Smog test and ignition timing

With timing advanced that much (allegedly advanced) you may not hear any pre-ignition rattle when the car is staionary as that may become most noticeable when the engine is under a load. (accelerating, climbing mountains, etc.)
You mentioned a little ping during hill-climbing but sometimes a little ping may occur anyway and this is nothing to worry about.

If the timing was really advanced that much then it should have been rattling constantly like a rock in a coffee can when you go uphill.

Another side effect of severely advanced timing is that the engine may appear to be hard to crank over. This may remind you of a weak battery, starter motor going bad, etc. and the engine may have a tendency to kick back as it’s cranked or even backfire out of the intake manifold.

It’s difficult to say if there was an error made during the timing belt install. Timing should always be checked after a timing belt replacement even if the camshaft or balance shaft is not off a tooth or two and the distributor is locked down.

As you say, if the timing was that far advanced most or all of those symptoms should have been present.

Any possibility that the inspecting mechanic did not use proper procedures in checking the timing?

I thought of that, but I don’t know if it is worth trying to reconstruct what error was made to produce the wrong number written down. It could be a clerical error (which is how the 10 BTDC was written down after setting the timing to 5 BTDC). Or Seeing/thinking the wrong thing during the measurement.

As for methodology, the under-hood label indicates, “5 degrees BTDC at 950 RPM max with vacuum hoses disconnected from distributor and sealed”. Maybe some combination of not disconnecting one more more vacuum hoses and/or not sealing one or more hoses could produce the wrong timing.

If the distributor is one of those dual advance ones (2 vacuum hoses) then it is extremely critical those hoses be disconnected and plugged.
The older Subarus used a dual adavnce distributor and if the hoses were not removed and capped the timing would have about 10 degrees too much advance in it.

I’ve seen several Subarus come into the shop with major engine damage because someone did not follow the procedure when setting the timing.
Matter of fact, I even bought one of those cars because it was low mileage and very slick. The owner had gone into a “fast tune” place and the guys there did not follow procedure. The following week the owner hit the road for an out of state trip and a 100 miles down the interstate several of the pistons gave up with a big bang.
The owner did not want to fix the car and I had an engine I had rebuilt at one time awaiting a car to put it in, so a deal was worked out.

If the timing was really advanced too much (10-15 degrees) there should have been some obvious symptoms.
In the case of the Subaru I bought the owner stated he heard some clattering and figured it was bad gas. He intended to stop a bit further down the road and gas up again to solve this problem, but he never made it to the next gas station.

I took the car back to the smog-check station / Mechanic Z (as named in my earlier account). The results were a bit surprising. Before we checked anything, I discussed my questions about the 20 BTDC initial measurement.

  • He said 15 degrees excess advance ignition timing is “not that much”.

  • He said the catalytic converter can clean up emissions so a 15 degree excess advance might not result in an observable change in emissions relative to normal timing.

  • He said vehicle performance might not be noticeably different with correct timing versus 15 degrees excess advance. He offered to go on a test drive around the block with me with the timing set to 5 degrees, then set it to 20 degrees and test-drive it again. He was also willing to do a smog “pre-test” (meaning with no official certificate and no data sent to the smog agency) at both timings. He claimed there would be no difference in the behavior of the car while driving it at the two ignition timings. He did not agree that the engine would necessarily ping much with 15 degrees excess advance.

  • We went on a test drive with him driving. He said initially that it felt like there is something wrong with the rocker arm due to the car “lugging”. This was because he perceived a delay in response when he floored (or nearly floored) the accelerator and it felt like the timing is retarded. I heard no pinging at all during his driving, even up hills, so the timing certainly did not seem advanced at this point. I mentioned that I never floor it, and he said this would mean it would never have a full vacuum, so advance timing could be symptomless.

  • When he measured the timing after we got back to the shop, he measured it at 20 degrees BTDC again. I told him another mechanic had measured it at 5 degrees BTDC one week ago, after the smog shop itself (the present mechanic) had set it to 5 BTDC for the smog re-test. The mechanic said the problem is probably that the balancer is loose/spinning. This meant the “marks are wrong”, producing errors in the timing measurements.

