Impalass04 Posted October 5, 2022 Report Share Posted October 5, 2022 Hey there I have a 3.8 supercharged series 2 it’s not a Grand Prix but it’s a Impala SS it seems when the car is cold it doesn’t stutter as much or bog but when the car reaches operating temp it bogs and stutter above 50% throttle when hitting boost I’ve done coil packs wires plugs new cat u bend delete new maf IAC and tps aswell and at this point I’m stumped on what it might be if anyone has some input that would be amazing the car doesn’t throw a engine code either Quote Link to comment Share on other sites More sharing options...
94 olds vert Posted October 5, 2022 Report Share Posted October 5, 2022 Have you checked for vacuum leaks? What about fuel pressure? Possibly could be a bad fuel filter. Check the air filter recently? Quote Link to comment Share on other sites More sharing options...
Impalass04 Posted October 5, 2022 Author Report Share Posted October 5, 2022 Put a new high flo air filter in did not do a fuel pressure test yet Quote Link to comment Share on other sites More sharing options...
94 olds vert Posted October 5, 2022 Report Share Posted October 5, 2022 11 minutes ago, Impalass04 said: Put a new high flo air filter in did not do a fuel pressure test yet I'd probably check on the fuel pump/filter if it were my car. Quote Link to comment Share on other sites More sharing options...
Impalass04 Posted October 5, 2022 Author Report Share Posted October 5, 2022 Okay thank you I’ll do the filter first I don’t have to tools to do a fuel pressure test at home without paying a shop to do it Quote Link to comment Share on other sites More sharing options...
94 olds vert Posted October 5, 2022 Report Share Posted October 5, 2022 (edited) 2 hours ago, Impalass04 said: Okay thank you I’ll do the filter first I don’t have to tools to do a fuel pressure test at home without paying a shop to do it Auto stores will rent tools for free or at a very nominal cost. https://www.oreillyauto.com/detail/c/evertough/tools---equipment/rental-tools/engine---clutch-rental-tools/2a06ea1d698c/rental-tools-evertough-fuel-pressure-test-kit/ren1/67091/v/a/18752/automotive-truck-2006-chevrolet-silverado-1500 Best of luck to you. Hopefully you can get your car running right again. Edited October 5, 2022 by 94 olds vert Quote Link to comment Share on other sites More sharing options...
Schurkey Posted October 6, 2022 Report Share Posted October 6, 2022 Fuel pressure test, as said previously. Be sure the engine is under load, or the button on the side of the gauge unit is pushed so it's flowing fuel. Connect a scan tool, look at fuel trims, O2 sensor cross-counts, basically verify EVERY sensor and computer output--make sure the spark advances, the EGR works properly, etc. 94 olds vert 1 Quote Link to comment Share on other sites More sharing options...
Impalass04 Posted October 8, 2022 Author Report Share Posted October 8, 2022 Hey there guys so we replaced fuel filter nothing wrong with the fuel filter we did a live reading of the car all the sensors are working properly but above 2800 rpm in boost the car is missing on cyl 3 and 4 only so they told me my ICM has gone bad as when the car is cold it runs perfecty fine then when it gets hot under there it starts running worse and worse as it gets hotter and hotter I picked up a new delphi one so I need to put thermal or dialectic grease under the module to help dissipate the heat? Quote Link to comment Share on other sites More sharing options...
94 olds vert Posted October 8, 2022 Report Share Posted October 8, 2022 (edited) 4 hours ago, Impalass04 said: Hey there guys so we replaced fuel filter nothing wrong with the fuel filter we did a live reading of the car all the sensors are working properly but above 2800 rpm in boost the car is missing on cyl 3 and 4 only so they told me my ICM has gone bad as when the car is cold it runs perfecty fine then when it gets hot under there it starts running worse and worse as it gets hotter and hotter I picked up a new delphi one so I need to put thermal or dialectic grease under the module to help dissipate the heat? Thermal Paste or dielectric grease isn't required to replace the ICM. What I would do, is clean the mounting surface before mounting the new ICM. If you choose to, you could put a light coating of grease on the mount to prevent rust in the future. EDIT: Doing a quick search. I came across an interesting thread on the internet about this topic. https://forums.aaca.org/topic/298324-question-on-thermal-paste-on-mounting-plate-for-an-icm/ Edited October 8, 2022 by 94 olds vert Quote Link to comment Share on other sites More sharing options...
Schurkey Posted October 9, 2022 Report Share Posted October 9, 2022 (edited) Is this ^^^ like your engine/ignition? Cylinders 3 and 4 don't share a coil. MIGHT be the ignition system, but if so, why aren't 6 and 1 affected? If the spark is screwed-up for #3, it should be just as screwed-up for #6. If the spark is screwed-up for #4, it should be just as screwed-up for #1. What is the cranking compression of 3 and 4 compared to a "good" cylinder? What did the old plugs from #3 and #4 look like, compared to the others? What plugs did you install? They'd better be suitable for a waste-spark ignition system (Double platinum, or Double Iridium, NOT "single" Platinum or Iridium) If the cranking compression test results are acceptable, I'd be looking pretty hard at the injectors for those two cylinders. Edited October 9, 2022 by Schurkey Quote Link to comment Share on other sites More sharing options...
Impalass04 Posted October 9, 2022 Author Report Share Posted October 9, 2022 (edited) Yes that’s the ignition system off car I haven’t done a compression test yet but the entire ignition system was changed pretty much I did all new rapidfire acdelco platinum plugs acdelco premium wires and all acdelco ignition coils it’s just weird the car runs fine when it’s cold and as it warms up it gets worse and worse but if you don’t hit boost the car runs mint it’s only in boost it does it so he also said maybe a crank sensor not 100% sure the icm makes sense that when it gets hot it gets worse but I’m not a big expert on these cars I’m more familiar with the grand national 3.8s but we’ve had bad icms act like this on those cars so im not 100% I should add I did have the icm off and the back of it is corroded and the bottom of the ground plate looks pretty corroded as well so I’m hoping it’s just that and forgot to mention the old plugs were shot looked almost original they were all cracked on the porcelain aswell Edited October 9, 2022 by Impalass04 Quote Link to comment Share on other sites More sharing options...
Schurkey Posted October 10, 2022 Report Share Posted October 10, 2022 On 10/9/2022 at 7:59 AM, Impalass04 said: new rapidfire acdelco platinum plugs the old plugs were shot looked almost original they were all cracked on the porcelain aswell WHICH "Rapidfire" plugs? Are they DOUBLE platinum? The ACDelco site says "Platinum on center electrode..." which means they wouldn't be suitable for waste-spark ignitions. https://www.acdelco.com/parts/spark-plugs/professional-gold-single-platinum-performance-spark-plugs I meant, how did the firing end of the old #3 and #4 plugs look, compared to the firing ends of the "good" cylinders. Connect a scan tool as described previously. And report the fuel pressure under load, when the engine is misfiring, too. Quote Link to comment Share on other sites More sharing options...
Impalass04 Posted October 10, 2022 Author Report Share Posted October 10, 2022 Now that i think about it they are the single platinum plugs the old plugs all looked the same but I was chasing the misfire before aswell which is why I changed them these pics are what all the old 6 looked like I’ll take it back to my buddy’s shop to put the scanner on it again I ordered a new set of autolite cooper plugs which zzp recommends I went with the 104s Quote Link to comment Share on other sites More sharing options...
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