Contour Enthusiasts Group Archives Forums General Troubleshooting Strange Engine noises

Okay - here's where we're at: Got this basket case '95 2.5L Contour in and f-i-n-a-l-l-y got it to where it will at least start! (It's been to a number of dealerships and independant shops and they all gave up on it.)

It won't rev up over about 12-1500 rpm (tach not working). Seems to be a lot of 'noise' coming from the intake manifold area - like its trying to suck in a lot of air. And it sounds like its kinda poping back into the intake manifold. If I put my hand near the tailpipe I can feel it sorta puff out the tailpipe when ever it 'pops' back into the intake, but I can't feel anything when I place my hand on the UIM or the accordian between the MAF and the TB. At the same time it seems like maybe its only running on one bank. Or like the plug wires are connected to some of the wrong sparkplugs.)

I don't know how long this vehicle has been sitting, but I'm thinking it may have some stuck valves, or broken valve springs. I'd like to know if this 2.5L is considered an 'interference' engine. In other words, if the timing chain were to break, would the piston smack the valves? (Maybe the 'poping' noise is really a piston kissing a valve which is either stuck open, or left open because of a brken valve spring. Maybe one of the timing chains jumped a tooth or two.)

Thanks in advance for any thought/comments before we start tearing the top of the engine down. And does anyone know if the 2.5L is an 'interference' engine?

The Duratech pistons have valve reliefs in them to prevent hitting the valves if the timing slips or the chains break, but if the motor has ever been rebuilt with aftermarket pistons they might not have valve reliefs and then the pistons and valves will contact. ie. the speed pro's in my hybrid



If it sat for a long time the plugs, wires, coil, IAC, TB, TPS, Injectors, and Fuel Filter may all need to be cleaned/replaced before it will run right. Old gas will cause many running problems too.

Proper wiring configuration:

COIL
4-6-5
3-2-1

ENGINE
1-2-3
4-5-6

Make sure the wires connect the numbers

Air leak detection - Old school method - Spray(carefully) Quick Start or any starting aid for Trucks around the area in question , whilst(neat English word) running the engine. A sudden increase in engine RPM indicates an air leak. Becareful, one does not want to set the engine bay on fire - now how do I know that.......
Side Note:
For a starting aid on gasoline engines try WD40 in the intake. So this may work as well for air leak detection.

It is......

The reason that I say this, is that I just reviewed my procedures on replacing timing chains. If you crank is not at specific position damage can occur to valve, piston, etc.

I have rebuilt this engine and have a little experience in performing this....

Regards,
Bob

Is it unusual for one of these chains to wear to the point that they might jump a tooth?

I can't say.....how common...That chain would have to be rather very loose to jump a tooth...to say the least....

How many miles on the car..

118k miles

I supose I could try and rotate the crank pully forward and backward while watching the water pump drive pully for movement. Anything over 10 degrees of crank movement without water pump movement would be a lot????

Start with basics....

Take plugs out what do they look like. oil or gas fouled. are the worn, replace them is so. Check ignition wires, are they in good shape, are they connected correctly?

check fuel pressure. check if vacuum irmc is actuated when engine started. When engine starts it should pull vacuum and close secondaries. If not check for vacuum line leaks and /or replace irmc valve.

Do you have a cell light on? Purchase a 50 dollar tester and run a koeo test. See what codes are pulled. I recommend you do this before tearing into the engine. Once you start breaking it down you can't run anymore tests until it is back together and you may be back at square one.

If you have dtc codes what are they? Do a compression check on engine, what do you get?

Bob