Just finished gt40 h/i swap
08-05-2012, 07:48 PM
#1
1st Gear Member
Thread Starter
Join Date: Dec 2005
Location:
Posts: 112
Just finished gt40 h/i swap
1988 Gt Speed Density that had a bone stock motor. It ran just fine before the swap just burned some oil due to back valve seals.
Installed:
1) GT 40 heads and upper and lower intakes from an explorer along with new 65mm TB and Spacer. EGR was deleted before and after.
I got excited when it fired up and idled like a charm (after timing adjustment). Doesn't appear to have any vaccum leaks and isn't leaking coolant or oil. However, once i took it out it is running wierd. The car pulls hard and feels great until I push in the clutch and let the RPMs back down. It will even happen between shifts if i shift slowly. After being under load it will sputter/struggle to find an idle and even die sometimes until i give it gas again.
Here is what i have done so far in an attempt to fix it.
1) Messed with timing and it doen't seem to make a difference where i set it.
2) Reset base idle being that it is a new TB.
3) Ran codes with motor running and got 33, 44, and 94. However, i had these codes before the swap and the motor ran fine.
4) Check TPS voltage and got really confused. It was reading 1.75 with key on auxilary but motor not on. I bought a new sensor and it gives me the same reading. I don't understand how it could be so high and still idle nicely and drive well while giving it gas. At first I thought it was a faulty multimeter but when put on the battery it read 12 V.
5) That leaves the IAC and the next culprit. However, i doubt that is the issue as the old motor ran fine 2 weeks ago with it on.
There a lot of knowledge on this forum and hopefully you guys can help me narrow it down. I don't want to start throwing a ton of parts/sensors at it "hoping" it will fix it.
Thanks!
Installed:
1) GT 40 heads and upper and lower intakes from an explorer along with new 65mm TB and Spacer. EGR was deleted before and after.
I got excited when it fired up and idled like a charm (after timing adjustment). Doesn't appear to have any vaccum leaks and isn't leaking coolant or oil. However, once i took it out it is running wierd. The car pulls hard and feels great until I push in the clutch and let the RPMs back down. It will even happen between shifts if i shift slowly. After being under load it will sputter/struggle to find an idle and even die sometimes until i give it gas again.
Here is what i have done so far in an attempt to fix it.
1) Messed with timing and it doen't seem to make a difference where i set it.
2) Reset base idle being that it is a new TB.
3) Ran codes with motor running and got 33, 44, and 94. However, i had these codes before the swap and the motor ran fine.
4) Check TPS voltage and got really confused. It was reading 1.75 with key on auxilary but motor not on. I bought a new sensor and it gives me the same reading. I don't understand how it could be so high and still idle nicely and drive well while giving it gas. At first I thought it was a faulty multimeter but when put on the battery it read 12 V.
5) That leaves the IAC and the next culprit. However, i doubt that is the issue as the old motor ran fine 2 weeks ago with it on.
There a lot of knowledge on this forum and hopefully you guys can help me narrow it down. I don't want to start throwing a ton of parts/sensors at it "hoping" it will fix it.
Thanks!
08-05-2012, 08:33 PM
#4
6th Gear Member
Join Date: Nov 2006
Location: Spfld, MA
Posts: 9,240
TPS voltage is too high. Whats happening is the computer thinks the throttle is partially open, giving fuel to compensate to a proper A:F ratio. Because the butterfly isn't open, you're going so rich that you're drowning spark out, causing the stumble.
Since the idle voltage is that high, you need to check the incoming VREF signal. This is the incoming 5v circuit to the sensor. It should not be above 5.0 volts, at all. 5.01 is too high.
Disregard the term "breakout box" in these walkthroughs, just use a multimeter on the proper EEC pin. You'll need a meter with long leads.
The bottom picture is a wiring diagram that I claim no accuracy to. I simply included it to show you the pinout of the EEC. Pay attention to the orientation of the connector, that's how you know where the pin #'s start.
Since the idle voltage is that high, you need to check the incoming VREF signal. This is the incoming 5v circuit to the sensor. It should not be above 5.0 volts, at all. 5.01 is too high.
Disregard the term "breakout box" in these walkthroughs, just use a multimeter on the proper EEC pin. You'll need a meter with long leads.
The bottom picture is a wiring diagram that I claim no accuracy to. I simply included it to show you the pinout of the EEC. Pay attention to the orientation of the connector, that's how you know where the pin #'s start.
Last edited by mattdel; 08-05-2012 at 08:43 PM.
08-05-2012, 08:35 PM
#5
2nd Gear Member
Join Date: Dec 2011
Location: Connecticut
Posts: 272
i had to put my foot on the gas to about 2k rpms then slowly lower it to 900 and then it would idle fine, as soon as i gave it a little gas it would start to surge again, so i would have to lower it manually again. He did adjust the tps because he said it was off and i had my chip put in at the same time so it could have been many things. Where is Ptown?
08-05-2012, 09:03 PM
#6
1st Gear Member
Thread Starter
Join Date: Dec 2005
Location:
Posts: 112
It is confusing to me how the input voltage would change like it did. Why would it work fine before the swap and not after? It must have gotten messed up when the computer tried recalibrating with the new set up.
MAttdel-Thanks for that diagram. Performing the sequence should help narrow it down. Now i just have to find a few hours to do this! What you are saying makes perfect sense. There is what too much fuel being applied on the deceleration and the TPS is telling the computer that i am applying way more throttle than i really am.
Adrnljunky--It sounds like i am having the exact same issue you were having. Just out of curiousity, how much did a tune job cost.
I used to live in Peotone..40 miles south of Chicago. Now I live in the west suburbs of Chicago in Westmont.
MAttdel-Thanks for that diagram. Performing the sequence should help narrow it down. Now i just have to find a few hours to do this! What you are saying makes perfect sense. There is what too much fuel being applied on the deceleration and the TPS is telling the computer that i am applying way more throttle than i really am.
Adrnljunky--It sounds like i am having the exact same issue you were having. Just out of curiousity, how much did a tune job cost.
I used to live in Peotone..40 miles south of Chicago. Now I live in the west suburbs of Chicago in Westmont.
08-05-2012, 09:16 PM
#7
2nd Gear Member
Join Date: Dec 2011
Location: Connecticut
Posts: 272
well its going to very tuner to tuner, the one i went to charged 150.00 an hour and it didnt take that long so i was just over 200. I went to a place last week and they charged 200.00 an hour and said it would take 4 hours to tune. so i left. Depends on how close u are right now, it might just be somthing as simple as resetting your computer and clearing the codes.
