Mechanic types...got a potential problem

[w turner]

NOTE:  I am fairly handy when it cmes ot cars.  I can change my own oil, do my own brakes, etc. but this job was a little more involved that I fetl comfortable with.

I took my 1997 Honda CR-V to a local guy for a new timing belt.  Before I took it in, the engine sounded normal and ran like a sewing machine.  Decent power, 25mpg, and no hint of knock or pinging no matter what kind of gas I used.  This guy had done work for me before and was professional, honest, and competent (he had replaced the A/C compressor and accompanying parts). 
Unfortunately, I was called into work this afternoon and called him to make sure it was done.  He said it was  and that I could come get it.  When I got there he asked me if the engine had ever made "noise" before.  I told him that the valves had chattered at times, but not excessively so.  He cranked my car up and the engine sounded normal except for a deep rattling sound that follows the RPM's.  He had test driven and nothing had changed.  He said for me to drive it and if it was still doing it after I got back from work to bring it back.  He also admitted that he was stumped on what could be causing the sound and was about to tear it down again to check it out before releasing it to me, but I needed it and he felt it was safe to drive it.  . 

Long story short-er.  I drove it to work and while under load (looong uphill climb) it knocked something fierce.  It performed fine.  Normal power, normal MPG as far as I can tell, etc.  but sounds like hell.  My wife called him and I am going to take it back to him tomorrow evening for him to look at it again.  My suspicion is that the timing is off, but he said that when he drove it, it didn't act like the timing was off at all.

Anyone have any ideas as to what it could be?  I know he know what he is doing so I don't plan to change mechanics at this point unless he refuses/is unable to make this right.

He replaced the timing belt, idler pulley, and the required gaskets. 

Thanks,
W
       

[garyk/nm]

Sure sounds like a timing issue. Easy enough to check, just have him throw a timing light on there and check it out.

[mtnbkr]

Probably timing and probably advanced enough to knock, but not enough to harm performance.  I bet if you put some premium fuel in it, the knock would lessen.  If you can get Shell's racing fuel, that's somewhere around 100octane, it might even go away.

Chris

[280plus]

I used to put about 5 gallons of 105 Octane AVGAS into my AMC Eagle and fill the rest with premium. The Eagle would FLY!!

 

Yup sounds like a timing issue to me as well.

[mfree]

The trouble here is that this is a computer controlled, distributorless system. The computer has complete control of ignition timing.

So, if it's a timing issue, the question isn't what the timing is, it's *why* is it off?

Ask the mechanic if there's any adjustment to the crank position sensor and if it's proper, or installed backwards (it can happen with some); or if the engine runs off camshaft position that the cam is properly lines up and the same deal with it's sensor.

You may also have a disconnected/broken knock sensor. Most modern cars listen to the knock sensor and then crank the timing advance until it *just* starts to ping then back off a little.

Also if your mechanic isn't pulling codes before doing any of this, he's a moron. The computer knows what's going on and keeps book on anything spooky like slow sensors. You just have to *ask* it.

[charby]

He may have put the timing belt on and missed the line up marks by one or two teeth on the cam or crank pullies. This would screw the timing up. Not sure how the timing belt is on a Honda.



 

[Brad Johnson]

He may have put the timing belt on and missed the line up marks by one or two teeth on the cam or crank pullies. This would screw the timing up. Not sure how the timing belt is on a Honda.

Most likely scenario - it's very easy to get the belt off by a tooth unless you are extremely careful. Hopefully the knocking is preignition and not valve-to-piston contact.

Brad

[mtnbkr]

He may have put the timing belt on and missed the line up marks by one or two teeth on the cam or crank pullies. This would screw the timing up. Not sure how the timing belt is on a Honda.

Most likely scenario - it's very easy to get the belt off by a tooth unless you are extremely careful. Hopefully the knocking is preignition and not valve-to-piston contact.
Brad

Yuck, hadn't thought about that.  Though, I would expect it to run MUCH worse if that were the case.

Chris

[p12]

Could also be the belt tensioner. Sometimes after removal of the belt and relaxing of the tension the tensioner will not go back to its proper position. This is especially true if the tensioner is adjusted by oil pressure. Sometimes it has to be replaced
when the belt is replaced.

[w turner]

I took it in last night and he called a few minutes to let me know it was fixed.  He said that the tension was wrong on the belt which allowed one of the cams to be off just a bit. 

I will pick it up this evening, test it out and let you guys know how it looks tomorrow when I am back at work. 

