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Automotive Technical Theory Forum

Professional automotive forum for discussion of the theory of operation for any automotive system or component. Discussions include electrical and electronic theory, engine propulsion theory, fuel system theory, ignition systems theory, and much more. This forum is for experienced automotive repair professionals only, membership required.

Continue to the description of our next automotive discussion forum, the Technical Tips Forum.

Recent Automotive Discussions in the Automotive Technical Theory Forum

Crank No Start Silverado With AFM
06/21/2018 in the Technical Theory Forum
This truck had no codes, has spark / fuel / compression. Would crank - flutter - stall. Cranking vacuum was zero (0) to +1-5 psi. Removed upstream O2\'s, cranking vacuum now over five (5) inhg. Clear flood mode started, very black exhaust until clear...
Battery Current Sensor
06/21/2018 in the Technical Theory Forum
[Electrical: 15 GMC Yukon Denali 6.2L] I may have asked this before. Is it possible to use the factory Battery Current Sensor to check for a battery killing current draw?? Checking old school way with an ammeter in series it only has 0.03 amp draw after ...
Nissan Native Fuel Trim PIDs - A/F Alpha
06/20/2018 in the Technical Theory Forum
I have a 2003 Nissan Primera with the QR20DE engine ( sold in Israel ) in front of me which does not support EOBDII, so I've only got native Nissan PIDs for fuel trim. There are two pids that I'm interested in understanding their meaning and interaction w...
Xenon headlamp coming on slowly
06/19/2018 in the Technical Theory Forum
[Electrical: 09 Nissan Murano SL 3.5L] Just spit balling here. The complaint is the left Xeon comes on slowly. Customer already tried a Philips replacement bulb. I verified (quick) 12 on the power side (relay and fuse good) and 0 volt drop on the ground....
Mechanical causes of high maf readings
06/15/2018 in the Technical Theory Forum
Dirty maf sensors and engine issues such as vacuum leaks typically cause the maf to underreport airflow. Assuming the maf sensor and circuit are operating normally what sort of engine issues would cause higher than normal air flow readings? All I can come...

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