Real Fiero Tech

wow car ran normal before, new plugs ngk and an oil change and now it backfires every once in awhile, n it will stall out sometimes. This is just revving in the driveway, havent driven car yet. I didnt gap them, n I saw on some old post they need to be around .50. advice?

shem

shemdogg wrote:wow car ran normal before, new plugs ngk and an oil change and now it backfires every once in awhile, n it will stall out sometimes. This is just revving in the driveway, havent driven car yet. I didnt gap them, n I saw on some old post they need to be around .50. advice?

shem

what weight oil did you put in it? I've seen cars do this with oil that was way too thick. also, make sure you seated all the plug wires and they are in the correct order (all GM 60degree V6's fire sequentially 1-2-3-4-5-6). gapping the plugs is always a good idea, at a minimum, you should check the gap before install and make sure they are all the same and not all over the place. .050 sounds ok, I wouldn't go any bigger though I'm pretty sure the factory spec is .045. is the check engine light on? have you checked the codes?

Plug wires arent fully seated on new plugs or plug wires in wrong order. I am guessing you mixed up a plug wire on the wrong cylinder. The symptoms of backfiring leads me to believe that

Now I really screwed up, got the wires all mixed up. They were routed all weird and I got switched up. When the line on the crank pulley is lined up w the timing mark, thats tdc on #1 yeah? def dont wanna pull a valve cover. I put 15-40 in it 4.5 qts

thanks for the replies
shem

shemdogg wrote:Now I really screwed up, got the wires all mixed up. They were routed all weird and I got switched up. When the line on the crank pulley is lined up w the timing mark, thats tdc on #1 yeah? def dont wanna pull a valve cover. I put 15-40 in it 4.5 qts

thanks for the replies
shem

assuming the ring on the balancer hasn't moved, then yes. they have a tendency to move over the years though, and are not all that accurate.

I'm pretty sure the factory oil spec is 10-30, not 15-40, using the right weight oil does make a difference in performance and economy. do I think that is your problem, probably not, do I think it could make a problem worse, yes.

I would start, by verifying the plugs are in the right order on the distributor cap, start at cylinder one, then work your way around. I would recommend assuming #1 is in the right place, then adjusting from there. if you haven't changed timing at all, then you could get them in the right order, then adjust placement on the cap until it runs again. did you replace the wires too? are they still the stock wires? you may have a damaged wire which is not giving a plug enough (or any)voltage to ionize the gap. IIRC, plug wire resistance should be somewhere around 1500-2500 ohms per foot, don't quote me on that though. you can measure the resistance with a multi meter to determine if you have a bad wire.

is the check engine light on?

have you checked the codes?

if no codes, can you upload a video so we can hear it?

Check engine lights always off after the engine starts, no codes now. Ill play w it some more today. I did pull the cap and check the rotation and tried the wires in different positions in the right order. jeez havent made this mistake since high school lol

shem

how are the wires? ohm them out. how does it idle? high? low?

I don't think it's the root cause of your problems, but I would recommend putting the right weight oil in it, it does make a difference.

I run 20-50 oil and no problems at all. Its not the oil. The plug wires aren't on the correct plugs.

Oil is not going to cause a backfire.

Find number one location on dizzy and work your way around. It will be fine then

you probably also run rotella T. seeing as the OP hasn't mentioned anything about the plug wires other than removing them to install plugs, I would say he probably has a wire that was degraded, but still functional, and then the removal and replacement caused it to fail, or wires are in the wrong place, or some combination of the two.

I got it fellas! Went out this morning and moved the balancer close to tdc. didnt work the first time so I moved the rotation 1 forward n it runs like a champ. Jeez what a rookie move lol. I hear what yr sayin about the oil, thicker is more friction so more gas but not much. They used to recommend 20-50 for anything over 100k miles back in the day. Cant even find that stuff anymore. next oil change ill try the 10-30. Itll be soon im sure this motors been sitting and itll dirty this new oil quick. It was some clearance oil at kragen, I got 12 gallons in quarts n jugs for 79 cents a quart. Its what I run in my diesel.

Thanks again
shem

I run standard valvoline Dino oil 20-50. Never had a misfire or no start after changing the oil. No rotella never used it

I was correct with the plug wires being off. Glad you got it going. Now make a mental note of where cyl one is on dizzy cap, or only change one plug at a time so you don't have multiple plug wires dangling at a time causing a potential mixup

When I time an engine, I find TDC #1, then install the distributor so the rotor points at the #1 cylinder.
That makes it easy to find TDC in the future, even if the ring slips.

Good call ill put some paint on mine. It needs a new cap anyways the terminals are covered in green corrosion. I cleaned em up for now

thanks
shem