Scary Brief Engine Misfire

[BodybyFisher]

OK, so today I get into my car after it sat since Friday, start it, and for the first time in six months NO MISFIRE! However, now, I am experiencing long cranking (3 times), ICM?

Can a bad ICM cause misfiring?, or just starting problems?

[Cadillac Jim]

I didn't determine whether 1 and 3 were on the same coil or not, but if they are I would look there first, then at the plug wires, then at the plug connectors and boots, then at the plugs themselves.

As for slow starting when cold, I would look for codes; no codes and hard cold starting points to the fuel pump relay. The fuel pump is an in-tank electric high pressure pump. You can check for that by sitting in the car when all is quiet, then turning on the ignition. You should hear it run for about ten seconds, then shut down. If it doesn't do that, then it won't turn on until the oil pressure light goes out, which explains hard starting when cold. The relay that does the 10-second dance would be the culprit there.

[KHE]

As for slow starting when cold, I would look for codes; no codes and hard cold starting points to the fuel pump relay. The fuel pump is an in-tank electric high pressure pump. You can check for that by sitting in the car when all is quiet, then turning on the ignition. You should hear it run for about ten seconds, then shut down.

The pump usually only runs for two to three seconds to prime.

[BodybyFisher]

I didn't determine whether 1 and 3 were on the same coil or not, but if they are I would look there first, then at the plug wires, then at the plug connectors and boots, then at the plugs themselves.

As for slow starting when cold, I would look for codes; no codes and hard cold starting points to the fuel pump relay. The fuel pump is an in-tank electric high pressure pump. You can check for that by sitting in the car when all is quiet, then turning on the ignition. You should hear it run for about ten seconds, then shut down. If it doesn't do that, then it won't turn on until the oil pressure light goes out, which explains hard starting when cold. The relay that does the 10-second dance would be the culprit there.

Cylinders 1 and 3 are not on the same coil.

Do you think the fuel pump relay would cause it to run poorly for less than five minutes?, then it runs fine?

The longer cranking is intermittant and has just begun.

Can a bad ICM cause a misfire?, or just starting problems?

[JimD]

....Do you think the fuel pump relay would cause it to run poorly for less than five minutes?, then it runs fine?

I doubt if the pump relay would cause it to run poorly.

Can a bad ICM cause a misfire?

Most certainly. So could marginally corroded contacts. It might be productive to R & R the individual coils and clean/inspect the contacts between the coils and the ICM.

I believe the ICM can be tested but that requires the use of a Tech II.

It might also be productive to check the electrical connector at each crankshaft position sensor.

Good luck, Mike!!

[BodybyFisher]

....Do you think the fuel pump relay would cause it to run poorly for less than five minutes?, then it runs fine?

I doubt if the pump relay would cause it to run poorly.

Can a bad ICM cause a misfire?

Most certainly. So could marginally corroded contacts. It might be productive to R & R the individual coils and clean/inspect the contacts between the coils and the ICM.

I believe the ICM can be tested but that requires the use of a Tech II.

It might also be productive to check the electrical connector at each crankshaft position sensor.

Good luck, Mike!!

thanks Jim, Ill pull it in the morning and report back. I want to pull the plugs from cylinders 1 and 3 also and check the cylinders for coolant. I seriously doubt i will find coolant however I have lost none thanks

[adallak]

....Do you think the fuel pump relay would cause it to run poorly for less than five minutes?, then it runs fine?

I doubt if the pump relay would cause it to run poorly.

Can a bad ICM cause a misfire?

Most certainly. So could marginally corroded contacts. It might be productive to R & R the individual coils and clean/inspect the contacts between the coils and the ICM.

I believe the ICM can be tested but that requires the use of a Tech II.

It might also be productive to check the electrical connector at each crankshaft position sensor.

Good luck, Mike!!

ICM may be taken out and checked at Advance Autoparts for free. When my ICM went out I just could not start the car. I had misfire with old ICM and still have it with new one. This does not mean ICM cannot cause misfire though.

[BodybyFisher]

....Do you think the fuel pump relay would cause it to run poorly for less than five minutes?, then it runs fine?

I doubt if the pump relay would cause it to run poorly.

Can a bad ICM cause a misfire?

Most certainly. So could marginally corroded contacts. It might be productive to R & R the individual coils and clean/inspect the contacts between the coils and the ICM.

I believe the ICM can be tested but that requires the use of a Tech II.

It might also be productive to check the electrical connector at each crankshaft position sensor.

Good luck, Mike!!

