Hey, im new to this forum... always liked the looks of the tpi setup and finally was able to afford the swap.. so me and my dad converted my carbed 305 to tpi.. took us a week to do it. 700r4 tranny, got wiring harness of a guy on ebay that made it how i wanted( eliminated emission crap etc) and got it all back together.. and for some reason it wont go past 75!? anyone have a clue why this is happening? I know its caused by tpi casue when it was carbed ive had it a lil past 75

(yes its clean now.. and the hood is all flat black now...)

 

Just a guess but it may be your speed limiter?? If you have real low rear end gears it may think you are going over 100 MPH.

I am by no means the best person to answer this but it's something I would check.

 

i got a 4.10 gear.. and my speedo is correct. i thought tpi didnt have a speed limiter?

 

Could be anythying. What ecm did you use?

It might be something more serious. What RPM does it happen at? can you repeoduce it at the some rpm in a lower gear going slower?


-- Joe

 

i got the wiring harness/ecu off guy on ebay... it happens at like 3100 rpm at 76ish mph.. i put it in 3rd and it still did it at 76ish mph.. and the rpms were higher. only happens at that speed. very weird and annoying. any help would be appreciated!

 

This really sounds like your speed limiter now..

 

so i need to buy a chip to over ride it or what?(new to fuel injection)

 

What ECM?

I'd get a prom burner, some blank chips, download some free software and start learning..

-- Joe

 

Q: How can I bypass the speed limiter?

A: Try the following steps:

Install a Zemco Performance Timer and instead of using the speed sensor supplied, tap into the electronic output from the normal sensor in the tranny (there shouldn't be a problem driving two sets of electronics in parallel).
Then fit an ON/OFF switch into the speed sensor wires that goes into the ECM.
Wire the torque converter so it's not controlled by the ECM, but rather by on ON/OFF circuit switch. This results in non-lockup when the shifter is manually put into 1,2 or 3. Selecting OD will get normal up-shifts without lockup until 4th when lockup comes in. The while in OD, if the tranny downshifts due to speed/throttle settings, the TCC stays locked unless drop it out using the switch (except for 1st gear which doesn't allow pressure to the TCC anyway due to the hydraulics).
The Zemco unit can be easily recalibrated if you change tire size or rear gear ratios. When you want to push the car past the speed limiter in the ECM, just switch OFF the speed sensor input to the ECM and use the Zemco unit to show your speed. All that happens with the ECM is the normal speedo stops working and you lose cruise control. After about a minute the ECM realizes that the pulses are missing from the sensor and gives you a service engine light. This does not affect the normal operation of the engine and the light goes out again after a few seconds when the sensor is switched back on.

All of that info is at https://www.thirdgen.org/newdesign/faq/thirdgen.shtml just before the half way point on the page.

 

With all that in mind you should learn to burn your own proms anyway because that will get you more HP and fix this problem at the same time..

 

As asked before, what ECU was used? Speedo cable or electronic? What tranny is being used?

My suggestion at this point would be to data log the truck as you're running.

BTW, nice job.

 

Hes better off burning a prom with fuel cut MPH disabled.

-- Joe