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Old 11-12-2012, 11:33 PM   #1
ccguy
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Default 7mgte stumble HELP

i need your help again. i fixed the tps wiring and the tps is working perfect (as you will see in the video it shows how much throttle is open in volts).
itis a bone stock 1987 7mgte motor.
there is a hesitation, stumble, hiccup at around 2500 rpm.
it is running very rich and getting horriable milage.
if it is a cold motor it runs good for about 40 seconds then this stumble starts.
i have an inline walbro and a intank OE supra pump.

while driving it can rev above the biccup but if the throttle is barely cracked it accels like i am flooring it. when the speed catches up to how much the throttle is open it acts like there is a dead spot. and the throttle is like a switch between on or off.

if i rev it up and hold it at like 4k and let it off it revs down and almost dies or dies.
most i have boosted on that crap gauge is 4psi.
io have great vacuum.

video HELP
http://www.youtube.com/watch?v=vOdnP...ature=youtu.be
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Old 11-13-2012, 12:06 AM   #2
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just compression tested it.
#1-145
2-145
3-145
4-145
5-145
6-135
also i dont have the factory boost sending unit hooked up. the wiring showed that it went to the gauge only.
what rpm does the stock trim start to boost?
when does the fuel up vsv open? it does not matter if the fpr has vac or not.
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Old 11-13-2012, 12:22 AM   #3
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plugs gaped at .028

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Old 11-13-2012, 01:19 AM   #4
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scratching my head

Last edited by ccguy; 11-13-2012 at 04:56 AM.
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Old 11-15-2012, 02:34 AM   #5
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No diagnostic codes stored in the ECU? The CEL doesn't even come on for most of them so if you haven't checked then do so. There's a how to in the MKIII FAQ section.
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Old 11-16-2012, 03:53 AM   #6
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no cel and nothing stored. so????
i am thinking it is a boost leak but cant find it.
do you think the video resembles a boost leak?
when i turn the steering wheel it does not idle up. the ps pressure switch is working and the lines are clear.

Last edited by ccguy; 11-17-2012 at 02:18 AM.
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Old 11-18-2012, 04:04 AM   #7
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Something just hit me....


Why are you running a second fuel pump, inline with the stocker? I'm assuming they aren't plumbed parallel.
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Old 11-19-2012, 03:17 AM   #8
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i put in a second pump (intank) because i was thinking that the inline walbro (up on the fender) was loosing suction due to it is higher than the tank. so i put it in there.
started the motor (with 1 pump going) let it warm up, then when the stumble hit i turned on the intank pump. there was no difference between 1 or 2 pumps going.
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Old 11-19-2012, 04:19 AM   #9
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You're sitting in the front row of Trouble 101, waving your arms and shouting "Oh me! Me, me! Pick me!".

And I still can't imagine any reason on Earth why you'd run a second pump (much less an in line, in series with the stocker) on a stock setup. Shit, people run over 400hp on the stock pump without any issues. So, again, WHY are you running the second pump? Is it plumbed in series (I presume it is which is awful)? Is there a bypass to ensure that neither pump can cause a catastrophic failure or the other due to its own failure? Did you at some point delete the in tank pump completely and install an inline instead (you know that in tank pumps generally last longer and are more consistent as they're better cooled)?

This doesn't sound like an issue with the fuel pressure up VSV to me. Could be a failure of the fuel pump relay and resistor pack... Might try bypassing them to see if that helps. You're not going to be boosting enough to see any significant stumble from a boost leak at that RPM unless you've got a full fledged hole somewhere.

Personally, I'm suspicious of your inline fuel pump, the AFM, fuel pump resistor pack/relay and your spark plug gap may be too tight.

What other mods are you running?



EDIT: Please don't mistake me for having a negative or mean tone in any of this. I'm not a fan of that particular setup but it has its place... The Supra just doesn't have any significant deficiencies in the fuel system so I really can't see the point in adding another point of failure and extra complexity.
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Last edited by cre; 11-19-2012 at 04:42 AM.
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Old 11-19-2012, 04:42 AM   #10
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there never was a intank pump. the truck is a 1980 so there was just a draw tube that went down into the bottom of the tank. there was a mechanical fuel pump on the old motor. i am only running 1 pump at a time. the second one was just for a test.
i am just running the cor.
i have swapped out the afm and no difference. i think i am going to run new wires from the afm to the ece and see it that changes things like it did when i rewired the tps (a previous thread).
3" exhaust from the turbo back, no cat, everything else is stock.

it acted the same with the .028 gap as it did the .032 gap.
thanks for helping me troubleshoot this
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