So I've got a 305 TPI, it was not running real well, had flat spot around 1500-2000 almost sounds like its not running on all the cylinders... so I did a search, found some advise to do a tune up.

So I put new plugs, wires, rotor, cap and coil in. fired it up and it ran great, took it for a little ride... 5-6 miles, still had a slight hesitation around 2000rpm but that was very slight and it was running wonderfully. went back home and parked it.

Next day... it's back... almost running exactly the same as it did before I tuned it up.

50 degrees in the morning and it takes 5 to 6 trys just to get it to stay running.

It's just like everything I did before was undone.

Thanks in advance....

Robert

 

pull the trouble codes. Jump A & B in the ADLD port and note the codes so that we can narrow this problem down..

 

If theres one thing about thirdgens that I double check, it's plug wires, make sure the boot is tight to the spark plug.. Happens to me all the time..

 

No codes to pull... just double check ed them.

 

well that's a real simple check... I did make sure the cap had them all on real well... will double check the plugs too.

 

Could this flat spot have anything to do with the TPS?

 

plug wires are fine.

with it idling, if i give it a little throttle, sitting still it sputters, flutters, pops a little then I get some rpms...

 

Could it be a fuel problem? I would put a gauge on it at the rail and check your tps voltage just to rule those two things out.

 

Did you tune up the TPI system?

http://74.125.155.132/search?q=cache...&ct=clnk&gl=us

http://mpikas.blogspot.com/2008/08/t...june-2000.html

 

yes I did, it helped a little but still the flat spot problem, with sputter and slight backfire.

 

brand new fuel pump and filter, sending unit and screen.

 

Do you get a smooth voltage increase from your tps as you open the throttle? TPS still sounds suspicious to me with the "flat spot" you're describing.

 

Just got back from a new friends house... he been dealing with TPI and LT1's for years... He manually adjusted the TPS and found a vacumn leak in the hose that goes from the mainfold to the fuel pressure regualtor. That pretty much eliminated the flat spot. He had hooked his fuel pressure gage up when I first got there and saw the pressure was fine... about 10-15 minutes later the engine running that whole time it finally did what it's been doing... peeked at the fuel pressure gauge and it had dropped to 20 LBS and the engine was about to die. This is with a brand new fuel pump. turned the key off and waited a little bit; it start right back up and ran fine for a couple of minutes and did the same thing... so It's been a new faulty fuel pump all along.


One question; thought I've had. when I replaced the fuel sending unit, I put the 1 week old pump on the new sending unit. my kit came with a hose long enough to bypass the pulsator. I didn't do that, I used the old pulsator. Should I have tossed that and just used the rubber hose?

Ordering a new fuel pump today...

 

I would of replaced with the new rubber hose due to the fact that you may run into future problems. But now that you have to drop the tank agian, I would do the switch. Better now than later now that the tank will be down.

 

I would put a new pulsator valve on it, it does serve a purpose plus they're cheap enough.