I just got an 86 mustang 3.8 auto trans. but it idles rough and when I stomp the gas it bogs down before it takes off then after 1900 rpms it acts fine. The fuel pump, fuel filter, fuel regulator, fuel injectors, pcv valve have been replaced. I'm wondering if its a vacuum leak but I don't know a much about a vacuum system. Any help at all would be much appreciated!

 

Try cleaning your IAC and throttle body. also check your plugs ( or change them & stay with stock oem motorcraft replacements) and if the wires are old change them. pull the distributor cap and check for worn out terminals and arcing ( spider) marks. sounds like it might need some further tlc is all.

fogot to add in case you needed this is what the iac looks like:


and they get clogged with carbon. some carb/choke or throttle body cleaner will work to clean it.

 

I had to take the throttle body apart to replace the fuel injectors and I don't remember seeing that piece. Where do I find the IAC?

 

My bad the 3.8 might not have a iac. It would look like the unit above but in any case clean the TB, and check the other things. If after this it still has a flat sopt then might have to move onto ignition.

 

Check your cats

 

Alright ill try that thanks. It doesn't have a cat. It was taken off b4 I got it.

 

I'm glad there's another '86 3.8l out there. Thank you!

 

Yeah from what Ive seen on dif forums there's not many of us. Am I not looking in the right places or is it impossible to find parts? I've had to order every part I've replaced so for except my pcv valve.

 

I thought I had it all figured out but I guesss not. Changed my plugs and it was still acting the same way. I finelly figured out that my pcv was sucking a ton of oil into my throttle body. So I put a K&N valve cover breather on it an tossed the pcv. That helped a lot and stopped most of the surging. It alsotook care of my vac leak but it still randomly surged so I took the hose off my egr and capped it and it hasn't surged in 2 weeks. But the hesitation is still there! I took my plugs out an they r all white. So I'm thinking since I deleted my egr my plugs r getting baked by the higher temp. And I'm stuck again. 4 weeks, few hundred bucks and all I did is go from oil soaked plugs to well done plugs...

 

Any ideas how I can get the temp down so it won't bake my plugs?