Severe Engine Miss

[lennyrebel]

Help .Today on the way to work my o6 H2 showed service engine light. OnStar said drive slowly to dealer la la la. I have about 5000 miles on truck and this is second occurence. First time truck was about a week old when said same thing. Onstar says it is a severe engine miss. Last time they said bad plug, but it shouldn't be fouling plugs at 5k miles. This is not a 2 stroke outboard. Any ideas or thoughts? I'm on my way to dealer tomorrow. Thanks Lennyrebel

[GLBLWARMR]

There are a lot of things that it could be. Could be a bad plug or plug wire. One of the plug wires might not be on tight. The electronics that control the firing could be screwed. Let us know once it is fixed.

[H2 Bill]

What's the verdict?

[lennyrebel]

Okay--tech jargon 9472 OBD2 CODE PO300 [9999] missfire happens at 65 kil/hour [35mph] most collected on cyls 5+7 Replaced 5&7 sparkplugs and clear DTC. So thats the verdict, first time it was one sparkplug at about 500 miles. This time 9400 kms about 5500 miles. No other info from dealer, anyone else have any strange occurences like this? Regards The Rebel

[lennyrebel]

I'm Wondering -are they platinum plugs in the 6 litre engine? I've never experienced this problem with my Avalanche that I drove 4 years. Service engine light never came on. Yukon before that I drove 9 years and only saw light twice. Any advice? Regards The Rebel

[ssgharkness020147]

Does the H2 have a EDIS system?

[f5fstop]

That many spark plugs in 5500 miles, makes me think something else is wrong. If it happens again, recommend to the dealer to a compression check on all affected cylnders for a start.

ssgharkness020147
What's EDIS? It does have an electronic ignition system if that is what you are asking.

[ssgharkness020147]

EDIS stands for Electronic Distributorless Ignition System. It can also be called a direct coil system.

[f5fstop]

EDIS stands for Electronic Distributorless Ignition System. It can also be called a direct coil system.

Wow, we have not called it that for years in house....:D

[lennyrebel]

That many spark plugs in 5500 miles, makes me think something else is wrong. If it happens again, recommend to the dealer to a compression check on all affected cylnders for a start.

ssgharkness020147
What's EDIS? It does have an electronic ignition system if that is what you are asking.
A friend just told me samething. He said he ws getting missfire one cylinder, the compression test showed one cylinder 30 pounds low--discovered broken top ring. Separate coil for each plug with crankpulley inductive pickup. regards The Rebel.

[ssgharkness020147]

You should use it more often, especially around people that know very little about cars. People will think that you are really really smart. :jump:

Either way your right. The term is like sooo 90's:D



Wow, we have not called it that for years in house....:D

[f5fstop]

A friend just told me samething. He said he ws getting missfire one cylinder, the compression test showed one cylinder 30 pounds low--discovered broken top ring. Separate coil for each plug with crankpulley inductive pickup. regards The Rebel.


If the same cylinder's plugs are being replaced, then I would suspect a mechanical problem. If different plugs are being replaced, I would suspect an ignition problem. So, if it happens again, make sure to compare the cylinders where the problem is.

[f5fstop]

You should use it more often, especially around people that know very little about cars. People will think that you are really really smart. :jump:

Either way your right. The term is like sooo 90's:D

GM still make an engine that has a distributor.:beerchug:

[lennyrebel]

If the same cylinder's plugs are being replaced, then I would suspect a mechanical problem. If different plugs are being replaced, I would suspect an ignition problem. So, if it happens again, make sure to compare the cylinders where the problem is.
Did happen again. Last Saturday as a matter of fact. Did compression test myself all cylinders at 210 Psi. Dealer told me first time it was #5 plug second time #5 + #7. Third time I wiped a little soot off plugs ,5+7 blew them out and service engine light went out and miss disappeared. Dealer service manager returned my call on Monday considering cylinder leak down test but are presently as stumped as I am. Regards The Rebel

[f5fstop]

Might be the problem, but no guarantees...
All I could find on the subject....