Thanks for all the replies,

W

[Brad Johnson]

The tensioners should be automatic. If the tension is "off" that means the tensioner was either improperly installed or misfunctioning for some reason. Or they just got the belt on one tooth off and didn't want to own up to it.

My first action would be to pull a plug and take a long look at the top of the piston (if you can - borescopes are nice for this). Make sure that the piston tops don't show any piston to valve contact.

Brad

[Hawkmoon]

Sure sounds like a timing issue. Easy enough to check, just have him throw a timing light on there and check it out.

It's not that simple. The timing belt controls the relationship of the valves to the crankshaft and pistons. If he got the belt installed off by a few teeth on the belt, the valves aren't opening and closing at the correct times relative to piston movement.

It sounds like he really screwed the pooch. I'd give him ONE more try to get it right. If it's not right after his next try, take it to a Honda dealer, get it fixed right, and take him to small claims court to pay for both his bill AND the Honda bill.

[French G.]

Yes, it sounds solved now but I did notice a few folks mixing up the concept of ignition timing (firing impulse in relation to crank angle or position) with cam timing, the relationship of the cam(s) position with the crank. I 2nd the notion to try to look at the top of your pistons, engine do not necessarily self destruct when moving parts meet, but it is not good and if you assume no damage occurred just because it is burning all of its rice then you may be ignoring a problem such as a bent valve.  I recall one yutz who had a set of flat top pistons with valve reliefs cut in them. Said yutz installed the pistons upside down. The motor apparently did a good job of beating in its own new valve reliefs since the motor raced two seasons and was functional when disassembled... Anyway, back to timing belts.

If you think you need to change yours, first find out if your motor is an interference motor or not. In an interference motor the valves and pistons occupy the same airspace at different times. When your timing belt decides to take a time out these components tend to hit each other really hard. A non-interference motor and you are probably just looking at a long walk and a tow truck. Interference? Time for a lot of new engine parts $$$$$  So, suck it up now and change the belt at the recommended interval.  Or be a real man and drive something that has pushrods, a timing chain, and fires 1-8-4-3-6-5-7-2. Just sayin'

[280plus]

I don't know about these newfangled motors but in the old days the camshaft drove the distributor so if the camshaft was out of time with the crank so was the distributor.

[mfree]

280plus, nowadays there is no distributor. Most cars have DIS, which uses either a coil pack per two cylinders (wasted spark, it fires on the exhaust stroke for the "off" plug) or one per, which sometimes are mounted to the plugs themselves.

It's a big advantage, even more so with coil-on-plug because you aren't trying to pass 50KV down a thin wire, because modern computers are fast enough that the "go" signal for each cylinder can be tailored... if the knock sensor tells the computer that cylinder #4 is knocking, then the timing on #4 gets dialed back and #4 alone. With a standard distributor, you're locked into a systemwide timing curve and any dialback gets all the cylinders and really sucks out the power.

That's part of how they're getting 300hp out of 3.5 liter naturally aspirated V6's these days, on regular pump.

[w turner]

Sorry for the slow update....

Picked up my car on Tuesday afternoon and it was fixed and back to normal with what may be a slight improvement in gas mileage.

Talked extensively with the mechanic and he showed me the diagram that came with the belt and owned up to his mistake.  If you look at the diagram, the crank is centered at the bottom of the motor.  The belt runs into the R side of the crank and out the left side at approximately a 30 degree angle, across the top of both cams, down to the R side of the water pump to the R side of the crank with the tensioner about halfway between the WP and the crank. 

When he was installing the belt all of the slack between the crank and the first cam was not taken out completely, which caused a timing issue.  He said that he checked it out thoroughly and did not see any damage.  He also said that if ANYTHING comes up to bring it right back to him and he will will repair it free of charge. 

Frenchy- I have changed my own timing chains, plugs, plug wires, heads, distributors, etc. in the past.  All on a pushrod V-8-driven vehicle.  The same vehicle got 12 MPG and I had to constantly have my hands in it.  I don't mind getting my hands dirty, but it's not worth me buying $100 worth of specialty tools you need to do the job right and $100 for parts when I can pay someone else $250 who needs the money and is capable of doing it just to be able to say I am a real man.

W 

[Brad Johnson]

Talked extensively with the mechanic and he showed me the diagram that came with the belt and owned up to his mistake. 

He said that he checked it out thoroughly and did not see any damage.  He also said that if ANYTHING comes up to bring it right back to him and he will will repair it free of charge. 

Sounds like a stand-up kind of guy. Glad you've got someone it looks like you can trust.

Brad