QuestionQUESTION: Last week, the car gave me a hard time staring in the morning, once it started it was stalling all the way to work. Then it completely died. I changed the ma sensor, cranck sensor and distributor cap. Now the car starts with difficulty but it keeps stalling and backfires once it runs. At higher speeds it runs great but when I slow down it starts backfiring again at the slightest touch of acceleration and some time shuts off. What could it be?
ANSWER: Hi Nick,
One general approach is to ask the engine controller what fault codes it has stored in its memory. Use the ignition key:"on-off-on-off-on and leave on", doing that in 5 seconds or less elapsed time. Then watch the check engine light to begin to flash, pause, flash, etc. Count the number of flashes before each pause, then repeat to be sure you have an accurate count. Then group the numbers in pairs, in the order of appearance to form the two digit fault codes. The last two set of flashes will always be 5 each, which is the number 55 and means the "end of readout".
Thn write back or or to www.allpar.com/fix/codes.html for a code translator.
One thing that commonly causes what you experience is a sticky egr valve. That valve is located in a small pipe that runs from the front exhaust manifold to the throttle body area of the intake manifold. Once you locate it, find the rod in the flange area between the valve body and the round vacuum actuator top of the unit. It has a circumferential slot and if you put the tip of a screwdriver in the slot you can move the rod back and forth against spring action in one direction That is the valve stem and the spring is for the purpose of closing the valve positively. If the valve stem gets sticky the spring can't always get it closed tightly, and that will make it hard to start and/or die when decelerating. When the valve doesn't close all the way it dilutes the mixture which cause the missing, etc. If you find it sticky, then just spray some WD-40 on the valve stem where it enters the valve body and work the stem back and forth to loosen it up.
If you get some codes and need specifics write me back.
Roland
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QUESTION: Hi Roland;
I did exactly that, the code I received was 12 which tells me that the battery/computer was recently disconnected. I used some WD-40 (Although I didn't feel that the valve was sticky) and it didn't change a thing. If I were to run a diagnostics on the car at the dealership, DO you think I could find the issue?
AnswerHi Nick,
Of course the dealer has many other diagnostic tools to look at the detailed function of the engine. The fault code approach only picks out the most obvious. So that is always an alternative. But I would want to know about how good their tune-up expert is and not give them a blank check.
It may be a leaky injector or a vacuum leak somewhere with a hose or a fitting that is connected to the intake manifold. That is about all I can suggest at this point. You say that the touch of the accelerator causes backfiring. That would suggest taking a look at the the throttle position sensor to see if there might be an electrical discontinuity in the wiper connection. Put an ohmmeter between either outer pin and the center pin of its plug. Then gently move the throttle to see if the resistance varies smoothly as you edge it open. It should.
Roland
