A hesitation between 1500-2000 rpm?

So my 2008 Tribeca, 3.5L H6, has developed some kind of a hesitation when accelerating at low RPM (usually in 1st or 2nd gear, I assume). The problem is most pronounced at starting at 1500 RPM, and it may last all of the way upto 2000 RPM, before everything normalizes again. What could be causing this?

Yousuf Khan

Reply to
Yousuf Khan
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How many miles on the plugs??

Reply to
clare

First check your spark plugs and wires. If they haven't been changed yet, change them.

Reply to
dsi1

They had been changed maybe 30,000 km back, relatively recently. Previous plugs were working fine until about 130,000 km (a little over the limit, I know, should've been changed at 100,000 km, but they had no problems). There's no Check Engine Light that comes on to say there's anything wrong with the plugs yet.

Reply to
Yousuf Khan

Did you replace them with the specified OEM platinum or dual plat plugs, or some other plug? You can get a fair amount of sporadic misfire before the CEL comes on - and a misfire from ANY cause will turn on the CEL. It doesn'tKNOW what caused the misfire.

90+% it's plufs or wires or coil - and bad plugs WILL kill wires and coil ---
Reply to
clare

Could you be interpreting vibration as hesitation? That opens up a larger range of possible problems. That is such a narrow and specific range that I don't see it as plugs or similar -- normally bum plugs or wires will give worse symptoms the higher the RPM but having it stop abruptly as you accelerate doesn't seem right.

One test is to try going through the range going up and then going down (RPM that is). If it is vibration then you will feel it either way but if it is hesitation then it should be evident only while accelerating. Far easier with a stick than an automatic but it may be worth a try. What are the symptoms when trying to accelerate up a grade? Worse? Better? How about going down a grade?

Reply to
John McGaw

Was the vehicle worked on and afterwhich the symptom appeared? Did the battery get disconnected and not get reconnected for quite a long time later?

In the past, and after a couple repairs that had the techs disconnect power from the battery, I had to disconnect the battery for a while, like 30 minutes. Typically I'd remove the ground cable from the battery, come back sometime later, like an hour, or more, and reconnect the battery cable. Then I had to drive the car a while along with repeated engine starts. The computer re-learns how to adjust the idle mixture for smooth running. I could smell the fuel from the tailpipe so the idle mixture was way too rich. Had to do an "idle re-learn" by the computer.

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I don't remember the procedure that I was told to use to get the ECM to re-learn its idle mixture settings. Just remember having to go through a procedure.

Reply to
VanguardLH

I don't remember what type of plugs I used. But I didn't use OEM's, just whatever was available at Canadian Tire.

Reply to
Yousuf Khan

Actually, my first guess was that it was some kind of a vibration, but then I noticed that it only happens while accelerating up the range. Doesn't happen while decelerating. I have tried going up a grade, and the symptoms are more or less the same. Going down a grade, you're normally braking not accelerating, so the problem doesn't occur.

Reply to
Yousuf Khan

No, the battery didn't get unplugged at any time. However, now that you mention it, the symptoms started appearing after my last engine oil change, and as well there was a transmission/differential oil change that occurred around the same time. I was actually thinking that there was some kind of a connection to one of these oil changes, but eventually I discarded that idea.

Yeah, I used to actually use this method on my old Outback to have it relearn its engine mapping, but so far I haven't done that to my Tribeca. Is it possible that this is a fuel pump issue? And will a fuel pump issue be corrected by resetting the ECU?

Yousuf Khan

Reply to
Yousuf Khan

Then the FIRST thing to do is buy the right plugs and install them - I had the same issue on my PT Cruiser when I "upgraded" to champion irridiuma. Use OEM plugs ONLY on today's cars if you wannt assurance you will not have issues. On engines with waste fire ignition using the "double platinum" option if it is available is often worth the extra expense as one plug per coil fires in reverse polarity

Reply to
clare

Not likely, and no. Could be a transmission issue - who changed the trans fluid? It takes a SPECIAL trans fluid. Using the wrong fluid could very well cause a problem that COULD manifest itself as a "stutter" on accelleration in certain gears.

