2007 Subaru Forester with new engine hesitates at 20mph

I have a 2007 Subaru Forester, bought from a dealer with 7,000 miles on it in 2007. I religiously had the oil changed every 5,000 miles and had other recommended work done. At 90,000 miles I did not have the work done immediately, but waited until 92,000 miles. My car then ran out of oil, with no smoking, no oil in the driveway, no warning light, so I believe the dealers didn’t fill the oil at 85,000 miles. But that’s not why I’m writing. I had a remanufactured short block assembly installed and the other work done at the dealer to the tune of over $6000. Now that I have my car back it hesitates at least once a day, sometimes several times, sometimes several times in a row. It hesitates at about 20 miles per hour, when the gears are changing. Of course, it didn’t hesitate when they checked it and their computer says “nothing’s wrong”. In addition, there was a tapping sound in the engine. Again “nothing’s wrong”. When I had my car smogged, the smog tech said “OMG, you have a problem with your valves.” I took it to the dealer and they then admitted I had a problem with my valves (or lifters) and they fixed it. The hesitation continues. What could be causing the hesitation? They’re not smart enough nor do they care enough to figure out what it is. Thank you.

only to align your trust:

My car then ran out of oil, with no smoking, no oil in the driveway, no warning light, so I believe the dealers didn't fill the oil at 85,000 miles.

Cars do not go 10 miles let alone 7000 miles with no oil. As you may have learned now to check your engine oil every 2-3 fuel fillups and I am quite sorry it turned out this way.

Is there another Subaru dealer in any distance to get a diagnosis(eg 2nd opinion)? Your engine repair if done at dealer carries a 1yr/12,000 mile warranty at any Subaru dealer.

7000 miles is way too long to go without checking your oil.

A new short block does not come with new heads and valves, they just took the heads (off your engine and bolt them onto the new block. If they corrected that for free, they were giving you a gift, probably because they felt bad for not noticing the valves were bad.

With all the work that has been done, it is impossible to guess what the problem could be without putting hands on the car.

I think andrewRA gave you the best advice you are going to get.

If you want to give your Subaru dealer another try ask them to give you a loaner car while they keep and drive yours until they figure out te peoblem. After all, you dud spend a lot of money for a repair that has left you with a problem.

bad bottom end. dealer said remaned motor? and you said shortblock only and reuse heads with no freshening? i would like to hear what mechanic said when he cobbled together old/new parts. probably was taking bets with his buddies on when motor would fail. why didnt you get a quote for a remaned long block? i bet they are $2899 at bobs engine world, plus install of course.

I am the car owner checking in. To reply to Cavell, the dealer told me what they were going to do. They didn’t ask me. I’m not a mechanic and I don’t know about engines and blocks. If they had asked me, I would have told them to replace other parts even if I had to pay for them. I never even said they reused the heads. I don’t even know what a head is.

A hesitation could be caused by any one of a number of things and there may be no codes set in the ECM,or computer. Offhand, some possibilities could be an air leak in the intake tract, faulty MAF sensor, insufficient fuel flow/pressure, timing belt off a tooth or two, etc, etc.

The engine on your car has 2 cylinders heads. These are part of the engine top end. With a short block it’s quite common to service the heads and use them on the new short block. Hopefully they were serviced and this would more than likely be a sublet job done at an auto machine shop.
Your copy of the repair order (if done correctly) should show any head servicing as “Sublet” or something to the effect.

As to the tapping, that sounds like valve lash changed on one or more valves. That will hurt nothing as long as it’s not ignored over the long haul.
After the installation of a new engine it’s always a good idea to go back in about 500-1000 miles and recheck head bolts and valve lash.
I’ve done a bunch of these and wouldn’t even think of not rechecking them.

The short block is the lower part of the engine where the pistons and cylinders are, the head is the upper part where the valves are. Both parts need to be lube’d by the engine oil. This lube of the upper part is especially critical for variable valve timing (VVT) engine designs. Does VVT apply to yours?

