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Discussion Starter #1
Hey all, I installed a speed density TPI set-up on my 82 and am having a problem. When I'm at cruising speeds (40 - 60mph) the car starts jerking erratically, it will quit when I accerlerate and get the rpm up only to start again when i back off. I've ruled out transmission or rear end because none of this gave me problems when I had a carburator on the car...it started after I installed TPI. All the sensors etc are brand new too.

Thanks!
 

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Any other mods to your engine? Are you running a larger cam?What's your fuel pressure. Timing set right? Bad EGR valve can cause surging.
 

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Discussion Starter #5
Any other mods to your engine? Are you running a larger cam?What's your fuel pressure. Timing set right? Bad EGR valve can cause surging.
Engine is stock, it's a 1982 Corvette engine w/ cast iron heads. The computer chip is custom for a stock 90-92 f-body 5.7 TPI.

No EGR, written out of chip and using a block off plate..

Not sure on fuel pressure, still need to check that. I'm using a new stock TPI fiuel pump, pressure regulators, and rebuilt 22 lb injectors.

Timing is set 6 degrees btdc, I disconnected the timing plug in the harness first. My cap, coil, distributor, rotor, and plugs are brand new. Wires are installed in the right firing order...they are new custom cut to fit wires. They worked fine w/ my carb set up but I'm going to change them out with ac delcos as soon as they come in.

Harness is a custom job done by TPIparts.net , computer is rebuilt, and chip is a custom job w/ smog, egr and vats delete.

All the sensors are brand new, and gaskets are new. Throttle body is nice and tight....

The engine seems to "shake" more than it did with the carb set-up so something still isn't right.....
 

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Engine is stock, it's a 1982 Corvette engine w/ cast iron heads. The computer chip is custom for a stock 90-92 f-body 5.7 TPI.

No EGR, written out of chip and using a block off plate..

Not sure on fuel pressure, still need to check that. I'm using a new stock TPI fiuel pump, pressure regulators, and rebuilt 22 lb injectors.

Timing is set 6 degrees btdc, I disconnected the timing plug in the harness first. My cap, coil, distributor, rotor, and plugs are brand new. Wires are installed in the right firing order...they are new custom cut to fit wires. They worked fine w/ my carb set up but I'm going to change them out with ac delcos as soon as they come in.

Harness is a custom job done by TPIparts.net , computer is rebuilt, and chip is a custom job w/ smog, egr and vats delete.

All the sensors are brand new, and gaskets are new. Throttle body is nice and tight....

The engine seems to "shake" more than it did with the carb set-up so something still isn't right.....
Sure sounds like you went down all the right paths. The only thing in your list of parts that I found odd was the 22# injectors because factory is 24# in my vette, but your chip programmer could have tuned them to spray longer. So that probably is not the problem. You need to check fuel pressure at the rail. Hook up a fuel pressure guage at the fuel rail. When you turn the key on,(but don't start it), The pump should come on for about 2 sec. and the pressure should go up to 35-38lbs with a stock regulator and hold there.(might drop a pound or two but should hold there) If it drops off, you have a problem in the fuel system. I just had one that was leaking off pressure in the tank. The coupling between the fuel pump and metal fuel line was bad. The car ran, but had a crappy idle and poor drivability.
 

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Discussion Starter #7
Sure sounds like you went down all the right paths. The only thing in your list of parts that I found odd was the 22# injectors because factory is 24# in my vette, but your chip programmer could have tuned them to spray longer. So that probably is not the problem. You need to check fuel pressure at the rail. Hook up a fuel pressure guage at the fuel rail. When you turn the key on,(but don't start it), The pump should come on for about 2 sec. and the pressure should go up to 35-38lbs with a stock regulator and hold there.(might drop a pound or two but should hold there) If it drops off, you have a problem in the fuel system. I just had one that was leaking off pressure in the tank. The coupling between the fuel pump and metal fuel line was bad. The car ran, but had a crappy idle and poor drivability.
So stock injectors for corvette is 24lb?? I may have made a boo boo when I had my chip programmed. I told the guy 22lb injectors because I was under the impression that's what all 5.7 TPI injectors were.

