New motor, won't idle won't start right...
 

I put my new motor in over the weekend, and it will not start correctly and when it does turn over it shuts off right away. We did get it going by holding the throttle open a little and it ran great but as soon as you let off and the rpm's drop it shuts off again. I'm running 38 psi fuel pressure on 30# injectors along with a 70mm throttle body and everything else in my signature. Anyone have any ideas? I ajusted the timing all over the place and it changed how it ran but didn't fix anything. I don't know if it is getting too much fuel or if it is the computer. It should be getting plently of spark with my msd 6al, blaster coil, and distubter. Any suggestions would be great. I have a couple little things i might try but other than that i don't know.

Brian

Did you fool with the TPS at all? Is it hooked and adjusted properly?

Re: New motor, won't idle won't start right...
 

do you have a vacuam line unhooked, or one hooked up where isn't not supost to?



-Josh, aka the tireburner

Well for one you are flooding the hell outta your engine.

Your sig says 5.0 conversion so I am assuming it is a 5.0.

Your heads are huge for a 302 and the injectors are way too big especially at 38 psi.

If your engine is a 302 then you went to the extreme, I hope you plan on turning 8500 rpms to make power.:eek:

Turn the fuel pressure down to about 30 psi and see if that helps.

Yeah, a vacume leak could also cause it, but I still think somethings up with the TPS.

I adjusted the TPS and checked my vaccum lines. It started alot better but you still need to be the throttle and it seemed to run alright but the headers got BRIGHT red and i shut it off and i have to do is let off the gas and it will just drop in rpms and shut off. I'm going to try lowering the fuel pressure and i think i might have to drill like a 1/4 hole in the throttle body.

Thanks for your help
Brian

Did all the headers glow or just a couple. Sounds like you still have a vacuum leak somewhere. If just a couple glow then you have a leak where the upper to lower intake mate. If they all glow you are lean. Does it only glow when you sit the motor at 1800-2400 rpms?
As goes for the F/P keep it at around the 36-38 w/o a vacuum signal. That should drop it to around the 30-34 psi w/ vacuum, depending on how much vacuum you really do have.

What is your vacuum reading when it idles at what ever rpm you can idle it?

What's your timing at with the spout connector disconnected?

What did you set the tps sensor to at Approx. 800-900 rpms?

Do you have the EGR valve and Tap/Tad sensors hooked up?

Did you check compression?

What's the compression readings?

Did you do a Leak-down test?

Are you running on all 8 cylinders? Spark,etc

Your combo really doesn't sound all that off. It's just sounds like a high rpm engine. Should pull hard from the 3500-6500+ range with the right valve train parts. Is it still a 302-306 or is it bigger?
PM if you want to keep this hush-hush for some reason.
Car should wake up on a little shot.;)
MY.02's

Oh yea,....get rid of that spacer. It's for more bottom end grunt. It hurts your top end. Your GT-40 intake don't like to go past the 5800-6000 rpm range as it is.
If you could,.. swap out for another intake set-up. Will make more power with an Edelbrock RPM II or a Twisted Wedge intake, Holley Sytem Max intake, etc, etc, etc.
May-be I missed it, but is this a 5-speed car and how much does it weigh?
If not, what auto trans does it have and what rated stall speed and size?

If the headers are glowing you're running rich. The glowing is them heating up from unburnt fuel burning in the headers.


-Josh, aka the tireburner

Actually we are both right, now that I think about it. You can get the headers to glow lean or when you are overly rich.

The car weighs about 3200 pounds and yes it is a 5-speed. I am going to try all your suggestions tonight and do all of those test and post the results tomorrow.

There is no doubt in my mind that his car is running pig rich. I bet he is running the spacer for the same reason I am running one. For clearance.

Pull your plugs and I bet they are black as hell.

yes i am running the spacer for clearance and yes the plugs were black as hell.

When I fired up my current engine for the very first time, it was so rich it was literly washing the cylinders down!!!!:eek: :eek:
I was getting blue and black smoke pouring out the exhust. Shit I went almost threw 1 gallon of gas in 20 mins. I thought I trashed the rings and bearings. But luckly I didn't. After changing the air bleeds and Idle feed restrictors it was all good!:D
By the way.....my headers never glowed.

Another thing is when you start to run bigger cams, the plugs will always look fouled out when ran at idle for a period of time, untill you put a load on the engine. I am not sure how big "Z-303" cam is, (don't really care about the a,b,c cams anymore) but it's another consideration to think about when looking at the plugs when it has never been driven yet. (I assume). When looking at the plugs, you need to check them after you put a load on them....not at idle. We are not at the "stock relm" of tune-up any more. These are modified street/strip cars, and pure race cars. Two completly different animals. Another reason why the plugs might be black is, no compression due to various reasons, leaky injector, etc. Lets all back up some and do some basic tests first. Then we can all see how off I am. :D ;)

I ran a 306 w/ 10.3 to 1 compression, t/w heads and a 232/242 @.050 cam and a modified, ported shortened Cobra intake w/ 30 pound injectors and it ran lean! I also had the Car-Tech Stage II fuel system on the car running 42 psi with a Speed Brain computer. (what a piece of shit computer:mad: ) I had to alter the stock fuel curve (add) to get it to run right. Another reason why I decided to just say the hell with it all and go carb.to save some $$;) :D