Strange issue(s) with 1.4 petrol

[pisten-bully]

New to this Forum! We are located in the US and we import a snow machine made in Italy and powered by the TU3JP L4 (1.4L 8 valve, petrol). In North America there have been no Peugeot cars since the early 90's but we've been importing these Peugeot-powered machines since '02.

Great engine for our application, it has been doing a wonderful job but all maintenance has been handled by the folks who've purchased our machines.

Currently we have a real mystery on our hands with one machine and I'm curious what the Peugeot community might have to offer for suggestions on how to proceed.

One of our machines, an '04 version has developed running problems that we can't solve. The fuel mixture seems to be running rich, fouling plugs, misfiring, and we get an intermittent surging in RPM's. P0110, IAT sensor circuit malfunction was the first code thrown by the ECU (a Sagem 2000 unit) usually coupled with P0115, engine coolant temperature circuit malfunction and P0170 fuel trim. No codes for misfires, injector circuits, O2 sensors, or other faults are showing up!

To date we've replaced almost every sensor on the machine at least once and also replaced the ECU with a new one but we cannot eliminate the problem. We think we've tested every possibility yet we keep coming up empty handed. (I won't go into it all because I'd like to hear what you think!) Currently we have it running "okay", but just the other day it began its surging again only to work out of it and behave properly again. The surging is very pronounced, at least a 500 RPM swing up and down.

Ideas???

So we turn to the Peugeot community and ask quite simply, what have you seen with the TU3JP and problems with fuel mixture?

Thanks!

[bettyswollocks]

This is everything i could find on the codes , plus that engine had a fault with water ingress on the injector harness causing injector number 4 connections to corrode , but i don`t think that applies to the use of your engine in a snow blower, hopefully some of the other guys have ideas.



The ECT (Engine coolant temperature) sensor is basically a thermistor that changes resistance with temperature. Usually a two wire sensor, a 5Volt reference from PCM (Powertrain Control Module) and ground signal to PCM. This is different from a temperature SENDER (which usually operates the dash temperature gauge and operates in a similar way as the SENSOR, only it's a different circuit than what a P0115 is referring to). As the temperature of the coolant changes, the resistance changes on the ground signal to the PCM. When the engine is cold, the resistance is high. When the engine is warm, the resistance is low. If the PCM detects a voltage condition that seems abnormally low or high, P0115 will set.

Symptoms

Symptoms of a P0115 DTC code may include:

MIL (Malfunction Indicator Lamp) illumination will always occur
Vehicle may be hard to start
May blow a lot of black smoke and run extremely rich
Engine may want to die or backfire in tailpipe
Engine may run lean and increased Nox emissions may be apparent (Requires gas analyzer)
Cooling fans may run all the time when they shouldn't be, or not at all when they should be
Causes

Usually the cause can be traced to a bad ECT sensor, however that doesn't preclude the following:

Wiring or connector damaged at sensor
Open or short in reference or signal circuit
Open or short in signal circuit
Bad PCM
Possible Solutions

First, visually check the sensor for damage to wiring or connector and repair as necessary. Then, if you have access to a scanner, determine what the temperature of the engine is. (If you don't have access to a scan tool, using the dash temperature gauge may not be an effective way to determine coolant temperature. This is because the P0115 code is referring to the ECT SENSOR, and the dash gauge is operated by, usually a one-wire SENDER. Basically a different sensor that the code doesn't refer to.)

2. If the engine temperature is abnormally high, around 280 deg. F, that's abnormal. Unplug the sensor on the engine and see if the signal drops to, say, negative 50 deg. F. If it does, then it's a good bet the sensor is bad, internally shorted, causing a low resistance signal to be sent to the PCM. However if you want to be sure it's the sensor and not the wiring, there's a couple tests you can do. With the ECT sensor unplugged, check that you have 5 volts on the reference circuit with KOEO (Key on engine off). Also you can check the resistance of the sensor to ground using an Ohm meter. The resistance of a normal sensor to ground will vary a little depending on the vehicle, but basically, if the temp of the engine is around 200 deg. F., the resistance will be about 200 Ohms. If the temperature is about 0 def. F., the resistance will be over 10,000 Ohms. With this test you should be able to tell if the resistance of the sensor matches the temperature of the engine. If it's not accurate according to your engine's temperature, then you probably have a bad sensor.

