: 79 coupe deville hesitation



79lac
06-06-06, 07:05 PM
my 425 with 80k is ideling fine, has just been tuned up, and everything. when i drive her lightly she hesitates. when im fully on the accelerator, its fine. any ideas?

Junkman
06-06-06, 10:35 PM
Spark plugs....... if you are using AC or Champion, pull them and install either Bosch, NGK, or Denso and it will run 1000% better!!!!! Junk....

Night Wolf
06-07-06, 12:22 AM
What!?!?

Bosch... NGK?

you've got it backwords man.... its the AC Delco that the engine likes (needs) Autolite owuld be a good plug too....

Its an off-idle hesitation? if the cap/rotor plugs and wires are fine, I'd say the carb needs a rebuild.... classic symptom of the Q-jet that hasn't been rebuilt in a long time (if ever) she'll idle fine and run fin under WOT, but part throttle/off idle is a little rough.

Junkman
06-07-06, 12:39 AM
What!?!?

Bosch... NGK?

you've got it backwords man.... its the AC Delco that the engine likes (needs) Autolite owuld be a good plug too....

As much as I like GM, and have been twisting wrenches on there cars since 1955, I can tell you without hesitation, that AC Delco spark plugs are not the product that will make your favorite ride do its best performance. The three brands of spark plugs that I have mentioned, are all far superior to anything that AC has made in the last 20 years. I have a turbo in one of my older cars and when I used AC plugs in them, under boost, the plugs would just about stop firing. I changed them out for NGK's and it ran like a raped ape and didn't spit or sputter again. Each person needs to follow their heart in the type of replacement parts that they use. I can only make suggestions. AC Delco still makes some great parts, but spark plugs are not one of them.

Night Wolf
06-07-06, 10:48 AM
I put Bosch +4's in my 4.9 and mileage went down and she ran rough.... brand new Bosch +4's spec'ed for the 4.9, I removed the origanal AC Delco platinums with 90k on them, and it was a mistake. 15k miles later I pulled all 8 of the +4's (all $60 worth) and replaced them with OEM AC Delco double platinums...... haven't looked back since.

Both my Olds and '79 got regular AC Delco plugs too.

Just aobut the only GM car I have seen that runs well on other brands, would be the s/c 3800, they do well with NGK platinums..... came factory with them.

But on these older engines.... the AC Delco plugs, IMO are the best you can get, I would keep it like that.... and realisitcally, a spark plug wouldn't cause the problem he is having, reguardless of brand.

79lac
06-08-06, 03:58 PM
yeah probably the carb needs rebuilding... i trust delco in the gms...