bad misfire...help before i spend money

[GreenTA/GT]

Allright recently my car has started acting crappy again. It's a 94 LT1 Six speed with about 60K miles on it. It has a hard time turning over...lifts really hard but eventually will start. idle's fine...runs fine...for 20 min untill heat soak sets in. Then in low rpm's a nasty misfire occurs when barely giving throttle. high rpms it's really fine. I checked in the dark for arching, didn't see any. and I've read alot of people having this problem through the searches but noone actually posts the solution. So those of you who have had this...what did it normally end up being? Before I dump a butt-load of money on opti,plugs,wires,injectors,fuel pump, coils, egr valves, all of that LT1 victimous stuff. oh and the misfire is in the left side because when i checked in the dark you could have cooked eggs on that red hot header.

[Trash man]

well red manifolds usually indicate a lean condition. computer throwing a code or flashing the SES light? is the car under a load or just a cruise type mode?

[fastTa]

Get it scanned. Both lean and rich conditions can cause the manifold to glow red. If it is only after the motor becomes warm, it is likely ignition related. The coil and ICM on the LT1 are prone to heat soak being attached directly to the bank 1(driver's side) cylinder head. Peopl have found success by spacing the entire ICM and coil away from the head with washers. I would use aluminum washers.

There are so many causes of misfires it is impossible to diagnose without at least some sort of scanned data. A scan will at hopefully point you in the right direction.

[97LT1Z28]

I agree with Fast TA. The ICM spacing is a good thing - do it.

On bank one, raw fuel is igniting in your manifold causing it to glow. To find the source of the problem, begin with the basics - check things out before buying any parts.

1. Pull each plug wire off the plug - one at a time - and check that end for corrosion or any damage that would cause the misfire
2. Choose a plug on each side that's easy to reach and pull it out and check for damage or fouling - just a random check...
3. Pull the coil wire off and check each end for corrosion or damage
4. Check all hose fittings at or around the water pump. If you have a leaky hose near the Optispark distributor, it will leak when things heat up and cause a random misfire.
5. Pull some of your plug wires off at the distributor and check that end for corrosion

If all of this checks out, then move on to the distributor and then fuel system. With only 60K on your car, this should be something simple - you'll find it! As they say in China . . . . .Good Ruck.

[Joe 1320]

Most times a glowing header is caused by a misfire. Unburned fuel from a cylinder ends up in the exhaust and is lit off by another cylinder's combustion event and the fuel burns in the manifold rather than starting in the cylinder and finishing the combustion as it exits the cylinder. I would check plugs, wires and optispark. The ICMspacing should help but that may or may not be the problem.

[zer0signal667]

Get it scanned. Both lean and rich conditions can cause the manifold to glow red. If it is only after the motor becomes warm, it is likely ignition related. The coil and ICM on the LT1 are prone to heat soak being attached directly to the bank 1(driver's side) cylinder head. Peopl have found success by spacing the entire ICM and coil away from the head with washers. I would use aluminum washers.

Just a pointer here - if you're trying to use washers/standoffs to insulate the ICM, don't use aluminum. Aluminum is a good thermal conductor, something like steel or a high temperature polymer would be a better choice.

[fastTa]

Just a pointer here - if you're trying to use washers/standoffs to insulate the ICM, don't use aluminum. Aluminum is a good thermal conductor, something like steel or a high temperature polymer would be a better choice.

Common misconception. The superior thermal conductive properties of aluminum actually assist in preventing the transefer of heat from the head to ICM bracket. The better conductive properties allow the aluminum to better dissipate the heat into the air rather than attempt to send it through the other washers. Heat is thermal energy, and energy always takes the path of least resistance....the air. This is why aluminum heads are better at keeping CC temps lower.

With an infrared pyrometer, take a measurement at the ICM/Coil bracket with both aluminum and steel washers in place......the bracket is cooler with the aluminum washers.

[zer0signal667]

Common misconception. The superior thermal conductive properties of aluminum actually assist in preventing the transefer of heat from the head to ICM bracket. The better conductive properties allow the aluminum to better dissipate the heat into the air rather than attempt to send it through the other washers. Heat is thermal energy, and energy always takes the path of least resistance....the air. This is why aluminum heads are better at keeping CC temps lower.

With an infrared pyrometer, take a measurement at the ICM/Coil bracket with both aluminum and steel washers in place......the bracket is cooler with the aluminum washers.

I don't want to drag this thread off topic, but I don't buy it... air is a terrible thermal conductor; HIGH resistance. Maybe what you're suggesting happened for some reason in reality, but your reasoning is flawed - superior thermal conductivity prevents heat transfer? I should be lining my kilns at work with aluminum then, not refractory brick

[fastTa]

I don't want to drag this thread off topic, but I don't buy it... air is a terrible thermal conductor; HIGH resistance. Maybe what you're suggesting happened for some reason in reality, but your reasoning is flawed - superior thermal conductivity prevents heat transfer? I should be lining my kilns at work with aluminum then, not refractory brick

Wrong. Nothing I said was flawed. I specifically said the aluminum's better conductive properties helped to prevent the transfer the heat from the head to the bracket, not through the aluminum itself. You should learn to read more carefully. It's widespread common knowledge that aluminum dissipates heat better than metals such as steel and iron. Also aluminum's greater linear thermal expansion coefficient lends itself to an even more efficient heat dissipation element. Steel retains heat more so than aluminum, so the steel washer retains heat and the correspondingly adjacent ICM/coil bracket picks up the heat, the aluminum washers dissipate a significant amount of heat before it ever even reaches the bracket; it's a no brainer.

We used four aluminum washers and four steel washers, and then allowed the engine to fully become heat soaked. When pointed at the exact same spot on the bracket, the infrared pyrometer meter showed significantly lower temps at the bracket with the aluminum washers in place. Proof is in the pudding my friend.

[fastTa]

Back on topic ....GreenTA/GT, did your waterpump ever fail and get the optispark wet? Could be opti related considering you have the non-vented version. Get it scanned and then we will know.

[GreenTA/GT]

allright gang sorry for the delay...I'm gonna scan it tomorrow...i took some tips though and checked the coil and wire. I did see some corrosion on that wire so that will be my next step I think. I also looked at that coil and it looked like hell and for 15 bucks for a stock one...why the hell not replace it. 20 min and the new one was in... I noticed a stronger attempt to start but still a wicked kick back...I didn't see any evidence of water damage to the optical distributor but who knows...I'm going to replace that at some point just because my cars 12 years old now (oh and Happy new year),and i've read some on people rigging up a ventilation system, that'll be done. no ses light but i'm going to scan anyway. also during idle i think that there is a relay somewhere kicking on and off about ever 18-20 seconds,probably alot faster than normal. perhaps a vaccum leak?...I'm going to scan and replace some wires on monday-tuesday probably...I'll let you know how it goes. Thank you for all the input gratefully.

[SteveH95Formula]

Actually copper is one of the best materials for heat transfer.

[fastTa]

Actually copper is one of the best materials for heat transfer.

You would be asking for electrolysis with copper in between the head and ICM/coil bracket.