I put a junkyard TBI on my old CJ. Its a 360 AMC. It runs great and I have burnt a few chips for it. I just cannot figure out why it does this: If I roll up to a stop sign or light sometimes the CJ will die. There is no VSS. It runs like gangbusters except for this 1 issue. What am I looking for to fix it.
Maybe the VSS is needed to reset the Idle Air Control (IAC)? Sometimes there is a difference between "Nice" and "Necessary". Is the VSS "Necessary" ... NO. Would it be "Nice" to not stall at a stop sign ... YES.
The attached "Tuning the TBI" has helpful information on setting the Minimum Air at Idle.
dave w
I think it has more to do with the throttle closing too fast and the maybe the IAC is not keeping up?Its almost like the idle is set to zero. When I coast after giving it gas it wants to and sometimes dies. Other than this issue it runs great.
All I have to say is, Wow. You ask for help with "What am I looking for to fix it" which I believe you know the answer to when you say "There is no VSS". A well respected and knowledgeable member answers your question and you choose to argue by describing how an ecm often responds when lacking a VSS signal. I'm sorry, carry on.Originally Posted by jrotten67
Ed
Did you read his post? A VSS is not needed to run the GM TBI. I do believe he said that. That being said he didnt answer my question, so I was not arguing with his answer. I thought maybe a better explanation of what I'm seeing might help. I have the same tuning page he had. My issue is not at idle it is at decel. I was just describing what It feels like and maybe some other knowledgeable soul will get what I am looking for. Do you make it a habit of attacking people who come to this forum? A few other people on other forums sent me here suggesting they once heard maybe could be the throttle follower? LOL!!!!! They could not tell me where that was. Some skalar, or table.........I have been unable to find it. I always went by the rule on the forums I frequent, that if you dont have somethiung to add to the conversation......don't.
It always unfortunate when the conversations go less than positive.
If the minimum air is correctly set, and vehicle continues to stall, I recommend installing a VSS. See post #2 for the minimum air information
Information below is from the Painless TBI Harness Installation Manual: https://www.painlessperformance.com/Manuals/60201.pdf
dave w
VEHICLE SPEED SENSOR AND TRANSMISSION LOCKUP FUNCTION
Before you install the harness, please decide the following things:
a. Are you going to use a 700 R4 Lockup Transmission that you want the
computer to control the lockup on?
b. Does the engine have to be emissions legal; i.e. does the EGR valve and /or
air solenoid, and diverter valve need to be connected?
If you answered yes to either or both of these questions then you must connect the
wires labeled VSS to a vehicle speed sensor that will provide a two (2) pulse signal to the
computer. The Throttle Body the sensor should output a square wave.
If you answered no to both of these questions then you may choose not to use a vehicle
speed sensor, but the vehicle will operate more efficiently with one.
What ecm are you using? The old C3 ecm's suchs as the 747 used a VSS control strategy that really relied on VSS input. Without the VSS to alert the ecm the engine is in a moving vehicle, deceleration and engine driven coasting causes the ecm to close the IAC valve attempting to lower engine speed. I know people who have fought with IAC trying to eliminate the need for VSS but it's definitely work. So is the VSS needed? No. Does it help? Tremendously.I think it has more to do with the throttle closing too fast and the maybe the IAC is not keeping up?Its almost like the idle is set to zero. When I coast after giving it gas it wants to and sometimes dies. Other than this issue it runs great.
My 304 AMC runs since i have this :https://www.rennsportshop.com/de-fah...RoCiEIQAvD_BwE
VSS build in. Problems i have depend on the SA-table.
Buy one and put it on place.
My 304 AMC runs since i have this :https://www.rennsportshop.com/de-fah...RoCiEIQAvD_BwE
VSS build in. Problems i have depend on the SA-table.
Buy one and put it on place.
Is this 304 in a Jeep? Curious if that VSS fit the speedo cable? I am also using the 7747 ECM. It takes the 2 pulse correct?
Yes it is in a CJ7 year77. You have to cut out a short piece (3-4 cm) of the cable cover.Mount the cover to both sides of the VSS and then remount the soul.I have the 16196395.
What do you mean cut a short piece of the cover? Do you happen to have a pic? I thought the speedo cable just screwed onto one side while the other screwed onto your transfer case.
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