RWD - ECU and Intake Manifold Gasket didn't quite fix it

Volvo RWD 200 Forum

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ECU and Intake Manifold Gasket didn't quite fix it 200 1989

Hi Mike,

First, let me apologize to you for your frustration in trying to solve this by changing parts. Surely we all lead you and others to believe troubleshooting is just an elimination process of finding and changing the bad part, using a list of the "usual suspects." You've changed a lot of them.

For your questions: The "limp home" mode is peculiar to each of the engine controllers, and it acts in different ways.

Ignition: For instance, the EZK ignition system will allow safe limits to spark advance in case the knock sensor signal is absent. There isn't any limp home correction if the CPS is intermittent, because the computer cannot know where the engine is without that signal being correct. No, the EZK computer is very robust and we never hear of one being confirmed faulty, while its amplifier (in front of the battery) is a more common trouble with various symptoms between no spark and most-of-the-time spark. The coil could be faulty and give the same performance, yet most of my experience is with wiring harness connections and terminations causing the intermittent troubles. This "harness" is the one part that is never swapped, of course.

Fuel: LH2.4 limp-home is set rich to protect the motor. You'll note a 113 when it is confirmed set, and often an accompanying 232. There are many things that can cause it to lock into limp-home, as we've already discussed. It does so when the air/fuel ratio, as reported by the oxygen sensor and the fuel computer's knowledge of spark timing don't fall into correctable limits. Your Volvo mechanic will be able to check fuel pressure and oxygen sensor response. Please post back what she finds.

Art Benstein near Baltimore

Experience is something you don't get until just after you need it.


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