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Car Forum / Pontiac / Pontiac Fiero / July 2007Is there an easy way to check 2.8 Timing?
Camshaft timing, that is. My '86 2.8 v6 with 80,000 miles runs rough as hell - no power, coughs, backfires, etc. No ECM code, all I get is a constant stream of "12"s indicating all is well. Ignition timing seems okay - sort of. At TDC of the crank, the distributor rotor DOES point to the wire going to #1 plug, and then 2-3- 4-5-6 are correct, but #1 isn't #1 as stamped on the inside of the dist cap. It's almost as if either the timing chain has jumped timing and the previous owner just moved the plug wires to compensate, or the previous owner just put the distributor in randomly and called where the rotor landed as #1. I can tell somebody's had the distributor out because they've permatexed the old O ring rather than replacing it. I suspected a jumped timing chain, but I get good compression - 140 to 150 on all 6, not bad for an engine with 80K. Am I correct in assuming that good compression rules out a jumped timing chain ? My next step would be to check the camshaft to crankshaft timing. But I don't want to pull off the harmonic balancer if I don't have to. Is there another way to check camshaft timing other than looking at the gear timing mark ? Or does good compression rule out the need to do this ? To check the timing you will need a timing light. Put the ECM in dianostic mode then set the timing to 10Deg BTC Your compression would indicate that cam timing is OK > Camshaft timing, that is. > [quoted text clipped - 22 lines] > gear timing mark ? Or does good compression rule out the need to do this > ? > To check the timing you will need a timing light. Put the ECM in > dianostic mode then set the timing to 10Deg BTC Your compression would > indicate that cam timing is OK Thanks for the reply. I can't keep it running long enough to get a timing light on it. It'll start but will stay running only as long as I have my foot on the gas pedal, it'll die immediately if I either let off the gas or put a load on it. And it stumbles, coughs, backfires the whole time. If I put the ECM in bypass by jumpering 1-2, it'll run marginally smoother and will last maybe 5-10 seconds before dying if I let off the gas, still not long enough to get a timing light on it. That's why I'm going back to the "basics" and doublechecking the mechanical setup. Previously owner apparently did a lot of unknowledgeable fiddling on it before giving up and selling it to me, so God only knows what I might have to go in and fix or undo. But I only paid $300, so I'm not complaining. at top dead center the rotor won't point to the number one plug because at idle your timing should be around 15 degrees before t.d.c. initial timing. while not running , when you spin the motor back to 15 degrees b.t.d.c, on the compression stroke, then the rotor will line up to where ever you have #1 hooked up to , and if it doesn't you need to make it line up. it does not matter if you use "# 1" on the cap or not. when the motor is running at idle with everything hooked up you should be at about 23.5 degrees btdc. if not, you CAN spin the distributor to acheive your engines prefered timing, every engine is different. >Camshaft timing, that is. > [quoted text clipped - 22 lines] >gear timing mark ? Or does good compression rule out the need to do this >? cam timing is a little more complicated but basically put #1 cylinder to tdc and put the cam to where both the lobes are causing the lifters to rise for that cylinder. this is right at the intake opening and the exhaust closing even on the cam. then put the chain on and call it a day. check your rockers for proper adjustment. some idiot might think its a ford and torque them down. on that motor proper adjustment is 0 lash and a 90 degree turn (3 thou preload) >at top dead center the rotor won't point to the number one plug because at >idle your timing should be around 15 degrees before t.d.c. initial timing. [quoted text clipped - 12 lines] >>gear timing mark ? Or does good compression rule out the need to do this >>? I don't recall a posting with as much mis-information as you have in the last two. Static ignition timing is 10° BTDC. A prior post explained how to set it properly so I won't rehash that here. >>at top dead center the rotor won't point to the number one plug because at >>idle your timing should be around 15 degrees before t.d.c. initial timing. >>while not running , when you spin the motor back to 15 degrees b.t.d.c, on >>the compression stroke, then the rotor will line up to where ever you have >>#1 The distributor rotates one revolution for every two engine revolutions. That means that +/- 5° distributor revolution will be pointed at the correct distributor terminal. I don't know about anyone else, but I find it pretty darn hard to tell within 5° where a rotor is pointed, particularly when there are, what, 12 teeth on the distributor so each one of those changes the rotation by 30°. If you pick the gear engagement that gets you as close as possible to the terminal you want to point at, you should have more than enough cable/wiring to rotate the distributor to the proper timing. IOW, line the thing up with the terminal and go from there. The easiest way I've found to do that is to simply put the cap on the distributor with it out of the engine and mark the distributor body in line with the #1 terminal. Take the cap off and extend that mark to the top of the housing area so you can easily see it, then drop the distributor in