# 99 Escalade misfire code, multiple cylinders



## Midwest (Oct 16, 2004)

I'm going to try to keep this short, but am looking for some help. 

I have gone through extensive repairs trying to locate a misfire code on my personal ride. Plugs, wire, cap, rotor etc. Even new intake gastkets. Throughout all the repairs, the symptoms have gotten better, but still shows up. I thought i had it licked with the last repair of the intake gaskets. But, on the way to florida this weekend, the code popped up again. It was at the end of a long hill, when it had required the extra power for a long period. It happened twice, once it lit up the SES light and once again, caused the SES to flash as it was happening again. I would appreciate any help you could provide, I am at a loss on this one.


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## haejinjoe (Nov 13, 2003)

Midwest;561123 said:


> I'm going to try to keep this short, but am looking for some help.
> 
> I have gone through extensive repairs trying to locate a misfire code on my personal ride. Plugs, wire, cap, rotor etc. Even new intake gastkets. Throughout all the repairs, the symptoms have gotten better, but still shows up. I thought i had it licked with the last repair of the intake gaskets. But, on the way to florida this weekend, the code popped up again. It was at the end of a long hill, when it had required the extra power for a long period. It happened twice, once it lit up the SES light and once again, caused the SES to flash as it was happening again. I would appreciate any help you could provide, I am at a loss on this one.


Sounds like a P0300 code? Unfortunately with that code, there are any number of possibilities. A couple that come to mind are low fuel pressure, or a possible faulty dist. rotor if it has been in for a while and the replacement wasn't a premium quality part.
ussmileyflag


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## B&B (Nov 4, 2006)

haejinjoe;561141 said:


> Sounds like a P0300 code? Unfortunately with that code, there are any number of possibilities. A couple that come to mind are low fuel pressure, or a possible faulty dist. rotor if it has been in for a while and the replacement wasn't a premium quality part.
> ussmileyflag


Excellent comments Joe.

Are you ONLY getting the random multiple code Midwest? Haven't had any individual cyl misfire codes...ever?

Like Joe mentioned already, there's many things that can cause a multiple cyl code (you have a P0300 correct?). Primary and secondary ignition problems, fuel (or lack of), a sticking EGR valve, dirty MAF, weak/dirty injectors...or a vacuum leak.

You already covered many of the common and failure prone items for the earlier Vortec motors. But one thing that causes many issues on these engine is using an aftermarket cap & rotor. They've created more misfire problems on these engines that I even care to recall. It's important to use nothing but genuine GM caps as well as rotors on these things specifically, or else your asking for problems.

And just an additional tip if you pull the cap & rotor off again; If you look in the base of the distributor body you should see a small vent hole with a screen in it. The vent is to allow any moisture build up inside the dist (from normal hot & cold cycles) to escape in order to prevent corrosion of the cap terminals. The problem is that the screen plugs up and restricts the hole...causing the caps to go bad prematurely and can also create a no start condition. GM recommends knocking the screen out of the hole with a screwdriver. Doing this can double the life span of these caps...which aren't the cheapest ones out there.


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## Midwest (Oct 16, 2004)

Thanks for your help so far guys. Let me get more detailed and maybe you could give me the next step.

Yes, that is correct, it is the P300 code. At first, it was a couple of specific cylinders. this code had a TSB that led me to clean and tighten the grounding connection on the back of the passenger side cylinder head, oh boy what fun.:angry: That didn't fix it. So then, I went ahead and replaced all the spark plugs with titanium, that didn't help. The code did change by now and it included multiple cylinders. This is what led me finding the intake leak. I replaced the intake gaskets with FEL-PRO, new cap, rotor, wires--all OEM. All seemed well after that. Drove it for a week with no code being displayed. Even brought back some horsepower and was running better than it had since I purchased it. I could actually pass someone again.

Driving from Missouri down to Florida on Saturday, it came back. It was at the end of a major 1/2 mile hill, where I was maintaining the speed of about 70. right before the end of the hill, the codes pops up again. Runs great, just as it did before, just the code has been stored. 

any idea's on what my next stepprsport would need to be?


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## B&B (Nov 4, 2006)

When it first started with specific cylinders...which cyls was it?

Ideally you would want to get a data scanner on this truck and watch the misfire counts for each individual cyl....

Ever have a fuel pressure gage on it?

Ever replace the fuel filter? Might seem like an elementary question but they get over looked often.

Sounds like you have the ignition side of it covered, and with your additional info I'm going to say it's a fuel delivery (or lack of) problem. Still many possibilities on that side as well though. Clean the MAF, clean the throttle body, and run a couple cans of Sea Foam through it (good stuff, available at most parts stores)....and change the fuel filter if it's been a while. All cheap and easy to do.


Only other well know issue with these engines is under a long pull where your working the engine hard the exhaust valves will fail to seal due to a slight warpage of the valve itself under high demand/high heat conditions...which your symptoms do fall under. There was a TSB on them for the '96-'98 model years...GM knew the exhaust valves had problems coping with the heat....they replaced a ton of them when these trucks were still under warranty.


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## Midwest (Oct 16, 2004)

I definatley appreciate your tips on this BB. I have not thought of the fuel delivery system. It does make sense now, being that it happens at the the extreme stress level on the vehicle. It's as thought the fuel pressure has a steady drop and will cause the misfire as the engine requires a constant supply. Before when this was happening more often. It would happen every time I attempted to floor it to pass someone, or it downshifted as it was climbing a hill. The fuel filter is no problem, probably needs one anyway. I have a fuel pressure gauge and will check once I get back home, what should the optimum fuel pressure be on this 99 5.7? I'll also clean the MAF. throttle body was cleaned when I had it off the truck. Hopefully this will fix the issue, I'd hate to break the engine down again.xysport


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## B&B (Nov 4, 2006)

You want to see no less than 55 psi under any conditions...except maybe idle (may drop down to around 50psi at idle). These CPI equipped trucks need 45 psi just to start and run at all. 