ICM may be taken out and checked at Advance Autoparts for free. When my ICM went out I just could not start the car. I had misfire with old ICM and still have it with new one. This does not mean ICM cannot cause misfire though.

Thanks Adallak

[BodybyFisher]

Did some work today to diagnose this misfire

As I noted above cylinders 1 and 3 were misfiring. Today I added about a half a gallon of coolant, that probably explained my slight overheating. Note to self, USE a FLASHLIGHT when checking the coolant level. I added so much coolant I was surprised the low coolant level did not come on. I have a new coolant tank so I know the level sensor is good, but I must check the connection, maybe its off. Anyone know if the coolant level connector being off sets a code? My water pump body seal leaks under pressure, I need to seal that up

When I started the car, I had a very strong fuel odor from the exhaust, no coolant smell. #1 and #3 plugs smelled of fuel. They were not burned white, which I understand is evidence of coolant burning

My fuel pressure was 42 PSI at idle

I cleaned the coils supporting cylinders 1 and 3

Checked the coils with an ohm meter, the primaries (12V side) were 0.5 ohms and the secondaries were 5.9 K ohm

Pulled the #1 and #3 plugs, both lost their platinum pads, #3's anode was badly dished and probably .070, my engine calls for .050, #1 was about .060, no cracks or carbon tracking

I replaced both plugs and will replace the other 6 soon

I started the car and the engine was smooth with no MISFIRE... When it cools, Ill start it and see if the misfire returns, keeping my fingers crossed.

What I don't understand is why the MISFIRE would STOP at 111 degrees? Closed loop, leaner mixture?

[Cadillac Jim]

My guess is that at closed-loop, the near-perfect mixture would fire with the bad plugs. The open loop program is slightly rich which should also fire easily, but if it goes to closed loop and burns cleaner that might give the plugs a little boost in effectiveness.

In any case you have nailed the problem as the plugs.

My experience in buying plugs is that once in a while you get one that was dropped or banged on the end at some point. You can spot them as not having the correct gap. A box of 8 is less likely than a single to have this problem but I have seen it in the end plug of a boxed set too. For many years, whenever I see a new plug that has a low gap I throw it out. There's some likelihood that there is other damage to the plug and the hassle of changing them on the newer cars is more than enough for me to not go there anymore.

[BodybyFisher]

I was getting raw gas out of the exhaust when the engine was cool, is it possible that a rich mixture would not fire with a poor spark from bad plugs? (sort of like throwing a match in a bucket of gas?), the plugs have about 80K on them

[BodybyFisher]

Just went out and started the car, its raining, engine cold and no misfire. Bad plugs and wires. This was a learning experience, I never knew that a bad plug would misfire when the engine is cold and stop misfiring when the engine is warm.

I need to replace the other 6 plugs this week.

This could have been worse, I got to a point where I thought I might have a head gasket problem, I even saw vapor out of the exhaust at start up (probably normal till warmed up), had I known that I was in fact low in coolant, I would have been sold that I had a head gasket problem.

[Texas Jim]

Just went out and started the car, its raining, engine cold and no misfire. Bad plugs and wires. This was a learning experience, I never knew that a bad plug would misfire when the engine is cold and stop misfiring when the engine is warm.

Yep...think about it.

The cylinder is cold...the head and combustion chamber is cold...the fuel coming thru the fuel lines is cold and that makes vaporizing the fuel harder.

When the engine is cold, I would think that the droplets of fuel fuel in the combustion chamber are maybe a little larger and harder to ignite.

The 2 plugs that had lost the tips had almost a FORTY PERCENT TOO WIDE of a gap, thus increasing resistance to firing BIG TIME.

PLUS you are in open loop and therefore running a richer mixture which is harder to fire when cold.

Once the engine warms up and goes to closed loop, and the mixture goes leaner, it makes it all work a little better.

Glad to hear that you got it all sorted out.

[BodybyFisher]

Thanks Jim! You know so many things pointed to this being a head gasket problem, plugs last 100K, coolant loss, adjoining cylinder misfire, cold misfire that disappeared when warmed up (classic head gasket symptom), vapor from exhaust, and 126,000 miles

[Texas Jim]

Thanks Jim! You know so many things pointed to this being a head gasket problem, plugs last 100K, coolant loss, adjoining cylinder misfire, cold misfire that disappeared when warmed up (classic head gasket symptom), vapor from exhaust, and 126,000 miles

Yes, I agree that it did kinda point to that, but you have had so much STUFF happen to you in the last year or so, that I refused to believe that you had a HG problem.

