while I had my hood off for painting, I decided it would be a good idea to change some of the electrical components that are harder to get to with the hood on the car

The car ran great before, but I had no idea how old the components were.

Here's what I changed..
Coil, Cap and rotor (all MSD)
wires (taylor)
spark plugs (delco rapidfire, all gapped to 45)

now when I start it, it doesn't idle as smoothly, it has a miss when I accelerate, and a backfire when I let off the gas

any ideas what I could have messed up? I have double checked the wires, and they all seem securely on the plugs and cap.

I shouldn't need to reset the timing if I didn't move the distributor, should I?

 

nobody?

I'm going to get out there and check my vacuum lines again. It's possible something got knocked loose when I was changing the coil

I'm wondering if gas could go bad or crap in the tank after sitting for 3 months could have messed something up

 

If water is in the tank now, it would cause the car to run bad. 3 months seems kind of short though to have fuel go bad. Try getting rid of whats in the tank now and adding new gas with a water remover and see what happens.

 

Did you gap your spark plugs yourself or were they pre gap? I always gap my plugs even when they come pre-gapped.Once I just put them in and it ran like crap,I pulled them out and three of them were out pretty significantly.Just a guess.

Did your car run good then sit for three months or run good just before the tune up?
Floats could be gummed up a little.

 

What my car calls for is exactly what they were preset for. I double checked in anyway


MPFI, No carb or floats

Car ran perfect before I changed anything. I thought I was doing preventative maintenance

 

I'm sure they are but, double check your wires to the cap. Maybe you could have mixed them up??

 

Possible the dizzy is off + or - a tooth, not quite giving enough turn to set it.
That's all I can think of.

 

Check your firing order. Sounds like you could have crossed a couple of plug wires.

 

That crossed my mind too I will check it in the morning.

 

checked the firing order today. it's fine.

I found one patched vacuum hose that might have been loose (rubber hose over the smaller plastic hose) I enlarged the plastic hose with a bit of electrical tape, and then put it back together. I think that helped, as the car is running better.

It could have just been funky from sitting up for two months.

I'll know more as I go through a couple tanks of gas

 

Its not so much "off a tooth", as the timing is off. Distributors dont "jump a tooth", and that's not exactly what you said, but that myth gets repeated enough I wanted to pre-empt it. To say it's "off a tooth" isn't really wrong so much as it's misleading because the ignition components on the top of the distributor dont care what teeth the distributor and cam are engaging to each other, and the distributor and cam dont care either. You dont have to clock the distributor gear to get it to drop into the cam gear right like you would a timing chain. You do have to orient it carefully installing it but that's only to make sure the oil pump drive rod engages.

More likely he messed up the firing order or the timing is off. Double check both of those.

 

firing order is fine. I changed one wire at a time, and double checked it this morning. It could be several things, but that's not it

 

You know, no one ever took a minute to tell me that!! I've been told a dizzy off a tooth is the 2nd biggest cause right behind #1 TDC.
Honestly, I did have to think about what you said for a few.
Makes life easier...LOL...
Thanks for the info!!!

 

I dont know what kind of plug wires you got, but I've had fresh wires that didnt grip the plug heads very well, so they didnt make a very good connection. So I had to take some pliers and compress them so they'd click on more securely. See if you can rule that out somehow.

Beyond that, I would just start swapping old parts back in one at a time until the problem goes away.

Are you sure the timing is correct?

 

I dont know, but it ran great before I changed the parts. If the problem continues after I drive it for a bit, I'll check the timing. I thought the timing was controlled by the ECM, do you still adjust it at the distributor?

 

What MSD dizzy? Coil?

Was there a thread awhile back about MSD, something was needed that wasn't included the package list, but MSD sent it for a small fee?
I don't recall if it was for the coil or dizzy but it helped.

( edit )
IIRC it was a Street Fire system

 

Timing advance is controlled electronically, base timing still has to be set via the distributor. But that shouldn't have changed if all you did was remove the cap and rotor/coil etc. But if you turned the distributor base at all or removed it in the process of all your changes, the timing can be off.

 

today I hooked up the old coil back again, and the problem was still there. Next step is to replace the rapidfires one at a time with OEM plugs. I hate to do the job over again, but I need to find out what's wrong.

I still haven't gotten the car out and driven it. I'm wondering if there's any chance of the problem going away after I get it out and drive it, and put fresh gas in...

 

I've heard of bad gas causing the engine to run like sh**. Usually water. Try some dry gas stuff. Did you get gas the same time you did the tune up?

I had water in one of my pickups awhile back. I drove it till it ran out. I had a gas can in the bed to get me home. It did run better afterwards.

 

the last time I got gas was the beginning of June, the car has sat since then, in a garage. It probably has half a tank of gas, maybe a little less.

I'll try some gas drier, see what happens before I do anything drastic. I relaly don't want to have to change out all the plugs unless I have to

 

Second thought, you don't want to run out of gas if you have an in the tank fuel pump. You could wreck the pump.

 

Exactly. My sister ruined 3 fuel pumps bu doing that. Storing anything for a period of time that runs on gas, you always want to store it with the tank full. Anything less causes moisture to build up. I would try sucking all the gas out of it now and filling it up with like 5 gallons of new gas. See what happens.

 

im thinking maybe condensiation under dizzy cap,can cause dist to fire wildly

 

I have been going through surging at idle, stalling when I disengage the clutch rolling up to a light, and hesitation in accel and running rich for the last 2 weeks ever since I changed my plugs.

 

Not sure if my problem was bad gas or just that it sat up for a while, but after I drove it and added the gas dryer, it ran much better, practically perfect

 

I'm gonna try cleaning cleaning my fuel delivery system and tank.