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Steve, Auto Service Technician
Category: Car
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Experience:  25+ yrs experience as a professional working technician; ASE L1 master technician
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1996 Chevy Cavalier: car until..smell..the interior..fuel injector

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1996 Chevy Cavalier: 72K mi.Never had an ounce of trouble with this car until now. We had a bad smell of gas in the interior which we found out to be a leaking fuel injector. Our mechanic suggested replacing all four injectors even though only one was leaking. 900.00 dollars later the car has never run more terrible. We took it back 7 times in the past two months since the work was completed. The mechanic just does not have an answer for what is going on and we are in a terrible bind because my daughter whose car it will soon be needs the car for practicing parking and such for her drivers test in two weeks and I can't have the car tied up in the shop any longer. Problem: The car hesitates,coughs and misses which eventually causes it to stall out. It happens when moving through a line of cars in a drive through type setting- ie waiting in line at a Mcdonalds or when you lightly accelerate from a traffic light or while parking. Always when LIGHTLY accelerating.Car runs great on open road. We had the fuel filter replaced,the fuel system cleaned,the fuel pump checked and we even had the mechanic remove and replace all four injectors again as the local Cevy dealer suggested maybe the "new" parts were defective. The timing, spark plugs have all been checked as well. The car is running like a jalopy at this point. If it were not for the smell of gasoline and tghe safety factor involved we would have been better off leaving the damn injector leaking seeing that the car has not been right since. PLEASE, PLEASE HELP.
Is the "service engine" light on in the vehicle?   Sounds like a possible throttle position sensor failure.
Another possibility is worn ignition components (spark plug wires in particular) which will tend to cause a misfire condition under load; ie acceleration or starting from a stop.
Customer: replied 11 years ago.
Reply to Steve Rapp's Post: The Check engine light has come on at times during this two month situation but the mechanic just clears the codes after checking whatever code he gets such as #2 cylinder misfire. However,the mechanic also said these could be false codes. We just picked the car up tomight after they say they replaced all four injectors AGAIN.
can you provide any more information or details which may help to diagnoise this condition? in particular:
*does the problem occure warm engine only, cold engine only, or anytime?
*is the service engine light on, or does it ever flash?
* does the car appear to be idling normally when your foot is off the gas?   does the idle seem rough, does it surge at idle, does the idle speed seem too fast or slow?
* Does dampness, such as during a rainstorm seem to affect it?
* Has teh previous tech been able to retrieve any fault codes from teh computer memory during diagnosis? if so, do you know what they were?
Customer: replied 11 years ago.
No Comment Added
If you are getting a repeated #2 cylinder misfire code, it would seem reasonable to assume there is some problem related to #2 cylinder.   False codes are rare; tehre is always a reason that they set; teh challenge is to figure out why.    After 3 sets of injectors, I think it safe to assume that they are probably not the problem here.
   I would suggest starting to look at teh #2 misfire condition.   You may ahve a plug wire or coil failing there; if #2 misfires, then it's companion cylinder will also misfire, in effect killing half of the engine momentarily.   Has anyone scoped this engine, particularly under load, to verify that it doesnt have a bad plug wire or coil?     If ignition components are all indeed OK, then I would think testing for air leaks affecting #2 cylinder; a smoke generator works very well at finding small intake manifold gasket leaks that could cause one cylinder to run lean and misfire under load.
Steve, Auto Service Technician
Category: Car
Satisfied Customers: 5494
Experience: 25+ yrs experience as a professional working technician; ASE L1 master technician
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Customer: replied 11 years ago.
Definitely when engine is warm.And I have seen the check ngine / check gauges light start to errantly flash just before stalling out or in the middle of a bad "miss"
Customer: replied 11 years ago.
No,Sir. I don't beleive the mechanic has scoped it but I'm not certain. I would have to ask him.
Customer: replied 11 years ago.
However he syays all the plugs look good but he never mentioned the "wires" or any ignition component.s
Customer: replied 11 years ago.
If you were in my shoes what would be your best guess at what I should do? I need the car fixed quickly.
Customer: replied 11 years ago.
Steve,are you still there ????
Your car has what sounds awfully like an ignition misfire (although there are other possibilities).
   You might want to try purchasing and installing a set of good quality spark plug wires on it, just for diagnostic reasons.   It is almost 10 years old; if it still has it's original plug wires they are long overdue for changing fmaintenance purposes anyway, so even if it did not resolve the issue it would not be wasted money.    Another possibility would be a failing ignition coil.   An engine requires teh highest voltage to fire the spark plugs when fuel mixture is lean (more air than fuel available).   When an engine is cold/ warming up, the computer adjustes the mixture to be slightly rich. After it is warm, the fuel mixture is adjusted leaner. When the throttle is opened (starting from a stop/ climbing hills/ accelerating)thesudden inflow of air into teh engine results in a temporarily very lean fuel mixture, untill the computer can respond by injecting additional fuel; this sudden throttle opening is the point where marginal ignition components cannot perform their job and often fail momentarily.
   Try a set of plug wires; they are inexpensive, easy to replace yourself, and needed for maintenance every few years anyway.
Customer: replied 11 years ago.
Steve,my main concern is "Why has all this begun ONLY AFTER the injectors were replaced. There was NEVER a performance issue until now???
If your car has a Quad-4 engine, there is a coil housing under the cover for the spark plugs that I have dealt with repeatedly. This acts as kind of a "distributor cap" for the coil packs. It is easy to replace and fairly inexpensive, about $30 if I remember correctly. Also, has the oxygen sensor been replaced?
Customer: replied 11 years ago.
Reply to craig's Post: Yes , my friend , the oxygen sensor has been replaced along with the fuel filter and air filter (all of which were fine to begin with but we changed them anyway).The spark plug wires are rock solid ( according to the mechanic). How would I know if I have a "quad-4 engine" ?? I know it's a four cylinder.
If you have a quad-4 , it will say QUAD-4 on an aluminum cover on top of the engine. It will be hard to miss.
have you had the catalytic converter checked? if it is clogged, it will definitely cause problems such as yours if it is.
Customer: replied 11 years ago.
Reply to craig's Post: Craig, Thank You Sooo much for the free replies, we certainly appreciate it.Best Regards,Customer
   Fromt ehs eervice information I had available, teh quad 4 2.4 engine was not an option in this year vehicle; the engine involved here is a 2.0 4 cylinder with the coild mounted to teh rear of teh engine over the cKp; otherwise the advice offered by Craig is good. The coil housing he is referring to is the equivalent of plug wires on a quad4 engine.
   A failed catalytic converter is always a possibility too, like craig mentions; it should be checked for during the course of notrmal diagnostics, definitely.    I'm more concerned with the MIL illumination and #2 misfire code though; these are probably closer to teh root of the problem even if the CAT is degraded. If the CAT failed, it is likely due to a misfire condition allowing raw fuel to go down the exhaust and burn in the CAT melting the ceramic inside...
   Good thoughts though!   I still stand by checking teh ignition wires and plugs for degradation, leading to the misfire condition...
Customer: replied 11 years ago.
Reply to Steve Rapp's Post: Steve,the #2 misfire code has long since been done with. That code came up immediately upon picking up the car from the shop on day 1 when the original and only injector that I found leaking was replaced.Then once I started having all the performance issues (immediately) the shop recommended replacing The other three injectors at a total cost of 900.00. They "cleared out the codes" and that has'nt seemed to be an issue according to the shop tech's at least.they did run across a couple of "manufacturer codes" during this two month episode but thay attributed these as possible "False" codes since they had already changed the Oxygen Sensor,Fuel Filter, Air Filter, also flushed and cleaned the entire fuel delivery system.I took the car back this afternoon and the shop agreed and setup an appointment with a Chevy Dealer on Thursday morning for two hours of diagnostic time.I HOPE THEY FIND THE PROBLEM because I am stuck renting a vehicle for my daughters Drivers Test because I can't have this car stalling during the road test as the State will flunk her for this. P.S. The shop assured me that the Plug Wires were rock solid.I'm hoping it is as you suggested an ignition component that can be easily replaced.
   Hmm; if they scoped the ignition system and the plug wires are OK, then they obviously arent the cause. that still leaves a possible coil or crank position sensor intermittently malfunctioning, although these components should also show up on an ignition scope test if they are marginal.
   There really aren't any such things as "false" codes; they all are there for a reason and have a definition and diagnostic routine. Perhaps by "false" he means that they may not be the root cause of teh problem, but are a secondary issure? At any rate, any codes that are stored deserve investigation; on a problem like this one any clue may be helpful.
   Do you have any idea what any of the current codes are then? I was under the impression that it was consistently generating a #2 misfire code...    In particular, are there any codes related to idle air control, throttle position, EGR, manifold pressure, or lean running conditions?
   <smile> still trying to help you out here; just need a little more information...
     
