Norbert Posted December 21, 2023 Report Share Posted December 21, 2023 Hi, Today my car developed a new issue. Under heavy acceleration it loses power around 4k rpm. The engine can still rev the whole range under light to modorate acceleration. No CEL, and no other symptoms. In fact under 4k rpm the car drive as you would expect. - I already checked the air filter (1.5 years, looks mint). Spark plugs changed 2 years ago (<10k miles). O2 sensors are giving signal. Any idieas how to diagnose this? Thanks! Quote Link to comment Share on other sites More sharing options...
Norbert Posted December 21, 2023 Author Report Share Posted December 21, 2023 Also important to mention that car car failed co emissions two days ago (lambda ok, HC ok, CO around 0.6). Quote Link to comment Share on other sites More sharing options...
GmanB Posted December 21, 2023 Report Share Posted December 21, 2023 If it has been wet recently, I'd look a the coils first. If they are cracked, the are prone to water ingress which can cause loss of power/hestiation type feel to accelerating. Quote Link to comment Share on other sites More sharing options...
Nobbie Posted December 21, 2023 Report Share Posted December 21, 2023 Would be worth checking the Mass Airflow Sensor. If you disconnect it the car reverts to a default map. If the car runs fine on the default map then the MAF is faulty. Quote Link to comment Share on other sites More sharing options...
Everywhen Posted December 21, 2023 Report Share Posted December 21, 2023 Definitely worth checking the Coil packs, I replaced mine recently - none were cracked - but cyl No3 had a misfire. I think it was just age, I have no record of them ever having been changed. With the new coil packs the car revs to the red line so much more smoothly that it did before Quote Link to comment Share on other sites More sharing options...
BBB Posted December 21, 2023 Report Share Posted December 21, 2023 If HC are fine then you must be fuelling okay and presumably burning them okay. As you have high CO readings and hesitation above 4K, I wonder if you’ve got a failed catalyst and it’s blocking gas flow in the exhaust? 1 Quote Link to comment Share on other sites More sharing options...
Norbert Posted December 21, 2023 Author Report Share Posted December 21, 2023 Coil packs are old for sure, however, I would expect other issues if it was misfire: CEL, rought idle and truble starting. I didn't see any of these. That being said I remember that I saw hairline cracks on the rubber coat of the coil(s) around a year ago. They are surely on the way out... MAF I will check tomorrow! Quote Link to comment Share on other sites More sharing options...
Norbert Posted December 21, 2023 Author Report Share Posted December 21, 2023 Yes, I was thinking about that. I can remove the u-pipe tomorrow and look inside. Quote Link to comment Share on other sites More sharing options...
½cwt Posted December 21, 2023 Report Share Posted December 21, 2023 1 hour ago, Norbert said: Yes, I was thinking about that. I can remove the u-pipe tomorrow and look inside. That might be less easy than you think. Be prepared to replace the joint sleeves, and even to have to cut them off... Quote Link to comment Share on other sites More sharing options...
Everywhen Posted December 22, 2023 Report Share Posted December 22, 2023 19 hours ago, Norbert said: Coil packs are old for sure, however, I would expect other issues if it was misfire: CEL, rought idle and truble starting. I didn't see any of these. That being said I remember that I saw hairline cracks on the rubber coat of the coil(s) around a year ago. They are surely on the way out... MAF I will check tomorrow! Oddly I didn’t get CEL, rough idle or trouble starting, misfire only manifested itself between 1500-2500 rpm. Quote Link to comment Share on other sites More sharing options...
Norbert Posted December 22, 2023 Author Report Share Posted December 22, 2023 I ran a diagnostic and nothing came back. All sensors report normal reading. Today the engine didn't cut ... I will keep monitoring and see if it comes back. Quote Link to comment Share on other sites More sharing options...
GmanB Posted December 24, 2023 Report Share Posted December 24, 2023 Dry today? Quote Link to comment Share on other sites More sharing options...
Norbert Posted December 24, 2023 Author Report Share Posted December 24, 2023 16 hours ago, GmanB said: Dry today? Yes, new ignition coils are now top of the list. 1 Quote Link to comment Share on other sites More sharing options...
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