  • He also mentioned the distributor vacuum advance as a possible problem.

  • Summary: Mechanic Z concluded the car drives as if the timing were retarded, but measured it at 15 degrees excess advance. He mentioned initially a problem with the rocker arm. But then he emphasized the balancer and vacuum advance (not mentioning the rocker arm again). He mostly focused on the balancer as possibly causing the timing readings to be incorrect. He said when timing is set based on the readings with the balancer spinning, the actual timing being set is unknown.

I took the car straight to another shop about one mile away (Mechanic X) to have the timing measured again. There it was measured it at 10 degrees BTDC. The mechanic there agreed it might be a problem with the balancer or the distributor’s mechanical advance. He said it probably was not the vacuum advance because he could hear the change in idle speed when he plugged or unplugged the vacuum hoses.

Does all of this jibe so far? What about the rocker arm?

I don’t buy the rocker arm thing for a nano-second and I stronly disagree with any mechanic who thinks 15 degrees extra advance is “not that much”.
That amount is astronomical.

The things you’re being told about a loose balancers and faulty advance mechanisms are all things that can be easily checked within 5 minutes.
A timing light will reveal a bouncing timing mark if the balancer is bad and can also show if the vacuum advance is working correctly.
How hard can it be to pop the dist. cap and inspect the advance weight mechanism and perform a vacuum test on the dist. advance disphragms?

As to the rocker arm business, a loose rocker arm will be rattling and a tight rocker arm will cause a dead engine miss by not allowing the valve to close, which in turn kills the compression. This means a rough, loping idle and bucking. If this were the case the emissions specs would be through the roof; not where they’re at now.
If this guy claims a rocker arm problem then throw a vacuum gauge on it. Only takes a few seconds and an alleged rocker arm problem will show up instantly; and in my view, this problem does not exist anyway.

Wished I could be of more help and I have no idea what they’re doing, but I will say this. No reputable mechanic will casually dismiss 8 degrees of timing, much less 15, as not being much.

I think the mechanic’s idea about the rocker arm was only initially. He seemed to associate that with retarded timing which he perceived during the drive. But then did not mention it again.

I gather that the marks were not bouncing around under the timing light. So the slipping seems to occur during driving, then remains stable in the shop while timing is being measured.

Both mechanics said it is difficult to get at the balancer. “Z” was going to demonstrate how it could slip, but could not get into that part of the engine compartment easily so he used some other items he had lying around as props. “X” said checking the balancer and mechanical advance will be about half an hour of work, as the balancer will require removing belts to get to it.

Anyway, it looks like the things to check are the balancer spinning and the distributor mechanical advance, and possibly the vacuum advance. I gather that if the balancer proves to be the problem then the timing readings have been essentially random numbers not closely related to the actual ignition timing.

Too bad you haven’t found a knowledgeable mechanic, yet. I’m not sure where you may find one. Your questions to these mechanics have been Automotive 101 kind of stuff, and, they flunked!
The harmonic balancer is bolted firmly to the engine crankshaft. It CANNOT spin independently of the the crankshaft. Marks on it are compared (with a timing light) to a stationary point.
Any changes in the (ignition) timing will be the result of malfunctions in the vacuum and centrifugal advance…NOT, the harmonic balancer.
The knock sensor must be doing its job (irrespective of the quality of your mechanics). The knock sensor prevents ping by informing the engine computer, and the engine computer, in response, retards timing.

You mean the harmonic balancer will not slip? I was just reading about this topic – for example, http://www.fordforums.com/f496/harmonic-balancer-timing-mark-alignment-93848/ – and it seems slipping balancers can create problems in measuring or setting timing.

Other mentions of harmonic balancer spinning:


("…A harmonic balancer is a hub with a rubber sleeve around it and a hub pressed over that…during racing and reving…they can slip." This may describe what happened today. When I drove the car home from the second smog check two weeks ago, after timing was set to 5 BTDC, I didn’t rev it very hard. On the way to the other mechanic last way, no reving, and the measurement was 5 BTDC. Today the smog-check mechanic did rev it pretty hard while we were test driving, then he measured 20 BTDC at the shop.)

