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The ECT is a little low at that temp @ 34K ohms but in the general area of 40K ohms at a temp between 50-65 deg F. What does it read when the engine is fully warmed up? It should be around 3K ohms at a temp of 180-220 deg F. Also make sure the 5 volt V Ref is at it's 2 wire electrical connector & the sensor has a good ground to the engine block.
I checked the sensor this morning after the truck sat overnight in the garage. I measured sensor again, it read 43K Ohms (approx). I also measured the voltage, it's 4.5V. There are only 2 wires to the sensor, not 3.
I started the truck up with no issue at all and backed it out of the garage. Just to test my case, I turned off the truck immediately (while engine was still cold) and restarted it, no issue, it fired up immediately. I ran for 15 mins or so, I would say the engine was fully warmed up, I barely could touch the radiator hose. Then, I measure the sensor again, it read 3.4 Ohms.
Two wires on the temp sensor causes me not to be clear on which temp sender you have a question about. There are Two coolant temp sensors on our engines, the Single wire one is for the dash temp gauge, the Two wire one is the Computer engine temp gauge & the one you need to be measuring if your concern is a engine coolant related temperature problem, or your looking for an answer to a trouble code.
I always thought that was the temp sensor for the PCM. I read some posts, they say the one with 1 wire is for the dash temp gauge. This has 2 wires, so I assume it's for the engine's computer. If you are correct, where is the one for the PCM???
Woooops, looks like I engaged my keyboard mouth without fully engaging my oldy moldy memory banks & checking. Yup that's the ECT, your correct the Dash temp gauge is a Single wire & the ECT is a Two wire setup. Looks like the cold resistance range is within reason, but the warm resistance of 3.4 ohms reading is way low, the info I have indicates it should be around 3K ohms/that's 3000 ohms, at a temp between 180-220 F. Are you certain you read the ohm meter setting right?
So the ECT resistance range seems ok, how about the IAT sensor = Intake Air Temp sensor, how does it's resistance range measure?
When it's in one of the delayed restarts, what does the fuel pressure measure then?
What happens if you cycle the ignition switch from off to on/run, (but Don't go to start to crank the engine), say 3-4 times, pausing at on each time long enough for the fuel pump to come on & cycle off, to build fuel pressure & prime the system for a start, then on the fourth time, crank the engine & tell us if it'll start without delay.
May I ask which 2 pins to measure the resistance? What Ohms I should expect?
I would think you are talking about the MAF sensor?
I did turn the key to ON/RUN (Not Start) few times, made sure the fuel pressure was built up good. No help though. I did not measure the actual fuel pressure though, need to get the tool.
On this year, the IAT sensor is in the air intake duct, (later years had it in with the MAF sensor assy) & it too has a negative temp profile. At a temp of 68 F it'll be in the 27K ohm range & at higher temps of say 160F it'll be lower, around 7K ohms but if it's having problems it'll usually set a trouble code & so far you haven't posted any.
It too gets a 5 volt reference from the computer.
This year model also uses some vacuum motors to move cold & hot intake air blend doors as temps change, so can mess with air density if they're acting out & sticking.
The procedure for checking them out is lengthy, so refer to your repair manual for details on how to check out its operation if you come to suspect them.
With no trouble code clues, right now I'd concentrate on getting a fuel pressure check when its acting out on a hard restart.
You mean the black air duct from the air filter box to the throttle body. My year doesn't have any IAT sensor in it.
I will do a fuel pressure check once I get the tool from Harbor Freight. Somehow I could not find the valve you mentioned ... will keep looking later tonight. Will update you guys.
You mean the black air duct from the air filter box to the throttle body. My year doesn't have any IAT sensor in it.
I will do a fuel pressure check once I get the tool from Harbor Freight. Somehow I could not find the valve you mentioned ... will keep looking later tonight. Will update you guys.
Thanks so much for helping me so far.
Yes in the black intake air tubing, it should be close to where it connects to the throttle body. If you don't have one, has it been removed, or has the intake air tubing been modified?
The computer needs to know what the intake air temp is, as it measures the air volume with the Mass Air Flow sensor, as the engine sucks in air, in order to calculate air density & volume, so it can properly adjust the fuel injectors squirt time & keep the air/fuel ratio in check at 14.7:1. SO, if any of the temp sensors, or MAF sensor measurements are corrupt, it'll cause the computer to corrupt fuel trim, all a vicious circle!!! lol
I finally found the IAT sensor, it's actually in the air filter box near the bottom facing the alternator. I measured the resistance, it reads 46.3K Ohms when the engine is cold (65F approx). The voltage is 4.6V.
I went ahead and bought a new one since it's pretty cheap (like $13). I measured the new one out of the box, it reads 30K Ohms. I will try to install it later today, see if it makes a difference or not.
For the fuel pressure's value, I looked everywhere along the rail and did not find it. The only thing I found is the fuel regulator which I replaced earlier. I guess my model ('94 Mazda B2300) doesn't have the valve for checking the pressure.
Ok good find on the IAT sensor. Not sure I've heard of one in the air box thats so far away from the MAF sensor & throttle plate. Ford kept moving the IAT closer & closer to the MAF sensor, then finally incorporated it into the MAF sensor assy, so the air flow & temp measurements were being made as close to each other as practical & this made them more accurate & fuel trim was made more accurate.
With no trouble codes, no need to keep tossing parts at the problem on a hunch, consider waiting until you find a suspect is bad, Then replace that puppy.
The fuel pressure Schrader valve test port should be on the fuel rail. It'll look sorta like a tire air valve & it should have a cap screwed on to keep out dirt & moisture.
Look here Part 2 -How to Test the Fuel Pump (1990-1997 2.3L Ford).
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