Would 24lb injectors with a 22lb chip setting make that much difference?
 

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So stock injectors for corvette is 24lb?? I may have made a boo boo when I had my chip programmed. I told the guy 22lb injectors because I was under the impression that's what all 5.7 TPI injectors were.

Would 24lb injectors with a 22lb chip setting make that much difference?
Possibly. I run 30lb. injectors with mine, and have a custom chip from Motorvation. I know that when I changed from stock to 30lb, they had to burn me a new chip. I tried the car with the new injectors, but left my first chip in just to see what it would do, and it idled like ****. Put the new chip in they burned, and it runs great. So there is something to it. But factory is 24lb.
 

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i don't think it has anything to do with the injectors being off. If it wasn't enough fuel it would just run hot and weak. It sounds like it could be the spark plug wires arking or something in your ignition or not ground properly. It could also be the MAP sensor acting up or a vacuum leak. Just food for thought
 

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What about your torque convertor? The C4,s use a nonlock up style converter that the computer locks up after a certain RPM.Maybe the converter is trying to lock up.
 

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Discussion Starter #11
I was thinking it could be the torque convertor, I guess unhooking it would be the only way to tell.

I still have a slight miss, there is a possibility that I could have a vacuum leak to, I'm going to try and check that. I just installed a brand new set of AC delco wires and it's still missing a little..


I ordered a cable to hook to my laptop yesterday, I'm going to try and hook my car to my pc and see if I can get a better idea on whats going on

All I know is I'm ready to blow the car up :thud:
 

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Discussion Starter #12
I wanted to give you guys a idea on my whole set-up so you can better help me:

Engine:

Stock 1982 Corvette Crossfire Engine, cast iron heads
No modifications to engine
Tested good on compression, new stock oil pump and stock water pump

Ignition:

Stock remanufactured HEI distributor, AC Delco Wires, Bosch Platinum 2 plugs, New coil, cap, and rotor. All ignition components are new.

Double checked TDC and firing order of wires….everything correct. Base timing set at 6* BTDC and actual timing at idle is approx 17* BTDC

Transmission:

Rebuilt 700r4 w/ overdrive
Has shift kit and new TC w/ a slight stall
Also using a 4000 pulse speed sensor in transmission
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&viewitem=&item=220095546113

Engine Control Unit:

Remanufactured ECM 1227730, custom harness and custom chip
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&viewitem=&item=8071872892
1990 – 1992 Speed density set-ups
Chip is written for a Stock 1990 – 1992 Camaro TPI w/cast iron heads


Sensors:

All sensors are brand new
Map, IAC, Oxygen, TPS, VSS, IAT, CTS, and Knock sensors
New relays for fuel pump and fan
http://tpiparts.net/inc/sdetail/357

Fuel Delivery:

Brand new stock TPI in-tank pump
New crossfire fuel filter
Stock 22lb injectors, flow tested and checked w/new o-rings
Fuel regulator, used, stock and looked fine




TPI unit:

Stock 1986 TPI unit removed from a camaro
Has cold start delete using the plug and cap on fuel rail
Stock 48mm throttle body, throttle plates nice and tight
Brand new gaskets
New K & N filter on throttle body

Emissions:

No emissions – EGR taken care of on the chip
Has EGR block-off plate
No fuel canister purge, removed from chip. Throttle body has vacuum cap on that hook-up.
No pvc valve, spot in manifold is capped off
Have hose ruuning from passenger valve cover to throttle body vacuum.

