More rough-runnin' Six...
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Junior User
Joined: Jan 2004
Posts: 57
Likes: 0
Same thing happened to me
Clyde- Same thing happenedd to me when I replaced my TB gasket. Ran great for a few days then back to its old stumbling and rough running. I soaked mine in styarting fluid [ a little bit of exageration] and discovered that the intake manifold was leaking. The intake on this has an upper and lower half. There is a gasket between the 2 [ u can see it easily from passenger sside of engine compt.] My theory is that once I re[placed the TB gasket, the vac in manifold increased and sucked in pt of the manifold gasket.
Idle it warm, then spray starting fluid along the seam of the gasket. My impression is the leaks tend to be up against the firewall around cyl #6.
Idle it warm, then spray starting fluid along the seam of the gasket. My impression is the leaks tend to be up against the firewall around cyl #6.
Elder User
Joined: Dec 2003
Posts: 660
Likes: 3
From: Northern California
GWTarpon.....
I've read your posts over the lasts few months with great interest as we seemed to be having the same "difficulties" with our trucks.
I may have "stumbled" (yes, pun intended
) on a solution.
You and ClydeWigg3 may want to take a look at my (last) post under "Stumbling, pulled codes, now what ".
Lemme know if it works !!!!!
Bob
I've read your posts over the lasts few months with great interest as we seemed to be having the same "difficulties" with our trucks.
I may have "stumbled" (yes, pun intended
) on a solution.You and ClydeWigg3 may want to take a look at my (last) post under "Stumbling, pulled codes, now what ".
Lemme know if it works !!!!!
Bob
4wd Low
Joined: May 2003
Posts: 10
Likes: 0
From: Texas
Replace the injectors!
90 F150 4.9 163k miles
My son and I replaced the injectors without removing the intake manifold. Its not easy but it's doable and easier if you can find another pair of hands. New injectors fixed the idle, intermittant stalling and stumbilng, hard starting problems, and greatly improved the driveability. I am not saying its a cure all but I bet it would fix over half of the higher mileage EFI inline six driveablility problems I see in these forums. We'll see if the HC readings are better when its inspection time again. It barely passed before (by 1 ppm). Haven't verifyed the gas mileage yet. Its tough to get a teenager to write down the mileage at fill up.
Rebuilt, flow tested, injectors can be bought for about $112 delivered on Ebay.
The best money I ever spent on the teenager's Ol' Red.
Jeff
My son and I replaced the injectors without removing the intake manifold. Its not easy but it's doable and easier if you can find another pair of hands. New injectors fixed the idle, intermittant stalling and stumbilng, hard starting problems, and greatly improved the driveability. I am not saying its a cure all but I bet it would fix over half of the higher mileage EFI inline six driveablility problems I see in these forums. We'll see if the HC readings are better when its inspection time again. It barely passed before (by 1 ppm). Haven't verifyed the gas mileage yet. Its tough to get a teenager to write down the mileage at fill up.
Rebuilt, flow tested, injectors can be bought for about $112 delivered on Ebay.
The best money I ever spent on the teenager's Ol' Red.
Jeff
New User
Joined: May 2004
Posts: 21
Likes: 0
Problem Fixed
Thanks for the advice. However I permantly fixed my problem. Okay everybody, cover your eyes.......I bought a Chevy Colorado Crew Cab. I-5 engine, 225 HP, runs great, great gas mileage. This little bugger will get out form under you if you aren't careful. My F-150 had 161,000 miles on that "great" 300 engine, but it also had a tranny I had to rebuild 3 times, and once a tranny seal. From 85,000 miles on it was one problem after another. I hope the Chevy can offer me some maintance free (or a litttle less maint.) driving.
Freshman User
Joined: Jul 2004
Posts: 29
Likes: 0
From: North West Germany
OK, very interesting topic 4 me as well. My EFI 300 I6 has a rough idle as well (and a bad mileage too). Which new injectors should I take , I remember to a discussion here about some guys preferring "bigger" injectors for better performance, or do I misunderstand something? Which manifolds precisely are to be changed?
Thanks for your assistance !
Joachim "JoJo", Germany
Thanks for your assistance !
Joachim "JoJo", Germany
Postmaster
Joined: Apr 2003
Posts: 3,587
Likes: 0
From: Virginia Beach
Bigger injectors DO NOT help performance on a stock engine. They really don't provide any performance gains on a higher hp engine till a point, after which bigger injectors are needed to prevent the engine from running lean. There is also another thing I have noticed at the local junkyard. People strip the exhuast manifolds off the EFI 6's all the time, and this leaves the head open for inspection. ALL of them were caked with carbon gunk. Looked like the varnish you would find in an old carb, mixed with chunky soot. There is enough gunk that it looks like it would put a hurtin' on the amount of air reaching the engine, especially at idle. Also, injectors that are 15 years old, and have hundreds of thousands of miles on them are limiting on an engine.
