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Chevy 1999 tahoe 5.7 vortec

car hesitates engine light reads random misfire at auto zone. took to dealer said 10 degres out of time on his diagnostic machine
replaced just about every thing on engine dealer said he couldnt fix because he couldnt adjust distibutor , i told him on my car that you
couldnt adjust timing from distibutor who`s right

I expect there’s a way to correct a 10 degree timing problem, but twisting the distributor – that’s the way I do it on my early 90’s Corolla and my early 70’s Ford truck – that may not be the way to do it on your car. The Chevy dealer says this is impossible to fix? Really?

I’m assuming the engine routine maintenance is up to spec. I guess the first place I’d look is the crankshaft sensor if you have one. After that there are timing components probably on the inside of the distributor that may be on the fritz. The ignition coils would be next. Finally, the ECM could be failing.

thanks

Has the individual who has been working on your truck ever removed the distributor? I suppose if they had, then installed it incorrectly, that it could be ten degrees off, but I think it would actually end up farther off than that. Your truck has a fixed distributor. Once it’s in, you cannot turn it to adjust the timing like in the old days, but you can still index it incorrectly when dropping it into the engine. It wouldn’t hurt to verify this, but I don’t think this is your problem. The incorrect timing reading your mechanic is seeing has me thinking you may need a camshaft position sensor. It’s a simple Hall effect switch located in your distributor, and when it starts to go bad, it can send faulty information to the ECM regarding your ignition timing and cause the issues you are having. Given the clues, the camshaft position sensor would be my first suspect.

Also, does your engine have central port fuel injection? I think it does. If so, has your mechanic pulled the upper plenum to verify there is not a leak in one or more of the poppets (the “legs” of the “spider” unit, as it is often called)? This is a common issue and can cause a random misfire. If you find an issue there, keep in mind those poppets can be replaced individually much cheaper than replacing the entire unit.

when you buy a new distributor is the camshaft position sensor come with it

It does, but you can save a lot of money by replacing just the sensor. It’s the part of the distributor with the three pin harness plugged into it. The price difference between the two is over a hundred bucks, so unless there is a problem with the distributor itself, it’s worth it to replace just the sensor. They are equally challenging to replace.

thanks for your input. one more question, whats a ecm??

the ecm is the “engine control modual” or the black box

Mark 9207, Thanks for all the information you have given me, I appreciate it. This is what I replaced on my 1999 Chevy Tahoe and still the engine light comes on and says Random Missfire. Any other suggestions would be greatly appreciated. By the way, I had a rebuilt engine put in, about 1 1/2 years ago and it ran fine for about 1 year and 3 months.This is what i’ve done to it :
changed wires - spark plugs - mass air flow sensor - new distributor cap rotor and cam shaft position sensor - new 02 sensor bank 1 - catalic converter right side - changed fuel injector { spider} - changed fuel filter -
car runs but it still hesitates at different speeds and sometimes after stopping and accelerating. I’m out of answers and ready to give up, and so is my mechanic!!!

if anyone could help any suggestions would be great

This should be simple to fix once we know what the problem is. The P0300 Random Misfire code isn’t much help, you already know the engine is misfiring, right? You’ve had your mechanic look at it, take it back to him and have him tell you which cylinder is misfiring and under what operating conditions, and have him give you long term and short term fuel trims. All this data is easily read through a scan tool, and it will give us a direction to head towards solving your problems.

Your dealer is not entirely correct. You can adjust the cam retard. To adjust it, the engine is held at about 1000rpm, the distributor hold down bolt is loosened and you turn the distributor in the appropriate direction until cam retard read 0, plus or minus 2 degrees.
FYI: I’ve seen GM vehicles with the cam retard off by 10 degrees that were running fine and weren’t throwing DTCs. So that may or may not be your problem. But it should be the first step.
There’s a chance some of your valves are binding (not rotating) in the guides.
Have your Chevrolet dealer specifically look up document id 1539013.
It’s also called PIP3081. It’s not a technical service bulletin, so you won’t find it looking for TSBs.
One more thing, although the code reads P0300 random misfire, the misfiring may be more prevalent on specific cylinders. In other words, the misfiring may be isolated to one bank.
Have the mechanic look at the PIDs, not just DTCs.
Ask one of the more experienced and computer-savvy guys work on your truck. Some guys are better at finding information than others.

thank you everyone for your input on my 1999 tahoe 5.7 vortec.
finally fixed, it was a hairline crack in my distributor only 2 months old,
never taught to check again since it was so new. will no better next time

zlots

Thanks for the update.
May we assume that the crack wasn’t visible until the distributor was removed?
Were you able to get that 2 month old distributor warrantied?