Hi,

The saga continues on my 86 wagon that's been sitting for many years. Just did the timing and drive belts and after I finished the car starts dipping at idle from 800 to maybe 4 or 500 rpm for a second or two then goes back to normal. A few seconds later it does it again and that's how it runs now, almost dying when the rpms drop if I'm not careful. Seems to drive okay. Manifold vacuum dips regularly with the rpm drop which is supposed to be a sticky/burned valve according to my vacuum gauge manual? Also the dollar bill at the exhaust tip gets sucked in and blown out rapidly. Checked the timing marks re the timing belt and it is fine. Can't find any vacuum leaks. It didn't do this before I did the timing belt. I am an amateur at this but I am facing the thought that since I used the "rope trick" (putting some rope in cylinder #1 to stop engine rotation to get the crank pulley bolt off) for the timing belt job that I bent one of the valves using a foot more rope than was recommended (timing mark on crank was about 20 degrees or less plus or minus the zero mark as I tightened and loosened the bolt). Any thoughts would be greatly appreciated. Would a compression check help nail down if it is indeed a damaged valve?

Thanks,

Mike

Update FYI: It was the crankshaft that was off its timing mark use this to get correct position:

https://www.brickboard.com/FAQ/700-900/FAQPDFVersions/B230FTimingBeltAlignment.pdf


Solved!

Hi,

I agree with Art that your timing is off for the spark.
If you did not use a mirror in front of the intermediate gear, that turns the distributor, to align the dot to the mark in the plastic housing, you are off one tooth.

This would explain the Twenty degree reading on the crankshaft when it should be twelve degrees at idle. This is + or - two degrees. The eight degrees is giving you a early burn before top dead center. This might be conceived or perceived as a combustion knock and the computer is trying to adjust for it.
Whipping the timing around across four cylinders is a task that might take a second or so at idle and by then the readings from the O 2 sensor comes in.

With all this Jockeying around by the computer, the Horses, in the engine, are confused!

You might get by just moving the distributor in the slot on a 1986, if it goes the right way, to bring it in correctly. BUT pity the next guy, of which might be you, who will put the gear on the mark and cause this all over again.
Of course, this might be that next time and the mark really is dead on!

Phil

Hmm...I think the dealer did the last timing belt 60k miles ago. I will double check the mark on the intermediate shaft sprocket with a mirror and hopefully get it back to spec if it's off or whatever other problem is has. I've set it up to run on E85 so it can handle advanced timing without pinging and right now it runs fine at 20 degrees advanced or more because of the ethanol. If I were running on normal gas it probably would be too far advanced at 20 degrees. Thanks a lot!

Hi Mike,

A compression check would reveal a damaged valve. But also, you wouldn't have a damaged valve if you used the rope trick with its most vital direction -- ensure the TDC you chose is the one with the valves closed. You don't mention any concern about this.

An alternate explanation is your positioning of the sprocket for the intermediate shaft is wrong, or as is sometimes the case, right, after some previous belt-changer has made up for an error with the distributor. Check that the distributor contact points at the index mark when the crank is at TDC. Or check ignition timing with a light.

Which you do first, the compression check or the ignition timing check should be guided by your confidence in how you used the rope. An extra foot of rope is not a problem, if the valve timing is respected. I'm thinking the ignition timing is at fault or your intake vacuum would be way off.


--
Art Benstein near Baltimore

Thought for the day: Never be afraid to try something new. Remember that a lone amateur built the Ark. A large group of professionals built the Titanic.

Thanks a lot guys, so after putting a timing light on it I discovered that it was way too far advanced so I backed it up and the problem is gone! Phew. If I rotate the distributor as far as I can to retard timing I still get around 20 degrees of advance so that's a lesser problem for me to ponder on. I checked the distributor rotor and it does line up with a mark on the distributor housing but the mark is immediately clockwise to the dist. wiring harness plug, Bentley manual says it should be somewhere else, so I might be confused on that. The intermediate sprocket timing marks line up with the others, maybe I installed it 180 degrees off, is that possible? Rope trick vindicated, you guys save my bacon again!

Mike

Does the car run like it should with normal acceleration?

When was the last time the throttle body, Idle air control valve, and flam trap/ pcv system was cleaned?

Dan

If the car was functioning 100% before your timing belt job and this issue appeared immediately after, it does seem that the timing may be off a bit.

But...my car has occasional similar symptoms and it's due to a sticking idle air valve. As soon as I open the throttle the slightest amount, which shuts off the idle air valve's function, the engine runs smoothly at steady RPM.

In any case, Dan's advice to clean and check the maintenance items he lists is always a good idea.
--
Bob: Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), 98 S90 (recently sold) and XC60. Also '77 MGB and four old motorcycles