alright guys im almost done with the tbi swap on my previously carbed 350, heres the setup im running 80 350 block, tbi setup off of 88 chevy truck including intake manifold and distrubiter, throttle bodie and all sensors, im using a howell harness with a custom chip in the ecm to eliminate vss and egr stuff, well heres my problem, the engine will start but as soon as it does it immediately dies unless i give it some gas to keep it running, i can sit there and rev it up and it seems to be running smooth, but then when i let it drop back down to idel it either immediately dies or idels poorly for about 5 seconds then dies, it is also running VERY rich, i have a brand new 3 wire heated o2 sensor in it also, and the funny thing is the service engine soon light comes on and when i run the code it sais the engine is running lean, whats up with that, cause i know its running real rich, and one last question i have a 16 and a 10 inch electric fan, when i turn the 10 inch fan on all is good, but whenever i put battery power to the 16 the engine immedialtely dies, and if i turn on the 16 b4 i start i, the engine wont start it just backfires through the throttle body and dies, but when i unhook the fan the engine will start but has the symtopms i described earlier, also there is no short in the 16 inch fan, im just running a simple hot wire from the battery and touching it to the power wire on the fan no switch or anything so whats the deal please help:smokin: ohh ya im running the howell fuel pump for tbi the inline one

ohh ya it is also going into closed loop if that makes a differnece it takes about 2 minutes b4 it goes into close loop though

Originally posted by BIGASSYJ
alright guys im almost done with the tbi swap on my previously carbed 350, heres the setup im running 80 350 block, tbi setup off of 88 chevy truck including intake manifold and distrubiter, throttle bodie and all sensors, im using a howell harness with a custom chip in the ecm to eliminate vss and egr stuff, well heres my problem, the engine will start but as soon as it does it immediately dies unless i give it some gas to keep it running, i can sit there and rev it up and it seems to be running smooth, but then when i let it drop back down to idel it either immediately dies or idels poorly for about 5 seconds then dies, it is also running VERY rich, i have a brand new 3 wire heated o2 sensor in it also, and the funny thing is the service engine soon light comes on and when i run the code it sais the engine is running lean, whats up with that, cause i know its running real rich, and one last question i have a 16 and a 10 inch electric fan, when i turn the 10 inch fan on all is good, but whenever i put battery power to the 16 the engine immedialtely dies, and if i turn on the 16 b4 i start i, the engine wont start it just backfires through the throttle body and dies, but when i unhook the fan the engine will start but has the symtopms i described earlier, also there is no short in the 16 inch fan, im just running a simple hot wire from the battery and touching it to the power wire on the fan no switch or anything so whats the deal please help:smokin: ohh ya im running the howell fuel pump for tbi the inline one

I run TPI, so this may be slightly different for you..............you have what is known as an IAC (idle air control) system, which is basically a stepper motor somewhere below or around your throttle body (under the air intake on a TPI) that probably needs to either be replaced or reset. The reset procedure on a TPI is this - jumper the ALDL (diagnostic plug that should be in your dash area) between the A and B terminals, which puts the computer in the diagnostic mode.............then you turn key ON, but not start the motor. The IAC motor will make a noise like it is 'running', it is normal, and is trying to move the pintle to its fully extended position. OK, let it do its thing for 30 seconds...........then with key still ON, unplug the plug going into the IAC motor. Remove the AB terminal jumper (paper clip is the best thing to use by the way). Then start the truck...............(again, sorry if this is not exactly the same for TBI as TPI, just trying to help :eek: ) You may need to play with the throttle to keep the truck running, again NORMAL, so don't worry. Run motor until it warms up (good job having a 3 wire O2 sensor, shouldn't take long), and adjust the idle stop screw until it is about 400 RPM in DRIVE or 450 in neutrral with a manual tranny.

Then after you get the idle set, turn motor off, reconnect the IAC, clear codes if any appear, and restart the motor.................THEN key point, adjsut the TPS (throttle position sensor) to read .54 volts +/-.075..............with either a scanner or voltmeter. That .54 V is for TPI, I am not 100% sure what it is for TBI..............good luck.

Can't say anything about the fan..............get the truck running well on the IAC adjsutment first, that may also fix your lean running condition.............as right now it is probably sounding like it is sucking air like crazy. CHECK for vac leaks too, by the way............

Originally posted by BIGASSYJ
ohh ya it is also going into closed loop if that makes a differnece it takes about 2 minutes b4 it goes into close loop though

Perfectly normal to need about 2 minutes to get the O2 sensor to get the computer into closed loop.

Do you have a scanner by the way? VERY good idea to get one...........I use the Auto Xray. www.autoxray.com ..............got mine at Schucks/Kragen/Checker.

anyone else?????:smokin:

Sounds like you have the TPS wired up backwards. If it is wired backward it is telling the computer that you have the throttle wide open and is giving the engine more fuel than it needs. rewire the TPS and it ahould run fine.....

unless i have the plug in upside down i doubt i could have wired it wrong cause i didnt do anything its the howell harness, so maybe the plug is in wrong i will go check

went and checked the plug was in the right way, so i guess its wired right
adam:smokin:

Check your ECM grounds, and your ECM power. Some of the symptoms sound like a power problem because of the fan.

Could also be a faulty Tach signal. Are you using ESC or just the tach signal? Some aftermarket tach's need a line cleaner (like MSD) so that the GM (Howell) ECM can read the tach signal properly.

If the ECM isn't getting tach signal, it will die.

How's your fuel feed pressure? Should be between 11 and 15. Check it. Also check your return line pressure and insure it's less than 5 (usually way less than 5 with a 3/8 line)

Tim

Do those throttle bodies have a set screw to hold the butterflies open a little bit? Can't remember, but if those are closing it's going to die at idle from lack of *fuel*.

TPS position doesn't increase fuel. IIRC these things use the TPS for acceleration compensation and little else.

Make sure the O2 is wired up correctly, but if howell did the harness i'd say it's probably OK.

What did you do with the EGR manifold? If you had EGR disabled in the ECM, you have to make sure you do something with the EGR valve.

Check fuel pressure, check ignition timing.

Squash

I agree with Wolf on the power thing. Check your ecm grounds and voltage at the computer. Checking the fuel pressure is a good idea as well, and like was said make sure your EGR is adequtely blocked off.

Pete

Sounds to me like the IAC motor is not working properly. I had a simular problem on my BBC. The computer will most likely not throw a code for the IAC. If you can borrow a scanner check the values of the IAC and the O2. The o2 senser should jump around some what. The iac should be moving in and out slowly.

One more very important thing to check is the tps. When throttle is closed the voltage yshould be between .45-.65. any less and it will run lean. At WOT the voltage should be about 4.5 volts. You can adjust the TPS by bending the tab on the crossshaft through the TBI

skinny,

I'm having the same problem with my truck. How did you fix it? Thanks

I had the same problem with a buddies rig that I built last year. The engine would run then quit. I thought it was the harness that I built took it out and checked it ok. He had swapped batterys out and changed a few sensors on it before I had a chance to work on it. The problem turned out to be the mapp sensor had shorted out internally and was kill the refernce signal to the computer. After replacing it the jeep was fine.

If I remember correctly...88 TBI didn't have heated sensors...did you wire this o2 sensor correctly?

From what it sounds like, the IAC is fawking up...have you tried to drive this piece around? Does it run right? Have power? If not then you should check timing. If that's correct then check your coolant temp sensor...it might not tell you puter that you need warm-up enrichment.

Best thing to do is build a Win-ALDL connector and plug that shit in...it will tell ya exactly what you need to know.

cool:D