3. Now, if the temperature of the engine according to the scanner is around 280 deg. F. and unplugging the sensor doesn't cause the reading to drop to negative 50 deg. F, but it stays at the same high temperature reading, then you'll need to repair the short on the signal circuit(ground) to the PCM. It's shorted directly to ground somewhere.

4. If your temperature reading of the engine according to the scanner is showing negative 50 deg. F or so, (and you don't live in the arctic!) unplug the sensor and check for a 5V reference present at the sensor.

5. If there isn't, then check at the PCM connector for proper 5V reference. If it's present at the PCM connector, then repair the open or short on 5V reference from PCM. If there is no 5V reference present at the PCM connector, then you're done with your diagnosis and you may have a PCM fault. 6. If the 5V reference circuit is intact, then check the ground signal to the PCM using the previous ground resistance test. If the resistance isn't normal for the temperature of the engine, then ohm the resistance of the ground signal to the PCM by removing the ground signal wire from the PCM connector. The wire should have no resistance, unplugged from the PCM to the sensor. If it does, repair open in the signal to the PCM. If it doesn't have any resistance on the ground signal wire and the resistance test of the sensor is normal, then suspect a faulty PCM.
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It also indicates that the fuel trims reached their limit of adding fuel while trying to compensate for a actual or perceived rich condition. When the fuel trims reach their rich correction limit, the PCM (Powertrain Control Module) sets a P0170, indicating a problem or malfunction in the fuel trims. It may also have a P0173 referring to the same malfunction but on bank two.

Symptoms

Symptoms of a P0170 DTC may include:

MIL (Malfunction Indicator Lamp) Illumination
Start and stall
Poor fuel economy
Black smoke at tailpipe
Hesitation/misfire at idle or under load
Causes

Potential causes include a vacuum leak, unmetered air leaks Fuel saturated engine oil Leak in turbo air charge hoses (if equipped) Possibly bad O2 sensor (If Mercedes, may require adaptation with M-Benz compatible scan tool.) Oil contamination in MAF connector or O2 sensor connectors. Also check ignition coils, cam and crank sensors, and oil sensor for leakage contributing to oil intrusion in wiring harness. Defective MAF (Mass Air Flow) sensor (especially on Mercedez-Benz and other European autos. There are a lot of problems with aftermarket MAF sensors.) Defective fuel pressure regulator Leaking camshaft adjuster solenoids (Mercedes-Benz).

NOTE: for some Mercedes-Benz models there is a service recall for a crankcase vent hose located under the intake manifold. It should be checked for leaks/cracking and also operation of check valve in the hose. The check valve should flow only one way.

Possible Solutions

It should be stated right off the bat that the most common problem associated with this code is the MAF sensor or air mass meter. This is especially the case with Mercedes-Benz and Volkswagen and other European cars. At time of writing, you don't normally see this code with American-made cars, and minimally with Asian, and, to be honest, I have no idea why. It appears to me that the PCM (powertrain control module) logic used by some European car manufacturers to set a P0170 (or P0173) fault code simply isn't used by American vehicle manufacturers. It is more common to see P0171, 0174, 0172, 0175 codes set with regard to fuel trim malfunctions on American cars. There is very little information on the setting conditions for a P0170, or P0173, but what information that is available almost seems to be a redundancy of the P0171,4,2 & 5 setting conditions. I'm sure there's a reason for it, but I can't get anyone to tell me what that is. The similarities between them may be why we don't see this code surface on domestic vehicles very often. It's simply unnecessary. So, simply put, if you have a P0170, your PCM noticed that the fuel trims reached their rich correction limit. Basically it's adding fuel to try to compensate for a lean condition, real or perceived.

If you have this code and access to a scan tool, observe the MAF sensor reading in grams/sec. The reading will be different for different automobiles, so get a good spec. I'm going to stick with what would be normal for a Mercedes (1.8L), since they have the bulk of the trouble. Expect to see at idle 3.5-5 g/s (ideally). At 2500 RPMs with no load it should be between 9 and 12 g/s. On road test, at WOT (wide open throttle) it should be 90 g/s or well above. If it's not in specs, replace it. Be careful of Ebay MAFs. Often they don't work according to OE specifications. If the MAF checks out and there is no oil intrusion at the connector, check fuel pressure and ensure that there are no leaks at the regulator internally or externally. Check all vacuum hoses and confirm none are cracked, disconnected or missing. Make sure there are no vacuum leaks at the intake manifold gaskets or tears in the air supply hose. If the engine is turbo charged, be sure the hoses are in good condition and have no leaks. Leaking turbo pressure hoses could cause a rich condition. Inspect the condition of crankcase vent hose under intake manifold and operation of check valve in the hose. (In the "What are the causes?" section) If there doesn't appear to be any problems with the fuel pressure, MAF or vacuum hoses, then inspect the O2 sensor connectors for oil intrusion. A bad O2 sensor could cause a P0170, or P0173. Repair cause of oil leak and replace oil-fouled O2 sensor.
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[bettyswollocks]

