Re: What does it mean when engine backfires during cold start
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Sounds like a lean "pop" on cold start. Fuel management diagnosis is super easy and most above average techs should have no problem with that. An injector problem would be constant, timing as well. Grounds are always critical, but they are easiest to verify and diagnose (check my other posts). Start with verifying long term fuel trims as they are controlling fuel on cold start. any minor problems hot which are being compensated by closed loop will have major effect on warmup. Check coolant temp and intake temps should be the same on startup. check MAP voltages if speed density or do Volumetric Efficiency test if Air flow controlled. Range test o2 sensors. All should take 10 minutes. If your tech doesn't understand, find a new tech.
Richard Stratford
CA BAR certified Instructor and Technician 23 ASE certificates ?
On Monday, March 20, 2023 at 04:57:29 PM PDT, Noras dad <norasonlydad@...> wrote:
Hey John, The injectors in these engines can't be refurbished. Ask your mechanic to replace all of them with new ones. Check the lines, if any look suspect change them all.
It kinda sounds like you may have a leaky/pissing injector. It sound's like the fuel in one of them isn't atomising properly. Once that cylinder gets hotter that condition will go away. Get all four injectors changed, cos chances are they have all done the same amount of work. I never clean/refurb/change one on an engine. Bon chance
On Fri, 17 Mar 2023 at 16:57, John Lauterbach via <cigtoxdoc= [email protected]> wrote: My '91 Subie Vanagon just started backfiring on cold start.? Engine runs fine once started.
What does that mean?? What should I tell my mechanic to do?
Thank you,
John
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