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1990 olds delta 88 3.8lt. ,auto , fuel inj,79,000 miles Hello i have a problem with idle sometimes the idle will be high when you start the car after running for awhile . I have cleaned the trottle body with spray cleaner , replace the idle air control , complete tuneup , checked for vacum leaks none,no computer codes set, the idle sometimes increases while u drive and will not go down until u shut down and restart . I have ck the trottle cable for free movement . please any advice thanks bob
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Hi,Bob,
Check the battery cable connections,make sure they are clean and tight,also check your ground cable leading from the battery to the side of the transmission,there is a stud with a locknut,also along side there are 3 more grounds to the engine,make sure they are also clean and tight.
Perform an idle relearn,you need to do this if the battery was replaced or disconnected,to do this locate the diagnostic connector located in the lower center of the dash,with key on eng not running,ground the diag connector a and b terminals for 5 seconds then remove turn key off for 10 sec,restart and recheck,if that fails,remove both battery cables and short both pos and neg cables without battery connected,together for at least 10 seconds,reinstall the battery cables and recheck for normal idle,if you still have a problem,contact me,Thanks
ED
Hello ED , Thanks for the reply. I cleaned every ground i could find and tested them with volt meter good, alt output good, replaced the O2 sensor (it was cheap), ck all fuel injectors for pulse gd ,cleared computer code 12 was only code set, still have a high idle at startup when hot must shut down and restart for idle to go down . Still getting low idle sometimes . ? thanks bob
Answer -
Hi,Bob
Ok,sounds like we may have an IAC{idle air control}problem,either its sticking with excessive carbon build up or it needs to be replaced,GM has issued a new IAC valve for replacement and is less prone to excessive carbon build up.
The IAC is located on the throttle body,looks like a can with a 5 wire connector,the valve is black in color,you can remove this and attempt to clean the valve and the bore with carb cleaner such as gumout,reinstall and if it still has the idle problem,then i would replace the IAC.let me know if you need more help.
ED
Hi ED , The IAC valve was one of the first items i cleaned with trottle body cleaner and the trottle body also, that did not help so i repalced it with a new IAC still did not solve the problem. I was told to replace the MAF sensor but would like your input first since this is a pricey item and only comes rebuilt ,please tell me what u think thanks again BOB
Answer Hey,Bob
Hmm,yes a MAF could cause an idle problem but its pretty expensive to just replace,i got an idea,i usually need data from the scan tool to truly diagnose a MAF,but heres and old trick,start the engine and get it warmed up,with the engine idling,tap on the body of the MAF and see if there is a noticable idle change,if there is then yes the MAF is faulty.let me know what happens.
