: 95 fleetwood miss, and injector readings



CadillacPimpinNOLA
12-21-10, 04:18 PM
95 fleetwood has a miss feeling at idle in park, neutral or drive. i can feel it through the pedal and steering wheel. car has 28K miles on it now. the cap/ rotor/ wires/ plugs are about a year old. any ideas

im thinking maybe a bad injector thats about to go out or is malfunctioning. if i put a fluke meter on them what should they read.

drewsdeville
12-21-10, 05:08 PM
Most, if not all older GM multiport injection, uses high impedance injectors. Putting a multimeter on them should yield a resistance in the teens, maybe 12-16 ohms. If you run into one with a resistance near 0 ohms (short circuit) or one with an infinite resistance (open circuit), that's the one that needs replaced.

If they all check out ok, you might want to find yourself a noid light to verify signal from the PCM. Otherwise, it'll probably be time for a compression check.

drmenard
12-21-10, 05:18 PM
check out this thread.. I said what I do...
http://www.cadillacforums.com/forums/rwd-19xx-1984-deville-fleetwood-1985/216398-1996-fleetwood-lt1-misfire-will-not.html

CadillacPimpinNOLA
12-21-10, 06:21 PM
ill try it out, gonna check with the meter and removing the plug on the injector, i dont think it would be compression with 28k miles but stranger things have happened

CadillacPimpinNOLA
12-21-10, 08:06 PM
ok this is a lil odd if your saying between 12-16 ohms. maybe its cuz i just got done driving the car and everything is still hot but mine all tested steady either 40 or 90ohms...

anyway i may have found the problem. hooked a snap-on computer to the car. everything was good on the computer except one thing. its about 50 degrees outside and i ran the car for 10 minutes. my climate control computer is telling me the engine temp is 175 degrees after that short run. the snap on computer is telling me 215 degrees.

if the coolant temp sensor is bad and telling the computer that the motor is running hot, it may cut back fuel or mess with other sensors that affect the motor. anyway its about a $10 part so ill try it tommorow and see what happens

jayoldschool
12-21-10, 08:26 PM
You need to remember that there are TWO coolant temp sensors on the LT1s. One is for the gauge, and one is for the computer. They are in completely different spots. One on the water pump, and one under the passenger manifold in the block. That is why there are two different readings ;)

drewsdeville
12-21-10, 08:29 PM
ok this is a lil odd if your saying between 12-16 ohms. maybe its cuz i just got done driving the car and everything is still hot but mine all tested steady either 40 or 90ohms...


You probably did something wrong then. Not only do the high numbers make no sense, but even the 40-90ohm variance makes no sense.

Even if the temp switch is bad, which is unlikely, it will not cause a misfire symptom isolated to one cylinder (I'm assuming you've already isolated the cylinder. You have, right?).

You still need to find what's causing the misfire on the affected cylinder.

CadillacPimpinNOLA
12-22-10, 12:00 AM
im changing the one in that screws into the waterpump, im 99% sure thats the one that goes to the computer.

and i dont know how i could test the injectors wrong, you turn the meter on, turn the dial to ohms, unplug the injector and touch the red lead to one prong of the injector and the black lead to the other prong.

i didnt say it was a miss i said it has a miss feeling, like a vibration. tell me this. if the coolant temp sensor is bad, and its telling the computer the coolant is too hot, could the computer get that false reason and retard the timing ect, play havoc with the whole system.

ill change that tommorow and see how it goes

turbojimmy
12-22-10, 11:09 AM
You need to remember that there are TWO coolant temp sensors on the LT1s. One is for the gauge, and one is for the computer. They are in completely different spots. One on the water pump, and one under the passenger manifold in the block. That is why there are two different readings ;)

I would think the SnapOn tool would get what the PCM is seeing (and therefore what the climate control is displaying).

I have a similar problem with my car. Heater fan runs when the car is cold. It reports like 95 degrees on a cold start-up. I know the sensor under the water pump is for the PCM. I thought the other one on the RH head was just a switch for the idiot light (doesn't actually report anything)?

CadillacPimpinNOLA
12-22-10, 12:52 PM
well heres what happened. called up chevrolet, i wanted a good factory direct sensor. no cheapy from autozone, pepboys, ect. so it cost me $20

2 minutes later its installed and everything is 100, car even revs up better