Ok guys,before you tell me to search,I have,numorous times. I think Im just looking for other ideas.
Here goes.
Ive got a 350 tbi tranplanted were a 2.8 used to live. I did this swap last year with the only mods being an open element air filter and a set of headers.Last year it ran great.
This year it was changed a little.
416 heads with .043 gaskets(engine guy says its around 10.5:1)
very mild porting(mostly just gasket match and clean up casting flash)
same headers
same air filter
Ultimate tbi mods
4bbl dual plane with an adapter
1.6 full roller rockers
iac around 20 it idle
O2 switching good
map is 30 kpa at idle
tps is .68v

Heres the problem. When the engine is cold,its a beast. But the more it warms up the worse the stumble/sometimes backfire gets when the pedal throttle is stabbed. the only way I have been able to drive it is by advancing the timing off the charts and being gentle with the gas so i dont Knock or ping to much.With timing set anywhere from 0 to 8 btdc its horrible. Any ideas will be appreciated.
trevor

 

well id imagine ud benefit from chip tuning

 

Update
While at my wits end tonight I decided to try to look for odd things. Odd being my brand new cts. I unplugged it and it ran perfect (well at least as good as last year).Strange though,my scanner did not show anything weird. Could I get a good temp reading and still have a bad cts,or is it showing such a cold temp to the ecm and fattening up the mix that its running right.I dont think my mods would have that much of an effect especially since when I rebuilt my tbi,I found a broken and rotted regulator spring,and it ran fine even with that last year.Ever see a cts do that before?

 

This may be a stupid question, but did you swap to a V-8 ecm and chip??? You didn't specify which ecm and prom you were running so that's the first place I would start.


A dead CTS will most deffinately cause all kinds of crazy problems, if you are scanning and it says the temp reading is good....it's good. It sounds like you have the wrong chip for the engine.

 

Sorry, all electronics were from the donor,1991 Suburban,747 ecm, stock chip.Realized its not the cts when I went to start it this morning. ran like crap.I plugged it back in till it warmed up, then unplugged for the rest of the ride to work. So, this is obviously a fuel problem.until I get a programmer to mess with,any ideas.Maybe a higher psi fpr? Different tbi? At the moment Im just plugged into an old cts just sitting ON the intake so that I dont get full rich all the time, This worked for the ride home, but I dont like doin it halfass.the fuel pressure is at 11.5 with no deflection.

 

Most deffinately keep the CTS hooked up, with it unhooked the ECM see's -46 degrees or somthing like that and you'll go full rich. As engine temperatures rise the mixture is leaned out, so by using a non-installed cts you're actually richening the mix.

You may have a dying O2 sensor, with the CTS reading cooler than actuall you inadvertantly keep the ECM from gonig into closed loop and the O2 is kept out of the equation. I say more than likely the tune just no longer matches up with your combo.

If you have a scanner then there is not any information a burner is going to give you that the scanner won't already tell you. I ASSume by "scanner" you mean a snap on type handheld unit. While these give you information they are hard to look at the big picture with. You need to look into WINALDL and get/make a cable and start logging with that. It has BLM tables that will help you visualize what areas your are lean and rich in. For the time being check and see what your BLM's are when the engine is acting up. If it's locked at 128 while the engine is obviously in distress then you are most likely in open loop...which your scanner should also tell you. Once in closed loop, what do your BLM's look like? This will tell you what the ECM thinks is going on with your fuel mix.

Hope that gets you moving in the right direction.

 

Timing set to 6* BTDC with the connector unplugged
Fuel pressure about 14 psi
Adjust the Minimum air screw on the TBI to give 5-10 IAC counts at a fully warmed up idle in park/neutral.

To adjust the IAC jumper A to B in the ALDL. Turn the key to the run position, but don't start the engine. Wait 30 seconds. Unplug the IAC. Unjumper the connector, start the car, then adjust the minimum air rate to give an idle of approximately 600 rpm. Shut-off the engine. Now reconnect the IAC. With these three items set correctly, the engine should run very well.

Keep in mind I am speaking from experience on a very similar engine that I ran in the Van with no tuning to the ECM. It ran decently and I experienced none of the driveability problems you are having.

My engine combo was a

.030" over L05 350
Ported 601 HO 305 heads
10.3:1 compression
Melling MTC1 RV camshaft (204/214 @ .050, .423/.446" lift, 112* LSA)
Edelbrock Performer intake
454 TBI unit
68# injectors @ 12 psi
Headers, 2 1/2" duals

Suprisingly it ran very well, even on the stock tune, although I now realize that it could have been much better.

 

Thanks guys, Friday night Im going to try them all.Also , my scanner is a snap on modis, so the only limiter is my ecm as far as info goes. FAst 355, would that bbc tbi flow more fuel at stock fp? Also, at this point,everything electrical has been replaced within the last 2 weeks( no old sensors or modules).Also,does anyone have a pick of a good spray pattern? I think mine is ok,but in our day and age i see more civics and camrys in my shop than tbi's.

 

Also, my modis scanner is showing tps volts but shows 0% throttle angle at any position,any ideas?