Customer: replied 11 years ago.
Thanks For All Your Help !!! First off,the engine will finally be scoped by the Dealer this coming Thursday AM. I do not know if my shop has scoped the engine or they are just relying on visual / intuition etc.. I guess I should ask if they even have a scope. This is my first encounter with this shop but they were highly recommended by my neighbor (a former Pep Boys mechanic for many years)who worked with one of the owners of this shop in past years.Truthfully, I do not know what diagnostics they have performed (if any)on thier own. I can only hope they know what they are doing.
   If I can be of any assistance with this problem in the future, please don't hesitate to ask...
Remote diagnostics of a driveability problem when you cannot see the vehicle or have any concrete test data available to look at is an inexact science/art at best involving a certain amount of intuition regarding what questions to ask that might elicit the right combination of clues based on past experience.
   I would be most interested in knowing what the cure for this one is, when the GM techs fix it.   A few of the possibilities I can think of include crankshaft position sensor, ignition coil or module, idle air control, EGR system fault, worn throttle body or leaking intake manifold gasket, MAP sensor, mass airflow sensor, and throttle position sensor; I just dont have enough data yet to be able to pinpoint the exact component...
   By the way, I really dont think at this point, based on the evidence so far that the shop that replaced the fuel injectors created the problem, and it sounds like they have gone out of their way to try to help you out with the comeback.   Test equipment, experience, talent, and diagnostic information varies widely among shops (both dealer and independent); and this may be one of those elusive ones that is difficult to pinpoint for even an experienced tech with the best facilities.    I wouldn't be afraid to give them another shot in the future; they may be perfectly able to handle more routine problems quite easily for you.   It's a tough business sometimes!
Customer: replied 11 years ago.
Reply to Steve Rapp's Post: Hey,Steve. You'll be the first to know if and when I hear what the heck it is.The Dealer won't be doing the fix,we are only paying for the diagnostics($165.00).The shop will most likely make the repairs(at what cost I don't know)I just hope the repair is not too expensive. We paid $1500.00 for the car and have not had a problem in the two years that we have owned it.Now all of a sudden I have spent almost another $1500.00 in trying to get the thing running the way it always did before we had the leaking injector replaced.
I agree with Steve on the possibility of the crank position sensor, sorry I overlooked that yesterday. In the experience I've had with these being bad, the car would run fine most of the time, and then be weak at take off and occasionally stall, but all of us who do this know that each case can be unique. It seems as though you are running out of things to fix. On the curious side, has anyone mentioned the possibility of the ECM, engine computer, being at fault?

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