QuestionHi Ray,
I have a 1990 Volvo 760 GLE (6-cylinder) with an intermittent problem. Most of the time it runs great, but every now and then it just starts running rough like a plug wire is off. It may run bad for five minutes or five days and then it just goes away and runs perfect again. It has been doing this for at least three years. Doing the work myself, I changed the plugs, plug wires, dist. cap and rotor, coil, both fuel pumps, fuel filter,and air filter. I checked the fuel pressure, the vacuum, the injectors, hoses and lines, compression on all cylinders, and other things I can't remember. It does not show any trouble codes by the service engine light coming on, but that is all I know about that system. If possible, I would really like some information about the diagnostic trouble code system, if there is one in my vehicle. Is there a self diagnostic system in this vehicle? If there is, how do you read or retrieve the codes? What type tool does it require to read the codes? Where do you hook the tool to retrieve the codes and how to erase the codes? etc. I read on one of the websites that some vehicles have this box mounted under the hood and you just plug the wire into different places and push a button. Nothing like that on mine, that I could find. I also read where you can make your own tool with some wire, clips, L.E.D., and spade lugs. It was still vague and didn't say what model Volvo or exactly where to connect the leads. I can read electronic schematics and diagrams,and have some mechanical ability, but this has me totally confused. Please help. Norman H.
AnswerNorm,
Most 1990 cars had the blinker box, but those were 4 cylinder ones that had LH 2.4 fuel systems. If you can not find someone that knows what to look for send me a photo under the hood, to revolvstore@revolvstore.com
If on your car the MAF has an adjusting screw that would be a system that does not have any diagnistic ability.
Here is something I found on the ignition system
1990 Volvo 760 V6-2849cc 2.8L SOHC B280F
Vehicle Level Powertrain Management Ignition System Testing and Inspection Testing and Inspection Procedures Ignition System Trouble Shooting W/ Volvo Tool #5280
Ignition System Trouble Shooting W/ Volvo Tool #5280
Notes
EZ115K
In order to use the VOLVO tester diode #5280 (or equivalent) for fault tracing, the engine must be able to start.Testing With Test Diode
1. Connect test diode (VOLVO tool #5280) to the test connector located on the driver side wheel housing (yellow-red lead). Connect the red lead to the positive terminal of battery.
2. Run the test diode into the passenger compartment and close the hood.
3. Turn ignition ON. The diode should now display a steady light.
4. Start and run engine, the diode should now turn off at700 RPM or higher.
5. Drive the car a short distance under low and high engine load conditions.
6. Fault Code Information.
One Flash: Engine knock has occurred, activating knock-controlled timing retardation. Knock may be due to inferior grade fuel, excessive engine temperature, faulty plug, intake system leakage or engine carbonization (due to frequent cold starting and idling).
Two Flashes: Faulty signal from temperature sensor. See Ignition System Testing EZ115K sectionJ10.
Three Flashes: Not used.
Four Flashes: Faulty signal from knock sensors, or faulty knock detection circuit (internal to control unit). See Ignition System Testing EZK115 section J11.
Five Flashes: Faulty load signal from fuel system control unit. See Ignition System Testing EZ115K sectionJ12.
Five Flashes: Faulty signal from No.1 cylinder detector. See Ignition System Testing EZ115K sectionJ13.
7. After test drive, check and repair indicated problem and retest.
8. Disconnect the test diode. Fault codes will be erased as soon as the engine is turned off.
