Mechanics

WHERE IS AIR CHARGE TEMP SENSOR? OR DOES 3.3L ENGINE NOT HAVE ONE?

1994 Dodge Caravan • 208,000 miles

Here's my car question: On my 1994 Dodge Grand Caravan LE, 2WD, 3.3L engine I cannot find the Air Charge Temperature Sensor (also known as the Intake Air Temp Sensor). So. Where is it? Or does my car not actually have one?

Background:
My car is cold start stalling. That is, it starts up great, runs great for the first mile, but once it starts warming a bit I get hesitation during acceleration and stalling at idle. Once it reaches normal operating temperature, it runs great again. These kinds of drivability problems often mean the air temp sensor is failing. But I can't find it! It's not on my Chilton Manual wiring diagram. It's not on the intake hose. I can't find it on the intake manifold. I looked all through the manual and all over the internet.

Originally it was stalling while driving at speed. So, stuff already done:
1. Replaced camshaft sensor
2. Replaced crankshaft sensor (was getting codes for these two; after these two, it only stalled at stops)
3. Replaced Fuel Filter
4. Replaced Idle Air Control Motor
5. Cleaned out Throttle Body
6. Replaced Spark Plugs
7. Replaced Spark Plug Wires
8. Found and repaired vacuum leaks
9. Replaced EGR Valve. (After this, I noticed that it only stalled during warm up)
10. Replaced Engine Coolant Temperature Sensor
11. Replaced damaged fuel pressure regulator o-ring

Other diagnostics
1. Intermittent check engine light, code 36, "air switch solenoid circut" and code 37 "Part Throttle Unlock Solenoid Driver Circuit"
2. Ignition coil replaced with known good, no change.
3. MAP sensor replaced with known good, no change.
4. Computer replaced with known good, no change.
5. Listened to fuel injectors with stethoscope, all are clicking.
6. No gas spitting out of fuel pressure regulator--diaphragm is probably fine.
7. I've got a bit of a coolant leak.
8. Fuel pressure is good.
9. Spark is good
10. Battery is good.

Other recent repairs:
-Serpentine belt
-Radiator
-Fuel pump replaced 5 years ago
Avatar
Ice_1
September 27, 2011.




Wow, you have been busy. If it has one, it will be in the big rubber air hose between the air filter and the throttle body.

Does the motor idle up when cold or just stall? There is an adjustment for the base idle on the throttle body that needs to be checked.

Roy

ASEMaster6371
Sep 27, 2011.
Thanks, Roy!

Nope, there's no air temp sensor on the hose between the air filter and the throttle body.

My Chilton manual shows a diagram for a 3.0L Dodge Caravan engine that has the Air Temp Sensor on the passenger side of the intake manifold, very close to the Engine Coolant Temp Sensor. But I can't find it there. Autozone's website says "Under hood, center/rear engine area, mounted in rearof the intake manifold." But the only thing on the back of the manifold besides vacuum ports is the MAP sensor.

As far as the symptoms: Starts up great. Runs great for about one mile. Then I get hesitation when accelerating. At stops, the idle will go up and down a bit--usually between 500 and 1500 RPM--but not for long before the engine stalls. Sometimes I get a brief check engine light, but not usually.

How do I go about checking and adjusting the base idle? The Automatic Idle Speed motor is supposed to keep things in line, but obviously something is out of whack.

Tiny
Ice_1
Sep 27, 2011.
No, the idle motor sustains the idle but the base isle is a setting from the throttle body.
I will look more into the air sensor but it is not your issue.

Roy

ASEMaster6371
Sep 27, 2011.
One mechanic who actually looked at the car suggested replacing the fuel injectors, but said he could not guarantee it would fix the problem. I did not have the injectors replaced.

Another mechanic who has not seen the car, but whom I talked with over the phone, said he thinks it is the timing chain. He said that he's seen a lot of old Caravans that have their timing chains go bad around 200,000 miles. He said the camshaft and crankshaft sensors need to be getting proper readings, but a worn timing chain is hard for them to read and needs to be replaced to get them sending good signal back to the PCM. No explanation as to why it runs well when hot.

I'm not sure what to think. A new chain is only $40, but getting it installed will take a ton of work. What do you think?

Tiny
Ice_1
Sep 28, 2011.
Just as much of a gamble as the injectors. In my opinion, based on your statements, I would go with the injectors first. Spray patterns are so important especially when the motor is cold.
Why dont you try having them cleaned wit the direct injection method first? Only 80 bucks give or take.

Roy

ASEMaster6371
Sep 28, 2011.
Well the trouble with this engine is that half of the injectors are under the intake manifold, so labor would be a lot more than $80. New injectors are only $30 a piece, so maybe I'll replace them myself.

Tiny
Ice_1
Sep 28, 2011.
The cleaning does not involve removing them. The fuel pump is turned off and the cleaner is what runs the motor hooked up to the pressure port.

Roy
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ASEMaster6371
Sep 28, 2011.
Ok, now I replaced the PCV Valve and the Throttle Position Sensor. I also cleaned the Engine Temperature Sender/Switch (not the ECT sensor, which I already replaced). Problem persists. It's still stalling, surging, knocking on warmup, but running great cold and hot.

Other suggestions I've received: -Replace the torque converter clutch solenoid
-Replace transmission temp sensor (Although I'm not sure my vehicle even has one of these since it's not on the wiring diagram.)

Tiny
Ice_1
Oct 1, 2011.
My only code is "37" which I looked up again. On my model it means "Torque Converter Clutch Solenoid CKT" -- open or shorted condition detected in this circuit.

So which route do I take to troubleshoot this?
1. I could rebuild the solenoid pack with a $30 kit
2. I could replace the solenoid pack with a $180 part.
3. I could look for shorts and grounds with my voltmeter, especially around the connector to the pack. I'm having trouble tracking down the connector, but I'll find it.

I'm pretty sure I've got the A-413 4-speed transmission

Tiny
Ice_1
Oct 1, 2011.
You have spent way too much money chasing this problem and spending a ton of money with no results. Why dont you get a real diag from a real shop and let them tell you the problem before you go broke here.
The othere guesses are just that guesses. They are expensive and useless if they dont fix it.

Roy


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