4.0L SOHC Knocks and backfires after timing chain job.

[erms2006]

Well this is my first thread post on this site and not sure how well this is going to turn out so im going to give it my best shot. I though I also add that this is my first car and that im 17, and im more of a geek than a motor head if you know what i'm saying.

Anyway I just had a "tune up" on my 98 explorer Sport (timing chains, heads re-machined, new spark plug and wires, valves fixed, etc. all from when the timing chain tensioner failed).

With all these parts it should run perfect, right? nope.

Turns out the left cam shaft had to be replaced due to the bolt loosing up on the end (what might of caused this whole disaster in the beginning by what im told.) Ok, with that replaced it should theoretically run right? Apparently not, we came along another snag.

When we first started it up, it made a rattling noise, almost like a lifter tick, but when he reved it, the sound seemed to go quiet, then the engine backfired and he turned it off, then we scratched our heads not knowing what it could be.

Fuel pressure is up and all gauges read properly, and it only has 154,x.. + on it.

Im thinking that the timing might be off, but he says he has torn it apart 3 times and can't find the problem.

Please let me know if you may have any ideas, ill give any imput to the mechanic, I just want to get this whole nightmare over with.

BTW: My dads paying for his stupidity for choosing this mechanic. I honestly don't think he knows what he is doing.
Josh

 

[yavapaires]

Sounds to me like you need a,new mechanic. I have never worked on a SOHC engine, so I would be of little help.

 

[2000StreetRod]

helpful threads

read my helpful threads on SOHC V6 timing

 

[bluestream1]

Cams can be installed 180 degrees off and the engine will still run although roughly..

 

[erms2006]

Thanks for the help. Ill through the ideas to the mechanic. If he can't straighten this mess out, Im sending it up to my Grandfathers mechanic. Maybe he can do something about it.

 

[koda2000]

gotta be your cams aren't timed correctly. either that or your plug wires are not installed correctly (it would be nice if it were that simple, but my luck doesn't work like that...

 

[erms2006]

Well got some good news last night: had to be taken to the machine shop again, had broken timing guide pieces in the head, Bent 2 valves and some other stuff. The backfire was caused by a broken bolt to something in the cam. another $300 in parts later. Hopefully he will run soon. And hopefully I don't end up paying an arm and leg in labor. We decided on $750 on labor which brings the total to around $3,000, which probably is the cost for a rebuilt engine, not including labor.

 

[koda2000]

and that's good news? hate to see what you call bad news... lol

 

[drdoom]

Could it possibly have been timed incorrectly? I mean it sounds like you had a piston to valve collision (interference).

 

[boominXplorer]

Is the mechanic even using a special tool to set the timing? I think you would of been better going to the stealership and getting the job done right the first time for the same cost.

If he installed new chains and re-did the heads then HE is the one who timed the motor wrong and you should not come out of pocket for anything now. I bet he never torqued the cam bolt correctly and it slipped and caused everything to go to hell.

 

[koda2000]

it sure sounds like the cams weren’t timed correctly if you bent valves. doesn't explain the broken parts under the valve cover though. i think i'd be having a conversation with the mechanic about what happened. it doesn't seem like he can being claiming it had nothing to do with his repairs.

during your timing chain replacement did the mechanic replace the hydraulic cam tensioners? as far as i know there are two. one on the front driver's side head and one on the rear/lower passenger side head. these are supposed to provide timing chain tension using engine oil pressure. that's one reason to make sure you always use oil filters with anti-drain back valves (like motorcraft or wix). it seems to me the rattling on initial startup must be caused by these tensioners. either because of weak/worn springs or the wrong oil filter being used. i don't know if these tensioners can cause the timing chain to skip a tooth but i guess it's possible. as far as him finding a broken bolt... what/how did that happen? bolts (at least grade 8) don't just break if they're torqued correctly.

I realize you’re only 17, and it may be hard to confront an adult, but I think he may be taking advantage of your youth and inexperience.

 

[boominXplorer]

Just to add.... Even if EVERY tensioner broke on the engine it would still halfway run and it WOULD NOT retard timing enough for the piston to make contact with a valve. That is why I think he did not time the cams right or torque the sprocket bolt correctly.

