I have a s10 that I've put a 383 stroker into than ran just fine with the carb it had. I've since upgraded to tpi and have had a hell of a time getting things to work.

My motor is pretty built, not the bigest or badest but should put out about 400+ hp. It maintained about 16 lbs of vac when it was carbed. I bought a complete tpi intake and a custom pcm and wireing harness for it. The custom harness and pcm eliminates the emissions and vats. Also, it is a speed density (map) system. I bought refurbished 24lb lt1 injectors for it to replace the "good" stock 350 injectors it came with. Only 1 out of 8 actually injected. I also bought a new map sensor for it. The tps is set to .54 and at wot it reads a little over 5v. I was told it should be around 4v? I don't have any vac leaks that I am aware of. The egr is blocked off with a plate and I am using a 1 wire o2 sensor. The wiring harness and pcm are built for the older large hei efi distributor which is new.

My problem is that it takes a lot of cranking and maybe some help with starter fluid to get it to fire up and then it will run very poorly and stall easily. Also you have to hold the throttle open a little for it to even start and stay running. I've tried all kinds of timing settings to get it to start more easily but with out much luck. I have a new walbro 255 fuel pump and when the pump primes it goes up to about 45-48 psi and when the pump stops priming it falls to about 42 and stays there. And if I get it to start and run for any length of time it starts to backfire after a little while and then stall.

The prom is custom burned to work with the cr and other specs of my motor and I'm pretty certain that the pcm is working right. If I unplug the timing wire I get error 42 and if I unplug the tps I get error 21 so I think its working correctly. And it also shows 12 (no errors) when everything is hooked up.

I'm almost at my wits end but I've got one more guess. I don't think the iac is working. I've removed it and turned the key to on and the plunger doesn't ever move. It did move once after playing with it but that was the only time. I seem to remember that it should move out every time you turn the key to the on position so it can test itself.

Any ideas? I tried to cover all the bases and if you need more info just let me know.

 

well if you hold the throttle open a bit maybe to 2500 does it run better?

 

Yes, but it starts out running better but it will start poping and backfiring and then stall about a minute later.

 

Are you sure the PROM was properly configured with the cold start tables? Sounds like it is not getting enough fuel to idle.

 

Sounds like a tuning issue to me as well.

Only other thing I can think of right now is the spark plugs...sounds like they get fouled and thats whats causing the backfireing/stalling.

I say run it till it stalls and pull a plug ASAP and see what it looks like. If its wet/soaked its a tuning prob.,if not I'd look into timing/vacuum leaks.


Whered you buy the intake? Did you replace any of the many gaskets the TPI uses? Did you ever clean the IAC valve? Its located on the pass. side of the throttle body and takes a 1 1/8" wrench I believe it is and often gets gummed up w/ crap.

Hope this helps man

 

it sounds like it may be a vacuum leak

and just to be sure, i think u mean 16 inches of vacuum, 16 lbs is not possible (max 14.7)
and your tps should never read more than 5volts because only 5 volts are applied to it to begin with, your voltmeter may be slightly off


i would definately check for vacuum leaks first, what is your idle rpm?
does the motor ever stall at part throttle?
if there are no vacuum leaks, then i would say yea, probably the iac

 

I told the person who was doing the prom that I wasn't going to use the cold start injector. How would I check if it is programed for the injector or not?

I bought the intake through ebay but I bought all new gaskets for it. If it is a vac leak then I can't hear/find it. That was one of the first things I thought of.

I did mean 16 inches, sorry. I'll get a new volt reader to see if it's acurate and check the tps again. The truck will not idle or start without pressing the gas or putting something to hold the throttle open so I don't know the idle speed. I have cold start injector, I'll try hooking it back up to see if it improves things.

Thanks for all the help so far.

 

If the PROM programming has omitted the cold start injector, then putting it back in will cause your car to run extremely rich if the injector fires. You will need to ask who burned the PROM for you.

I was also thinking vacuum leak might be another source of the problem.

 

The harness and pcm are custom and the harness has no cold start provision so I would hope the guy who made it removed the cold start injector instructions. Also, I believe I have teh 1227730 pcm so it shouldn't even have the cold start injector instructions.