QUESTION: I have a problem with my 2005 Nissan Altima. My "check engine" light came on, so I went to the mechanic to have him pull the code. He said it wasn't really reading anything, reset the code and told me to come in if it happens again. The next day it came on again. I stopped at the gas station since I needed gas and filled my tank. When I went to start my car, it wouldn't start. I sat there for 15 minutes before it started. When it did start, I had to give it some gas because it was sputtering. The "check engine" light was still on so I brought the car to the mechanic the next day. He reset the code again and said to let him know if it came on again at the gas station next time.
I filled up about a week later, and once again it wouldn't start. I told my mechanic this and he said to try to get gas with the car running next time. So once again, I got gas but this time left my car running.
This time, as I was pumping gas, the car was sputtering and the tachometer was fluttering the entire time. But when I was done pumping, it seemed to run just fine. My car acts up only when filling gas; otherwise it runs great.
R.S.
ANSWER: What's interesting about this question is that the mechanic is trying to pinpoint the problem by asking the car owner to do all the work! Try this, try that, etc. Since the "check engine" light has come on each time, a scan tool should identify the specific DTC fault code associated with this problem. The comment "wasn't really reading anything" doesn't make sense - the "check engine" light was on!
I suspect the DTC will relate to the evaporative emissions system, which includes the purge valve. If the purge valve is stuck open, raw fuel/vapours can be pumped through the charcoal canister directly into the induction system during refuelling, which, of course, would create exactly the symptoms you've described.
Q: I have a 2004 5.7-litre Dodge Durango with 260,000 kilometres. As I come to a complete stop, the tachometer will drop momentarily from around 750 r.p.m to less than 500. The engine will occasionally stall. I must depress the gas pedal slightly to get it restarted. Initially, I had the throttle body thoroughly cleaned, then replaced it this past weekend. I also replaced the oxygen sensors, but nothing has helped. I should also mention that the "check engine" light has never come on. Any ideas?
K.D.
A: The 5.7-litre V-8 in this vehicle is equipped with a "flyby-wire" throttle system. Instead of a mechanical cable or linkage connecting the throttle pedal to the throttle body, an accelerator pedal position sensor, or APPS, is fitted directly to the throttle pedal and electrically connected to the powertrain control module, or PCM. In simple terms, rather than the throttle plate being opened and closed mechanically by movement of the throttle pedal, the position of the throttle pedal is communicated to the PCM, which operates the throttle via signal to the electronic throttle body.
Now that you've cleaned and replaced the throttle body, which includes the throttle and idle air control valve, I'd suggest plugging in a scan tool and having the APPS swept/checked for dead spots in its potentiometer. Also, check for any type of vacuum or air leak in the induction system that would allow unmetered air into the system.
Q: I have a 1998 Chevy S-10 and I am getting the smell of antifreeze coming from the air vents. It seems to be stronger when the heat is on. There is no antifreeze leaking anywhere in the engine or under the dash. The heater core hoses are tight, and they are both hot after warming up the engine. I just recently bought the truck and a short time after that the A/C quit working. I don't know if that would cause the smell to occur. I would hate to replace the heater core if I am not sure that that is the problem. Any advice you can give would be greatly appreciated.
R.G.
A: Your thoughts about the odour coming from the heater core are well founded, as this is the only area within the truck cab where antifreeze exists. It's possible also, but less likely, that leaking coolant odours are coming in with the ventilation air from an under-hood leak.
Typically, when a heater core begins to leak, one may notice fogging of the windshield when using the defroster; damp-slimy carpet beneath the right/centre of the instrument panel; and a citrus-like odour, similar to what you've described. There would also be a loss of engine coolant, but the rate may be less than you'd expect - it only takes half a litre of leakage to create the above symptoms - and this might not be immediately evident looking at the coolant overflow bottle level. A leak from under the hood should be easy to spot on the ground.
Your heater core is a cigar box-sized mini-radiator that transfers engine heat to the passenger compartment via circulating engine coolant. This part resides deep within the heater/ventilation system, and most aren't very pleasant to renew, as quite a bit of instrument panel disassembly is often required. Most heater cores are made of thin-wall aluminum, with a large network of finned passages that provide maximum surface area for heat transfer. Over time, accelerated by deferred cooling system maintenance, internal corrosion will find a weak spot, and pressurized coolant will begin to seep into the surrounding housing, and eventually to the carpet beneath.
I have a hunch your heater core may have a tiny leak, and most of the liquid may be vaporizing, causing the odour, or hasn't yet reached a seam of the heater housing. To be sure, you may need to drill a small hole in the lowest part of the plastic housing. Slide a piece of hose or tubing on the drill bit so it can't bore more than one-quarter inch deep - you don't want to cause new problems. Then, after shutting off the fully warmed up engine and waiting perhaps 15 minutes, check for signs of coolant leakage at the test location. Even one drop of coolant means trouble.
I can't fathom how the air conditioning working or not would be a factor regarding this odour. Refrigerant is odorless, should leakage occur. It's likely a coincidence the A/C has recently quit.
Paul Brand, author of "How to Repair Your Car," is an automotive troubleshooter, driving instructor and former race-car driver. Readers may write to him at: Star Tribune, 425 Portland Ave. S., Minneapolis, Minn. 55488 or via email at [email protected].