 

[erms2006]

and that's good news? hate to see what you call bad news... lol

At least it will be back on the road by the end of the year.

 

[erms2006]

Could it possibly have been timed incorrectly? I mean it sounds like you had a piston to valve collision (interference).

Thats what I thought.

 

[erms2006]

Is the mechanic even using a special tool to set the timing? I think you would of been better going to the stealership and getting the job done right the first time for the same cost.

If he installed new chains and re-did the heads then HE is the one who timed the motor wrong and you should not come out of pocket for anything now. I bet he never torqued the cam bolt correctly and it slipped and caused everything to go to hell.

He said he bought a "timing kit" from AAP for $500. Not sure if that includes that tool or not.

 

[erms2006]

Just to add.... Even if EVERY tensioner broke on the engine it would still halfway run and it WOULD NOT retard timing enough for the piston to make contact with a valve. That is why I think he did not time the cams right or torque the sprocket bolt correctly.

Ill tell him that. And he claimed that I put the pedal to the floor. Thats a bunch of ****. The only time I ever did that happened to be more than a year ago.

 

[erms2006]

it sure sounds like the cams weren’t timed correctly if you bent valves. doesn't explain the broken parts under the valve cover though. i think i'd be having a conversation with the mechanic about what happened. it doesn't seem like he can being claiming it had nothing to do with his repairs.

during your timing chain replacement did the mechanic replace the hydraulic cam tensioners? as far as i know there are two. one on the front driver's side head and one on the rear/lower passenger side head. these are supposed to provide timing chain tension using engine oil pressure. that's one reason to make sure you always use oil filters with anti-drain back valves (like motorcraft or wix). it seems to me the rattling on initial startup must be caused by these tensioners. either because of weak/worn springs or the wrong oil filter being used. i don't know if these tensioners can cause the timing chain to skip a tooth but i guess it's possible. as far as him finding a broken bolt... what/how did that happen? bolts (at least grade 8) don't just break if they're torqued correctly.

I realize you’re only 17, and it may be hard to confront an adult, but I think he may be taking advantage of your youth and inexperience.

My dad was the stupid one to have him fix it. I honestly think the guys full of ****, but my dad thinks he knows what he's doing. Let him suffer for his mistakes.

And for what he replaced, he never said anything about the timing springs, and as far as I know, the correct oil filter is being used.

 

[Blacksheep Josh]

The Advance Auto Parts kit does not include the timing tool. I did this job back in March on my own vehicle, and to be honest I didn't use any specific tool... I did it very carefully with impact tools to loosen the sprockets and had a friend with a pry bar on the back of the cam to keep it from moving.

On each side of the cam is an area where you can use a screwdriver or prybar to keep the cam from moving. A friend applied slight opposing force so when I used the impact to loosen the sprocket/chain the Cam didnt' move, we repeated the same in reverse when I torqued down everything new.

Engine didnt' want to start up right away but it's been running perfect ever since. The problem ended up being a spark plug wire hooked up wrong lol...

You don't HAVE to have the timing tool to do it, but if you want it 100% right beyond a shadow of a doubt you should get and use it.

Also, check to see if the AAP kit comes with the O-rings to go around the hydraulic tensioners, I had a horrid oil leak because my ebay kit didn't come with one. Just trying to save you some trouble down the road.

 

[2000StreetRod]

proper timing

The timing tool kit (OTC-6488) contains instructions on how to install each tool but not how to time the engine. The timing process is rather involved. Some mechanics have performed the process incorrectly and the engine was damaged immediately upon engine start.

When selecting a paid mechanic to time the camshafts on a SOHC V6 I suggest requesting to see the timing tools the mechanic plans to use. If the mechanic does not produce the OTC-6488 tool kit then find another mechanic. If the mechanic produces the OTC-6488 tool kit, ask how many times it has been successfully used in the past. If the answer is once or less find another mechanic. Otherwise, ask the mechanic to explain how the tools in the kit are used. Compare his answer to the instruction in this thread: SOHC V6 Camshaft Timing

 

[erms2006]

Got tony back today! Runs like new, got some belt noise but that's because I was retarded and sprayed some belt dressing from prestone on it. Never going to put that **** on it again, probably will eventually put the old one back on. (better condition anyways). Happy holidays to all who read this!