PO300 at cold start
#1
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O2 Formula with 75k was throwing a PO300 code on cold start, once it warmed up it ran perfect. No other codes and plugs-wires all check ok.
I found ALL the intake bolts were loose, easy fix!
I can't believe how loose they were, I turned them ALOT to get them tight again, I'LL bet over two turns just to get to 75inlbs. I'm not going any higher even though it calls for 89inlbs. I don't need any broken bolts to fish out.
I found ALL the intake bolts were loose, easy fix!
I can't believe how loose they were, I turned them ALOT to get them tight again, I'LL bet over two turns just to get to 75inlbs. I'm not going any higher even though it calls for 89inlbs. I don't need any broken bolts to fish out.
Last edited by O2Form; 12-04-2010 at 09:18 PM.
#2
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Wow same thing happened to me today, po300 code with cold start. It was the coldest day of the winter here so far, about 18F last night. Started it this morning, SES light was on, actually not just on but BLINKING, ran like crap. Took it to get scanned over lunch at autozone, showed po300 code, they cleared it though, and now it's running fine. Well, I've only driven it about 3 miles since they cleared it, but so far the light has stayed off. And it's running fine too. I'm assuming it's because the car is warmed up now and the outside air temp is a few degrees warmer now that it's noontime. I just hope this doesn't become a regular problem. I'll check my intake bolts since that's the tip you gave. Just to be sure I know what you're talking about, they are the actual bolts holding the intake manifold on?
#3
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Well I guess I found the intake bolts, the ones that are pointed straight down. I think there were 10 of them. They were a bit loose, I tightened them up..not sure if that was causing the problem, but I read some other threads about the po300 code and someone said that a common thing that causes it (well I guess there are many things) is it could be a cracked vacuum line. They said the one coming out the right side of the throttle body is a common one to crack, I looked at mine and sure enough it was cracked too. I duck taped it as a temporary fix...it the problem doesn't return I'll assume it was either the cracked vacuum hose or the intake bolts as the culprit.
Anyone want to add anything here?
Anyone want to add anything here?
#4
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Well I guess I found the intake bolts, the ones that are pointed straight down. I think there were 10 of them. They were a bit loose, I tightened them up..not sure if that was causing the problem, but I read some other threads about the po300 code and someone said that a common thing that causes it (well I guess there are many things) is it could be a cracked vacuum line. They said the one coming out the right side of the throttle body is a common one to crack, I looked at mine and sure enough it was cracked too. I duck taped it as a temporary fix...it the problem doesn't return I'll assume it was either the cracked vacuum hose or the intake bolts as the culprit.
Anyone want to add anything here?
Anyone want to add anything here?
Most cold start rough running issues are from a dirty MAF.....
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#5
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You should use a inch lb torque wrench on those intake bolts. They are very hard to judge how tight they are. I tightened them without the torque wrench then later when I had time I checked them with the torque wrench, I wasn't any where close to what they should have been.
#6
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I just know some people said they had cracks or holes at the bottom of the elbow in that piece and it had been apparently causing some problems.
I guess I'll look up how to clean the MAF if I have any more issues.
thanks
#7
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You should use a inch lb torque wrench on those intake bolts. They are very hard to judge how tight they are. I tightened them without the torque wrench then later when I had time I checked them with the torque wrench, I wasn't any where close to what they should have been.
I tried not to get them TOO tight..
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#8
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thanks, I just figured that out after reading the other threads again..
I just know some people said they had cracks or holes at the bottom of the elbow in that piece and it had been apparently causing some problems.
I guess I'll look up how to clean the MAF if I have any more issues.
thanks
I just know some people said they had cracks or holes at the bottom of the elbow in that piece and it had been apparently causing some problems.
I guess I'll look up how to clean the MAF if I have any more issues.
thanks
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#9
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Remember this is INCH LBS not FOOT LBS, huge difference!
Last edited by O2Form; 12-06-2010 at 06:08 PM.
#10
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I have seen builders do this when tightening head bolts too.
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#13
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My 99ta had 130k on it and I purposely pulled the MAF apart to check it and it looked brand new, no dirt on the sensors at all......I can't see what could make it dirty unless oil was getting on it from a oil type filter. The dry air type sheds nothing.
#14
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#15
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I used a magnifying glass and couldn't see anything, I cleaned it anyways with some alcohol but i didn't feel any difference in performance. Now this was a completely stock 99, maybe a modded engine dumps more blowby into the intake and I suspect thats where some of the dirt could come from when the engine is off and everything heat soaks.