99swatburb

So i am having a problem with my 99 suburban 5.7L 4wd. It misfires intermittently instead of under load. It almost seems like a mass air flow sensor. What will happen is sometimes when I start it the engine will buck or knock and then start but the idle is rough between the 1000-2000 rpm mark. Sometimes it drives fine then will start to misfire and not accelerate and when i give it gas it sputters and almost sounds like a back fire in one of the cats. Then if I park it the idle will drop and almost stall and then go back to regular idle and do this over and over. I have about 198 thousand miles on it. Havent had a tune up and it is due for one and i plan on putting a new fuel filter on it. The fuel pump sounds fine but I dont have a pressure guage to test it. Just recently put some fuel system cleaner in it now I am having this problem. But I have heard that other people have done the tune up and it then leads them to the fuel pump or filter cause the tune up didnt solve the problem. Also my sender must be bad as well because ever since I have owned the car the fuel guage needle has a really fast vibrating almost movement all the time. It reads correctly just flutters. So my question is does anybody think it is 1.bad mass airflow sensor 2.bad cat 3.bad fuel filter 4.coil 5.fuel pump 6.injectors. The threads i have read never said what the problem was and if it was fixed. From what i understand the bacfire in the cat is caused by a lean condition which would lead me to fuel delivery. Any help would be great thanks guys
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sheldon 97suburban

iv heard of this problem before i think its a spark timing problem, check you distributor rotor for play, if there is play you timing is constantly changing and the distributor gear needs replaced

99swatburb

Thanks sheldon, i will check that for play. And from what i understand you can just replace the gear and not the whole unit. Im about to go put a new fuel filter on it and check the fuel pressure make sure thats ok too.

sheldon 97suburban

yes the just the gear is around $30 bucks no need to replace the hole unit. let me know how the fuel filter gos

20redfrogs

I had issues similar issues with my 99 Yukon. After changing plugs, wires, fuel filter, and air filter i found that I still had an intermittent spark issue. Come to find out it ended up being clogged catalytic converters. Now it runs like a top again!

Chevy Pit

I had kind of the same issue after I changed my intake manifold gasket. Started it ran fine pushed the gas it died. everytime I slowed down it died RPM's would go down everytime I slowed down. I figured it out after a few hours. Throttle body was dirty and gummy like no other. Cleaned it and the Tahoe ran like new. Check that and clean it could be a cheap fix.

99swatburb

well i havent done anything except for seafoam the intake and put some in the gas and now it is running fine. unfortunatley i have already purchased the magnaflow cats for this thing. a whopping 350 bucks so i might as well put em on. i was underneath and i smacked the cats and heard the guts rattle around so i think it is due anyways. proly gonna do the fuel filter when i do the cats. i will keep you guys posted. the fuel filter is real easy seeing as how it is on the frame rail. my buddy has a 2000 and his filter is tucked up under the tranny feel sorry for him. but thanks for the help guys

99swatburb

Well it has been a long road but the burb is fixed. The seafoam worked for about 3 days and then it was back to the misfire. So i bought the magnaflow direct fit cats and had them installed by midas which took about 5 days and then I get it back with an oil leak from the timing chain cover. Great huh? So even after the cats it still is running like crap so I decide to do a tune up which consisted of: cap, rotor, plugs, wires, cam sensor, and crank sensor. When I was done it fired right up and ran great but then there was the issue of the oil leak. I could have done the timing chain cover myself but was worried if I did it that it would end up leaking again or I would break more stuff then I fixed so I left that to the pros at the GM dealership. Yeah I would pay more but it is worth it to have it done right. So GM had it for about a week. So they started with the timing chain cover and once they got into they said that the chain had play so they replaced the chain and gears. Then they tell me my oil cooler lines are leaking, ok replace those too. Then I asked them to put a new fuel filter on it well guess what, the gas lines were leaking. So they put a new return line and replaced the feed line from the filter forward. I had them sand and lube the driveshaft and yoke to get rid of the clunk. Then they tell me the oil filter adapter gasket was leaking well damn might as well fix it all. So this is the total cost.
Cats and installation $550
Tune up I did myself $318
Alll the work GM did $1719
Total $2587 I could have took that money and traded my burb in on a new one but hey I love my truck.