4.9 timing is hard! Idles rough, stumble on acceleration

Wipeout · #1 (**permalink**) 12-02-05, 10:41 PM

Hey guys,
I'm the proud owner of a 4.9L powered Fiero (probably not the only one on this board), but am having a couple problems. I can't get the ignition timing straight. The harmonic balancer does not have the proper marks on it, and so I put the #1 cylinder at TDC and marked on the harmonic balancer 0 degrees. I then jumpered the ALDL and set timing by twisting the distributor until the mark lined up with the middle indent, which would be 10 degrees BTDC. The car idled really well for about five minutes, but stumbled when I tried to rev it. If I slowly increased throttle it would run up and down the revs fine. It sounds like a normal car with timing that is too far retarded. After about five minutes of idling really nicely (one of the first times for this beast) it started idling like crap and trying to die, misfiring bad. I turned the car off and haven't ran it since. I don't know what could have happened! Any insight? I've already replaced the ISC motor, which was bad before. If this helps, I have new Summit 8mm wires and an Accel cap and in-cap coil. I'm using the Cadillac ECM and the 4T60-E.
Adam

chevelle · #2 (**permalink**) 12-03-05, 12:31 AM

Why wouldn't the damper have the correct timing mark on it for TDC?? Are you setting the correct cylinder to TDC to check this?? Number one is the front, left cylinder looking at the engine from the rear of the engine. If the factory TDC mark is not there when setting number one to TDC then the damper outer ring may be moving on the hub of the damper becuase the elasomeric layer bond has failed and the damper is faulty. Can you find the TDC mark on the damper at all??

Watch the timing when the hesitation is occurring using the timing light and see what happens to it.

it sounds like the timing is not set correctly and is retarded to the point that the engine is hesitating and idling poorly.

Wipeout · #3 (**permalink**) 12-03-05, 03:45 PM

Wait a minute.. front left cylinder? OK, so let's say the motor is in the back of the Fiero, facing the same way as in the Cadillac (so the car still goes forward..). Is it the near left cylinder? I've been using the near right. Near right in my car = back left cylinder in the Cadillac if looking at the engine bay like one normally would. It gets confusing to me since I swapped the valve covers too so I could still put oil in. :P

So basically, I should be using the cylinder closest to me, on the left side of the engine if looking at the engine like I normally would in my Fiero? Maybe that's why this has been so hard..

Caddy-chris · #4 (**permalink**) 12-03-05, 03:59 PM

If we agree that the front of the engine is where the waterpump, balancer, etc are located, #1 cyl. is first cyl. on the right of the block ( directly adjacent to the waterpump pully.

If your engine is oriented as it is in the cadillac, # 1 will be on the right hand (passenger) side, in the cylinder bank facing the interior of the fiero.

Regards,

Chris

adalla · #5 (**permalink**) 12-03-05, 05:03 PM

#1 cylindder on 4.9 is the closest one to the radiator cap...just like CHEVELLE described. Oops... yours is not a Cadillac!

Wipeout · #6 (**permalink**) 12-03-05, 05:42 PM

Oh jeez. So if I look at my engine from how I normally would, it's the FAR right cylinder? The one closest to the water pump pulley?
Confused,
Adam

adalla · #7 (**permalink**) 12-03-05, 06:49 PM

Quote:

Originally Posted by Wipeout

Oh jeez. So if I look at my engine from how I normally would, it's the FAR right cylinder? The one closest to the water pump pulley?
Confused,
Adam

Yes.

Wipeout · #8 (**permalink**) 12-04-05, 02:21 AM

Ah, crap. Thanks. Wait, I kind of remember using that cylinder a long time ago and it still didn't line up with anything. Plus, I've had the distributor turned everywhere imaginable and I can't get it to idle as it should. Hrm.

adalla · #9 (**permalink**) 12-04-05, 02:30 AM

Wait. I am posting a pictire. Hopefully it will help you to position the distributor.

adalla · #10 (**permalink**) 12-04-05, 02:41 AM

Hope these pictures will help.

Wipeout · #11 (**permalink**) 12-04-05, 02:44 PM

Thanks for the pictures. OK, so it IS the hard to get to cylinder on the passenger side of the car. Now, the picture with the distributor - I have an Accel cap and coil, would you happen to know approximately which way that points? :P I've had it pointing everywhere from 30 degrees below left horizontal to 45 degrees above left horizontal, looking from the left bank of the motor (so the distributor is on the left).

adalla · #12 (**permalink**) 12-04-05, 03:01 PM

Quote:

Originally Posted by Wipeout

Thanks for the pictures. OK, so it IS the hard to get to cylinder on the passenger side of the car. Now, the picture with the distributor - I have an Accel cap and coil, would you happen to know approximately which way that points? :P I've had it pointing everywhere from 30 degrees below left horizontal to 45 degrees above left horizontal, looking from the left bank of the motor (so the distributor is on the left).

You are welcome. I am not familiar with Accel, but I would keep it close to 45 degrees to start with. There are only 4 possibilites with 45 degrees orientation (speaking mathematically). I do not know if making say, 180 degrees mistake will ruine the engine

.) One of them should work. For future reference, measure angles just like it is done in the picture.

Wipeout · #13 (**permalink**) 01-16-06, 03:47 AM

So here's an update along with a couple more questions. I used the correct cylinder and the marks still aren't lining up. I had been jumpering the wrong two pins on the ALDL connector before to set timing - oops. I jumpered the correct two and guess what. Starts beautifully, idles wonderfully, and has plenty of power and no hesitation. What the hell? If the pins aren't jumpered it's back to its usual self - hesitation, bad idle, etc.
What gives?

Capt Fiero · #14 (**permalink**) 01-18-06, 02:14 AM

Hmm sounds like you could have a couple of issues an idle learn problem, or something to do with the timing still.

Is it throwing any codes. If you don't mind me asking who did your chip for you.

A Bad Map sensor can cause what you are describing but I am pretty sure it should still do it in diagnostic mode too if it were the map.

I would try bumping or retarding the timing 2 degree's and see if it improves in either direction. If you are using a modified chip, by either RockCrawl or Aaron it has an increased timing curve that almost requires the use of 92oct or better fuel. I get horrid detonation if I try and run 87 and even 89 on hot days.

I have been following your thread on PFF as well. Glad you go the cyl and aldl ports sorted out.

Wipeout · #15 (**permalink**) 01-19-06, 12:08 PM

I will have to check if it threw any codes. I haven't had the instrument cluster plugged in for a while now. It was plugged in when the problem started and it didn't show anything, though. There is some pitting on the central pickup of the distributor cap, although that's not a problem yet (since it runs fine with the ALDL jumpered). The guy who burned my MEMCAL is pretty well known for specializing in 4.9L Fiero swaps. I trust the burn to be correct (especially because it ran great for 1600 miles), but I don't know if I trust the ECM. Oops, forgot who I was talking to. Yeah, Rockcrawl burned the MEMCAL. I've had the timing every which way in a range of about 45 degrees. You think it'd be worth it to purge the tank, replace the filter (it's gone through four filters already..), and dump in some 91? It ran fine on 89 octane all the way back from Kansas.

I know I sound like a moron, but I don't know what detonation/ping sounds like. If the timing is too far advanced, it misses, and if it's too far retarded, it misses. It doesn't really make a pinging sound.