More strange problems now with SES light.

Okay, I like you guys and all but visiting here can only mean I have problems since I rarely have any advice. Now I have a 2001 Jimmy that has developed a strange problem just overnight. My wife drives the car, so keep that in mind. However when you start the car in the morning, or after any period of a few hours it knocks very badly. It's not like a spark knock either, more like lifter chatter and it runs rough and the SES light either comes on and stays or it flickers. After it warms up, the engine runs fine and no SES light. So, any ideas? The oil is full and clean. It's going to the shop on Friday but I thought some of you might have ideas if you'd seen or heard of this problem before. I was thinking maybe O2 sensor/s but I'm not sure about the knocking sounds.

HELLO,of course u need to scan.it sounds like a lifter,,,or does it sound deeper.computer could be retarding timing because of knock.so i'd be interested to no what code is stored.there are good additives if its a lifter Good Luck,let us no

Yeah, it sounds more like lifter chatter and is not deep, like a rod knock. Also, with every rod I've ever heard knocking, the knocking was irregular and sometimes squeaky. This is a really clean very regular knock that comes and goes. Not sure what it is but hopefully we'll find out Friday. I think there must be some kind of timing issue and that could be making the knocking worse with the timing retarded, etc. Someone said could be camshaft/crankshaft position sensor or they said it has been known to cause a similar problem.

Okay so here's what the shop said. They said the chatter is the lifters. They wouldn't say which ones only to say they all need replaced! I saw that coming :)

Anyway they also say I'm leaking anti-freeze around the intake so it needs to be replaced, at least that's what I thought he said and he said that that would be the time to replace the lifters as well. Total bill ---> $792 including the oil change they did today.

They changed the oil today and added some Lucas oil treatment to it and they said it quieted it down some. They are going to keep it over the weekend and see how it behaves Monday. Here is my question: Should I just go ahead and have them change out all the lifters or just wait for a few months and maybe a couple of oil changes later with heavier oil to see what happens? I don't believe the intake leak is that bad because I'm only having to add a little bit of coolant every couple of months or so. My thinking is that the last time the oil was changed we flushed it out with a solvent and some of this residue may have been left behind and contaminated the oil that was in it and made it too thin causing lower pressure. I just don't buy the fact that in the span of only 2 weeks I need ALL new lifters. I might do the job eventually in a few months but that's a big hit right now and I don't have the time to do it myself.

What do you all think?

HELLO Sky,as long as the coolant is an external leak you could wait.i dought that a few more oil changes is going to help.as far as lifters they should all
be replaced.i'd also be looking at the cam lobes.if it is a lifter & is just causing the tapping then puting off the repair for awhile wont hurt.
GOOD LUCK!!!

I have a tahoe that did the same thing. The lifters would chatter like crazy until it was warmed up. I know this is different motors and vehicles, but I used a quart of resolone and within a week it went away. From what I have heard if you get carbon build up it will cause this. It wouldn't hurt to give it a try it only cost about $4.

Since the intake manifold gasket is leaking anyway I'm going to go ahead and let the shop do all the work. I need to try to get another 60-70K + miles out of this vehicle (already have 134K) if I can and doing all this work myself would kill a couple of weekends at least for me, not to mention all the vehicle down time. Thanks for all the advice.

Since the intake manifold gasket is leaking anyway I'm going to go ahead and let the shop do all the work. I need to try to get another 60-70K + miles out of this vehicle (already have 134K) if I can and doing all this work myself would kill a couple of weekends at least for me, not to mention all the vehicle down time. Thanks for all the advice.

Remember
Gm has a class action law suit against them that may help out on the repair.

http://www.girardgibbs.com/news.asp

http://www.dexcoolsettlement.com/

http://blogs.cars.com/kickingtires/2008/03/gm-pays-out-for.html