wont start and is backfiring thru the intake

1bigdawg · 07-11-2007, 05:27 AM

brought it to the dealer now the news is low compression in the 3 ,6 cylinders they want to take the top of the engine down to see if its the valves or somthing else in the top of the motor they are convinced the problem is in the top but then the service guy also said it may be a broke crankshaft isnt that in the bottom???? what would yall do from here

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GrayPony · 07-11-2007, 06:41 AM

What were the events leading up to the problem??

billybix76 · 07-11-2007, 11:23 AM

sounds like a plain old blown engine. Only way the can happen is pushing it way past design limits...running at the rev limiter all day, or in rare cases parts (crank, timing chain, etc) failure...... and Ford will never admit that...

1bigdawg · 07-11-2007, 12:20 PM

the events were that i parked it 1 nite woke the next morn went a few blocks and the eng lite came on and it started runnin lke s*** real ruff auto zone diagnosed it and claimed i needed plugs i changed them then it wouldnt start at all

my first mustang · 07-11-2007, 09:53 PM

In the old days this sounds like burned valves or blown head gasket,but what ever its bad news.Hope car is under warranty.

stilbo · 08-24-2009, 07:43 PM

I know this is a bump to a two year old post but in the sake of informing members that might be freaking out over backfires through the intake on their 4.0, I'd like to add some resolve to this problem since there was never a follow-up posting.

I've torn down three 4.0's (2002 Explorer and two 2006 Mustangs) to find a broken valve. These engines had less than 70,000 miles on them but were out of warranty. A bent or stuck valve would have the same symptoms.

Why the broken valve stems? Not sure.... but the tensioner cassette may be part of the problem. I've heard and seen instances where the valve timing has actually jumped. Over revs with a weak tensioner assembly might be a contributing factor...

The labor to R&R the heads in the car adds up to a LOT of $. A LOT. Pulling the engine actually makes the job easier and the flat rate on labor is actually less to R&R the engine. Add the parts cost (a LOT) and the lingering fear that valve pieces might still be floating around.... you might consider the following.

Because of the costs and fears associated with repair of the engine in or out of the car, we have replaced all three engines with low mile salvage engines ($600.00, 58,000 miles average) with the total cost being slightly below repairing the original engines. We have pulled the valve covers, inspected the tensioner assemblies and have peace of mind...

The up side of replacement is that now you have a spare engine that can be stripped and rebuilt because salvage yards do not want the core. You can sell the engine or save it for parts.

Hope this helps any future "backfires through the intake" questions.....

stilbo