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Also suggest checking air flow sensor (AMM) Posted by walt [Email] (#2707) [Profile/Gallery] (more from walt) on Thu, 3 Feb 2011 08:12:12 In Reply to: Re: Car back from shop..still not running now and then, Jon Jennings, Wed, 2 Feb 2011 16:27:05 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Also have a 1992 900s that would not run cold until engine warmed enough for oxygen sensor to put out a signal. Then engine fuel injection computer (ECU) switched from AMM open loop to oxygen sensor closed loop fuel metering and ran great. Coasting down a long hill or long exit ramp would cut fuel off, lower oxgen sensor voltage to zero (lean), and make ECU return to open loop mode resulting in stuttering until opening throttle for a few seconds opened injectors, reheated oxygen sensor, restored sensor output, and returned ECU to closed loop mode. If you remove rubber boot behind AMM connector and hook a digital voltmeter on 0 to 20 volts DC setting red probe to orange wire and the other black voltmeter lead to an engine ground, you should see around a 1 volt increase in voltage at 2000 rpm while AMM is wired to engine harness and connected to intake air system. AMM can be bad even though it passes the hot wire glow test on engine shut off, which checks continuity of tiny platinum air flow sensing wire. Also fuel pump could be failing intermittently because its brush/commutator contacts are worn or due to intermittent signal from EZK ignition, ECU, CPS, or fuel pump relay. On trips I carry a hall sensor distributor with harness to swap if my CPS hall sensor quits. Fuel pump can be checked electrically with an oscilloscope per Swedecar's post below. For DIY troubleshooting, the 16-valve Bentley manual is indispensable.
posted by 72.49.18...
Swedecar's electrical fuel pump check
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