C4m4roJoe

Hello everyone, I'm new here and figured I'd let the experts hadle this. I've done 2 weeks research and can't find anyine with the same problem.

Cold engine: it will hard start (2-5 sec) then stumble awake. Also when accelerating, it wants to go but its poor (feels as if every couple of secs I would increase throttle even though I accelerate steadily.
hot engine: it starts fairley quickly but when it does, it stumbles over itself like i mentioned before. Acceleration is just fine slow or fast
Also cold or hot, after it cranks, it doesnt idle up like its supposed to, it starts low then goes up (after a sec or 2) then idles down like its supposed to.
Now for the fun: this happens only on a wam engine. Ill go to work, let the car sit for 45min-1hr Ill go to start it (stumbles alive) then idles really rough, shaking the whole car. (1) ill either try to drive away and it will miss and shake you forward and backward BUT after like a minute it will go away and run fine. (2) i wont drive it but ill hold the throtle steady until it goes away. (3) I will just let it idle rough to see what it does and it eventually dies out and wont crank until cold (it will try for a few seconds but feels rough like running off 3 cyl).
Also if i go to the store (5-10min) itll start and run fine. So it only does it if it sits long enough to get a little cool but not at all cold
Also if i start it up cold it will idle all day just fine.
One more thing, my battery voltage gauge drops sometimes at red lights just at the top of all those little lines but will go back up as soon as i take off

C4m4roJoe

Mind you, im no gear head but i can turn a wrench lol i have no fancy scanners or anything like that, so please feel free to ask questions, tell me to do things, whatever i dont care...id rather talk to you guys and it be a $20 fix than take it to the shop.
Thanks for your time guys!

DelSoto

On a 20 year old car, there are rarely any easy $20 fixes. I'll be honest with you, I could not make it all the way through your post. One question, how long has it been since you have done a tuneup on the car? Without a scanner, you are asking the impossible as far as diagnosis. Do you have a laptop? With a cheap cable and free scan software, you can scan it for trouble codes. The software and more info here -> https://www.camaroz28.com/forums/lt1...bs-srs-874325/

Injuneer

As DelSoto points out, a scanner is essential to diagnosing these cars. GaryDoug has written software (Scan9495) that is far superior to anything out there. It will scan the PCM, ABS and SRS systems for codes. And, even better, it can record a data log of all the critical sensors and PCM parameters as you start and drive the car. There are a few of us who can do a detailed review of that data.

Second critical piece of equipment is a fuel pressure test gauge. It needs a long hose, so you can tape it to the windshield and check the fuel pressure with the engine under load. This is a $35-40 item.

The value of doing this can be seen in your first problem, which appears to be extended (2-5 sec) cranking time. That can be caused by the fuel system losing pressure rapidly after the pump primes for 2 seconds and shuts off. Or is could be due to a faulty coolant temp sensor, causing the PCM to set the wrong cold start A/F ratio because it has bad temp info.

You also need to provide additional details about your car - is it auto or manual transmission - affects the PCM idle speed settings - which affect whether the alternator is turning at sufficient RPM to keep the battery charged. Has the engine been modified in any way - programming, intake and exhaust upgrades, cam, under drive pulleys for the serpentine belt (another contributor to low alternator capacity at low engine RPM), or is it totally stock? Does the vehicle still have a cat, EGR, AIR and EVAP systems?

As DelSoto asked, miles play a critical part in the analysis - has the Optispark distributor ever been changed? If so, what brand. Heat soak can affect the fuel pump, the ignition control module (ICM) and the optical cam position sensor in the Opti. Have the O2 sensors ever been replaced?

C4m4roJoe

Okay sorry for the lack of data.
The engine has just over 102k miles, automatic trans, an afternarket exhaust, and a cold air intake, thats all i know as far as modifications.
I was going to do a tune up but these problems happened and i dont have enough money to do both.
I bought the car in april and since then, ive replaced the waterpump and the thermostat. Also i had a coolant hose bust on the wp so i just cut the end and slipped it back on.
I think the fuel pressure is fine. When the car is running good, it will go high in the rmps around 5k 5.5k maybe 6k

Injuneer

With limited funds, diagnosis BEFORE starting to play "parts replacement roulette" will probably save you money. The Scan9495 download is free. A cable from ALDL Cables or Red Devil River is about $50 I think.

I would pull a couple spark plugs to check the condition (free), and open the hood in the dark, and look for arcing on the plug wires and around the coil/ICM (free). If you have a multi-meter, you can check the accuracy of the coolant temp sensor (free):

Courtesy of Shoebox

4th Gen LT1 F-body Tech Articles

There are also test methods for things like the ICM and the critical cam position signals form the Opti (free):

4th Gen LT1 F-body Tech Articles

It is often possible to borrow a fuel pressure test gauge form an auto parts store for a refundable deposit (= free).

In order to insure the info we need to help you is included in every post, you might want to read this:

https://www.camaroz28.com/forums/lt1...nature-879835/

If you are working from a phone, often the "signature" feature will not work. You are putting yourself at a disadvantage, and will need to type the signature info in each post.

C4m4roJoe

I had a new thing tonight after work.
It was hard to start (5sec) didnt start, tried again (5sec) didnt start, tried again (2sec) started up then died after 2sec then tried again (2sec) started up and stayed running...
Its late so i will review all this in the morning and do what i can that you told me.
I did run it at night to see if there were sparks, seems to be good. Thank you