Timing

"Timing" is an adjustment. I suspect you are referring to replacing parts that affect timing, but there is ignition timing, meaning when the spark plugs fire, and valve timing which is controlled by a "timing chain" or "timing belt". You did not list which engine you have. The only one I am aware of uses a timing chain, but in addition to the many other engines that use them, yours has a tensioner assembly and chain guides. Replacing those is very involved.

You did not list the engine size or any symptoms or problems, so it is not possible to give you an accurate answer. You also need to be specific as to which parts need to be replaced. Almost all procedures are listed in a "flat rate guide" according to model, engine size, and year. The amount of time the jobs should take are listed so every shop that uses those guides quotes the same amount of time. The variables are their hourly shop labor rate, and the additional parts or services they feel are necessary to insure the quality of the repair.

I had to wade through a number of drop-down menus to get to one of the labor charts. I selected the 4.0L engine with an automatic transmission. Under "Engine - Mechanical", it lists replacing the timing chain at 7.9 hours, add 0.8 hours if it is equipped with air conditioning, and add 0.3 hours if it has power steering, because removing those parts is necessary as they interfere with engine disassembly.

Timing chains develop wear that matches the sprockets they run on, so it would be foolish to not replace those sprocket too. Since the mechanic already has the engine taken apart to get to the chain, replacing the camshaft sprocket only warrants an additional 0.1 hour and the crankshaft sprocket gets another 0.3 hours.

If your mechanic is conscientious and has your best interest at heart, he is not going to ignore other parts that can cause the new ones to fail before their expected life span. That includes replacing the hydraulic tensioner that prevents the timing chain from slapping around. It also reduces the chain's tendency to allow valve timing to vary as you drive, which would cause surging or stumbling. Your engine is very unusual in that it uses two of those tensioners. The left tensioner calls for 3.2 hours, and that includes removal and replacement of the intake manifold. Once the intake manifold is removed, the right tensioner only warrants an additional 0.5 hours.

I come up with a total of 13.1 hours. These times never include stopping to pick up a dropped tool, searching for the correct size wrench or a specialty tool, stopping to talk with other customers about their repairs, getting to and removing any bolts that break off, scraping off old gasket material, and many other things like that. You can expect a thirteen hour job to take two to four days, once all the parts are received, but you will still be charged only 13.1 hours. The variables are the dollars per hour the shop charges for labor, the quality of those replacement parts, and how much they mark them up, just like every other store does. Some gasket sets include paper gaskets. Some require the mechanic to use a tube of gasket sealer instead of some of the paper gaskets. Some sets include a tube of that sealer. All of those gasket sets cost different amounts and some require the parts department to provide additional supplies. It all depends on what the mechanic thinks is the best value for your money, or will help him do the highest-quality job.

Thirteen hours is about double what this job is supposed to take on most other engines, so that tells me this is a pretty involved job. I would never second-guess a professional's diagnosis when I'm not there to see the engine myself, and I will never defend anyone who is trying to defraud a customer, but I am not convinced the diagnosis correlates with your description of the symptoms. The simple fact you said the engine ran fine, "at times", after the first loss of power occurred tells me the timing chain did not jump a tooth or two. That would cause a permanent loss of power. The hydraulic tensioners are a different story though. One of them might pump up properly with engine oil then leak down and let the chain develop excessive slack. That would cause a noticeable drop in power, and it could do so intermittently. The proof will be if the problem is solved with this repair.

Be aware too that in most states you have the right to have the old parts returned to you. Some parts must be returned for "core" charge to be rebuilt and sold to the next customer, just like reusing old pop bottles, but you still usually have the right to see those parts and inspect them. A lot of mechanics will not put the old parts in your vehicle when they are dirty or greasy, unless you ask for them. Some mechanics go through a lot of effort to use plastic bags, lined boxes, and other means to put old parts in your vehicle in such a way that you can dispose of them without getting anything full of grease. That is another one of those things they do not get additional time to do.

As far as not returning calls, my only comment of value is in most shops mechanics are not allowed to talk with customers unless the service writer specifically brings the customer into the shop. Talking with one customer is not fair to the current customer who is waiting for their car, and it is not fair to the mechanic who has to stop working on his current project. The time clock does not stop, so he is not earning anything while he is not working on his project. Normally you speak with the service adviser or service department manager when you call or stop in. It is their job to take what they think they heard from the mechanic, and translate it into something they think you will understand. Just like doctors, carpenters, accountants, and butchers, mechanics speak their own language, and they typically have extremely poor communication skills when working with customers. That is why service writers are hired to be the middleman. If you are expecting a return phone call from a mechanic in a larger shop, that would be like expecting a call from a cashier at Walmart or the mail room person in a large corporate office. None of them are free to speak for the company or make decisions. Those people might be consulted regarding a customer's inquiry, but they do not represent the company when it comes to making decisions.

If you are working with a smaller independent shop, often the mechanic has to do everything from answering the phone, setting up appointments, locking the doors to run for parts or take a test-drive, cleaning up the spills, putting parts in inventory, and if time permits, working on multiple cars. Those are the people who do not leave until 8:00 p.M, and they work on Saturdays with the doors locked. They often answer three or four calls per day from an impatient customer. That cuts into their productivity, and it will not get the job done any faster. Unfortunately those customers hold mechanics to much higher standards than for doctors, and they are the ones who assume every mechanic is out to get them. In my extended community of about 100,000 people, we used to have one well-known independent shop owner who was a crook, and he has been out-of-business for at least a year. We still have the local Chevrolet dealer who is also well-known throughout the state for having a whole pile of customer-unfriendly business practices, but other than those, we have over a dozen new-car dealers and about fifty independent repair shops that are extremely reputable. I have former students at many of them, but there are a lot of mechanics who quit the field because they are tired of being assumed to be crooked. The really good mechanics and shops can turn work away and just work for their good customers. The really bad mechanics get invited to look for a job somewhere else, but not after they damage the shop's reputation. That leaves the "okay" mechanics for you to pick from. Most of them want you to be happy, even though they know you will need to spend a pile of money, and that is why I am not ready to suggest your mechanic is doing anything that is not in your best interest.