Opel GT Forum banner
1 - 5 of 5 Posts

·
Just Some Dude in Jersey
Joined
·
15,337 Posts
Discussion Starter · #1 ·
I've been chasing wildly fluctuating or impossible AFR gauge readings on my 2.4 Motronic FI system since May. I've replaced and redone all sorts of stuff and found a badly clogged with sealer fuel rail issue that fixed most of the problems. The engine generally runs like a clock now with full power and I've done 6 hours of highway driving and it has been very consistent. But that darn AFR gauge drives me crazy. One minute it says I'm perfect at 13-15(idle-acceleration) and the next minute it's reading off the scale at 19+.
I've redone or replaced just about everything and the only thing reasonable to try next, assuming a vacuum leak, was to put a new manifold-block gasket on. But I've done numerous spray tests at the manifold-block and other vacuum connections and I have zero evidence that there's even the slightest leak. Today, armed with an entire case of electrical contact cleaner, I decided to really go wild spraying stuff to find what must surely be a vacuum leak. Nothing. Cans and cans and no leak.
Okay, so I've been taught that just about the only way to diagnose Opel FI problems is to go around unplugging stuff to see if that changes how the engine runs or makes the AFR change. Well, long story a fraction shorter, I just "TOUCHED" the plug to my AFM and the engine died. Restart and it did it numerous times. My whole FI harness is brand new and I checked the harness plug's wires, terminals, and how well it latches when plugged in and everything seems perfect. I tried to jiggle just the well-seated plug and not touch it's wires. The engine died. Hmmm....the problem seems to be at the terminals themselves. I think the harness plug is perfect, so that leaves the terminals on the Chinese AFM I'm using. Could the terminals be partially cracked loose from the circuit board in the AFM? I've had this happen with tv remotes that have the battery terminasl soldered directly to a circuit board. Drop the remote and the terminals fracture the solder where they're attached to the board.
So, let's forget the engine dying thing and answer me this question: Could a bad or intermittent signal from the AFM cause the FI computer to monkey with the air/fuel ratio and cause the AFR gauge reading to swing wildly lean? That's the issue I'm chasing. The engine never dies when I'm driving, but maybe an intermittent air temp or air flow signal, the 2 signals that the AFM sends, is what is causing my air flow ratio gauge to read improperly. Your thoughts?
 

·
Your Noble Friend ;-)
Joined
·
4,418 Posts
Yes.

Dieter
 

·
Registered
Joined
·
2,261 Posts
Connectors are rated for a certain number of insertions. Cheap connectors might only be rated for a few, after that they can become flaky. It’s a real problem for low voltages or weak signals. So, yes, they are a common source for problems like this.
 

·
Just Some Dude in Jersey
Joined
·
15,337 Posts
Discussion Starter · #4 ·
I seem to recall, back when I first got into this 2.4 Motronic thing, someone saying they was very reliable, but were known for having problems with the electrical connectors. Anyone recall that?
 

·
Just Some Dude in Jersey
Joined
·
15,337 Posts
Discussion Starter · #5 ·
Ah! Here is the mention about Motronic having a problem with bad connectors. Read at the bottom about version 1.5:

Wikipedia:
<<<
Motronic 1.x
Motronic M1.x is powered by various i8051 derivatives made by Siemens, usually SAB80C515 or SAB80C535. Code/data is stored in DIL or PLCC EPROM and ranges from 32k to 128k.

1.0
Often known as "Motronic basic", Motronic ML1.x was one of the first digital engine-management systems developed by Bosch. These early Motronic systems integrated the spark timing element with then-existing Jetronic fuel injection technology. It was originally developed and first used in the BMW 7 Series,[1] before being implemented on several Volvo[2] and Porsche[3] engines throughout the 1980s.

The components of the Motronic ML1.x systems for the most part remained unchanged during production, although there are some differences in certain situations. The engine control module (ECM) receives information regarding engine speed, crankshaft angle, coolant temperature and throttle position. An air flow meter also measures the volume of air entering the induction system.

If the engine is naturally aspirated, an air temperature sensor is located in the air flow meter to work out the air mass. However, if the engine is turbocharged, an additional charge air temperature sensor is used to monitor the temperature of the inducted air after it has passed through the turbocharger and intercooler, in order to accurately and dynamically calculate the overall air mass.

Main system characteristics
  • Fuel delivery, ignition timing, and dwell angle incorporated into the same control unit.
  • Crank position and engine speed is determined by a pair of sensors reading from the flywheel.
  • Separate constant idle speed system monitors and regulates base idle speed settings.
  • 5th injector is used to provide extra fuel enrichment during different cold-start conditions. (in some configurations)
  • Depending on application and version, an oxygen sensor may be fitted (the system was originally designed for leaded fuel).
1.1
Motronic 1.1 was used by BMW from 1987 on motors such as the M20.

The systems have the option for a lambda sensor, enabling their use with catalytic converter-equipped vehicles. This feedback system allows the system to analyse exhaust emissions so that fuel and spark can be continually optimised to minimise emissions. Also present is adaptive circuitry, which adjusts for changes in an engine's characteristics over time. Some PSA engines also include a knock sensor for ignition timing adjustment,[4] perhaps this was achieved using an external Knock Control Regulator.

The Motronic units have 2 injection outputs, and the injectors are arranged in 2 "banks" which fire once every two engine revolutions. In an example 4-cylinder engine, one output controls the injectors for cylinders 1 and 3, and the other controls 2 and 4. The system uses a "cylinder ID" sensor mounted to the camshaft to detect which cylinders are approaching the top of their stroke, therefore which injector bank should be fired. During start-up (below 600 rpm), or if there is no signal from the cylinder ID sensor, all injectors are fired simultaneously once per engine revolution.[5] In BMW vehicles, this Motronic version did not have a cylinder ID and as a result, both banks of injectors fired at once.

1.2
Motronic 1.2 is the same as 1.1, but uses a hot-film MAF in place of the flapper-door style AFM. This version was used by BMW on the S38B36 engine in the E34 M5 and on the M70B50 engine in the 750il from 1988 until 1990. [6][7]

1.3
Motronic 1.1 was superseded in 1988 by the Motronic 1.3 system[5] that was also used by PSA on some XU9J-series engines (which previously used Motronic 4.1).[4] and by BMW.

The Motronic 1.1 and 1.3 systems are largely similar, the main improvement being the increased diagnostic capabilities of Motronic 1.3. The 1.3 ECM can store many more detailed fault codes than 1.1, and has a permanent 12-volt feed from the vehicle's battery which allows it to log intermittent faults in memory across several trips. Motronic 1.1 can only advise of a few currently-occurring faults.[5]

1.5
This system was used on some of General Motors engines (C20NE, 20NE, C20SE, 20SE, 20SEH, 20SER, C20NEF, C20NEJ, C24NE, C26NE, C30LE, C30NE, C30SE, C30SEJ, C30XEI...). The system is very reliable and problems encountered are usually caused by poor contact at the associated plug/socket combinations that link the various system sensors to the Electronic Control Unit (ECU). Predecessor of the ME Motronic. Also used in the Opel engines C16SEI
 
1 - 5 of 5 Posts
Top