Reply to
clare

I went to Mr. Lube, and they said they looked up the specific differential fluid and looked to see that they had that type in stock, and they did. I've had them change my diff fluid before, and no problems developed before.

Reply to
Yousuf Khan

What about the trans fluid? And Mr Lube can screw up something as simple as greasing a door hinge - v- - -

Reply to
clare

They changed the trans fluid too. I think the front diff and trans are part of the same assembly, so one gets done when the other gets done.

Reply to
Yousuf Khan

There was a report on the Audi forums some time back where the owner of one of the more expensive Audis took his in for an oil change and discovered after the fact that the techs had cut a huge hole in the underbody shielding to get at the oil drain plug. One would have thought it would have been faster to remove the screws holding the shield in place, but that apparently did not occur to the Mr. Lube staff.

I wouldn't take any decent vehicle to Mr. Lube. Yeah, it may save a few minutes of your time, but at what cost if they screw things up?

Reply to
Darryl Johnson

Yousuf Khan wrote:

Before my verbose content below, how much did you pay Mr Lube for that tranny flush, drain/change, or whatever they did? Was it $200 USD? Or under $50 USD? Was it THEM who told you that you needed tranny service (which is not a flush)?

It takes little to get the wrong ATF. For example, I saw a video that showed 2 bottles of ATF for Toyota. One was for newer vehicles and the other for older vehicles. The bottles were almost identical. Both said Toyota and ATF but one had Type T-IV and the other had WS. I think one had a black cap and the other a red cap. If you looked carefully you could see the difference. There is also incompatibility within fluid types. One Amsoil synthetic is compatible with the T-IV type but not with WS, and another Amsoil synthetic is compatible with WS but not T-IV. Plus the shop might be using a hosed system from barrels of lube instead of individual bottles or cans like you and I would buy at the store. That means when changing to a different lube that there is still all the other lube (from a prior job) still in the length of hose.

Unfortunately those type of quick-lube joints do NOT flush the tranny. They do not use a machine to cycle the fluid through the tranny WHILE moving through the gears. They just unscrew the drain plug, collect what drains out, and then fill up. No flush at all. Using a flush machine takes time with is the antithesis of a /quick/ lube joint. A tranny change is not the same as a tranny flush. A drain and change means old dirty fluid left behind to contaminate the new fluid. The plug is often recessed or at an angle so not all the fluid will drain.

As I recall, there is also a filter in the tranny. It is not an easy to replace one, like for the engine oil filter that is external and unscrews. The tranny filter requires dropping the tranny pan to get at the filter, plus the shop must have a replacement on hand (don't know if a tranny filter can be cleaned). That means removing the old gasket and putting on a new one for the pan. Used to be there was a drain plug in the pan. Nowadays, I think, there is no drain plug so the choice is to stick in a suction tube or drop the pan. Did this /quick/ lube joint actually drop the pan?

Just dropping the pan won't drain out all the old fluid. There's the fluid in the converter, too. Dropping the pan, replacing the gasket, running the tranny through all gears while cycling in new fluid and to flush out the converter takes time and more labor. Even a flush won't get out all the old fluid. To run the car to cycle the tranny through its gears and to flush out the converter means not all old fluid can be extracted. The parts wouldn't have any lube while running. The flush pumps out some old, pumps in some new, and repeats. This means there will still be some mix of old and new fluid in your tranny after the job completes and also why you need to make sure the machine and hose were cleaned after the prior job and they used the exact same fluid for your flush. Think of doing this to get a new gallon of milk. You pump out a few ounces from the old jug. You pump in some new milk. While you are vacuuming out old or pumping in new milk, you swish the jug around to mix the contents. Then say you had whole milk but had "replaced" (partially) with skim milk. Do you end up with a jug of just skim milk? No, there will still be some whole milk in the jug. Then used a highly warped jug where you cannot put the hose or tube to the bottom of the jug. It has a huge cavity off to the side (converter) and a whole bunch of internal interference or baffles (tranny gears). A drain (or sucking out) and change gets little of the old fluid out. A fluid flush is not perfect but much better. What is left behind pollute the new stuff put in, and then there's a filter that inside the jug that is still there and still dirty unless you replace it.

