99 cavalier z24 2.4 won't start

i'm stumped:banghead: i don't know much about cars but this is where i'm at. driving home my car felt gutless. i got it to my driveway and it just felt like it was only running on one or two plugs. not making alot of noise or anything just like it was dying. i got up the next morning prepared to try anything. i started by changing the plugs. no change. then i tried the coil pack. now it won't even start at all. will turn over but won't fire. then i changed the cam sensor and the crank sensor. still the same turns over but won't fire up. when i pull the plugs they are wet and smell of gas so fuel is deffinitely getting there. i dry them off. blow out the holes to clear excessive gas and try again thinking it might be flooded. nope same thing and the plugs are wet again. tried changing the pcm. still the same. i'm told if the timing jumped it would have run very rough or just died. it didn't do this, it just got gutless and now won't start. there are no leaks at all. starter and battery are good. don't know what else i can add. what about this antitheft system? how does it work? could it be faulty? code says:P0240: Catalyst System Efficiency Below Threshold. but it also says that code isn't for my car. please help. transit is on strike here and my kids are out of school till i fix this.

my mechanic has deemed my car's motor as scrap.:banghead:

why does tech fell engine is scrap??whats the miles??are you sure plugs are wired correctly?did some 1 do a compression test??what type of spark plugs were installed??

he feels the timing has skipped for some reason and it would be cheaper to replace the motor then to do the timing. also could be the crank is too worn. plugs are new as of sunday as well as the computer, coil, cam sensor, crank sensor. did compression test on 3 and 4. 3 was 100 4 was 150.i don't know what that means thou. plugs are those titanium ones with 4 prongs on them. can't think of the name of them. haven't slept much this week. lol. thanks for the quick response. any ideas for me and him would help.

he just called me back. the timing is fine nothing wrong with it. which leaves the crankshaft is toast. (so i'm told). he's searching for another motor as we speak.

How does he know your crankshaft is toast? You said it ran with a miss until you changed the plugs ans coils now it doesn't run at all. Something doesn't sound right. I doubt it's your crankshaft did you check to see if your getting spark?

i'd like to see what the compression is on #1/2 see if a little oil in cyl #3 brings it up
whats the mileage??

it didn't have a miss. it just felt gutless. still seemed to run smooth just no power. he already has my motor out and is starting to put another one in. i'm going to bring the motor home and rebuild it myself to see for sure what was wrong with it. i think the problem is that i am the 7th owner of the car and i know the guy i bought it off of. he drove it like he stole it all the time. the motor only has 170 000km on it. i babied it, kept up on the maintenance and tried to make it last. i put 3 coils in it in the last 10 months and 3 sets of plugs always the most expensive ones(because a mechanic told me that was the problem)it always seemed to fix it thou. from what i here it is supposed to be a powerful motor for the size. i don't think it was ever real powerful but it seemed to run smooth whenerver i changed the coil. gets real pricey doing that all the time. i'll ask if he can do a compression on 1 and 2 before i bring it home. the motor is going in my shed and i'll do my first rebuild for when this other motor coughs on me. there is only 170 000km's on my motor. i've seen them for sale with over 300 000km's and still running great. i'm scepticle of the descision to change the motor too but i'm no mechanic. i just need my car back on the road.

i'm scepticle of the descision to change the motor too but i'm no mechanic. i just need my car back on the road.

I agree with you 100% on that. I was going to respond yesterday, but I lost my connection to the internet, possibly due to a blizzard going through. Anyway, here's what I wrote, sorry it's too late to help. "Luckily", my free internet connection is so bad that I copy every post before I hit Submit :)


Call the guy now and tell him not to touch your car again. Before you finish reading this, I'm not kidding, do it now. Do it nicely, just in case something was miscommunicated here, but it sounds like he's a moron or he's trying to cheat you.

Now, there is no way a bad crankshaft would cause this. The rod bearings spin sometimes, typically from inadequate oil pressure. The engine still runs OK, but makes one hell of a noise. It would be the same deal for the main bearings or crank. You'd ask about the noise before you notice a lack of power. If there was a very bad noise, now call him back and tell him you found the money to replace the engine (or whatever you used as the excuse).

On these engines, it's very common for the hose to the MAP sensor to deteriorate. This could cause your problem, the PCM sees full load on the engine (no vacuum=full load). As a result, it gives more fuel than it should. Small cracks for a long time could make it run slightly rich and take out the cat. The code for cat inefficiency is P0420, BTW, probably why you didn't see a -240 for your car :) As the cracks grow, it runs very rich and you lose power. You change the plugs to the 4-electrode ones which aren't very good for these engines in general, but make the problem worse here because you have 4 weak sparks instead of one strong spark which doesn't let it start after replacing them.

Check that hose and put the good "old fashioned" plugs back in.

When you get the engine back, plasti-gauge the bearings, I'd bet money that they're good. I had one of these engines in a Grand Am that almost made it to 200k miles and ran great until I spun a rod bearing driving way too fast for way too long with the A/C cranked up on a scorching hot summer day. Engine was just fine other than that, if it had an oil pressure gauge instead of a "dummy light", I'd probably still be driving it.

Which reminds me, if the engine is in need of rebuilding, use a performance oil pump.

Also, there's a good chance that the reason the coil packs kept going out is the spark plugs, if you were using the +4 design then as well. They're just an advertising gimmic, they have absolutely no performance benefits with a stock ignition system. Maybe with a high power aftermarket system, but stock systems just don't have the amperage capacity to make 4 sparks, which means they're flowing too many amps and they short out. Just buy the AC Delcos... either platinum or irridium.

thanks so much for all the advice. yes i wish it was a day sooner but on the other lighter side look how much i just learned from you and you can't put a price on knowledge. now when i get my motor home and in the shed instead of ripping it apart i will have a better idea of where to start. i will probably rip it right apart anyway at some point and rebuild it totally. you never know what the replacement engine will be like coming from a scrapyard. you talked about leaking hoses causing it... that makes total sense, even to me. i knew there where leaks i assumed they were vacumm. with the hood up and running i could give it gas and it would hesitate(this is when i would here the leaks) then it would rev up. i got oil changes every three months and it always looked the way it was when it went in. except this time. it was black. i'm told thats because there is fuel in the oil. i regret pissing away so much money over leaking lines but what can i do but learn for the future. thanks again.

and the award goes to............ J-Ri!!!! yeah!!!!! map sensor had electric tape covering a leak. tha cad was clogged almost solid. after installing a new(to me) motor and it still not running i told him what you said about the map and cad, since the map was changed with the motor that only left the cad. he changed that and away i go. probably the most expensive cad change ever for a cavalier. F#$K!!! thanks for saving my car. felt good to drive the kids to school today after forcing them to take a week off. next time it breaks down might almost be worth it to tow it right to you. lol.