Were leaving hea in a few minutes. Ill chrck out the exhaust when we get back

 

My '90 with the 302 had cracked manifolds.. The driver's side manifold came off in two pieces because the crack was all the way around it, the passenger's side manifold came off in three pieces due to two cracks all the way around. I put headers on mine.

My friend back home who has 400,000 miles on his '90 with the 302 has replaced his manifolds with new Ford units three times, they all cracked. He found some cheap knock off chinese ones that a junkyard offered for sale new at around $40 a piece and they've been going strong for years with no cracks for him.

I worked for a lawncare company that had an 88 and an 89 both with 5.8L engines, both trucks had cracked manifolds.

When I look under the hood of a '87-'91 Ford truck more times than not I find cracked manifolds.

In all the above cases there was no backfiring, but you are right it will suck in fresh air. So what will happen is the fresh air is mixed with exhaust moving through the pipe. Once it reaches the oxygen sensor the engine recognizes the fresh air and assumes your truck is running lean. So it dumps more fuel in, which causes your mileage to go down. At the same time the fuel/air mixture coming into your catalytic converter is too dense and starts to plug it. Between running too rich and plugging the cat your truck starts to lose power and the fuel mileage heads downhill.

So if it's a cracked manifold it needs dealt with, however, calling it a "death tick" might be a little exaggerated. But isn't that what you'd expect from chevy guys anyway?

 

[quote=lvin4jc33;10791402
In all the above cases there was no backfiring, but you are right it will suck in fresh air. So what will happen is the fresh air is mixed with exhaust moving through the pipe. Once it reaches the oxygen sensor the engine recognizes the fresh air and assumes your truck is running lean. So it dumps more fuel in, which causes your mileage to go down. At the same time the fuel/air mixture coming into your catalytic converter is too dense and starts to plug it. Between running too rich and plugging the cat your truck starts to lose power and the fuel mileage heads downhill. [/quote]

You mean I will get less than 10 mpg in my F250 with a 460V8?!?!

 

One more vote for exhaust leak, check to see if any bolts have broken off too. They like to do that, from the heat cycling of those thick cast-iron manifolds.

 

Ah great troubleshooting, i wasnt thinking exhaust tick. I was thinking detonation tick. Very good point.

 

Am I wrong in saying that the timing on these trucks is computer controlled?

 

Yeah, my 94 4.9L has had an exhaust tick for the last few months. Its kind of annoying as hell but i dont have much faith in all the manifold bolts coming out in one piece.

 

chain....well theres a timing chain....computer controlled chit didnt start till about 1996/97 when Ford and all them went to OBD2 standards....

 

Better research this statement, you're off a few years there Bud...........

 

They all have a timing chain setup...Except the Inlines...Which use timing GEARS.....

And they all have computer controlled timing..(1987+)....It simply advances/retards the timing as needed.......Why else would they need a computer?

 

And the box of rocks award goes to Jaime for the second straight week !! Seriously where do you get your info , or do you just guess ??

 

He just pulls something out of thin air right or wrong, like i said before, it's all about the post count!!!!



But I have to admit some of his answers make me laugh big time.... and I don't mean Ha-Ha funny either.....

 

x2. Need to chill out and learn more first. As ive said before.

LMAO!

Hes at 7.5 per day now. Going for 10 per day

 

I think Jamie's talking about (correct me if I'm wrong here) how some of the new engines have some type of variable cam timing on them. I had an older 'mechanic' who really know his stuff tell me his son's '08 5.4 had some variable cam timing thing on it. Anyway, I think everyone knows there's some form of ignition timing advance/retard and the chain just keeps the crank and cam in time.

 

I wouldn't be THAT sure of yourself.....