm just listening for everything now.
- At this stage of the game the "Service Engine Soon" is on all the time.
- A little while after the "little rev" started the car would occasionally buck and stutter. It would shake the whole car forward and back until I put it in park and revved it a few times.
- Then it started sputtering and stalling. Only occasionally and only when I was going slowly or even coasting. It always starts back up after a few tries.
- The lighter is out again.
- Then it would just stall whenever I put it in park.
- Now it takes a few tries to start at all and stalls almost every time I'm going slowly or put it in park. It has also been resetting my clock on the radio after it stalls and occasionally the Brake and ABS lights come on.
- Also the low fuel light has never come on and I've run it pretty low.

My neighbor checked the codes and he said it was running and MAF Sensor and O2 sensor codes. He suggested replacing the MAF sensor first. BUT I'm thinking with all of these different problems could that be it? or is the MAF sensor code caused by another failing issue. It seems almost electrical to me, but I don't know much about cars.

Any advice or guidance would really be helpful as I don't have it to throw a lot of money at the car trying to troubleshoot.

Thanks in advance for any help you can offer.

- anagy007

 

Hi `anagy,
Sorry to read about your problems, but they happen on all cars that are going on 13 years old ...You maybe able to clean the MAF & just get a new sensor. Please check back on your thread to see what our expert mechanic tech's post on your problem.

Thanks for your indepth post on your problem...

Wish you a easy/fast solution to your Monte Problem..
Wish you a Great Holidays.

 

First question on my mind, was this a flood car (was in flood waters)? Just seems a lot of weird electrical issues. If the car was in flood waters, water that got into the wiring/sensors and other items may be corroding contacts and wires causing odd issues to occur.

Also, can you post the actual error codes the car gave? There's mutliple codes for MAF and O2 issues.

As for the stalling and performance problems, here's my advise (and it's pretty general without having the actual codes and only a vague description):
- First, what brand plugs did your mechanic put in? If the answer is BOSCH, change them. My experience with BOSCH is bad performance AND bad life in GMs (prematuely fail). Stick with AC Delco.
- Second, buy a can of MAF cleaner from the auto parts store. Usually a MAF is really expensive and simply needs cleaned, as per the instructions on the can. It's quick, easy and cheap to clean.
- Third, which O2 sensor is causing the grief? Upstream or downstream? If it's upstream, this can have a direct effect on performance. Replace it with a Delphi or preferably a AC Delco. If you use other brands, sure they may work, but the calibration may not be to spec with what the PCM is expecting. If it's the downstream O2 (this is after the catalytic converter) it has no effect on performance. Change with what ever cheap O2 you wish. BUT depending on the code you actual received that downstream O2 could be alerting you to a problem with the catalytic converter (which would be an issue that can cause poor performance and stalling in extreme cases).
- Check for vacuum leaks. Usually done by having the car idle and misting starting fluid around any vacuum line/connection. If it has a leak, it will suck in the starting fluid and you'll hear the engine change performance.

As for the stalling resetting the radio and power issues, have a battery/alternator test done (typically free at any auto parts store). You may have a battery with a dead cell or an alt on it's way out or both. I've never heard of a dead batter causing the car to stall. If the battery and the alt check out, you may have a bad ground connection somewhere. My '84 Camaro at one point stalled and lost all electrical for about 2 seconds, came back to life, I just popped into neutral, restarted, back into gear and continued my travel. Did this regularly. We finally found the problem. Corroded connections on the started. Unhooked them, cleaned them and put it back together, never had that problem again.
You could also have accessories (like an aftermarket radio or amp) miswired or malfunctioning causing a power drain. I suppose if you had a stereo amp drawing too much power from the battery and beyond what the alt generates, perhaps that could stall it.... But I'm not an expert there....

 

`Jason, Thanks again for helping one of our Member's with their problem(s)...It does not go unnoticed 4-Sure...
It's great that our December Monte of the Month winner share his time & knowledge with `all...It is appreciated & reflects your good character...Thank You

 

Thanks Space. I try to add value when I can. I think that's why we're all on this forum in the first place. Hopefully something in that novel I wrote is helpful.

 

Like Jason said check all your connections. I had a bad connection on my wifes Grand prix last week and it wouldn't run right. It was the Auxiliary post. Make sure the grounds are not corroded either.

 

Wow, Thank you so much for the replies. This is the best forum ever. I lurk here all the time. I did post when I had the starter issue. It took a mechanic that specializes in Montes to nail down that a clicking noise while I was turning right was the starter. LOL.

Any way, To answer some of Maniac's questions. The plugs were AC Delco and I think it was AC Delco and it came all together. I think it was some kind of pack. I ordered it myself from Rock Auto and my mechanic neighbor replaced it.

I don't know the actual codes, he just told me MAF Sensor and O2 sensor. I will ask him when I get a chance. It's funny that you mentioned the flood issue. My neighbor had brought that up one time. I don't remember what prompted it, but I can tell you that when I bought the car it was a mess. The carpets had deep brown stains all over, almost like soda was spilled everywhere.

I will start with Maniac's suggestions and get the MAF cleaner and have my battery checked. Thanks so much for the initial direction. I will keep this thread updated as I find out more.

Merry Christmas and Happy Chanukah

 

i think there only one 02 sensor on the 99 so ur problem is either that or the cat

sorry to hear ur having many problems with ur 99 Z i havent had too many with mine other than the valve body and the suspension which im tryin to still get sorted out.

 

Ok, So I was able to bring it to Autozone, but unfortunately they couldn't check my battery because of how it is situated in the engine. So I have to have my husband take it out and bring it up to test it. But he did clean the MAF sensor and I haven't stalled since. I'm still concerned about it though because I still have the "Service Engine Soon" light. I will keep everyone posted.

 

I would check your grounds there also could be a short if it is and it was me I would go to one of those places that all they do is chase and check electrics in your car . then if that is ok then the vacuum next . maybe some plug injector if it stalls or bad rails just a guess