Mechanic says the problem is the mechanical advance. Rotor does not spring back, just stays put after turning it.

His supplier indicates the distributor would be a special-order item, $447. So now I am checking around with parts dealers online. I’ve done this before, but for simpler items like side marker lights. Is it okay to get a distributor from a Corolla or other model (for example, 1986 Corolla or 1987 FX) for my 1988 Nova? These are some of the models that are coming up for parts when I search based on my make/model/engine.

I agree with hellokit about your mechanics flunking Memchanics 101.

The balancer does not slip, It may shear a Woodruff key in which case you may not move much further or the rubber in the balancer may separate to some extent. A partial separation could mean a bouncing timing mark, etc. A full separation usually means the outer pulleys with the belts go flying off the car.

If the advance mechanism is not returning then why not simply free it up and lube it rather than spend 400+ dollars on a reman distributor. I’ve done this a thousand times and there should be no reason why it can’t be done with this car either.

However, if you really need a distributor.
http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Distributor-Cardone_3851249-P_218_R|GRPTUNEAMS_516415008___

Just another FYI, and keep in mind that I’m not familiar at all with this model of car. Many vehicles of this era used various solenoids and thermovalves to control ignition timing, EGR operation, etc.
It’s possible to have a problem if engine vacuum is maintained, not released, or whatever depending on throttle operation. This means the timing could advance or it may not; the timing may advance or not return, etc. based on a fault in one of these solenoids or thermovalves.

If they say the advance weights in the dist. are sticking then that’s a 30 second deal to determine and not much more time to cure.

Don’t know why he did not just lubricate the centrifugal advance mechanism instead of suggesting a replacement of the distributor.

In my Haynes book, I do see that replacing the centrifugal advance mechanism involves removing a number of items – distributor, then coil, igniter, signal rotor, vacuum advance unit, and breaker plate assembly – before gaining access to the governor shaft. I am assuming the governor shaft is what needs to be lubricated. So the governor shaft possibly would have to be pulled out as well to lubricate it. Maybe it seemed easier to replace the distributor than to disassemble it.

I called to ask why not just lubricate the mechanical advance mechanism instead of replacing the whole distributor. The mechanic said the mechanism is probably too deep within the distributor, so the distributor would probably get damaged just taking it apart. The mechanical advance part is probably rusted anyway so lubricating would not have enough effect.

I am not sure whether that is a reasonable conclusion. From what I read in my service manual, it does not look like a thirty-second job to get at the mechanical advance mechanism and lubricate it. On the other hand, there is a procedure to disassemble the distributor and replace or just work on the centrifugal governor.

I called yet another mechanic for a quote on doing this work. This is a mechanic I have hired in a long time. I described the problem as narrowed down to the mechanical advance in the distributor, with the symptoms of odd timing readings and the rotor not returning after you turn it. He said it would be more cost-effective to replace the distributor than to try to get in to lubricate the mechanical advance mechanism. He said the bearings can also go bad in the distributor, so better to replace the whole thing.

The distributor does not use bearings; it has bushings. It does happen that bushings can wear and the best option is a distributor replacement as it is very difficult to locate bushings that are the right size. This may mean having them machined and this means it is no longer cost effective.
Worn bushings can be easily determined. Simply try to move the distributor rotor back and forth. If it’s tight, the dist. is good. If it wobbles, then the bushings are worn.

I guess to each their own but if the dist. bushings are good I don’t see what the problem is by simply repairing the advance mechanism; even if involves disassembling the dist. Especially considering this 4-500 dollar price tag on the dist.
It’s not likely at all the advance mechanism is rusted beyond repair. Some surface rust is normal anyway.

Just to follow up on this, I ended up buying a used distributor for $71 delivered, had a mechanic install it, and things ran fine until… today. Timing was checked yesterday and confirmed to be correct. However, something weird arose today at the mechanic’s garage, possibly involving the distributor. I posted a new message about it here: http://community.cartalk.com/posts/list/2148635.page