I just replaced my plugs with Motorcraft copper's gapped to .44-.46 with pro spark platinum wires.

The truck runs great now, however it won't high idle when it's cold, causing it to stall when I take my foot off the gas.

The truck didn't do this before I changed the plugs/wires

Any ideas?

1989 f-150 5.0 auto trans

 

Pull codes and engine vac and make sure you didn`t get a couple of spark plug wire wrong. Check timing.

 

Checked the firing order, which is fine. I can't visually see any vacuum hose leaks/cracks. No CEL is on, or has came on.

How Do I check the timing?


The problem is pretty much I have to leave my foot on the gas for around 15 seconds when I first start it to keep it running, after that it runs fine.

 

 

Take a can of carb cleaner and spray around major vacuum components. chances are you won't be able to see a vacuum leak.....

And just because you dont have a check engine light on doesn't mean that codes aren't present. there is a sticky that will walk you through step by step on how to pull codes OBD1.

And you'll need a timing light to check your timing. You can pick one up at your local auto parts store for 20 bucks.

I say start with pulling codes and engine vacuum, as Aktech stated

 

Sounds like vacuum to me.

 

Don't we have a sticky up on how to check vacuum. If not we should.

 

I`m sure people get tired of me telling them to pull engine vac. But it should be one of the top three things to do when trouble shooting problems. Even if you got 17-22 on the vac test if the needle is jumping it indicates other problems. Write it up Warlockk and see if they put it up. Go in to detail on how to plug the lines and test them with the hand vac. I think think spraying carb clean is only good for the in take gasket. Lines need to be tested with a pump. Also how to test egr,svr with multimeter and hand vac should be in the write up also.