What's up guys, I'm trying to get a fix on my 1990 cavalier z24 that is not starting, and occasionally backfiring through the intake. I have replaced the timing chain in an attempt to fix this, but the car will still not fire up. I could start throwing money at different sensors in an attempt to see if one isn't working, but that seems like something that can be avoided. Anyways, the car will crank, and sound like it wants to fire (you can hear and feel ignition in the cylinders), and then slow the cranking for a revolution or two, and repeat itself over again. I'm kind of out of ideas here ATM. Let me know if yall have any suggestions. Thanks!

I am pretty tired after a 12hr day so bare with me.DId the car before the timing chain install run? Next if it is backfiring that would indicate your timing is OFF.Granted I will say to time the car it has to run even if you got the markings correct(and verify with a timing light).The 1 item I would suggest replacing is your Crank position sensor.Reason I say this is because it also controls the timing on the car cranking up!IIf the car stopped cranking up prior to the timing components it (may) be your CPS could be bad or have a bad connection.Done as I realllllly tired.I also will bring this to some individuals far more fluent with your year model who could give some solid advice to save time and $$$$.R

The car did not run before the timing chain replacement, and also backfired before the timing chain replacement. I have heard about the cps sensor, but the owner before me put a brand new one in there before selling to me (I know, as he gave me the old one as an extra), which makes me think that's not the problem. I just had a thought that maybe not all the injectors are firing, which might explain why on some revolutions it sounds like it will start, while on others it sounds kind of underpowered and dry (the speed of cranking slows).

How many miles are on on the car?I would suggest doing a compression check on each cylinder.And on a alternate thought it could be a burnt valve (but that is iffy).I will pm another member who has a good knowledge of these year models and let him chime in.

There's 200k miles on the engine, and it is quite possible that there is low compression. Ill have to check that out as soon as possible.

What do the plugs look like, are they wet or look black? Are the ignition wires on correctly? Do you have fuel at the fuel rail and are the injectors pulsing? These are all things that you should check.

Ignition wires are on correctly, and the plugs looked fine when I took them off to do the timing belt chain. I'll go ahead and check them again. There is fuel at the rail, as i just replaced my fuel pump. I heard I can test for fuel injector pulse, but I'm not really sure how. I also heard you have to get some kind of test light. Is it possible to do this test with just a multi meter?

You can check the ohm value at each injector.The actual specs are 11.8-12.6 ohms .If any of the injectors do not fall into this value you will need to replace said injector.Oh duh yes using a multimeter.

Hey guys. It's been awhile since I've been on here last...I got really lazy with my car for a few months. Anyways, I was dumb and didn't do a compression test, but tore down the engine to the block to test the heads, and if the valves were leaking. I have two leaking intake valves (which I pretty sure got bent when I was messing with the cam and crank when I replaced the timing chain....rookie mistake), is that enough to make the car backfire through the intake like this and not start. Also...the spark plugs are alright, just some carbon deposit.

I'd check the CPS first, even though it is a rather new one. New doesn't mean much anymore due to all the chinese junk on the market these days. My 88 did the same thing your's is doing. I changed the CPS and it started right up and ran fine. Still runs fine today, 6 years later, 195,xxx miles. Maybe you did damage a valve, but that would be pretty hard to do, by hand. Now if you used the starter to turn the crank over while the chain was off, then damage is possible. If you turned it by hand, I doubt you hurt anything unless you forced it to turn with a big breaker bar or something.

Alright, I'll make sure just to order a new CPS. I ordered a bunch of gaskets and such along with the valves so I can build the top end of the engine back up. I figured that by fixing these valves that I might not get a backfire anymore.