Subject: P0300 Cylinder 7 Misfire Due To Fuel System Contamination - keywords CEL contaminated DTC engine gas L59 L76 L92 LC9 LMG LR4 LM7 LY2 LY5 LY6 LQ4 LQ9 miss P0302 P0307 P0308 SES tank water #PIP3055A - (09/26/2006)
Models: 2001-2007 Cadillac Escalade
1999-2007 Chevrolet Avalanche, Express, Silverado, Suburban, and Tahoe
1999-2007 GMC Savana, Sierra, Yukon
2003-2007 Hummer H2
--------------------------------------------------------------------------------
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A dealer may encounter a customer concern of a SES light on and a engine misfire. The misfires will accumulate mostly on the number 7 cylinder. A possible cause could be fuel contamination. If present, the contaminated fuel will collect around the #7 fuel injector due to the fuel rail configuration in these vehicles. Fuel contamination can also cause random misfires to occur on other cylinders.

Recommendation/Instructions:
If the published misfire diagnostic does not isolate the concern, the following suggestions may help if the misfire is related to fuel contamination:

Complete the SI repair procedure for Fuel Rail Assembly Replacement. When the fuel feed pipes are removed, cap off the fuel rail inlet so the contents can be inspected for contamination. Drain the fuel rail into a clean approved container, and inspect the fuel.
If contamination is found, follow the current SI Fuel System Cleaning procedure.
Once the fuel system is cleaned, refill the fuel system with new gasoline.
Advise the customer that they should only use gasoline from a high quality, high volume filling station.
If this is a 99 - 00 Chevrolet Silverado or GMC Sierra, also review 00-06-04-024. This bulletin relates to an updated EVAP vent valve to prevent water from being drawn in through the EVAP Vent Valve, which may lead to repeat fuel contamination.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

[lotus4s]

In other words, quit buying that cheap gas at the dot-head store...:jump:

[KenP]

In other words, quit buying that cheap gas at the dot-head store...:jump:Bwahahahaha!!!!

NO CITGO!!!!!

[GLBLWARMR]

In other words, quit buying that cheap gas at the dot-head store...:jump:

You mean 7-11 gas isn't good. Sh*t Habib is going to be upset once I quit filling up there.:giggling:

[f5fstop]

You mean 7-11 gas isn't good. Sh*t Habib is going to be upset once I quit filling up there.:giggling:

But, 7-11 did drop Citgo as the supplier a few months ago.:clapping:

[timgco]

Maybe someone dropped shXt in his gas tank?

:popcorn:

[KenP]

But, 7-11 did drop Citgo as the supplier a few months ago.:clapping:That's the only reason I fill up there. Plus they're always busy so you know the gas is "fresh".

There's a Citgo up the street from us that has some crazy hours. Just last night they were closed before 6pm. Last week they were closed in the middle of the afternnon. I swear, the local boycott is having an effect on them.:beerchug:

[ROADCAPT]

Lockin fuel door #1 mod.:clapping:

[lennyrebel]

Thanks f5fstop for the excellent researched info. Have printed it out . I have a locking cap so nothing was put in tank thatway. The gas station I used was extremely busy, maybe he was cutting gas with stove oil and water. I've switched to Sunoco and through a can of slick 50 Fuel conditioner in tank. So far so good. Merry Christmas ,The REBEL:beerchug:

[lennyrebel]

F5fstop, info you posted I believe is correct solution. After I cleaned 5&7 Plugs did comp. test switched gas stations and added jug of injector cleaner problem is gone. Mileage decreased about .5 mpg, 12 to 11.5. I found that strange until my son The Heavy Truck mechanic explained it saying map and 02 sensor recognize rich mixture because of missfire so auto. lean out mixture. So in summary I believe fuel rail cofiguration causes 5 & 7 to fail first with any contamination in fuel. Regards The Rebel:excited: