1994 Camry 6 Cyl. (Well maintained)
The car had an oil leak. Took it in and was told that the camshaft seals needed to be replaced. Authorized the repairs (cam out to 1K with a second leak from the lower oil pan plus a power steering hose leak). I am not complaining about the cost.
However after picking the car up this now happens: At almost exactly 3K RPM the engine just instantly drops RPMs back down to about 2K RPMs with a harsh sound and resulting jolt. It does this twice and then it appears to be fine once above that RPM level. This is obviously not transmission as it happens in low gear too at exactly the same 3K RPM.
The mechanic now says a camshaft pulley is the problem. Does this sound right? Or could that have been broken by the whatever is causing the real problem. The action when the RPMs drop is quite violent.
They have had the car for 4 days and have not provided an update and I am beginning to worry that the engine might have been damaged or that they may not know what they did to cause the problem.
Any edification as to what might be going on with the car would be greatly appreciated.
1994 Camry 6 Cyl. (Well maintained)
I worry when I hear of a mechanic say the camshaft is driven by a “pulley”. I wonder what was the mechanics experience on his test drive of your car? did he think you would not notice?
Hi. And thanks for offering any response as I’m freaking out a bit now. The mechanic said something about there being a different number of teeth on one part vs. another and that when that disparity comes about there’s an engine timing problem. I simply don’t understand the comment at all. I mean the engine revs normally up to 3K and I think it’s okay above 3K – but right when it hits 3K something just makes it instantly drop RPMs (the gauge drops to 2.5K or so in an instant). To me that has to be something mechanical (physical) otherwise it would just lose power, right? I mean the engine RPMs just DROP and car bucks. What could cause that to happen?
Is it possible that what I felt is the piston colliding with the valve? Would that cause the engine RPMs to slam downwars like that – but then why would it only happen at 3K RPM - again any help is appreciated. I think I need to get the car back from them and ask someone else to look at it – but I won’t be able to do that until the weekend (work of course)
The V6 in your Camry is not an interference engine, so what you’re hearing and feeling has nothing to do with pistons colliding with valves. Besides, if that happened, even once, the engine would not run well afterward (if at all), regardless of RPM.
The explanation about a different number of teeth sounds bogus to me. If this were the case it would be a continual problem, and not specific to a certain RPM, and it would mean the mechanic purposely assembled the engine with the wrong parts or with incorrect camshaft timing.
Who is “the mechanic?” Is this someone you’ve dealt with before, an independent, perhaps, or did you take the car to a Toyota dealer.
Or was this a chain shop?
I think you should consider taking the car elsewhere before things get even worse.
One last question: If you rev the engine in neutral, does it do the same thing at 3,000 rpm, or does this only happen while driving?
The piston coliding with the valve would be a one time incidient, not something you could repeat over and over. What is probably happening is the fuel is being shut off at that rpm, now the question is how and why.
Repairs like cam seals,timing belts,headgaskets, go both easy for the experienced mechanic and end up a disaster for the learning mechanic.
I compare it to the oil change mechanic,you can’t pay him much but he sure can cost you, as the learning mechanic can’t be paid more to slow down and re-check his work.
Chain store - actually Big O tires, but they do oil changes and other maintenance work. I’ve used them for oil changes a number of times. The owner said he had the same model of car (1995 Camry) and that he’s done this type of work before.
I did not try in neutral myself as I did not think of it. For some reason I do believe it does happen in neutral though as I sat in their office for a while and one of their mechanics was trying to figure out what was happenning and was reving the enging with the hood up. I think I heard the engine “do it’s new trick” during that time, but I cannot say for 100% certain. What would it indicate if there were different behavior? I can say that I experienced it low gear (under acceleration before the transmission shifted into 2nd) and at freeway speeds (top gear not accelerating as much) and it happened at exactly the same RPMs (as far as I can judge by the RPM gauge and engine noise).
Of course there’s a different number of teeth in the camshaft sprocket as there are in the crankshaft sprocket. It operates at 1/2 the speed of the crank. Each valve opens every OTHER time the piston comes up.
If the timing belt is jumping timing, it’s because he did something wrong. But that also means that once jumped, the belt remains jumped and performance suffers permanently. Jumped twice, I’d expect the engine to stall. In short, I don’t accept this as a possibility for the cause of your problem.
In summary, his comment about the difference in cogs is definitely bogus, and his explanation of the cause of the operating problem is HIGHLy suspect.
they’ve probably had the car for 4 days because they don’t know what to do now. Was this perchance a chains shop?
If it were me, I’d want to check the valve timing, ignition timing (this is probably based upon a cam position sensor signal to the ECU) and look for an unattached vacuum hose.
PS: apologies for falling behind in the thread. I’m multitasking and others were posting while I was in the middle of doing so.
There is a problem beyond the capabilities of the chain shop where your car sits now. If they had an answer you’d have your car back by now. At first I though perhaps the variable valves on the motor were not timed correctly since the problem is rpm specific (above 3K which is about the rpm when varaible valves come into play) but I don’t think a '94 Toyota V6 is equipped with variable valves.
That leaves a sensor out of order, or something electrical which may be telling the motor to shut down and not over rev. At this point you need a garage which is much more knowledgeable of the Toyota V6 to sort out the problem from all the possibles. Time to move the car to another shop.