I had a blown motor earlier this year and got a brand new crate 305 and it has new spark plugs and very occasionally itll have a pretty bad misfire where it has low power for a few seconds. Motor barely has about 600 miles on it and right before I took out my break in fluid it misfired badly and wouldn't drive, I could start the motor but it would just die immediately. I had it towed and the next day it started just fine and ran without a problem, triple a couldn't find a problem and i wanna make sure i dont have this problem again in the future and need another tow

 

Gonna need some details.

What are you using for fuel and ignition systems? Also, what have you already checked?

 

You didn't say what year Camaro or Firebird we're talking about here , but since even the last third gen F bodies are fast approaching 30 years old , you can 100% bet that the future will hold more mechanical work to be done .

PS , expect to take flak over the "brand new crate 305" thing , the 305 hate runs strong here with the 350 being the replacement of choice .....

 

Yeah it's going to be very hard to troubleshoot without knowing if this is a carb or fuel injection, and year, etc.

Ignition modules often cause such problems.....

GD

 

its a 1985 Camaro z28 with tuned port injection.

 

I'm prepared for a crapton more work on it and I wouldve done a 350 but my mechanic that had my car wouldn't do anything except "put back what was in it" and I didnt really know what I was doing or have the space or tools to do a motor swap

 

Doesn't sound like your problem has anything to do with "brand new", "crate", or "305", as such. All of that is just a list of red herrings.

A typical n00b mistake (or maybe I should call it instead, "learning experience" ) is to have a car with driveability problems like stalling, hesitation, hard starting, misfiring, and what have you; and buying a "brand new" "crate" motor, honestly and seriously thinking that getting the old tired "motor" out of there will "renew" it; and then putting the same old wore-out tired used-up fuel system, cooling system, ignition system, electrical system, etc. back on; and then wondering why there are STILL driveability or other such problems. Keeping in mind that NONE of that other peripheral stuff is involved in a "brand new" "crate" motor. When you buy one of those, you get the castings and major internal mechanical parts, which you might have needed in reality, or might not; but then you bolt back on all that other stuff, which may or may not be in anything resembling "good" condition.

Not saying that that's necessarily what happened here, but...

Personally I think you wasted your money, in more ways than one, on the "brand new" "crate" 305. But that's over and done with, no sense in beating a dead and buried horse's grave marker. What needs to happen now is, troubleshoot all that stuff that got re-used when this "brand new" "crate" 305 got dropped in.

Which would include carb or fuel injectors; fuel pump; electrical system such as fuel pump relay; sensors such as MAF MAP TPS etc.; ignition system such as distributor (the small-cap HEI is notorious IN PARTICULAR for wearing out in ways where the car will still "run" at least sometimes, but is NEVER right); and so on.

To that point, what make / year / model of car is it; what engine type did / does it have (carb, TBI, TPI); what else has been done to the car besides "brand new" "crate" 305; what you've tried toward fixing it, besides having it towed and triple A and "mechanic"; and so forth.

I would also add, if it's a 3rd gen Camaro or Firebird, it is an ANTIQUE. The youngest of them are now about 28 years old. It's not AT ALL like you're going to be able to PAY somebody else to keep it running for you, unless you're made of WAAAAYYYY more money than I am. The people on this forum are virtually all HOBBYISTS, for good reason; we all work on our own cars OURSELVES, and only pay other people to do things we don't have tools or space or time or other resources to be able to do ourselves. We exchange knowledge here, and you're welcome to that, but those other things draw a line around what any one of us can do ourselves. There are VERY FEW of us, if any, who have such pristine specimens of these cars that they are like new: that is, where everything about them is in such near-perfect condition like a car that dealerships will still touch, and only very occasionally, some ONE THING breaks, which we can then realistically pay to have fixed. Antique cars don't work that way.

Tell us more about the car and your history with it (and what you know of it before you got it), and maybe we can point you in the right next direction.

 

I see you answered some of those questions while I was rambling.

The 85 TPI is different from all the others; it has BY FAR the crudest electronics of all the TPI setups. They changed the computer in 86 to one that is far less slow, though still barely recognizable as a "computer" by modern standards. It uses a MAF, which is often the cause of all manner of strange problems. It has the large-cap HEI which is less prone to failure types that allow it to still "work" at least some of the time but to fail intermittently; the large-cap type tends to just... die; rather than half-die or sometimes-die.

