TBI stumbling/stalling

[maroman88]

my friend left his 92 camaro with me to look over and it has a stumble and sometimes stalls when at idle, usually only when in gear but i did get it to happen once when in park. its a 305 tbi auto with i think heads and a small cam.

i pulled the IAC out quickly last night and it looks clean, but thats as far as i got

[sweetbmxrider]

Any carbon crap on the tb blades? I'd use carb cleaner on them and the iac to start. Fresh gas in it?

[deadtrend1]

Check timing with the esc plug disconnected, give it a once over and make sure no vacuum lines are disconnected. Clean it like adam said. When was the last tuneup? Plugs wires fuel filter

[maroman88]

TB is clean... i sprayed it down completely anyway and in the IAC hole last nite... fresh premium gas, recent cap rotor plugs n wires. with my handheld plugged in everything looks fine, however when the stumbling does occur the IAC reads 0 steps

unknown on fuel filter, ill take a peek at that later and spray all the vaccum lines n see what i get

[maroman88]

vaccum lines all look good with the soapy water test. with TBI u can watch the fuel flow from the injectors to the throttle body and there is no less fuel flowing when it stumbles

[sweetbmxrider]

Cold, warm, hot, doesn't matter?

[maroman88]

doesnt matter, but not allways

[chrisfrom nj]

change the fuel filter if you still have a prob it can be the pump check the coil or the ign modual

[maroman88]

coil checks, swapped another in, TPS checks out good, wires are good, guna pull the cap and test the ignition module tmrw.

it seems to only do it after the car has run for more then a few minutes, never at start up or shortly after, and it doesnt matter if the car is cold or hot when started

AIR and EGR are gone from this car fyi

[sweetbmxrider]

That thing have o2's?

[BonzoHansen]

vaccum lines all look good with the soapy water test. with TBI u can watch the fuel flow from the injectors to the throttle body and there is no less fuel flowing when it stumbles

spray all around with carb cleaner. vac lines, base gasket, intake gasket, etc. listen for the idle to smooth out.

condition of plugs & wires? did you check static timing with a light? While the cap is off test the pickup coil as well. make sure the module has dialectic grease under it. make sure the connections are all good. I just got beat on that, cheap accel connectors loosened up when it got hot.

i forget does this thing have a MAF?

if all else fails what is the CTS reading?

[sweetbmxrider]

it seems to only do it after the car has run for more then a few minutes, never at start up or shortly after, and it doesnt matter if the car is cold or hot when started

This shouts out closed loop to me.....

[maroman88]

iirc they have one o2

spray all around with carb cleaner. vac lines, base gasket, intake gasket, etc. listen for the idle to smooth out.

condition of plugs & wires? did you check static timing with a light? While the cap is off test the pickup coil as well. make sure the module has dialectic grease under it. make sure the connections are all good. I just got beat on that, cheap accel connectors loosened up when it got hot.

i forget does this thing have a MAF?

if all else fails what is the CTS reading?

plugs n wires are new, dont have a timing light, ill try and get my hands on one. its got an MSD cap, unsure about the rest of the dizzy until i pull it apart.

no MAF on the TBI, they have a MAP

This shouts out closed loop to me.....

i was thinking the same thing... im guna watch this on my hand held again tmrw

[maroman88]

not affected by running in closed loop.
o2 checks good
fuel filter is on there good, doesnt seem to have any fuel issues tho, streams are steady and increse evenly as the throttle is opened
ignition module and cap check good

[maroman88]

this might be a stupid question... i was just comparing my 88 tbi with this 92 tbi... it looks as tho each plug wire on the dizzy is off by one to the right... if timed like this would it even run?????

[crainholio]

Time for a timing light. The plug wires can be clocked any way you want, as long as the dist is installed properly.

[maroman88]

bought a timing light and timed it... looks good until i plug the connector back in and then the mark shows up way to the left of where it was when unconected. and its still stumbling at idle, i even reset the IAC and adjusted the throttle screw, im at a loss now

[79camaro]

You should never have to raise the idle on a tpi or tbi car. The fact that it has a small cam in it tells me that it needs more timing and is possibly loading up with fuel from the timing being too retared. Stock tbi and tpi ecu's only respond to a few different cam grinds without requiring a custom prom. Im 100% sure your problem is timing and your afr is way rich because of it being too retarded.

[maroman88]

would the computer relay this thru the handheld scanner? im watching the rich/lean and it seems to be hovering right between the 2... i can watch as much as itll read lean until u blip the throttle and read rich for a second.

someone else had messed with the throttle screw, i found the procedure to set it back to the stock position and set the stock TPS sensor voltage for idle as well as reset the IAC motor.

i will try bumpin the timing up a tad with all the other stuff set to the stock settings

[79camaro]

The most you would be able to do is monitor the live data stream on a hand held scanner, prob wouldnt be of much help. The only last resort would to be to set the timing with more advance with the ESC unplugged and to leave it unconnected. Sometimes that can work with a mild cam, because when the ESC is plugged back in, it just adjusts the total timing to whatever the ECU wants to run. Hope this helps you.

[greenformula92]

yeah but then it won't advance it when you want more timing....with a cam, albeit a small one your probobly want base timing at least at 10 degrees BTDC, maybe a little more....the computer should advance it, not retard, unless its picking up knock

[maroman88]

k i set the timing to approx 10 BTDC with the esc unplugged, shut off the car plug the esc back in and start the car, check the timing and its arounf 30+ BTDC.

i pulled the esc plug out, and it went back to where i had set it, drove around for a little with it unplugged and it didnt stall

pulled the ecu out, its got a JET stage 2 chip in it

why is the ecu doing this?

[79camaro]

Exactly what I told ya, leave it unplugged8-)

[greenformula92]

that chip is probobly messing it up.....needs a burned stock prom most likely....30 is way to much advance at idle.....it should be like 30 total timing under a load