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ASE Master Tech 35yrs
ASE Master Tech 35yrs, ASE Master Auto Tech
Category: Car
Satisfied Customers: 2095
Experience:  ASE Certified since 1972,Master Auto tech,Heavy Truck Tech, foriegn and domestic
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92 olds 88 royal ls: coils..are the cam,crank sensor or ecm

Customer Question

I am a Journeyman Service Tech myself but i have a doosey, 92 olds 88 royal ls 3.8L car runs great when cold, runs like crap when hot. typical signs of ignition control module. replaced old magnavox style with NEW delco module and used coils, runs the same. no codes, really the only things it could be are the cam,crank sensor or ecm, but it really acts as though the icm gets too hot or somting and makes it run like crap. im getting 170 degrees celcius on the base of the icm, i would think it would be able to take more heat than that. Also replaced MAF sensor before I found out it was temperature related. Good coolant temp and iac counts on scanner, cleaned iac motor and throttle body.

I have lots more detail on running condition and symptoms.
Submitted: 6 years ago.
Category: Car
Expert:  danny replied 6 years ago.

I am thinking more like a temp senor or idle air mixture.


here is testing for idle air.

Customer: replied 6 years ago.
scanner reads proper coolant temp, iac counts are good, I cleaned iac motor, its def. and ignition issue but i cant track down the source. car WILL idle roughly but will die under load have you heard of a cam/crank sensor fault when it gets hot? forgot to mention i changed the maf sensor before i figured out it was a temp. related issue.
Customer: replied 6 years ago.
Relist: Answer quality.
Expert:  danny replied 6 years ago.
thanks was headed toward maf sensor next, is it dieing like a bad convertor? The coils are bothering me. did you say you replaced them with used coils or used the old ones?
Customer: replied 6 years ago.

Car runs like a top when cold. When it gets up to op. temps and you put a good load on it, say a hill(but doesnt need to be a hill) it will sputter and cough and eventually stall out. It will fire right back up but still run really rough. If you wait even a min then start it back up it will idle nice and you can drive about 10 feet before it sputters and dies again, like something electrical is overheating it seems.


These vehilces come with either the Magnavox coil pack (1 unit for all 3 coils) or the Delco style (3 individual coils) This car had the magnavox in it so i swapped it out for a delco style witch is supposed to be better. got a used delco module and coil packs from j/y, installed, and car did same thing it did with magnavox, got a NEW module and used the j/y coil packs, same thing. dont think its coils b/c it does the excat same thing with either style coil packs. Im leaning toward a bad crank sensor but ive never heard of one acting up even when it gets hot. and usually will throw a code, although im not reliying on that becuase it is a 92 after all.

Expert:  danny replied 6 years ago.
I am going to opt out so other expert may take a look.

Edited by danny on 7/1/2010 at 5:02 AM EST
Customer: replied 6 years ago.
Relist: Incomplete answer.
Expert:  ASE Master Tech 35yrs replied 6 years ago.
For it not to throw any codes, it sounds fuel related. A heat related problem would be an O2 sensor, or EGR but they would throw a code. When the problem occurs, check your fuel pressure to make sure it is adequate and change your fuel filter. A coolant sensor will sometimes not throw a code, but you said you checked it and was ok. Let me know what your fuel pressure reading is when the car is acting up.
Customer: replied 6 years ago.

thought of that already, checked fuel pressure when running rough, fuel pressure is at spec. and increases with throttle input. I pulled the fuel filter and could blow through it quite easlily. apperently these engines dont have an egr, so thats out of the question.... this is a weird one and im sad to say im kinda stumped.

Expert:  ASE Master Tech 35yrs replied 6 years ago.
When you say it's running rough, are you saying there is a miss or idle fluctuates or no power? Have you checked each exhaust port with a laser heat gun to see if all temperatures are the same? Have you checked to see if the fuel spray is equal for all injectors? Does the timing fluctuate when rough running? Have you checked all the grounds for good connection? Resistance goes up as temperature increases.

Edited by ASE Master Tech 35yrs on 7/1/2010 at 6:12 PM EST

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