1990 5.0 bronco popping through intake.

Chillest_bronc · Apr 23, 2017

Hey y'all I have a 1990 5.0 bronco that is popping through the intake. I took the heads off found a bent valve thinking that was the problem so I replaced the heads and valvetrain. Fired her up all excited and stuff and I still have the same damn problem. It pops through the intake right as you start it and you have to rapidly press the gas to even keep it running. I've checked all of the vacuum lines they all seem to be fine. I'm so lost and anything will help I just want to get this back on the road I love this bronco.. could it be a bad camshaft?

miesk5 · Apr 24, 2017

Yo Chillest_bronc,

Welcome!

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @ http://broncozone.com/topic/14269-code-reader/?pid=74587&mode=threaded

Some basics;
The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test.

and if possible, greater than 180° F for the Key On Engine Running (KOER) Self-Test.

Looking for some code related to the Manifold Absolute Pressure (MAP) Sensor, such as 22 or 26.

Buy or borrow a vacuum gauge and do the Vacuum test

looking for such as;

POOR VALVE SEATING: A small but regular downscale flicking can mean one or more valves are not seating.

WEAK VALVE SPRINGS: When the needle oscillation becomes more violent as engine rpm is increased, weak valve springs (6513) are indicated. The reading at idle could be relatively steady.

STICKING VALVE(S): When the needle (dotted) remains steady at a normal vacuum but occasionally flicks (sharp, fast movement) down and back about 13 kPa (4 in-Hg), one or more valves may be sticking. Etc.

Check plug wires for mis-routing and bluearcing at night or with hood down as far as possible. Check distr. cap for cracks or carbon tracks.

Check plugs for carbon fouling, see http://www.aa1car.com/library/reading_spark_plugs.jpg

Check fuel pressure :

Engine Running: 5.0L 30-45 psi

Key ON Engine OFF: 5.0L 35-45 psi

Carbon buid-up in combustion chamber. Many owners use Sea Foam.

Camshaft exhaust valve lobes could be worn or worse. Disable ignition, @ coil. Pull the valve covers off and see if the rockers are moving. One of the intake or exhaust valves may be stuck open as a result of this.

Do a compression test & cylinder leakdown test.

You can't check the timing without it running, but you can check to see if it's at least close. Bring #1 up to TDC and see where the timing pionter is at in relation to the timing marks on the balancer.

Looking for a stretched timing chain.

Skitter302 · Apr 25, 2017

@Chillest_bronc

I was wondering if your timing wasn't off. Would be worth looking into. I figure since you took the heads off and had a bent valve fixed you would of timed the engine as you put it back together but the cam could be off position from the crank.

1990 5.0 bronco popping through intake.

Chillest_bronc

New member

miesk5

96 Bronco 5.0

Skitter302

Active member

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