And definitely clean the MAF since you haven't done it yet...and especially so if it has an oil/gauze style aftermarket air filter installed in it like a K&N for example.


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## MickiRig1 (Dec 5, 2003)

Like B&B said run a few cans of Sea Foam through the gas tank on the trip back. It can work like magic !


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## Midwest (Oct 16, 2004)

That's definately what i'll do. It's the least I can accomplish from down here. I hate not having any tools with me. Thanks for the Idea, I didn't even think of that for the trip back.payup


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## MickiRig1 (Dec 5, 2003)

I do it everytime we take the family minivan on trips. I got a code for low flow on it's EGR. A can of Sea Foam and 100 miles it worked again!
I got in the habit of writing the date I replaced the disp cap in marker on it. I found the Ford / GM caps seem to last about 2 years. Might try looking at the engine running at night in the dark. Look for little blue sparks as you gently move wires around with a wood stick. I have found new ignition wires that were leaking current to ground. You would see little blue sparks where they touched.


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## Midwest (Oct 16, 2004)

Hey fella's made it back just fine. Ran 2 cans of sea foam through 2 tanks of gas on the way back. Full throttle several times, averaged 80mph and sometimes over 90. No misfires were detected:yow!: As a matter of fact, it had better response than ever before now. Running 80 mph, hit the gas and you could actually feel the power boost. Checked the fuel pressure a few minutes ago and is running a steady 57 lbswesport. Only dropped 2 lbs on road test. i'll be replacing the fuel filter tomorrow, I'm sure it needs it. i think overall, all the advice and maintenance i have done over the past 2 weeks has improved the driveability 200% Awesome, and as usual, your help has been greatly appreciated. 

One more question if you don't mind. I noticed on my trip that my headlights needed aligned. Easy enough right,,,,, wrong. i have adjusted the 2 t15 torx adjustment screws and nothing happens, any idea's??


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## B&B (Nov 4, 2006)

Thats why I use and recommend the Seafoam...it's one of the few fuel system treatment products on the market that actually works. Based on your descriptions it sounds like the truck is suffering from nothing more than dirty injectors. Run at least another can or two of the Seafoam through it. And an additional can at every oil change or so is a good idea as well. 

The only product I've found that works as good as, or better than the Seafoam is GM's own "Top Engine Cleaner". Unfortunately it's designed to be run through the engine with an injector cleaning machine, can't just pour it into the tank on the late model trucks.

Your headlight dilemma isn't uncommon on the older vehicles Mid. Be gentle with the Torx driver as the adjusters strip easily.They're just a little plastic/metal deal and freeze up/corrode over time, making adjustment nearly impossible. Best thing is to try pulling the head lights out and use a little penetrating oil on the adjusters to loosen them up and then go from there.


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## Midwest (Oct 16, 2004)

Thanks for your assistance once again BB. 

I am more than confident that i have stripped the darn adjusters. they spin freely both ways with no adjustment. Do they sell the plastic inserts, or will I need an entire new headlight assembly? Also, what are the two 10mm bolts coming from the headlights, through the core support? I had spun those many times as well and nothing happened??


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## B&B (Nov 4, 2006)

Midwest;561977 said:


> Thanks for your assistance once again BB.
> 
> I am more than confident that i have stripped the darn adjusters. they spin freely both ways with no adjustment. Do they sell the plastic inserts, or will I need an entire new headlight assembly? Also, what are the two 10mm bolts coming from the headlights, through the core support? I had spun those many times as well and nothing happened??


Yep sounds like they're already stripped Mid. IIRC the adjusters were once available separately but I believe they now only come with the plastic mounting assembly that the head light itself attaches to (part thats fastened to the core support). Have to check with a dealer to see for sure.

Can't recall from memory on the 10mm bolt. _I think _it holds part of the head light mounting bracket in place. Definitely has nothing to do with any adjustments. You can post a pic to jostle my memory. :crying:


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## Midwest (Oct 16, 2004)

Well, I replaced the fuel filter today. Checked the fuel pressure once again just to see if it was improved by the filter change. I could not believe it, I read the dam gauge wrong, its 51lbs:crying:. I'm assuming that i need a new fuel pump,, correct? Will an aftermarket pump work, or should I go with oem?


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## B&B (Nov 4, 2006)

Midwest;562087 said:


> Well, I replaced the fuel filter today. Checked the fuel pressure once again just to see if it was improved by the filter change. I could not believe it, I read the dam gauge wrong, its 51lbs:crying:. I'm assuming that i need a new fuel pump,, correct? Will an aftermarket pump work, or should I go with oem?


When is it reading 51 psi? If only at idle, it's ok like I mentioned before.


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## Midwest (Oct 16, 2004)

Yes, it was at idle, didn't even think about that. I was so pissed off when i realized i read the gauge wrong, I didn't even think about it. So I'll assume that it is ok for now and wait to see if the code pops up again. thanks for your quick reply, I would have purchased a new pump tomorrow and spent alot of money and time for no good reason. I appreciate your help once again BB.


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## MickiRig1 (Dec 5, 2003)

B&B saves another one !


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