As per my profile I'm in the UK.

An engine tune-up place has opened near me and I took my 88 305 TPI IROC there.
they hooked the car up to an Allen Smart Engine Analyser with a timing light.
One of the things they saiud was that at idle the car was running at 18deg BTDC and it should be 6 deg BTDC. I verified that it should be 6 by doing a search on this forum and looking at the sticker under the hood.

18 seems a LOT (we do have good fuel in the UK though, 95 Octane is std and I put 97).

The car does seem sluggish but I put that down to the 2.72 rear end.


Do you think the shop is right?


They showed me with the timing gun and the crank mark was way over to the left (compared to the timing tab).

But I did read somewhere on here that there is a wire that you are supposed to disconnect when checking the timing or the ECM will advance the timing anyways? I don't know if they did that (they were pulling a few wires and pipes to hook up the Allen SEA). If they didn't would the timing show 18 deg BTDC at idle or would you expect it to be higher than that if the ECM was still hooked up?


I have a Performance Resource chip that I want to install but I figure if my base timing is wrong that could do more harm than good...



Also, the engine has never been pulled apart (to my knowledge) so I have no reason to believe the timing tab should be wrong. I only say this as I read in a search of posts on here about the balancer being off (and thus the tab being wrong?)

 

Also, I need to replace the spark plug leads.
What are the best ones to get that are a direct replacement for the GM ones (ie fit the distributor and don't need you to cut them to length and crimp the ends yourself cos I don't wanna do that).

 

The people you had pulling wires out from your car don't seem to have a clue. Sounds like they didn't disconect the ESC. It's a tan wire that comes from the large loom near the back at the pass side.

 

Sounds like your dizzy is off by a tooth.
You can fix this by rotating the dizzy forward ONE TOOTH.
The shaft will drop in but won't line up with the oil pump shaft.
That's when you turn the car over real quick so the shaft spins and drops onto the oil pump shaft.

Try that.
I had it recently happen to me during a distributor rebuild.
Thought I was 180* out at first but then I got her started and I was idling at about 20* BTDC.

 

The UK uses differant way of measuring octane then the USA. Your "97" is equal to our "92".

 

That's what I thought!


I'll get them to double check the base timing then.
they did give me a figure for base timintg and a seperate figure for how much advance the ecu was also giving so I assumed they had the right figure.

The distributor being 1 tooth out or any other thing that could be giving a false reading is concerning...
It makes it a lottery setting the timing becuase I won't know if truly am 18 deg BTDC or bang on...


Anyone know of any ignition leads that don't require me to crimp them etc? I'd like a set or spiral core ones that are designed exactly for the car, straight from the box...

Any suggestions?

 

Hi from a fellow UK guy !!!.

Well your ECU needs to be in DIAG mode before you can even check the timing.

You need to short Terminals A+B on the ALDL connector. Once that is done you can check your timing at idle...

Your not far away !!, fancy meeting up one weekend ???

 

Yeah mate would love to!

The spec in your sig reads interesting to say the least!

Would be good to get an opinion on a few things with regards to the state of the car and what not...

I'm hearing so many things about how to chekc the timing it's confusing ther hell out of me.
the diagnostics machine it was hooked up to is supposed to do the test in a fully automated way so I would have thought it's readings are correct.
Might be worth buying a timing gun or something...

 

For what they cost it is worth getting a programable timing light. I am not a beleiver in these Engine Anylisers. ( I used to be a
saab technician ).

Also the Harmonic Balancers can spin. The center bit is made of rubber and the out part is metal. As the rubber gets old and the bonding breaks down the timing marks on the balancer become complete Bol+@cks.

As i said, short connectors A + B on the ALDL connector, the ECU will then be in DIAG mode. Then use a timing light to set the timing.
I also have a WinALDL connector adapter and the laptop software so i can tune and diagnose these engines perfectly !!!.
They are very similar to the TPI engines in my Fiero GT V6's just smaller......

 

So if the timing marks are out how do I set the timing?

 

Well i am not sure about the Camaro 305 i will have to have a look.
But on Fiero's i created a new mark using Tipex on the Air con driver pulley on the crank. This is metal and cannot move. Then i dialled in 6 Degrees into the Programmable strobe and lined up the marks at idle. Of course the ECU has to be in DIAG mode first.

 

Paul,

Which software are you using for editing the bin? Have you got any datalogging on the new IROC yet?

I've been getting into PROM tuning for the last few months and have been having good success so far. Do you mind if I drop you an email or a PM about some of this stuff?

Cheers,

Gordon

 

If the balancer was out of whack would it be worth getting it replaced?
Anyone know what that might cost?

Surely it will mean the engine ain't properly balance too?

 

How do I know where to make the new mark though?

I'm seriously baffled now...

Is the only true way to do it to stick something in No1 cylinder and see when it rises to the top and make a mark then?

I've bought a timing gun from Halfrauds but I'm new to this timing lark...

 

Well if you took a trip up the M4 i could do it for you...........

 

It may yet come to that!!!

I'm taking it back on Saturday to the place that did the diagnosis.
But in the meantime I will put it into DIAG mode and check the timing myself with my timing gun.
If I also get 18 BTDC I will try adjusting it to 6deg BTDC and if the marks are off then surely retarding it by 12deg form where it runs ok will cause it to run like a bag of spanners?

If so I don't see how they or anyone else can adjust it to the 6deg if we have nothing to go on...

 

I tried setting it last night.
There was a single brown wire going into a big round steel/alloy thing just below the distributor (drivers side). So I pulled that out (knowing my luck the wrong wire).
Used the timing light to set the timing to 6deg instead of 18 and the the engine changed in tone a great deal.

Took it out for a run and it was completely gutless and was in danger of stalling when pulling away on light throttle.
Set it back to 18deg and it woke up again...

I may have pulled the wrong wire out admittedly (it was the only single wire connector I could find) and assuming that was the case how much advance does the ecu add anyways? ie how much change should I see from pulling the wire out?

As I took a total of 12deg out manually (as I reduced it from 18 to 6) and if it was 6 with the ecu advance then without ecu advance how much would it be? Because I'm thinking I must've pulled the wrong wire out (I didn't check timing before and after pulling the wire, only after) and I've ended up setting base timing to like 0 or AFTC...

Either that or I did it right and the pulley is off in which case I don't see how I'm supposed to set the timing...

 

I thought the brown wire with the black stripe is the one that is near the battery. It comes out of the loom for about 2 inches, and then back into the loom.

 

So where do I unplug it?

Does it come out of the loom to a connector at any point?

 

Tan wire comming from a large loom on the pass side near the coil.

 

My v8 Fiero (350 TPI) drives the alternator from a v belt groove cut into the harmonic balancer. So, the outer rim slippage was about 15-20 degrees after only 6 months of driving. I noticed this when checking the timing, and had to re-mark TDC on the crank pulley hub (fixed to the crank) to proceed. This positioned the tilming marks behind the rear wheel (remember-Fiero-mid engine) and makes it very awkward to check timing.
Now, Paul comes up with the perfect solution! My water pump and AIR pump both run from a cog wheel on the crank hub, so I will mark them so that the very convenient AIR cog wheel has the timing marks!
Kudos, Paul!

 

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As tried to be mentioned before, you have to have the EST bypass disconnected, to set the base timing.

Location of the connector varies throughout the years, but on my '89 IROC it's behind the pass side strut tower brace, single-wire-connector,

IIRC, I'd expect about 18-20BTDC with it connected.

 

I think everyone is correct in this topic, but are not clearly separating the main ideas (me included!).

1- The spark EST wire must be disconnected to get the physical advance to read (at least on my 1990 MAP ECM) with a timing light. When the EST is connected, the computer controls idle speed by varying the idle spark advance, and I have typically found it to be about 15-25 degrees, and constantly varying.

2- The outer ring on the harmonic balancer (containing the timing mark) will slip over time. This backwards slip then makes the timing to appear advanced by the amount of slip, whether the EST is disconnected or not. The attempt to adjust timing back to spec then retards it by that amount of slip. The solution is to re-mark the HM ring, or better, another reference that is not going to slip, as Paul suggested.
Harry

 

Right, done some double checking...

1) I was getting 18deg with wire disconnected as my timing light is faulty.

2) The readings from the Smart Engine Analyser were also wrong because it wasn't "smart" enough to interrupt the ECM contrary to what the operator told me. Checking it on that analyser again with me pulling the wire myself gave a reading of 8deg BTDC. Can't trust "professionals" who've "worked on one of these cars before" it seems...

Checking it again with my own timing light gave the wrong figure again, back went the timing light to the store and guess what, the replacement one said 8deg...

So it's 6 now.


Thanks to all who patiently gave advice.
I'm just relieved my balancer is probably ok!