It’s not possible to say what the problem is. It might well be minor, like a sensor left disconnected or failing. A vacuum device on the fritz. EGR sticking. Etc. Etc. But from what you say, the first idea that came into my admittedly pinhead-sized-mind is that the lack of oil that damaged the short block also damaged the head, but didn’t get noticed during the lower part replacement. Yet.

First thing is to ask your shop to check the engine computer diagnostic codes, both stored and pending. That might provide a clue as to what is going on. You can post the codes they tell you here if you like and the experts here will explain what they mean.

Please understand for the sake of protecting yourself from future grief that if you didn’t check the oil level on an eight year old engine for 7,000 miles you were the reason he engine ran out of oil and thus the root cause of the problem. And if this has been your habit all along, you may have run the engine low on oil more than one time previously, and that is not good for it. You should check your oil at least weekly. I’m not meaning to criticize, only to teach. I apologize if it came out sounding like a criticism. I’ll say no more on this.

As to the current problem, OK4450 is one of the handful of guys here who really knows these motors inside and out, and I’d read carefully his recommendations, take them seriously, and answer his questions to the best of your ability.

Myself, I’d like to know what if anything was done to the heads during the rebuild. It should be defined on your paperwork. Type it here exactly as they wrote it. Like OK, the first thing I thought of was that damage from oil depletion happens to the valvetrain too.

The smog-tester that said “OMG, you have a problem with your valves.” ; did he write any detail on the paperwork? If so, exactly what did he write?

Please post back.

Owner responding- The valve problem was the “lifters” I think and they’re fine now. I believe what they did was " Remove engine. Replace engine block assy. Send cylinder heads out to machine shop to clean out metal debris and install new valve stem guides and resurface (deck) cylinder heads. Tech would reassemble reconditioned cylinder heads, remanufactured genuine Subaru short block assy and reassemble motor with all related parts and fluids."
I’m going to the dealer (who did the work) in a week or two. I will copy OK4450’s post and take it in with me, along with any other possible solutions. Thanks.

For what it’s worth, I worked for a few Subaru dealers and installed a fair number of Subaru short blocks. It sounds like the shop used the same processes I did except for the cylinder head servicing at the machine shop.
If the heads were not warped and in need of surfacing I did all of my own valve guide and valve/valve seat work personally instead of farming it out.

Without car in hand it’s near impossible to be precise as to the cause of the hesitation. The first thing I would check for would be any vacuum leaks. This can be easily done with a vacuum gauge.
If things are fine there then I’d check the intake tract above the throttle plate for any loose clamp, split in a boot, etc, etc.
Any problem there can affect the MAF sensor and there may not be any codes set.

One thing I might ask is this. I’ve been assuming the car is normally aspirated. This is not a turbocharged version is it? If so, that opens up another possibility or two.

But, then, I seem to recall that you do the good details like actually checking the valve springs, and without knowing what was done to the heads in detail it’s hard to guess.

It certainly does sound like a valve or metering problem, however. I find myself wondering if the car has variable valve timing, and the thought about the turbocharger is a good one. It never crossed my mind.

I wonder of there’s a “speed shop” near the OP where the car can be hooked up to some more sophisticated equipment than the average shop would use and properly analyzed hands-on. It might be the only solution.

My reason for asking whether this was a turbocharger model is due to the possibility that the turbocharger could be dragging a bit.
When an engine suffers due to oil sludge, coking, or being run out of oil the turbocharge usually suffers too. Just wondering if this could be some turbo lag due to the impeller not spinning as freely as it should be.

If not a turbo then that theory is flushed… :smiley:

Got it. It was my impression originally that the oil had not been regularly checked, and I would not doubt if the turbo was gummed up, and I’m fairly confident in suggesting that running out of oil didn’t do the turbos’ bearings any good either.

OP, one of the things a good speed shop will do is test the turbo(s) for proper operation.