The IAT (Intake Air Temperature) sensor is a thermistor, which basically means it measures air temperature by detecting resistance in the air. It's usually located somewhere in the intake air ductwork, but can be located in the intake manifold on some applications. It is usually a two wire sensor supplied with a 5 volt reference wire (which also acts as a signal wire) from the PCM (Powertrain Control Module) and a ground wire.

As air passes over the sensor the resistance changes. This change in resistance affects the 5 Volts supplied to the sensor accordingly. Colder air causes higher resistance and higher signal voltage & warmer air lower resistance and lower signal voltage. The PCM monitors this change in the 5 Volts and calculates air temperature. If the PCM detects a voltage that is out of normal operating range for the sensor, P0110 will set.

Symptoms

There may be no noticeable symptoms other than MIL (Malfunction Indicator Lamp) illumination. However, it could be possible that you may experience poor drivability complaints.

Causes

Potential causes of the P0110 DTC include:

IAT sensor shifted out of airflow
Bad IAT sensor
Shorted to ground or open on signal circuit to IAT
Open in ground circuit to IAT
Poor connection at IAT (backed out terminals, broken connector locks, etc.)
Bad PCM
Possible Solutions

First visually check that the IAT is in place and hasn't been dislodged. As a quick check of the IAT, use a scan tool & check for IAT reading with KOEO (Key on engine off). If the engine is cold, the IAT reading should be the same as the CTS (Coolant temperature sensor) reading. If it shows more than a few degrees variance (for example, if it indicates a temperature extreme like negative 40 deg. or 300 deg. then obviously there's a problem) unplug the IAT and do a resistance test across the two terminals.

Each sensor will have different resistances so you'll have to get that info from a repair manual. If the resistance of the IAT sensor isn't within specs, replace the sensor. There should be some resistance, so if it measures infinite resistance, replace the sensor.

Having said that, here is a little more diagnostic info if that doesn't take care of it:

1. If your KOEO IAT reading is at the high extreme, like 300 deg. (which obviously is inaccurate), disconnect the IAT sensor. If the reading now shows the lowest extreme (-50 or so), then replace the IAT sensor. However, if when unplugging the IAT, the reading doesn't change then turn off the ignition and disconnect the PCM connector. Use a voltmeter to check for continuity between a good ground and the signal wire to the IAT. If there is continuity, then repair short to ground on the signal wire. If there is not continuity, then the PCM may have a problem

2. If your KOEO IAT reading is at the low extreme, again disconnect the IAT connector. Check that there is 5 Volts on the signal and the other is grounded.

a. If you have 5 volts present and a good ground, jumper the two terminals together. Now the reading on the scanner should be at the high extreme. If it is, replace the IAT sensor. But if it stays low even after you jumper the two wires together, then there may be an open in the wiring harness or a problem with the PCM.

b. If you don't have 5 Volts present, then check for reference voltage back at the PCM connector. If it's present there but not at the IAT sensor, repair the open in the signal wire.

[pisten-bully]

Originally Posted by bettyswollocks

that engine had a fault with water ingress on the injector harness causing injector number 4 connections to corrode , but i don`t think that applies to the use of your engine in a snow blower, hopefully some of the other guys have ideas.

That's very interesting that you should mention that, we have not checked the injector harness itself, though we have checked the engine harness from where it connects to the injector harness back to the ECU. Curious as to where the aforementioned corrosion usually appears?

We have had the injectors and rail removed from the motor but still connected to the harness to verify spray patterns and that effort showed all injectors spraying the same pattern and in the correct order.... but one thing about corrosion is that it can cause intermittent connectivity I would say. So we'll check that!

Also, much of what your post describes for testing on the water temp sensor and IAT we have already done.... but not all of it, so that's a help as well!

.... and it's not actually a snowblower, it's a large snowmobile!
As I mentioned, open to any and all suggestions! Thanks.