If it had of been my car, I probably would have been thinking the same thing, but you just didn't deserve that problem on top of everything else.

The tips being gone from the plugs, could have been caused by slight damage to them before you put them in the car, like Jims_97_ETC said and you just didn't notice it.

It could also have been caused by some bad gas and some detonation that knocked the tips off.

I have had that happen before.

Anyway, I am glad that you got it fixed and it won't be very expensive.

[BodybyFisher]

Thanks Jim, the plugs were put in by the prior owner's mediocre shop.

The ignition wires were aftermarket junk, replacing them made a big difference. On the highway this car runs great still.

I was gearing up to do a timesert job, and to video tape the entire process, I had contacted my friend, an engine rebuilder to have him hot tank the case halfs and install the main seal, I had intended to do the case half seals also.

With all that HAS happened, I DID think this was a HG THANKS

[Cadillac Jim]

Just went out and started the car, its raining, engine cold and no misfire. Bad plugs and wires. This was a learning experience, I never knew that a bad plug would misfire when the engine is cold and stop misfiring when the engine is warm.

I need to replace the other 6 plugs this week.

This could have been worse, I got to a point where I thought I might have a head gasket problem, I even saw vapor out of the exhaust at start up (probably normal till warmed up), had I known that I was in fact low in coolant, I would have been sold that I had a head gasket problem.

When the engine is cold or running open loop, it runs rich (very rich when both cold and open loop), leaving carbon and perhaps a little gas, if it is missing, on the insulator. A damaged insulator will accumulate carbon in the scratches and crevices that won't burn off when the engine is warm and running open loop. Thus a substandard plug provides spark discharge paths across the insulator or perhaps deeper behind the center electrode where stagnant mixture may be too rich to fire. If the gap is wide, that makes the car even more likely to misfire.

When I was a kid with a car about the same age as I was and every expense competed with gas money and my social life, I often cleaned and gapped plugs. Eventually an old plug would begin to provide behavior just as you have been describing. But you could get them to go 20,000 miles that way instead of the usual 12,000 to 15,000 miles.

The prior owner's mechanic may have treated the plugs that way. Unless you are very careful with platinum plugs, you can ruin them just by checking the gap by scratching or peeling the platinum coating. Any plug checking, gapping, or cleaning that roughens or scratches the platinum or the porcelain makes the plug a 15,000 mile plug, not a 100,000 mile plug and thus not worth putting in a Northstar, particularly the back bank. Then, there is the opportunity to overtorque or undertorqe the plug.

[BodybyFisher]

Well I have been driving it all day and no misfire. What a relief, I had convinced myself, I had a HG issue

Oddly, having cleaned an gapped spark plugs since I was 6 (AC Delco 44, 45 and 45s among others), I have never seen a plug cause a cold misfire before, this is the first I have seen a temporary misfire. Nor have I seen it described here by anyone nor has anyone had the issue. This was a big learning experience for me

[Cadillac Jim]

Well, I have, because I'm so tight that my eyeballs squeak, and when I was a teenager I was poor as well, not having parents that saw fit to provide excessive allowance -- I sacked groceries for gas money. I would run spark plugs until the car would miss, balk at a hard launch or become hard starting.

[Texas Jim]

Well, I have, because I'm so tight that my eyeballs squeak, and when I was a teenager I was poor as well, not having parents that saw fit to provide excessive allowance -- I sacked groceries for gas money. I would run spark plugs until the car would miss, balk at a hard launch or become hard starting.

I don't know if I am QUITE that tight...but my brother (and others) say that I am.

I too was poor, and parents didn't have the money to give us an allowance.

I worked in a tire warehouse, loading and unloading 18 wheelers and stacking tires.

It was pretty hard work.

The warehouse was freezing in the winter and would bake you in the Texas summers.

I too did all my own maintenance and learned to MAKE DO on what I had to work with.

I have cleaned and regapped MANY a plug.

[BodybyFisher]

I mowed lawns for money before Americans decided they didnt want to do that job anymore

We were poor also, but my Dad and Mom drove to jobs for a living (they were entertainers), I was the pit crew, once they hit 15k miles and were not cleanable or gappable, they were pulled out and replaced. They only owned Cadillacs and my Dad drove hard and loved performance, so I kept the engine purring and running cool.