If they did a flush instead of drain/suck and change, was your car actually running in their shop when they did the job? If not, none of the fluid from the converter got exchanged (not replaced but exchanged as mentioned above), what was below the level of their exchange hose or tube was left behind, and nothing got ran through the tranny. You want a tranny flush, not to just exchange what was sitting in the pan or bottom of the casing. The only way to get a 100% replacement of the fluid is to pull the transmission, take it apart, and same for the converter. Drain/change does little to put some new fluid in with the old fluid. A flush does better but you still end up with old+new fluid (and the old filter is still inside). The longer a flush runs, the more percentage of new fluid resides inside with less old fluid. If the "new" container of the flush machine has the same capacity as your tranny, and the operator runs the machine until the "new" container gets emptied, you end up with a 50% flush. The longer the flush with refilling the "new" container means a higher percentage of new fluid in the tranny but it won't ever be 100%. Putting in 6 quarts of ATF into the new container in the machine means you only got a 50% flush. How many quarts of ATF went into the new container? 17, or more? A full disassembly and reassemble would be the most effective but very costly.

As I recall, a flush machine also uses a cleaner additive. Well, with the *exchange* method of sucking out some old to pump in some new, some of the cleaner additive will get left behind after the flush job is done. The additive is corrosive (so it can do its cleaning) which leads to early tranny failure. No many how cycles of suck/pump by the flush machine, it won't get rid of all the old fluid nor will it get rid of all the cleaner that it added to the mix inside the tranny.

All of that - cleaning/replacing the tranny filter, dropping the pan and removing and replacing the gasket, along with the real fluid flush - takes time which equates to a much larger labor charge. Also, even places that do a flush often do not clean out the "new" fluid container. They may put in the correct fluid for your car but the "new" container is left with ATF from a prior job so they end up mixing incompatible ATFs in the "new" container. That is, they pollute the new ATF with other but incompatible new ATF because they don't clean the machine (and the hose they run to the tranny). The prior job might've have T-IV and then they pour in WS that mixes with the remaining T-IV and you end up getting a mix of incompatible fluids.

I would never trust a quick-lube joint to do the tranny fluid (which is likely a change instead of a flush). Even a car shop that I use for some repairs is not where I would do an unattended tranny flush, especially since I would have to tell them and pay extra for the filter replace and dropping the pan and gasket replace. Another car shop I do trust because they do the job right which means it costs more than the other car shop (unless directed to do extra work).

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Mr Lube might be part of a chain but they are run by individual proprietors, and some are cheats. However, none of them, from what I can tell, will ever do a proper tranny flush.

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Reply to
VanguardLH

I can't remember how many we ran into when the Tercel first came out - thelub shops drained transmissions and overfilled crankcases. I can remember at least 3, plus at least 2 done by DIY owners. Cost a few transaxle assemblies.

Reply to
clare

Okay, let's get off of the kicking the staff at Mr. Lube here, it's getting off-topic. I've been going to their place for years, it's not like as if they've never seen Subarus before; and it's just an oil change, not rocket science. I hesitated to even mention that there was an oil change that happened prior to it, as I knew that this blame-game would start, and take away from the actual topic here. The problem might have already been developing, and the oil change was just a coincidence.

Let's just stick to discussing theories about why this hesitation might be happening. Shall we?

Yousuf Khan

Reply to
Yousuf Khan

Okay, I'm starting to regret even having mentioned the oil change, as I know it's always going to lead to a tangential blame game, which does nothing to actually answer the original question asked. So if you want to know all of the details of my trans oil change, to get it out of the way, here is it. Mr. Lube did suggest that I get the transmission oil changed, but I didn't let them do it at that point, I told them that I would first shop around and get price quotes. I just came in for an engine oil change at that point, and nothing else. A few days later, I had gotten quotes from various places, including the dealerships, and then decided to go back to Mr. Lube. They charged in the ballpark of $200, which was still cheaper than the dealerships were asking, but not by much. The dealerships had a week-long waiting schedule, so I decided to go with Mr. Lube.

Reply to
Yousuf Khan

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