so it lines up with that mark. (I'm assuming that you already have the engine at TDC compression #1 cylinder). As Phil said, you MUST put the ECM in the diagnostic mode to lock the ignition timing. Doing this disables the electronic spark advance. There is no way to do it other than with a timing light. A common mistake is putting the wires on in the incorrect firing order either by mistake in wire routing, mistake in cylinder numbering, or putting them on in the wrong rotation on the cap. I've seen all three methods (and more) and none of the people that did it were idiots, they simply made a mistake. I'd be more interested in knowing how and when this all started. Did it run perfectly and then one day, bang, it wouldn't run right? Was it a gradual thing that got worse? Did you try to time it or give it a tune up and it hasn't run right since? Did it get hot? Any unusual noises? More information would aid in figuring out what was wrong. > cam timing is a little more complicated but basically put #1 cylinder to > tdc [quoted text clipped - 4 lines] > cam. > then put the chain on and call it a day. I hope you never build an engine for me. There are timing marks on the cam and crank gear, they are there for a reason. I suggest you use them. > check your rockers for proper adjustment. > some idiot might think its a ford and torque them down. > on that motor proper adjustment is 0 lash and a 90 degree turn (3 thou > preload) 1/4 turn? .003 preload? Good luck on that one. Yeah, sometimes that's enough. Most of the time you're going to get at least one lifter that's going to clatter on you out of the 12. Often times more than one. IIRC, it was reported that the Haynes or Chilton manual has this listed incorrectly, something like 3 turns tight after 0 lash. That's way too tight. Normally a happy medium is about 3/4 of a turn, assuming you have found actual 0 lash, and most people don't really find that. Crane, Comp Cams, and GM all recommend between .020-.060" preload. With the Fiero rocker studs, that is between 1/2 and 1 1/4 turn. That's where the 3/4 turn recommendation comes from. John Stricker > I'd be more interested in knowing how and when this all started. Did > it run perfectly and then one day, bang, it wouldn't run right? Was [quoted text clipped - 3 lines] > > John Stricker The guy I bought it from said it just died one day on the road, then would crank but wouldn't start. He took it to shop #1. They told it it had a bad "Neutral Safety Switch" (yeah, I know, this is BS because a bad NSS won't let it even crank.) They supposedly replaced the switch and then it would run, but not run right. He then took it to shop #2. They say it has a bad ECM, and they replace the ECM for $400-something (Also BS, because an ECM is only $125 new at the Pontiac dealer). Now with the new ECM It would start but dies after a few seconds. It sits at shop #2 for a month, then they call him up and say, "Come get it, we give up, forget the $400". It sits in his yard for about 2 years, then he sells it to me for $350. First thing I notice is, the ECM give code 52 - bad CALPAK. I open up the ECM, it's not just a bad CalPak, it's a missing Calpak. Shop #2 apparently never transfered it from the old ECM. No problem, new CalPak for $25 from the Pontiac dealer. (Note to anyone: If you're ever in Portland Oregon, Breslin-Wallace Pontiac on Sandy Blvd are real good people, easy to deal with and they stock a lot of these older parts) Okay, now it'll start and stay running, but runs like sh*t. Exhaust reeks of half-burnt gas. Spark plugs smell like raw gas and are jet black. Next thing I notice is the distributor at TDC isn't pointing to #1 as marked on the cap, it's pointing to #2, but if I assume that #2 is #1, then the firing order is correct. I pull out the distributor. Somebody's obviously had it out before, they've permatexed it rather than replacing the O-ring. I put it back so that at 10 BTDC the rotor is pointing at #1 as marked on the cap, and move the wires to match. Okay, now it starts and runs better. I jumper A-B on the ALDL connector and set the timing for right at 10 degrees. Then I pull off the jumper and all is well. I've put maybe 100 miles on it over the weekend just testing it. Sheesh. Amateurs. What this seems to indicate, it really does care that you are using the correct #1 pin on the distributor cap. Everything I THOUGHT I knew said that it doesn't matter which pin is #1 as long as you have the firing order correct. But apparently it does. Congrats on getting it running, but it really doesn't care where you start as long as things are oriented correctly and it's timed correctly. If you had timed it correctly even with the different plug wiring on the cap, it would have run fine. All that said, I do like to put the wires on the way they're supposed to be, just for the fact of doing a "workmanlike" job if nothing else. It sounds like you used the GM O ring and that's good, the aftermarket ones tend to get hot, hard, and leak in a relatively short time. I've bought a few Fieros like you did yours. People just give up and cuss those "damn mid-engine cars". Hey, guess what, no matter WHERE the engine is it's not going to run right without being properly timed! Have fun with it, they are fun cars to drive. John Stricker >> I'd be more interested in knowing how and when this all started. Did >> it run perfectly and then one day, bang, it wouldn't run right? Was [quoted text clipped - 52 lines] > order > correct. But apparently it does. |
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