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Followup To
Question -
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Followup To
Question -
car backfires when warm, check engine light comes on, also when slowing dow for stop oil pressure guage drops to 0 and check gauge light comes on
Answer -
Hi Ron,
It sounds like you have an engine "driveability" issue. When responding please tell me which engine you have in the car. The first thing to do is query the engine controller as to whether it has noticed any malfunctions in in the engine system that it monitors. You do this by turning the ignition key "on-off-on-off-on" within a period of 5 seconds, then watch for the check engine light to begin flashing, then pause, then flashing, etc. Carefully count the number of flashes between each pause and make a mental note or have a helper write down the number for accuracy. The last two groups of flashes will number 5 in each. Then you take the numbers two at time to form two-digit numbers which represent codes for faults in the engine control system. For example the last number will be 55 (which means 'end of readout'). You can repeat the process as often as you like to be certain of the counts that are being displayed. Then write me back with the list of number for interpretation and suggestions. Do you have hand tools, and do you have a volt-ohmmeter, in case you want to do any repairs yourself?
Let me know and we'll move ahead on this.
Roland
AS STATED IN PREVIOUS FOLLOW UP THE CODE RETURNS ONLY A 55. THE MOTOR IS A 3.3 V6, 181,000 MILES WITHIN THE LAST YEAR I HAVE REPLACED THE CATALYTIC CONVERTER, WITHIN THE LAST MONTH I HAVE REPLACED THE RADIATOR AND THE AIR CONDITIONING UNIT, WITHIN THE LAST SIX MONTHS HAVE REPLACED THE FULE PUMP AND WATER PUMP AND HAVE HAD NEW SPARK PLUG WIRES AND TUNEUP WITHIN THE LAST 3 MONTHS. I HAVE NO TOOLS TO DO ANYTHING ON MY OWN SO WHAT SHOULD I ASK THE MECHANIC TO LOOK AT WITHOUT RUNNING UP A LARGE BILL.
FINAL SYMPTOM: YESTERDAY THE CAR WOULD TURN OVER AND THEN DIE. IF I PUMPED THE GAS PEDDEL IT WOULD CONTINUE TO RUN VERY ROUGH (DIESEL) BUT DIE IF PUT INTO DRIVE. I TRIED FOR 45 MINTUES TO GET IT TO START AND THEN IF BY MAGIC IT STARTED. THE MOTOR IS RUNNING FINE TODAY WITHOUT ANY BACKFIRING AND SEEMS TO HAVE MORE POWER THEN EVER. ? MAYBE ITS POSSESED
Answer -
Hi Ron,
I had a couple of more suggestions on why you have the backfire problem when the engine is warm. There are two sensors that measure the temperture of the engine block (coolant temp sensor) and the temp of the intake manifold to measure the temp of the incoming fuel/air mixture (charge temp sensor). If one of both of these were no longer responding to the rise in temperature of the engine then they would very likely mislead the controller such that the enrichment that is needed to start and run a cold engine would not be cut back after the engine is warmed up, thus a too rich mixture with associated backfire. So those two sensors would be good to check as to their resistance values after the engine is up to operating temperature:they should read 700 to 1,000 ohm when the engine is warm (200F).
Let me know how things go as the feedback is helpful to me.
If you have an ohmmeter I can describe where these sensors are located and you can check the resistances yourself for free and perhaps save the cost of a diagnostic test at the dealer.
On the spark test I suggested earlier, I just realized that the 3.3l has a direct ignition system (no distributor) so the way to check spark quality is to buy an extra spark plug (or use an old one from a prior tune-up) and after removing one of the spark plug wires from one of the 6 spark plugs insert the extra plug into the removed spark plug wire insulator to make it just like it was before you removed it. Then while holding onto the rubber insulator, position the threaded sections of the extra plug against the cylinder head, have the elper crankover the engine and observe for the quality of the spark that jumps across the gap between the plug's electrodes. Forget the other test I mentionned for arcing. But if you are not firing on all 6 cylinders what you would do is check each of the 6 spark wires using the extra plug to make sure that the coils are all doing their job to make a spark at each cylinder.
Roland
hAD THE SPARK PLUG WIRES CHECKED AND ALL ARE FUNCTIONSING CORRECTLY. CAR WAS RUNNING SMOOTHLY UNTIL YESTERDAY WHEN THE PROBLEM RETURNED. DID MANAGE TO GET A COMPUTER COED THIS TIME IT IS 12141355
WHAT DOES THIS TELL YOU. THANKS FOR YOUR HELP rON
AnswerHI Ron,
The only question I have is whether you got the read out in the order 12, 14, 13, 55, because they are supposed to read out in numerical order; so could the 13 actually be a 23? I would suggest that you repeat the readout to be certain. The 12 is usually a code for alerting you that the battery was disconnected sometime in the past 50-100 key on-off cycles, but my 91 manual interestingly does not show that code as applicable for that model year (this might just be an oversight). So that is another reason to re-read the codes.
The 13 code says that the MAP sensor is not producing a variable voltage output as would be expected between when you turn on the ignition and then when you start the engine. So that would mean either that the MAP sensor has failed, or that the vacuum line from the sensor to the intake manifold is cracked or disconnected so that it can't read the manifold pressure as it it supposed to do.
The 14 code says the voltage signal from the MAP sensor is either too high or too low which might mean an electrical wiring issue from the MAP to the engine controller, or that the MAP sensor is way off-value (though free of a wiring problem). A faulty MAP sensor or its wiring or vacuum supply line will certainly cause a driveability issue. Together those two codes, both pointing at the MAP, suggests that you look at both the wiring and the vacuum line for the MAP to see if you find any thing amiss. Let me know if you get a different set of codes from your re-read. The 55 means "end of readout".
Roland
