Engine Engine Swap - lots of upgrades, not running quite right
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I always recommend a tune; and here's why.
When going to a larger throttle body, when you set the TPS at, say .80v on the stock throttle body, then .80v on the new larger throttle body, then when you open the throttle to 1.0v (part throttle cruising), there is considerably more air entering the engine. Yes the MAF will read it, BUT, the load calculations and thus the timing and fuel will be off. We got away with it years ago and it wasn't ideal then, and not ideal now either--we just got away with it and ran with a degraded driveability, albeit slightly in a lot of cases.
but yes keep plugging, you'll get it. I'm in the same boat with mine but a lot bigger problem that nobody can figure out. Very frustrating.
When going to a larger throttle body, when you set the TPS at, say .80v on the stock throttle body, then .80v on the new larger throttle body, then when you open the throttle to 1.0v (part throttle cruising), there is considerably more air entering the engine. Yes the MAF will read it, BUT, the load calculations and thus the timing and fuel will be off. We got away with it years ago and it wasn't ideal then, and not ideal now either--we just got away with it and ran with a degraded driveability, albeit slightly in a lot of cases.
but yes keep plugging, you'll get it. I'm in the same boat with mine but a lot bigger problem that nobody can figure out. Very frustrating.
I probably will have it tuned later but the guy here locally that everyone recommends is $750 with the chip, tune and dyno time. Already have a bit sunk into this project so the tune will have to come later after I have it running descent enough. Its also not a daily driver, just a weekend toy.
If you are even considering $750 on a chip, for a few more bucks go with a megasquirt setup and have endless tuning capabilities. I did that and it is by far one of the best decisions I have made. I even know a great tuner who hangs around here.... he goes by the name a91what 
I agree with the tuner thing, every time you change something/upgrade you have to go back.
and with ms you do it yourself and it can transfer over to almost any internal combustion engine.
and with ms you do it yourself and it can transfer over to almost any internal combustion engine.
I got it back together today and got it fired up and idling but it still wont idle down. 1200 or so is about as low as I can get it. I replaced every gasket and checked for vacuum leaks again. Still none. At this point the only vacuum lines in use are the one going to the FPR and the one going to the vacuum block on the firewall. Everything else is capped off. I am going to put the factory MAF on it next to see if that changes anything. I am baffled. The only other odd symptom I have is that if you do "whack" the throttle it hangs for a 5 or more seconds brefore finally dropping back down. I ran codes and only had one for missing evap stuff and missing smog stuff.
08GT500
5 Year Member
Hi,
Going the distance I see. Well, my thoughts are the Butterfly hanging up mechanically inside the TB bore due to a Mfg’s oversight?
And salt & pepper shaker M/Female pin(s) were the cause of a quite similar idle issue for me, previously. Cleaning, closing the female pins a tad with a jewels screwdriver & a little dielectric grease worked, (after I’d pulled my hair out for a few days).
Worth a try?
Best of luck!
-John
I did check the throttle blade inside. It looks good. I put the old MAF back on and its marginally better. It seems to come back down from rpm quicker when you hit the throttle but I still have a high idle issue. Cannot get it blow 1200 or so. I did have the salt and peppers loose when I Pulled the engine. Maybe I will pull those back loose and clean them really good. But as of now I still cannot find the issue but I do have it idling smooth, just way too high for me.
08GT500
5 Year Member
Hi,
I know you’d plugged up the vacuum system for eradicating vacuum leaks, a couple others to consider.
Do the idle characteristics change when you enter closed loop?
Did you try looking for leaks around the TB’s shaft seals?
EEC should adapt here, but I’m reachin’, soo.. is the passenger’s side valve cover oil cap a vented breather? Live vacuum line from it to the TB...bypasses the MAF as unmetered external air. You’re running a closed PCV system- correct?
-Vac. line to feed the interior ac vent controls hooked up, more leak paths.
Not a first choice, think it may help when you’ve exhausted all other options, have
tseaked the TB’s throttle stop, done an idle relearn?
Best!
-John
I know you’d plugged up the vacuum system for eradicating vacuum leaks, a couple others to consider.
Do the idle characteristics change when you enter closed loop?
Did you try looking for leaks around the TB’s shaft seals?
EEC should adapt here, but I’m reachin’, soo.. is the passenger’s side valve cover oil cap a vented breather? Live vacuum line from it to the TB...bypasses the MAF as unmetered external air. You’re running a closed PCV system- correct?
-Vac. line to feed the interior ac vent controls hooked up, more leak paths.