A great place to start would be to simply LOOK AT everything; make sure all the wires and hoses are hooked up where they belong, nothing is visibly broken or disconnected, etc. It's all too easy during a motor swap to accidentally leave something hanging.

Next would be yerbasic tune-up. Maybe some of this got done during the motor swap, but who knows how much or how little. That would include spark plugs, plug wires, distributor cap & rotor. That's all pretty easy stuff you can, and should, do yourself, even if you don't have a garage. It only takes about 3 tools, all of which will fit in your pocket. We're not talking about a fully-equipped "shop".

Next thing would be the fuel system. Who knows how old and/or cruddified the injectors, fuel filter, etc. are. There are acoupla board sponsors, and other entities as well, that can supply you with a full set of cleaned, tested, flow-matched, verified injectors, for LESS THAN the price of ONE new one at the parts store. Avoid "miracle in a bottle" kind of stuff; if the car sat up for any length of time at any time in its past especially, NONE of that will do any good whatsoever. All it's good for is normal contaminant accumulation in a RUNNING vehicle; NOT, cleaning out the tar substance that old gas turns into.

Another possibility is the MAF. You can try unplugging it and see if the car runs better. It'll light the Check Engine light, but without that, the control system quits trying to make sense out of a possibly garbled signal, and instead uses other sources of information about the world around it to make decisions, and can often do MUCH better that way than it can with a defective MAF. Obviously if unplugging it makes the car run better, there's something wrong with it.

 

thanks for all that I'll start working on it when I can, the car was running fine with the old motor but then I blew it and needed a rebuild or new motor and I couldn't find anyone to rebuild it for less than I couldve spent buying an entire second 3rd gen camaro until I found the "new" motor for like 2k and it sat for about 4 months give or take while I tracked down a new motor and got the lazy a$$ mechanic to install it. Most of the other actual work I've done to the car myself including the pretty much entirely new cooling system and replacing my ignition lock cylinder which is my task for today. I have alot of basic tools and when I dont have a tool I need someone else in my household has it or if I don't wanna waste time looking since no one is organized in the slightest I have three auto parts stores within a 5 minute drive to go get what I need at. I seem to have trouble finding certain parts for this car (my radiator is zip tied in since I dont have brackets for it and couldn't find any)

 

As a real profession auto tech, I'm often ashamed by the things that so called professional "mechanics" do. The laziness and half-assed-ness of reinstalling a 305 in a car that could just as easily taken a 350 with a simple injector change. I would bet that the 35 year old injectors weren't sent in for cleaning and testing either. Of the two most common issues on that year, the injectors are one thing that never goes back in without first being cleaned and dynamic tested on an injector sonic cleaner/test bench. The other most common failure Sofakingdom already touched on. The MAF on the 85 is a one year only disaster with no good replacement option.

First off, check all wiring and connections for whatever the "mechanic" left loose or disconnected. Pay close attention to the grounds that connect to the back of the cyl heads. How long did the car sit before the new motor was in and running? I would strongly consider pulling the injectors and sending them to someplace like Southbay for cleaning and testing. They are hard to test on the car aside from resistance. You would need a labscope with a low current probe to monitor the current waveform of the injectors as a whole and then monitor the voltage waveform of each injector to try and catch the failure that is probably heat related. One test is to measure resistance of each injector cold and again hot. They should be around 12-14 ohms cold and 14-16 ohms hot. Any that lose resistance with heat have failing windings and should be replaced. Plus, electric testing doesn't tell you if the nozzles are producing a good spray pattern. Only the test bench can do that.

The MAF sensor and circuits on this old system are a headache. The sensor should have 12v from the relay, a good ground and a good signal path to the ECM. Alot of times I find broken connector latches and poor terminal contact at the sensor. If the sensor is faulty, good luck finding a good replacement. I think a reman is available. They are often skewed high or low and wildly inconsistent. Be wary of intermittent faults that can be caused by heat related failures or poor connections. Wiggle testing is one way to find poor connections or failing wires/harnesses. Sometimes you just have to hook up test equipment and drive the car looking for what changes when the failure occurs.

If you love the car, and the thirdgen F body is quite worthy of love, consider swapping in the electronics from a 90 or 91 with speed density and much better ECM. Get to know your car and get used to working on it yourself. If you were close by me, I could take car of it for you but the cost of my labor on a project like that would break you. So much better to learn the work and do it yourself. And don't be a hack either. Anything worth doing is worth doing right.