I'll try this again, Hello to everyone, I don't have a f-body, but this seems to be the best sight for tbi info. I have a 90 blazer with a 350, that I put a 454 throttle body on, and a 1 inch spacer. My motor is tired and I am putting in a 98 4 bolt vortec in a couple of weeks but wanted to finish the TBI swap before doing that, and work out any related problems. Anyway, the problem I ran into after the swap is when I stomp down the accelerator the engine stumbles very similar to a carberator with a bad accelerator pump. I tried switching back and forth with the big and small block injectors and fuel pressure regualtors but nothing seemed to make a difference. The only other change I had to make was to solder on new pigtails for the different style TPS and IACV, as the new throttle body is a 95 with different style connectors. I'm not getting any fault codes, but the engine is really tired, 140,000 miles using two quarts of oil every tank, I think it has a busted oil ring on the number one cylinder. I was wondering if anyone had any idea what could be causing this, the only thing I can think of at this point is to wait for the new engine to see if it is related to the worn out engine. But I really hoped to have the tbi system in order before starting the engine swap.

Thanks in advance for any help
Marv

 

what did you swap from??im not really followin ya

 

How does it run under regular conditions like cruising or accelerating slowly? What type of intake do you have now? Do you have any mods or just a bone stock engine? I you have a way to datalog any info from the ecm this also would be helpful.

Steve

 

This engine is completely stock with the stock intake, the big block TBI come off of a 95 one ton pickup. It doesn't have a catalytic converter, and the exhaust is three inch from the y-pipe out, and it has the stock 700r4. I don't have a way to check the computer data, the only thing I have is a code reader, but I don't get any fault codes. The engine seems to idle fine and cruise fine, the only problem is when I just step down the throttle it stalls out almost exactly like a carb with a shot accelerator pump. Once it does start going it seems to accelerate harder than the original 350 throttle body, so I would like to fix this problem and keep the larger tbi. The only other thing the engine does that is odd is after it is reved up and the throttle is released it seems to go to high idle for a second or two then drops down to regular idle. All of the sensors have been replaced in the past year and were working fine before swapping the throttle body, and the big block ran great that the throttle body came off of, any ideas anyone may have would be great, and thanks for the help

Marv

 

Hey Big marve, I also have k5 with a 454 in it but I got the whole engine (from pirate board). I am just finishing a swap from a carb'd 350. I dont have any info that will help but I can tell you my TBI454 does that EXACT same thing. Idles fine, runs vary strong at part throttle but as soon as I floor it I can hear her sputter a little at all rpms to. She also idles high for a split second when throttle is realeased fully from high RPMs. I think that may be intentional though. It sometimes running high rpms and quickly releasing the throttle would result in a dead engine with my carb.

Charlo

 

I think you are going to have to tune your chip. In the chip there is the equivalent of a accelerator pump. When you open the throtle now there is alot more air availible and no more "pump shot" then before. If your motor is bone stock you may be fealing the equivalent of over carberation. This could be corrected in the chip. My advise is to start hanging out at the DIY PROM board and get into chip burning. It is not as difficult as it sounds. And it doesn't have to be expensive. There are large gains to be found even in a stock motor threw chip tuning.

 

I though I may need to do something to the chip, but hoped there would be an easier solution. I need to learn how to modify the chip anyway since I'm not putting the egr back with the new motor. My next project for next years tax return is to put a 383 rotating assembly in the new vortec, so I will need to reprogram again at that time. Thanks for the help.

Marv

 

There is an easier solution. For $30 summit racing has a little thing that plugs into the connecotor between the TPS and computer I think. It is suppose to advace timing and some other carp and get rid of your problem.

Charlo