Not a first choice, think it may help when you’ve exhausted all other options, have
tseaked the TB’s throttle stop, done an idle relearn?
Best!
-John
I did have the PCV system hooked up but pulled it loose and have the intake open right now with just the hose and not hooked to vaccum. I did that to make sure I was not getting a leak. The valve cover is still hooked up as it was from the factory but I have a breather on it instead of the fill tube, but the hose is hooked to the breather and to the intake tract. I can try to remove that from the system and just use a breather.
I did adjust the set screw on the TB using the instructions for setting the idle with the IAC disconnected. Have done that a few times now. And I did check for leaks around the TB and Spacer multiple times. It does act like a vacuum leak but I cannot find one. Not saying it cannot be or isnt but I would like to think I have done this long enough to find an cure vacuum leaks. I pulled the intake back off and put new gaskets on and still the exact same symptoms with no change at all so at this point I am leaning towards something else.
I have had the battery cable off every day so it is re learning multiple times. I am also looking for anything odd. I have a question on the TPS. When I check voltage it will show me voltages a and then if I just have the key on and car not running I lose voltage. It stops showing me any voltage at all. Is this normal? Should it be consistent at all times? When it is showing voltage if I move it the idle heads uphill fast so I am wondering if a bad TSP could cause this stuff? I dont have another to test but I also dont want to spend $40 just to test the theory but if it is suppose to show voltage at all times then I need to get one.
Oh and the vacuum line to the interior stuff is one of the only two I have connected. I have pulled it loose while the car was running and plugged the hole with my finger. No change and I had no problems with idle and the controls before so those "should" be good. Like I said, I am starting to think looking for vacuum leaks is just chasing my tail.
I did adjust the set screw on the TB using the instructions for setting the idle with the IAC disconnected. Have done that a few times now. And I did check for leaks around the TB and Spacer multiple times. It does act like a vacuum leak but I cannot find one. Not saying it cannot be or isnt but I would like to think I have done this long enough to find an cure vacuum leaks. I pulled the intake back off and put new gaskets on and still the exact same symptoms with no change at all so at this point I am leaning towards something else.
I have had the battery cable off every day so it is re learning multiple times. I am also looking for anything odd. I have a question on the TPS. When I check voltage it will show me voltages a and then if I just have the key on and car not running I lose voltage. It stops showing me any voltage at all. Is this normal? Should it be consistent at all times? When it is showing voltage if I move it the idle heads uphill fast so I am wondering if a bad TSP could cause this stuff? I dont have another to test but I also dont want to spend $40 just to test the theory but if it is suppose to show voltage at all times then I need to get one.
Oh and the vacuum line to the interior stuff is one of the only two I have connected. I have pulled it loose while the car was running and plugged the hole with my finger. No change and I had no problems with idle and the controls before so those "should" be good. Like I said, I am starting to think looking for vacuum leaks is just chasing my tail.
I would think a breather on the oil fill tube with the hose hooked to the tb will be a vacuum leak or un metered air. 
I am not sure about your tps, how are you checking voltage on it?
I am not sure about your tps, how are you checking voltage on it?
I will try plugging the pcv and just use vents on both ends of the system or find another way upstream of the MAF to connect it but Lets say for arguments sake that I truly have just pissed off the factory computer and it does not like my combination of parts. What are my options with links and some pricing? I can have the custom tune and dyno time done here in town for $750 and I assume that does not include any labor for fixing whatever he might find wrong that needs fixing. If there is a stand alone computer system that is cheaper I work in IT and can probably figure that out but I want some suggestions from people who have actually used and own this stuff.
I was referring to the breather on the fill tube. Factory has a cap that seals this off.
Stop changing things that are not factory. Put the pcv stuff back to factory.
It may be a problem with the lower intake gasket.
This has been going on long enough to get confusing, put everything back to factory and stop disconnecting the battery. Not the h/c/i of course but everything else leaving off and plugging all the vacuum lines except the pvc and the fuel pump regulator. Start it and let it get warmed up to operating temp and do the idle reset. The instructions are in the surging idle checklist.
Do you have a vacuum gauge?
Stop changing things that are not factory. Put the pcv stuff back to factory.
It may be a problem with the lower intake gasket.
This has been going on long enough to get confusing, put everything back to factory and stop disconnecting the battery. Not the h/c/i of course but everything else leaving off and plugging all the vacuum lines except the pvc and the fuel pump regulator. Start it and let it get warmed up to operating temp and do the idle reset. The instructions are in the surging idle checklist.
Do you have a vacuum gauge?
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