Could you guys help me figure out a problem with my beater work car? - PeachParts Mercedes-Benz Forum

clintard · #1 12-16-2010, 09:03 AM

I really hate to come here and ask for help with a junk pontiac. Its my 1000$ beater work car that i drive in the winter to keep the salt off my 300D.

Ive been driving my 83 300D, RUST FREE, awesome condition, ON SALTED ROADS. For the love of god i have to get this thing fixed so i can put my baby back in the garage! Its breaking my heart to get salt on her!

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1996 Bonneville SE with 195k on the clock. Having electrical issue.

When coming to a stop sign, making a slow turn, or sometimes just idling in park or neutral the car will stall out. It only does this when the car is somewhat warmed up. Never when its completely cold. Before it stalls, the voltage gauge drops down into the red then it dies, BUT if you give it gas it will come out of it and the gauge goes right back up to 14. Never have a problem restarting the car and it cranks really fast even when acting up. I suppose im losing enough power somehow that the fuel pump slows down and the lack of fuel pressure causes it to stall. Ill also not that the headlights dim, the blower slows down, together at the same time so i think that eliminates it being 1 power source from sucking too many amps.

I checked the battery terminals, cleaned them, and installed new bolts. They are clean and tight now.

I had alternator tested, they said it was bad so i put a new ac delco alternator on. I sure wish i would have taken it off and had it bench tested, might have saved some money but oh well.

I bought a brand new battery and installed it.

Shortly after the alternator install, it was acting fine for a while but then started doing it again.

Bear with me here,

There is a repetitive clicking noise coming from somewhere around the serp belt that increases with engine speed. It sounds exactly like a lifter. I took the belt off and started the car, and the sound went away. I suspected it was the idler pulley. It spun freely but felt a little gritty so i changed it but im still get the noise. I took a long screwdriver and listened to all the accessories, and thought it was coming from the alternator but new alternator didnt fix it. Hope its not the water pump because i felt around on all the pulleys and the only one that had any play whatsoever was the water pump and just a tiny tiny amount.

I haven't changed the belt yet but i dont think its slipping. It never squeals and ive watched it as the car died several times and it dosnt seem to be slipping at all. Also, the spring in the tensioner is still extremely strong and isnt locked up.

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Could this be a bad ground connection at the frame or somewhere else?

Im not a very good mechanic, so i apologize if this makes no sense. I dont really feel like crawling around under the car in the slushy frozen winter that is Illinois right now. The new battery i got has top and side posts. So to test for a bad ground causing this, could i hook a negative terminal up to the top post on neg side of battery, and then run that to a bolt somewhere on the engine? Would doing that eliminate if its a grounding issue?

Im scratching my head like crazy over this one. I really appreciate any help i can get. Thank you!

buffa98 · #2 12-16-2010, 09:31 AM

Sound very much like a ground Issue. Try to find the other end of the ground connection to the car take it off and wire brush it. Or you could put another ground on . Just make sure it is to bare metal then cover with die electric grease. Hope this helped.

LUVMBDiesels · #3 12-16-2010, 10:23 AM

I would add a second ground too. Actually two more, one to the engine and one to the body.

Faulty grounds can be a real paint to diagnose. They can lead to everything from the car stalling to random lights and accessories operating...

aklim · #4 12-16-2010, 12:50 PM

Quote:

Originally Posted by clintard

When coming to a stop sign, making a slow turn, or sometimes just idling in park or neutral the car will stall out. It only does this when the car is somewhat warmed up. Never when its completely cold. Before it stalls, the voltage gauge drops down into the red then it dies, BUT if you give it gas it will come out of it and the gauge goes right back up to 14. Never have a problem restarting the car and it cranks really fast even when acting up. I suppose im losing enough power somehow that the fuel pump slows down and the lack of fuel pressure causes it to stall. Ill also not that the headlights dim, the blower slows down, together at the same time so i think that eliminates it being 1 power source from sucking too many amps.

The usual culprits been eliminated altogether? How are the plugs, wires and distributor cap if it has that? If not, how are the coil packs? How is the fuel filter?

I would get a known GOOD spark plug and pull plug wires one at a time when it is running. You must get a good blue flame. This checks for spark

Next thing to check is fuel. I am not sure but I would THINK that you could hook up a fuel pressure gauge and see what the pressure is. Consult a book to find out what the running pressure is. If you had a L98 engine I could tell you more but I am sure you are not running such an engine. When you shut it off, if the pressure drops rapidly, it could be the fuel pressure regulator or less likely, the injectors leaking. Crimp off the return rubber hose and see if it drops. If it doesn't, it is the regulator. While we are on fuel, I am not sure if there is crud in the tank clogging up the sock filter.

Get a scantool and see what the IAC counts are. It could be that the Idle Air Control solenoid is shot or the IAC passages are clogged.

PaulC · #5 12-16-2010, 01:58 PM

Quote:

Originally Posted by aklim

The usual culprits been eliminated altogether? How are the plugs, wires and distributor cap if it has that? If not, how are the coil packs? How is the fuel filter?