Charging system:

Rebuilt stock starter (brand new)
Rebuilt stock alternator (brand new)
Brand new battery
All new belts and hoses

Cooling:

Stock water pump
Dual spal electric fans
Aluminum radiator

I think that’s everything…

Now Symptoms:

1. Slight miss at idle
2. Seems to be running lean, fumes burning eyes like tear gas.
3. Chugging at cruising speed, goes away upon acceleration, comes back after letting off gas
4. Several plugs have white film on electrodes…sign of lean condition
5. Vacuum check shows vacuum at 19 inches at idle slightly fluctuates between 19 and 18….kind of like a heartbeat.
6. Vacuum at 2000 rpm holds steady at 25 or so inches…no movement.
I didn’t seem to have any of these issues until I installed the TPI system, it ran decent with a carburetor. Hopefully that’s everything……Thanks for the help!
 

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the ignition wires can be brand new but if they are arking off anything you can't tell or even see it till its completely dark at night and ur around no lights...I know it sounds wierd but check for it. You can also have wire to wire arking and like i said you won't be able to see it unless its pitch black and u pop ur hood. Also you can try elimanating senors by removing each one one at a time to see the changes. Sometimes scanners don't pick up everything. Another quick easy check is to try removing a spark plug wire one at a time to see if there is a change or no change to see if it could be something between the spark plug and the dizzy. Just things to look for. It doesn't seem like a vacuum leak, but more electrical. Hope this helps. I have had many and still do tpi cars
 

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Discussion Starter #14
the ignition wires can be brand new but if they are arking off anything you can't tell or even see it till its completely dark at night and ur around no lights...I know it sounds wierd but check for it. You can also have wire to wire arking and like i said you won't be able to see it unless its pitch black and u pop ur hood. Also you can try elimanating senors by removing each one one at a time to see the changes. Sometimes scanners don't pick up everything. Another quick easy check is to try removing a spark plug wire one at a time to see if there is a change or no change to see if it could be something between the spark plug and the dizzy. Just things to look for. It doesn't seem like a vacuum leak, but more electrical. Hope this helps. I have had many and still do tpi cars
I went out and checked ran it with the lights off...no visible arcing I can see. I also checked the fuel pressure and it's healthy.

But I did notice something weird, my battery showed 12.6 volts, but upon starting the car the alternator fluctuated between 6 - 10 volts and it never got higher than 11 volts.....it's a new alternator less than three months old. I've got a feeling that may be the source of my miss and other problems..

any ideas?
 

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Discussion Starter #16
Good news....found the source of my miss....it was the alternator

My troublehooting book said that if you have a miss it could be a defective alternator sending voltage spikes to the ECM.

It said to try two things

1. Disconnect the two prong plug off the alternator and start car up and see if miss goes away........it did and actually idle better

2. Check AC voltage off back of alternator w/car running....should be no more than .5 volts.....mine was 25.2 volts

Now I need to find a better stronger alternator..
 

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I went out and checked ran it with the lights off...no visible arcing I can see. I also checked the fuel pressure and it's healthy.

But I did notice something weird, my battery showed 12.6 volts, but upon starting the car the alternator fluctuated between 6 - 10 volts and it never got higher than 11 volts.....it's a new alternator less than three months old. I've got a feeling that may be the source of my miss and other problems..

any ideas?
I've bought bad alternators and starters right off the shelf. Especially at places like Advance or Autozone. If you want quality electrical components, go to NAPA. I've never got a bad electrical part from them. Always great quality. And yes, low battery voltage can cause an array of problems
 

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Discussion Starter #18
I've bought bad alternators and starters right off the shelf. Especially at places like Advance or Autozone. If you want quality electrical components, go to NAPA. I've never got a bad electrical part from them. Always great quality. And yes, low battery voltage can cause an array of problems
Yeah, that's what I heard. Autozone's site says this alternator is remanufactured with SOME new components.

It's less than 3 months old so I'm leaving in a minute to go do a swap for another one. I don't have my receipt...but hopefully since they asked for my phone number when I purchased this one....my address / purchase info is logged in the system.

If I have problems with this new one I'm going to def look for another supplier and see if there are other source of problems to as why I'm eating alternators this quick.
 
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