[Cadillac Jim]

My car was an old Chevrolet with the 216.5 cid stovebolt six with the cast-iron pistons and splash-lubricated rod and main bearings. I found that you could put 105 octane Golden Esso in it and advance the spark to something like 26 degrees BTDC (recommended was 5 degrees BTDC) and it would provide startling performance, improved gas mileage, cooler running, and a 75 mph highway cruising speed in 100-degree weather. Not everybody could drive, or even start, that car. I liked it that way because it would chirp the tires on the high gear shift, among other things. I had a buddy that occasionally drove his parent's new Ford with the 312 cid Interceptor V8 engine with a standard shift, an it was no match for that old Chevrolet.

I've been browsing some old racing history and I ran across an interesting note. Grass roots racing is still big in South America. The hot Ford engine is the Boss 302. The hot Chevrolet engine is the 250 cid OHV six-cylinder, which is sold in a special edition there to support the racing crowd. See http://en.wikipedia.org/wiki/Chevrolet_Opa...he_250-S_Engine; quote regarding a Nova-sized car with the 250-S engine and a Ford Maverick with a 302 cid V8: "In the racetracks, the accounting determinative factor for winning was pilots skill and pit organization on the track. The rivals walked side-by-side." Note English-as-a-second-language syntax; article probably written in Brazil. There are still a lot of racing parts for the Generation 3 inline six-cylinder engines; I found a bunch researching this post and looking for the Chevrolet Opala article. In fact, look at the RPM ranges for this selection of cams:

http://schneidercams.com/solidliftercamshaft-8.aspx

[Texas Jim]

Your StoveBolt 6 must have been a '53 or older.

Back in the old days, I had a '50 model, with a split manifold and twin straights on it.

It was a good running car.

From the link about the cams...

I bet that 250, with the cam and solid lifters, with open headers, running at 7,500 rpm, sure would sound nice.

[Cadillac Jim]

The 216.5 cid OHV 6 was sold for the 1937 through 1952 model years. The 1949 through 1953 model years used a 235.5 cid version of the same engine, cast iron pistons, splash lubrication and all, for more torque when Powerglide was ordered. In 1953 that same design was also used to provide a 235.5 cid engine with standard shift. From 1954 through 1962, the 235 cid engine was a aluminum piston engine with hydraulic lifters, and a 261 cid version was sold in Canadian Pontiacc and Chevrolet trucks. The Generation 3 OHV 6, which shared design and parts with the Chevrolet small block V8, replaced the "Blue Flame" OHV 6.

I think that the cams that are sold for operation through 7,000 RPM must be used on oval track cars. When you see RPMs over 6,000 on small block V8's you think drag race, but the 250 cid and 292 cid OHV 6's just aren't big enough to compete with the SBC V8's. However on an oval track, you can lay down the inline 6 by 45 degrees or more and get a lower CG than you can with any V8, particularly if you use an oil pan with a large kickout to the outboard side or a dry sump.

There is a company, Clifford Performance, that focuses on the market for domestic inline six-cylinder engines, including the Blue Flame engines.

Now, with all that support out there, why can't I find headers for my Northstar?

[Texas Jim]

The 216.5 cid OHV 6 was sold for the 1937 through 1952 model years. The 1949 through 1953 model years used a 235.5 cid version of the same engine, cast iron pistons, splash lubrication and all, for more torque when Powerglide was ordered. In 1953 that same design was also used to provide a 235.5 cid engine with standard shift. From 1954 through 1962, the 235 cid engine was a aluminum piston engine with hydraulic lifters, and a 261 cid version was sold in Canadian Pontiacc and Chevrolet trucks. The Generation 3 OHV 6, which shared design and parts with the Chevrolet small block V8, replaced the "Blue Flame" OHV 6.

I think that the cams that are sold for operation through 7,000 RPM must be used on oval track cars. When you see RPMs over 6,000 on small block V8's you think drag race, but the 250 cid and 292 cid OHV 6's just aren't big enough to compete with the SBC V8's. However on can oval track, you an lay down the inline 6 by 45 degrees or more and get a lower CG than you can with any V8, particularly if you use an oil pan with a large kickout to the outboard side or a dry sump.

There is a company, Clifford Performance, that focuses on the market for domestic inline six-cylinder engines, including the Blue Flame engines.

Now, with all that support out there, why can't I find headers for my Northstar?

Thanks for the good info on the old 6 cyl's.

I had known most of that (at one time) but had just about forgot all of it.

A buddy of mine...long time ago...had a 292 six, with a small cam and headers.

That thing would RUN.

If you find headers for our N*... "I WANT SOME."

That would really compliment my custom tune.