QuestionQUESTION: Car starts good, runs for about 12 minutes or to operating temperature then sputters & dies. Have replaced the fuel filter/regulator, cleaned the fuel tank. Also changed out the Map & TPS sensors. No trouble codes. Acts like the fuel is cut off, but the fuel pressure stays between 47 & 50 PSI.
Any advice will be appreciated.
Thks, Roy
ANSWER: Hi Roy,
Because it is a '96 it should still have fault code readout via 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 which remains 'on' to begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat to assure an accurate set of flash counts. Group the counts in pairs in the order of appearance to form the 2-digit fault codes. The last code is always 55 which is the code for 'end of readout'. Let me know the results and we'll go from there. A code 17 or 22 would focus us toward the engine coolant temp sensor which may be off-value and would explain the shutdown when warmed up, if that were the case.
Roland
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QUESTION: Thanks for the quick response. Found code #35 (rad Fan circuit). Put in new relay & no change. Talked to friend who advised that there is no shut down for the rad circuit, but maybe faulty ignition coil. Changed out coil & engine stll shuts down. Checked all related wiring, did not find fault. My scanner finally came up with code 1491, same as #35. Erased codes
But engine still shuts down.
Thks. Roy
ANSWER: Hi Roy,
I suspect the 35/1491 code is a diversion from the real problem. In the absence of any other codes we have to think and test. The next time it stalls why not check for spark at one of the plugs, and also listen for the fuel pump to run for a second or so when you turn the key to run. Let me know if one or the other of those is absent. As to possible causes, I have two thoughts;
Might a major fuse be opening due to carrying current and heating up? That can happen when the fuse wire has a crack which opens when heated up, closes when cooled. I assume that something happens after it shuts down to cause it to start again later. How much later? If that is consistent with a cracked fuse opening then closing that would be a posssibility. Take a look at fuse 21 (20 amp) in the power distribution box under the hood as that one powers almost every significant function on the engine. See if you find a subtle crack, and certainly when the engine stalls out check to see immediaely if the fuse is patent or not.
The other possibility is that this stall happens when the engine has warmed up enough to enter 'closed loop' engine operation and that one of the sensors/actuators that impact mixture is inaccurate and that is what causes the stall. But with no code we are left to guess. One common mixture-affecting item is the exhaust gas recirculation valve. It is mounted in a small pipe that braches off the exhaust manifold and threads its way to the area of the throttle body where the egr is bolted into the pipe, nearby the throttle body. Take a look at that valve and notice it has a rod located in the flange area between the round vacuum top of the valve and the body of the valve mounted in the pipe. There is a slot in the stem that lets you move it back and forth with the tip of a screwdriver. Make sure it moves to a closed position by the aid of internal spring-action. If it seems sticky, then spray the rod where it enters the valve with WD-40 and move the stem some more to loosen the action. Then see if that has solved the stall.
Please let me know if either of these ideas bear fruit.
Roland
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QUESTION: Thks again. Changed out 20 amp fuse. No change. When engine shut down checked for spark, no spark on #1 & 4, good spark on #2 & 3. Takes approximately 10 min. for engine to cooldown from 140F before it starts again. I cleaned & tested the EGR before reinstalling it. Seemed okay. Fuel pump working,good pressure, 49 PSI.
Tks. for the help
Roy
AnswerHi Roy,
Two possibilities come to my mind:
The coil pack could be failing when heated relative to the 1,4 plugs
The cam or crank sensor signal could be flaky when one or the other heats up, but not so bad as to set a fault code.
When the engine stalls:
test the primary resistance between between pins 1 and 2, then measure between pins 3 and 2 of the socket at the coil pack. The primary windings should read between 0.45 and 0.65 ohms.
Then measure the resistance of the secondary towers: between 1 and 4 , and between 2 and 3 should be 7,000 and 16,000 ohms. If these don't check out, replace the pack.
test the signals from the cam and the crand sensors. The common ground wire is black/light blue and the signal for cam is tan/yellow, while that for the crank sensor is gray/black. Check to see if the voltage pulses between 5v and 0.3v several times per crankshaft revolution as you turn the crank by hand with a socket on the crank pulley bolt and with the ignition in the 'run' position. Do this when it won't start, not when it will start. Replace a sensor that doesn't show the pulsing. The pulse rates will be different for the two sensors, so ignore that, just look for failure to produce the two levels of pulse.
Roland
PS Let me know what you learn.