I would get a known GOOD spark plug and pull plug wires one at a time when it is running. You must get a good blue flame. This checks for spark

Next thing to check is fuel. I am not sure but I would THINK that you could hook up a fuel pressure gauge and see what the pressure is. Consult a book to find out what the running pressure is. If you had a L98 engine I could tell you more but I am sure you are not running such an engine. When you shut it off, if the pressure drops rapidly, it could be the fuel pressure regulator or less likely, the injectors leaking. Crimp off the return rubber hose and see if it drops. If it doesn't, it is the regulator. While we are on fuel, I am not sure if there is crud in the tank clogging up the sock filter.

Get a scantool and see what the IAC counts are. It could be that the Idle Air Control solenoid is shot or the IAC passages are clogged.

I had a '94 Bonneville for five years ending in late 1998. This engine has three coil packs each servicing two cylinders. IIRC, the voltage regulator is part of the alternator, which means that it should have been replaced with the alternator. Not that it rules out the possibility that the new regulator is bad. I also seem to recall Schrader valves on the fuel rails, facilitating a fuel pressure evaluation.

It's been my experience that IAC valves that are viable in warm weather can act up as the temperature drops, so Aklim may be onto something.

I would first clean up the grounds, as a 14-year-old salt belt car is certainly a candidate for corrosion in those areas. I wouldn't ignore interior and underhood fuse boxes and relay blocks as corrosion-related culprits either.

aklim · #6 12-16-2010, 02:13 PM

Quote:

Originally Posted by PaulC

I also seem to recall Schrader valves on the fuel rails, faciliating a fuel pressure evaluation.

It's been my experience that IAC valves that are viable in warm weather can act up as the temperature drops, so Aklim may be onto something.

THIS might help

If he had an L98 engine I would say he should hook up a scanner and see if he gets about 20 counts but I would THINK that the principle should be the same. That is how I adjust minimum idle since my system is so "non stock". If his passages are clogged up, it could be an issue since the IAC might be commanded to close up but the carbon there might still allow air to go thru and it could be turning lean.

Also another thing that makes me wonder is this. If it acts up when the engine is warm, wouldn't that mean it is acting up in closed loop? IOW, it cannot compensate. Maybe the O2 sensor is lazy?

bhatt · #7 12-16-2010, 03:13 PM

Sounds like you are running out of juice at low RPM and it is stalling.

Which means:
a)alternator
b)battery
or c)ground/wiring

Can you get someone to do a charging system test for you? It isn't expensive and rules out the possibility of bad alternators/batteries. I know they are both new, but they can be bad (bad battery cell, alternator, etc.)

Once you have the results of the charging test and it passes, then start looking at the belt (does it slip?) and checking heavy ground wires.

As a check for shorts between two ground points, hook up a jumper cable onto each point (clean paint off the metal first so you make a good connection)

If the car runs perfectly with the jumper cable hooked up, you have a bad ground connection OR maybe the ground wire itself is bad. They can flex inside the insulator and crack. Still look good, but they are bad.

Pooka · #8 12-16-2010, 10:29 PM

Just to jump in here...

I once had a Dodge Omni that did this same thing. Being pressed for time I took it to a old guy that rebuilt alternators, generators and starters in his shop. These used to be called Generator shops and there might be one near you.

Anyway, he started it, let it die, and said I needed a new grounding strap. This was a flat naked wire that ran from the block to the body. He took mine out and it was burned almost in two.

The new strap fixed it.

I asked him what caused this and he just said it would take all day to explain it and if he was fixing or talking he charged $35 an hour, so I still don't know why this took place.

All I know is I never had the problem again.

tbomachines · #9 12-16-2010, 01:16 PM

Make sure you don't have oil or grease on the belt and that its properly tensioned on the new alternator. Just because it doesn't squeal doesn't mean its not slipping.

PaulC · #10 12-21-2010, 09:52 PM

You're right about the learning curve for an IAC. When I replaced one in a Ford Expedition, the service manual recommended letting the vehicle idle for 30 minutes.

4x4_Welder · #11 12-22-2010, 01:13 AM

Next time you deal with a stall at idle issue with a GM, clean the IAC and then disconnect the battery for a few minutes. Reconnect, start it and it'll run like crap for a few miles, then smooth out and figure out how to run itself.
Also, if it has a MAF in the intake tube, clean it and make sure the rubber intake tube doesn't have any leaks.

aklim · #12 12-22-2010, 01:21 AM

Quote:

Originally Posted by 4x4_Welder

Next time you deal with a stall at idle issue with a GM, clean the IAC and then disconnect the battery for a few minutes. Reconnect, start it and it'll run like crap for a few miles, then smooth out and figure out how to run itself.
Also, if it has a MAF in the intake tube, clean it and make sure the rubber intake tube doesn't have any leaks.

To what end? IF it isn't adjusted right in the first place, you will be adjusting it again and again. Find the problem first.