I posted this in the General Engine subforum, but I figured I would post it here as well, seeing that it's TBI specific.

I have a 305 TBI (220k miles) and I just started driving it again after a year not running.

Anyway, it starts up, a little rough to start but idles okay once it starts. It runs well for about three-five minutes and then a tick develops in time with the engine. Prior to the tick becoming louder and in time with the engine (the tick increases in frequency when the engine is revved), it sounds like a subtle rattle, sort of intermittent.

Eventually, the tick begins to sound sort of like a motorcycle when the engine is revved.

Also, the SES light has been on and it's giving a code 42. I've checked all the spark plug wires and they're all properly attached and free of damage (I've had a similar problem before where the car sounded terribly like a motorcycle and it was because of a spark plug wire that wasn't attached).

The Haynes manual states that code 42 is an error in the EST system and the probable cause is a "Poor electrical connection, open or short in circuit; defective ignition module; defective ECM."

Anyone have any ideas on narrowing the problem down and determining what the faulty component is?


Thanks in advance.

 

If its a tick i wana suggest its a valve. With it running take a piece of rod or something sticking it to parts of the engine and the other side to your ear, id say valve covers first, and see if you can pin point what side of the engine its coming from. If your able to figure out what side it is i would check the valve lash first.

 

I listened with a rod, I didn't hear any valves that were making any out of the ordinary sounds.

The sound is coming from the left(while standing in front of the car, otherwise the passenger side) side, rear of the engine. I think it could be the header/y-pipe connection maybe, I'll check that tomorrow.

Here's some more info on the tick, so it's in time with the engine when you rev it, but as soon as you let off the gas it stops ticking for about a second after it returns to idle, then starts ticking again. Does that shed any insight?

 

Bump.

I changed the oil today and checked the passenger side header/y-pipe connection and it's all bolted together still with nylon nuts and lock-washers.

The tick still persists. The valves ticked a bit on both sides when I first started the engine after changing the oil, but it went away after a few seconds. The tick that's been problematic was persistent throughout though. It definitely is coming from the passenger side of the engine near the back of the engine bay. You can't really hear it from the bottom, but more so from the top.

If it was a knocking rod it probably would be easier heard from the bottom wouldn't it?

I think this narrows it down to a problem with the ignition, considering the code 42 it's throwing off. If the tick was a lifter, I don't see why it would be throwing a code 42.

Anyone have any feedback? Otherwise I guess I'll just start replacing ignition components starting with the ignition module.

 

Nylon nuts on exhaust? Not the brightest idea. Even if you were using nylon INSERT locknuts, the nylon isn't going to withstand the heat of the exhaust.

I use BRASS nuts, they won't corrode to the steel studs. Something like this: NAPA p/n BK 6001817




First Guess: Exhaust leak at head-to-manifold/header flange.

By the way, "right" and "left" are always referenced to the position of the DRIVER, so the passenger side of a North American vehicle is always the RIGHT side.

Yup.

First guess: You have two separate problems: Exhaust leak AND ignition system. You might, however, open the hood at night and see if you've got a spark jumping to ground--you maybe are hearing a "snap" rather than a "tick". Even so, that shouldn't set code 42. Find the diagnostic tree for Code 42, and follow it exactly.

 

First guess: You have two separate problems: Exhaust leak AND ignition system. You might, however, open the hood at night and see if you've got a spark jumping to ground--you maybe are hearing a "snap" rather than a "tick". Even so, that shouldn't set code 42. Find the diagnostic tree for Code 42, and follow it exactly.

Had the same problem. Turns out the spark plug wire had a slight split in it. Mine was on the DS rear. Cylinder #7.

 

I don't think it could be a leak at the header to flange or header to manifold. I checked the header to flange/y-pipe the other night and it was still bolted together. Before I installed the lockwashers the bolts had completely fallen out of the header/y-pipe connection and that didn't even produce a problem. So I doubt it's a problem there.

While it could be a header to head leak, I highly doubt it considering #1 I've checked numerous times and #2 I installed the headers with Percy's deadsoft gaskets + Stage 8 locking header bolts.

As far as the ignition problem, it DEFINITELY sounds like what you're mentioning could be an issue, however, I've checked the wires numerous times by physically disconnecting them from the spark plugs and inspecting the length of the wire. No frays or anything were found and I reconnected each one well. The tick still persists.

How do I go about finding the diagnostic tree for code 42?

 

Locking header bolts is the first thing I'd check.

It'll be in the service manual for your vehicle.

 

Your tick, if not a valve, really sounds like an exhaust leak at head to header. Even though you have new gaskets if they got loose then the gasket blew out, then you re tightening will not help.

Codes change a little from year to year and car to car.
42. Fault at electronic spark timing circuit (sets when timing is set also, clear code and verify that it does not return.)
But 42 is always set if you disconnected your timing wire to set timing! Clear code by disconnecting battery or power to ECM for a minute. Then see if it comes back.

If it comes back and all wiring to distributor are OK then replace the EST, this is the module in distributor. It is known to be glitchy, meaning it will work even if failing. Some parts stores will check it for you but they have to do it three times. If it fails any time? Replace part.

Here's a link to codes and some pdf with GM testing procedures for TBI and TPI engines.
http://www.gearhead-efi.com/Fuel-Inj...-CEL-SES-Light

 

I'll check the header bolts today.

The Haynes manual states code 42 is a problem with the Electronic Spark Timing circuit/system and the probable cause is "Poor electrical connection, open or short in circuit; defective ignition module; defective ECM."

 

I'll check the head to header connection today.

I have not ever messed with the timing, so I don't see code 42 being thrown for that reason. I disconnected the battery for about five minutes the other night to remove the wiring for some fog lights and the SES light still is on.

The problem started about two days after I started driving it, I took it to get smogged and while I was driving the car home the SES light came on. The car still runs fine ( a little rough to start) but still has that tick.

Also, keep in mind that the tick cannot be heard much at all upon a cold start, but after about three to five minutes the tick gets a lot louder.

Does this above information point toward anything or rule anything out?

 

Update. So I was inspecting the header bolts today and the right rearmost header bolt looks as if there's about 1/16th of an inch exposed that could be tightened. I'm having a bit of trouble removing the locking clips and retaining clips, but do you guys think that small gap could be producing the tick?

 

Like I said above, it probably also blew out the gasket too... :(

 

MORE than enough.

Once you have them off...throw 'em in the scrap bin. They're worthless--as your 1/16 gap just proved.

 

Good to go.

I got them off. I'm having a VERY tough time tightening that rear bolt though, I remember installing these headers and I don't think I tightened this bolt enough because.

An 11 millimeter wrench will do it, I think I'll have to cut the wrench down to about three inches though, anything longer has no clearance to tighten the bolt.

Is there a chance that THIS is what's causing the code 42? I haven't started troubleshooting that yet, I'll use the PDF you provided EagleMark, which is very helpful by the way. But, I figured that I'll address the exhaust leak first, then move on.

 

I pulled the ignition module today and had it tested. It tested fine.

Any ideas where to go from here in regards to the code 42 problem?

 

^^^^^