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either in the mornings or when it(81 280zx) has sat for a while, it is hard to start. when i crank it up it will jump to 750-1000 rpm but then if u give it gas it(like trying to go from a stop) dies. but if i give it gas slowly and work it up to 3000 rpm and hold it there for about 30-45 seconds, it is good to go. the whole process takes only about 2 mins but it can be annoying and embrassing. when i am working it up to the 3000 mark it pops or backfires through the airbox. i was told that this could be the cold start valve. does it need to be replaced or could it be timin or what. also this morning i noticed a little water or something on the ground just below the tail pipe(i have a turndown tip) and occasionally there is some smoke but not always.

kinda off subject but this is especially embrassing when your out on a date with a new girl and she laughs when you have to put up with all the popping and stuff like that. :(

any insight on this problem would be great. is this a serious problem.
 

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Could be lots of things. Generally if it is backfiring through the intake that means it is ... help me out mechanics... i think it means it is running rich but I am not sure. Could be anything related to a tuneup, but the way it runs when it is cold is indicative of some kind of vacuum leak. THe cold start valve could be a problem (if it is stuckopen) but I don't think so. Try disconnecting that and see if that helps. It is only supposed to kick in when it is below -20 orsomething.

What I would do:

1. Check for a vacuum leak. ALl of the rubber around the intake must be in excellent shape. The tube to the PCV vavle must be in good shape.

2. Check all fo the electrical connections. I just replaced all of my plugs and the differenceis incredible.

3. standard tuneup stuff.

it does not sound good. these EFI systems are finicky but yo must just keep at them. Good luck.
 

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There is likely nothing wrong with the cold start valve (injector). It only functions when it is cold enough, and ONLY DURING the cranking of the engine. It only gets power when the key is in the 'START' position, and at no other time. The backfiring out of the air box is due to a LEAN condition. As john cross said check the air duct from afm to throttle body, and each and every air/ vacuum line under the hood. No cracks, checks, or leaks are allowed. Also can search archives under 'lean' for more checks. But basically no air should be allowed to enter the engine from anywhere except through the Air Flow Meter......period.
 
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