Question-------------------------
Followup To
Question -
Hello Roland.
I have a 1993 Mercury Villager,(mini Van). I know that's not a Chrysler vehicle. But there are no mercury experts on this web site. so i figure I'll ask you( a Chrysler tech)
I hope you will try to help me the best that you can.
My problem is that when the car reaches operarting temperature, it starts to backfire, stumble, loose power, hesitate, ETC...
The temperature gauge never goes beyond 1/4 of the way up. When it starts to do this, RPMs never go beyond 2000, and my speed is at around 20-25 MPH with constant and very vigorous backfiring,
It gets so bad, that i usually have to pull over and wait a few hours before starting her back up.
I have no idea wether this car has a diagnostic/OBD2 port. So I have no idea what the problem can be. The engine is a 3.0l
The problem only comes once the car is at operating temperature, or HOT. And I never know if its running hot, because the temp gauge is always 1/4 up from the cold line. But the car has never over heated.
Please try and help me Roland
Thanx
Answer -
P.S. Here is the way to get the codes from a Chrysler engine of the early to mid-90's:
You may well be able to do a self-diagnostic test that will help identify the reason because up thru the mid 90's the engine controller had a memory which stored fault observations as codes that the owner could readout without special instruments. Give this a try and see if it works : Begin a readout as follows: Take your ignition key and turn the ignition switch "on-off-on-off-on" and leave it "on". Do this switching quickly so that no more than 5 seconds elapses. Then watch the 'check engine' light to begin to flash, pause, flash, pause, etc. Count the number of flashes before each pause and make a note of them in the order that they come. The last two flash groups will be 5 in each. Repeat the readout until you have the numbers accurately (the same result, two times in a row). Then pair the numbers two at a time in the order they came, to form two-digit numbers, for example the last number will be 55 which is the code for "end of readout".
We might find that Ford used the same code system.
Hi Gerard,
I'll give it a try, at least a general suggestion or two.
First off, OBD-II did not start until 1996, but there also was a system (OBD-I) that is no doubt present in your van. I don't know exactly what the 'trick' is to get the Ford controller to self-read the memory for diagnostic trouble codes that would be possibly of help in determining what is the cause of your problem. I'll give you the Chrysler approach in a separate response to this response to try for yourself.
On the problem itself, I suspect that the coolant temp sensor may not be responding properly to the warming up of the engine and instead is saying that the engine is still cold, so the fuel mixture stays richer than it needs to be under the warmed up conditon of the engine. On the Chrysler engine, the temp sensor is located near the thermostat housing on the engine which is usually a round manifold on the top of the head out of which a large radiator hose is attached that runs to the radiator. So look for an electrical plug on the end of a short cylindrical device screwed into the cylinder head right next to the thermostat housing. Then remove its electrical plug and measure the resistance across its two terminals with an ohmmeter. When the engine is cold the resistance should be in the range of 7,000 to 13,000 ohms and when the engine reached operating temperature (200F) it should read 700 to 1,000 ohms. If it didn't decrease by that large an amount due to heating of the engine then that would be the clue that you need to replace that sensor. Of course if you can read the fault codes, and it says you have a coolant sensor problem that too would be reason to replace the sensor.
On the temperature gauge, you can't be sure if it is accurate without comparing it to the temperatrure of the coolant. The problem is that the system can get pressurized and it is dangerous to open it and measure the temp of the coolant. But if you had a meat thermometer with a metal sensor shaft that you can stab into a piece of meat, then you could take that and press it against the radiator or the thermostat housing to see if it reads anywhere near 200F or not. If not, and the engine is running too cool (as the gauge might suggest) then you may have a thermostat that is stuck open and not allowing the engine to reach its normal operating temperature.
Also, the fan could be coming on too soon when the engine hasn't really warmed up, but that would belie the analysis I did above because if the sensor wasn't reading the true temp of the engine, it would tend to turn the fan on too late, after the engine has gotten too hot. So notice when/if the radiator fan is coming on and see how hot the radiator or thermostat housing reads at that point.
By the way, do you know if that 3.0L might have been made by Mitsubishi (as is the Chrysler V-6 3.0L engine?) That would be of interest to me in figuring out what is wrong.
So try to find the coolant temp sensor and measure its resistance before you start the engine, and then at the point where you feel it is about as hot as it is going to get. And ideally get a temp read at that point to evaluate whether you have a stuck open thermostat.
Roland
Hello Roland
Thanks for the answer you gave, it was very instructive, and easy to understand.
I think the engine might be a mitsubishi engine. Because I looked at the fuses, and they all had mitsubishi written on them, The map sensor, also has mitsubishi written on it.
I also want to add that I recently let the car run for about 20 minutes, and of course it started to backfire once it got hot. and the radiator fan never came on, and also the temp reading inside the car was 1/4 up from the cold line, just like I stated before.
I just can't understand why everything works fine with the engine cold, but once it warms up, it starts to backfire as severily as my car does
You mentioned coolent temp sensor, how important is this to a car's engine, and can it cause such a backfiring problem. can it be that the engine is runing hot, thus cause pre-ignition of the fuel? Help me !
Thanx in advance for UR response.
Gerard
AnswerHi Gerard,
O.k. so we believe that it is a 3.0L Mitsubishi engine just like the one used in many Chrysler models of the 90's.
Going back to the behavior you describe, I continue to believe that it is likely that the coolant temp sensor is either not working or it is electrically disconnected from the plug that sends its signal to the engine controller. You will find the sensor to be located between the distributor and the thermostat housing that I ealier described to you. On the other side of the same housing is the sensor for the temperature gauge but that is not the one to worry about, it seems to be working. The reason that your car behaves the way it does is that it is sending excess fuel to the engine, thinking that the engine is still cool. So you can either check the sensor resistance as I described, or take a chance and just buy a new sensor and install it. But check the wiring and plug-toogether to make sure that is not at fault.
Did you try to see if the trouble codes will read out?
If that works and you get a code 22 that too would confirm the sensor is not working. If you get a code 17 that would indicate that your thermostat is stuck open, but don't believe that until we solve the bad running and coolant temp sensor issue because that may be a consequence of the code 22, not a cause of the code.
Once you get the engine to run right we can access the issue of the temperature gauge which may or may not be accurate.
That is my best advice to you at this point.
Roland
