98 hesitation, miss when warm

[jo66tr]

Hello, I have a 1998 Aurora with 133,000 miles on it. Lately I have had problems with it hesitating and missing a little while under acceleration but only when it is at operating temp. When I first start it up in the morning it runs fine until it warms up. Has anyone else had this problem? I have 20000 miles on ac spark plugs and I just changed the fuel filter in it today with no difference. I run 92 octane or higher fuel and have always run that since I have owned it at 50000 miles. I have had no other problems with this car. Please help.

[jo66tr]

noone???

[newscarver]

check out previous postings about wires....expensive,yes but great results for rough idle, backfires, poor acceleration,and bad gas mileage.a perfect gift for a seven year old...

[jo66tr]

Thats the thing I have read all of the post but was wondering why mine runs perfect when warm and while idling but misses when it is at operating temp? Wouldn't a plug wire miss all of the time even when cold? Also where is the best price online to get AC Delco parts? Thanks

[kayaman420]

Originally Posted by jo66tr

Thats the thing I have read all of the post but was wondering why mine runs perfect when warm and while idling but misses when it is at operating temp? Wouldn't a plug wire miss all of the time even when cold? Also where is the best price online to get AC Delco parts? Thanks

You would think so , but these cars get some strange problems. The plug wires are the culprit in misfire situations 99% of the time. I guess once it gets to normal temp the heat must aggrivate whatever the problem must be. But your wires would be the first thing to replace if it were me and if you havent had it done yet its definately due. ANd its not too hard to do yourself either.

I CANNOT STRESS ENOUGH. Only use OEM AC Delco plugs in these Auroras. The Northstar engines are EXTREMELY touchy when it comes to spark. The OEM plugs and wires are PERFECT for this car. You will not gain anything from aftermarkets and there are countless testimonails of people that have tried aftermarkets and had HORRIBLE results. Including myself. You might get lucky with some aftermarkets , but its not worth the risk. Trust me.

gmpartsdirect.com is a good source. I used to always use a place called gmpartscenter.net/ . But the last time I checked there site they removed the Olds section. They still might sell them though.

[jo66tr]

Thank you very much I will change the wires and see if that helps. I was just wondering why it only did it warm. I thought maybe a coil or something. Again Thanks

[kayaman420]

Coil would be my next guess. An easy way to check the coils is to get 1 new one ( or one that you know is good) and rotate it around the 4 different locations and see if it takes away the problem.

If your doing the wires I would do the plugs also . Your doing most of the labor anyway.

[jo66tr]

Whats the deal with the plug gap. I gapped mine according to the book at .060 and later heard that they should be .050. Also would the coils have to be AC Delco?

[kayaman420]

.50 is what you should gap them at. Your not going to notice much difference either way . I have tried both, but .50 is what it is supposed to be. I just noticed you said you changed your plugs 20,000 miles ago so you should be ok with those.

I would stay with the AC Delco coils as well. You will find them for about $35 each from a wholesaler.

My rule of thumb is to stay OEM as much as possible for these cars. Especially when it come to electronics. You can use aftermarkets for mechanical type repairs. Like brakes, shocks, .

[jo66tr]

where is this "Valuable northstar" thread? I have looked all over. Thanks

[jo66tr]

Well I changed the plugs and plug wires and the fuel pressure regulator hoping that the FPR would solve my hard start when warm problems and so far so good. The miss is gone. Thank you all for helping.