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Corvette
C4 Forum
89 C4 with mystery misfire/stumble!
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<blockquote data-quote="Corvince" data-source="post: 94023" data-attributes="member: 3128"><p>Hi. Hope someone has experience with this problem.</p><p>1989 C4 coupe with auto.</p><p>Problem: misfire at idle and under load. Intermittently clears for a few seconds then back to misfire. </p><p></p><p>Replaced:</p><ul> <li data-xf-list-type="ul">New injectors (from Fuel Injection Connection, stock size)</li> <li data-xf-list-type="ul"> " plugs</li> <li data-xf-list-type="ul"> " wires</li> <li data-xf-list-type="ul"> " fuel filter</li> <li data-xf-list-type="ul"> " distributor cap, rotor and module</li> <li data-xf-list-type="ul"> " intake manifold gasket (leaking china wall)</li> </ul><p>Tried:</p><ul> <li data-xf-list-type="ul">Timing set at 6 degrees BTDC</li> <li data-xf-list-type="ul">Fuel pressure check (40 #) Gauge bled down to zero after 10 min. Clamped return line, slowed pressure loss, clamped both return and feed lines, still bled down slowly. Might be that I used locking pliers to clamp off lines and pressure bypassing these.</li> <li data-xf-list-type="ul">Checked fuel pressure at WOT during test drive and all was good. Pressure stayed at between 38 and 44 pounds.</li> <li data-xf-list-type="ul">Injectors firing (noid light check)</li> <li data-xf-list-type="ul">Cleaned MAF</li> <li data-xf-list-type="ul">Vacuum test with propane</li> <li data-xf-list-type="ul">Compression test (all cylinders good and close together readings)</li> </ul><p>After all this, there is no change in the misfire/stumble.</p><p>Any ideas for a fix? I'm baffled.</p></blockquote><p></p>
[QUOTE="Corvince, post: 94023, member: 3128"] Hi. Hope someone has experience with this problem. 1989 C4 coupe with auto. Problem: misfire at idle and under load. Intermittently clears for a few seconds then back to misfire. Replaced: [LIST] [*]New injectors (from Fuel Injection Connection, stock size) [*] " plugs [*] " wires [*] " fuel filter [*] " distributor cap, rotor and module [*] " intake manifold gasket (leaking china wall) [/LIST] Tried: [LIST] [*]Timing set at 6 degrees BTDC [*]Fuel pressure check (40 #) Gauge bled down to zero after 10 min. Clamped return line, slowed pressure loss, clamped both return and feed lines, still bled down slowly. Might be that I used locking pliers to clamp off lines and pressure bypassing these. [*]Checked fuel pressure at WOT during test drive and all was good. Pressure stayed at between 38 and 44 pounds. [*]Injectors firing (noid light check) [*]Cleaned MAF [*]Vacuum test with propane [*]Compression test (all cylinders good and close together readings) [/LIST] After all this, there is no change in the misfire/stumble. Any ideas for a fix? I'm baffled. [/QUOTE]
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Corvette
C4 Forum
89 C4 with mystery misfire/stumble!
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