1988 olds delta 88 missfires when warm not when cold, what could it be?

Question

So far things that I replaced;
plugs, wires, 6 new injectors.
Stuff tested;
ignition module- OK
no vacuum leak on outside of intake-ok
test light for #6 injector-OK
EGR -OK
crank, cam,TPS,map sensor- OK
When engine is cold it has no missfire. #6 is the only one missing.
Also has no missfire when driving 65-70mph.
Only misses under load or when stopped at stop sign.

Today I am going to change out the coil pack will let you know what happened.

Answer 1

It's pretty hard to tell if it misses at 65 mph, isn't it? Maybe it is still missing then. I'm thinking an intermittent problem with the coil pack that was not discovered by testing. These cars were known for this.

Answer 2

A bad ENGINE TEMP SENSOR maybe, but start with TWENTY BUCKS and the local OIL CHANGE CENTER! Go there, and tell them that you need your THROTTLE BODY and IDLE AIR CONTROL VALVE cleaned up to SHOWROOM clean.; If you can bring a can of AMSOIL POWER FOAM (hard to find) and a can of GUMOUT spray! Ask them to run BOTH CLEANERS through yoru PCV VALVE! Start YOURSELF by going to a DIY car wash with a can of GUNK ENGINE CLEANER SPRAY< original formula, and power wash EVERYTHING! Alternator, starter motor,, anywhere you see ROAD SALT build-up, grunge or fluid leaks! By the time you get home the engien bay will be DRY and CLEAN!. The IAC valve fine tunes the amount of AIR entering your engine around town ( city stop and go) and yoru FOOT only adds AIR to the engien! It does NOT PUMP FUEL at all like the old carb engines used to! Once the IAC and T body are SHOWROOM CLEAN they will add the CORRECT amount of AIR to the INJECTED FUEL! The IAC makes small corrections most times from O2 sensor signals! ALL CARS with a clogged up CONVERTER begin by having a bad IACVAVLE which is CLEANABLE usually. Once the IAC and T body are cleaned up, remove factory junk plugs and install updated BOSCH IRIDIUM or DENSO IRIDIUM spark plugs! expect 20% MORE POWER economy and smoother runiinb! emission wil ALSO drop by more than 50% Things have changed a LOT since 1988!!! If it is decided that you nedd a new DISTRIBUTOR CAP and ROTOR< then use UPDATED BORG WARNER SELECCT parts and M+NOT the AC delco parts which had ALUMINUM contacts instead of BRASS ONES! If you want even MORE POWER and reliability andf LONGER ENGEIN LIFE< get a MILD motor flushign and hten use the upsdated MOBIL ONE 0W-30 engein oil whicch is a PURE SYNTHETIC formula! it keeps ALL your senosrs CLEAN< and removes most sludge and varnish deposits as you drive it! Your car was WEENED ON valvolien most likely which also means you wll have LOTS and LOTS of wax coatins, SLUDGE and even COKE on your PISTON RINGS and SKIRTS! Once MOBIL ONE is installed, it wil get DIRTY FAST because it is doing it's job, REMOVING THE SLUDGE baked in over the years! You will "FEEL" the difference in about ONE HOUR of drving it! DO NOT BE AFRAID to run car HARDER after this treament as egniens are liek ATHLETES! if they are treated LAZILY< they can sludge up and BAD FLUIDS wil even BAKE INTO the engine metals! CLEAN is the name of the GAME TODAY! BACKFIRING is either ELECTRICAL or it means that your AIR/FUEL mixture has gone OFF KILTER! This is a PRE-OBD II engine so it takes some educated guessing here! Once your IAC is SHOWROOM CLEAN the AIR/FUEL mixture will correct itself! THESE SMALL CHANGES make a HUGE DIFFERENCE in how LONG this engine will last, and HOW CLEAN it will BURN FUEL!<<

Answer 3

bout the only thing left is the distributor cap itself...if it was a valve it would do it all the time.....but it sounds like a bad plug or plug wire...I know you have covered that but check to make sure it's not grounding out. open the hood at night with all lights off and look for an arc somewhere...that should tell you.

Answer 4

appears like a difficulty with the valve body.The valves get varnished and could dangle up till temp rises and issues amplify.attempt an additive referred to as LUCAS.worked GM for 25 years and did trans for 15.wish this permits.

Answer 5

Check for spark tracking on #6 plug. or could have cracked porcelain or defective new plug.Try insulative plug grease.

Answer 6

i have the same car you got.mine is a 3.8 and mine use to do that till i changed the coil pach and module,and i also changed the gas filter.now its ok.

Answer 7

could be valve seal,defintly somethig wrong with head or parts in it