Intake/Engine issues?!
Thread Starter
|
Senior User
Joined: Jun 2004
Posts: 205
Likes: 0
From: Florida
Intake/Engine issues?!
Well, here it goes. I have a 90 F-150 ext cab long bed, 302 with AOD. The motor is a long block from Profromance Reman Engines, has 20000 miles on the engine and untill now it has run flawlessly. Here Is my problem, The engine keeps shutting off right after you start it, usually when hot. Pulled codes, and got 11, system pass. Brakes have become spongy, and the idle rpms are now around 900-1000. Idle flucuates sometimes, sometimes it doesnt. The other day i check my fluids before i took a trip and the water level was a little low and the coolant was a little milkly, checked oil it was clean. What does this sound like to you guys? I put the engine in myself and would really hate for it to be a head gasket or soemthing like that. Sounds like a lower intake leak to me, but not sure. Looking for some direction 
Posting Guru
Joined: Jan 2002
Posts: 1,346
Likes: 8
From: Baltimore
Usually you'll see coolant in the oil and not the radiator if you have a blown head gasket.
If you have a Autozone near you, rent the coolant pressure tester.
You attach a special radiator cap and pump up the pressure and watch the guage. Let it sit for a couple of hours and the guage reading should not move. If it does, you have a leak.
As far as the idle and the brake problem, look for a crack in the vacuum hoses. The idle problem and engine shutting off could also be a dirty IAC (Idle Air Control) which is mounted on the side of the throttle body. It may just need the carbon cleaned out of the bore and the IAC pintel.
If you have a Autozone near you, rent the coolant pressure tester.
You attach a special radiator cap and pump up the pressure and watch the guage. Let it sit for a couple of hours and the guage reading should not move. If it does, you have a leak.
As far as the idle and the brake problem, look for a crack in the vacuum hoses. The idle problem and engine shutting off could also be a dirty IAC (Idle Air Control) which is mounted on the side of the throttle body. It may just need the carbon cleaned out of the bore and the IAC pintel.
Posting Guru
Joined: Jan 2002
Posts: 1,346
Likes: 8
From: Baltimore
The IAC is a stepper motor that moves in or out of a bore in the throttle body. The more it opens the more air is bypassed around the throttle blades. The less it opens, the less air is bypassed around the throttle blades.
It's very common to get carbon buildup in the passage. This can cause the IAC pintel to not seat in the bore. Because of this, air can get by which can cause a high idle or if there is enough carbon build up cause less air flow and cause stalling.
One of the symptoms of a bad or dirty IAC is a hunting idle. The engine idle will not be stable and will go up and down.
The computer uses the IAC so the proper engine speed is maintained when different loads are placed on the engine.
Such as when the A/C compressor turns on or off or when you let off of the gas quickly.
It's very common to get carbon buildup in the passage. This can cause the IAC pintel to not seat in the bore. Because of this, air can get by which can cause a high idle or if there is enough carbon build up cause less air flow and cause stalling.
One of the symptoms of a bad or dirty IAC is a hunting idle. The engine idle will not be stable and will go up and down.
The computer uses the IAC so the proper engine speed is maintained when different loads are placed on the engine.
Such as when the A/C compressor turns on or off or when you let off of the gas quickly.
Thread Starter
|
Senior User
Joined: Jun 2004
Posts: 205
Likes: 0
From: Florida
When I pump my brakes the idle increases, so that doesnt sound right too me. Ive pretty much eliminated the head gasket, so im going to check the lines. Any way to test the intake to see if i have a vacuum leak?
Tuned
Joined: Nov 2002
Posts: 395
Likes: 11
You can also pull all the vac. lines off the top of the intake and plug all the ports then start it. I just went through a similar thing and found my stock lower intake was not sealing to the new Y-303 heads I installed. I ended up buying the Edelbrock upper and lower truck intake setup to fix my problem. I now have 19-20 in of vac. and the idle is smooth as glass better than it ever was even stock. Mine was sucking from the lifter valley so it was really hard to find. If you can find a mechanic with a very nice laser reading heat gun you can also measure the temps on the exhaust manifold or headers in my case and you can see what cylinders are running hot and confirm you have leaks.
Trending Topics
Thread Starter
|
Senior User
Joined: Jun 2004
Posts: 205
Likes: 0
From: Florida
I will try soon, hopefully. Just got done with Charley, luckly we are all ok here. Just some broken trees in the yard. Thank god my truck is ok. That storm was a big one. Ill let you guys know what I find out. Again, thanks for your suggestions.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote