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Author Topic: Idles Great! No power under load  (Read 7963 times)

Offline Jsvob03

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Idles Great! No power under load
« on: 06:51:34 PM / 06-Oct-13 »
Been workin on bens old SE. god its been a headache from the get go.

what ive done..

-proper rewiring of injectors
-new plug wires
-'new' (used, but in great shape) distributor - cap n rotor good
-new timing belt (is timed correctly)
-base timing set to 20*
-newer fuel filter
-reman maf (doesn't make a difference)
-new CHTS
-plugs not in bad shape, but will be changed soon

This things idles great. I fought and fought. finally got it to idle great when warm. cold...well its a vg, it doesn't idle nicely when cold, lol. under load, it feels as if its not fueling enough. I need to look and see if its a fuel supply issue, or a computer control issue. at last check fuel pump was providing the correct pressure and flow. multiple grounds cleaned, multiple connections cleaned. I still have more checking to do, but im looking to see if someone else has this issue?

as a side note, its got no exhaust. simply a ypipe and that's it. obviously with that its gonna have some issues, but not this bad. its got less than 1/2 power. itll get to 65, but it takes a while and anything over 1/2 throttle it just shits out. tps is adjusted properly.

anyone had this issue? quick fixes or tips? ill keep digging, just lookin for a shortcut..

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Offline Colonel Gustard

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Re: Idles Great! No power under load
« Reply #1 on: 11:18:49 PM / 06-Oct-13 »
O2 sensor plugged in? Is the MAF known to be good? Hows the coil? You try unplugging the tps? CHTS connector good? Juat a couple things ive had to deal with VG's
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what the hell is camber?

I thought about my s12 and the parts i want to put in her :P

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I saw some of his posts, he seems like more fun than a barrel of hookers.

Offline Wonderingraven

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Re: Idles Great! No power under load
« Reply #2 on: 11:22:59 PM / 06-Oct-13 »
First check your CAS inside the dizzy, I have been threw 4 of these so far.  When going bad it does weird crap IE: under load it fails, second check your MAF, Is the maf stock s12 sev6 or is it the z31? also advance your timing to 25 from 20 noticed this for some odd reason helps with the drive-ability.
« Last Edit: 11:23:42 PM / 06-Oct-13 by Wonderingraven »
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Offline Mr Amber Shades

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Re: Idles Great! No power under load
« Reply #3 on: 02:52:24 PM / 28-Dec-13 »
I am having the same exact issues. Hard to get idling smooth until it's warmed up some but it only takes a minute. When trying to drive it out of my driveway, it stutters and won't run right under load unless I try really hard at it. No way I can drive it like that.
A car that verbally tells me i forgot my keys in the ignition?  That's pure 80's gangster right there!


Offline Wonderingraven

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Re: Idles Great! No power under load
« Reply #4 on: 11:15:04 PM / 01-Jan-14 »
I am having the same exact issues. Hard to get idling smooth until it's warmed up some but it only takes a minute. When trying to drive it out of my driveway, it stutters and won't run right under load unless I try really hard at it. No way I can drive it like that.

What have you done so far to troubleshoot the issue?
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Offline Mr Amber Shades

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Re: Idles Great! No power under load
« Reply #5 on: 09:03:52 AM / 04-Jan-14 »
I figured out a few issues.  Not all settled yet.

I replaced spark plugs and wires and made sure they were gapped corrently.  Didnt do cap and rotor because they have less than a 1000 miles on them.  2 years old though.  Who knows.  Looked good on all the contactes.

I redid some of the vacuum lines while doing an egr delete.  Car runs great once its been running a few minutes.  idles good.  Idles high but thats only until its fully warmed up.

Im 90% sure its the carrier bearing (also known as center support bearing) thats causing the rattling and knocing when going from a stop to moving.  only happen between 10mph and 20mph when the drive shaft is speeding up its rotation.  The carrier bearing is totally blown, the shaft moves around in it, and after driving it a while I can feel it knocing from riight below and behind the center console.  Right where that bearing is.  I've orded a new carrier bearing so I'll take a whack at that next week.
A car that verbally tells me i forgot my keys in the ignition?  That's pure 80's gangster right there!


Offline Jsvob03

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Re: Idles Great! No power under load
« Reply #6 on: 08:26:22 PM / 02-Aug-15 »
ok, lets re-visit this disaster...

it just refuses to run good under load/free revving. im going back to square 1..but here's what ive done thus far

NEW (not reman or recon'd) fuel injectors, made a difference, seems to have more oomph, but not much
disconnecting tps (for setting ign timing) makes it idle higher (timing increases from 0bdtc to 20bdtc, so its set right on!)
EGR removed (no change of spent gas getting back in.
tps adjusted properly (0 ohms @ closed throttle)
cleaned CAS with electronics cleaner, no change. swapped in a different distribuptor, NO CHANGE
cleaned MAF, no change. Swapped in different MAF, no change. (ranges 2-4 volts, increasing w/ airflow, seems ok)
replaced spark plugs & wires, no change. cap n rotor too, no change.
drained all fuel, new fuel in. pressure & flow good!
new intake gaskets, valve cover gaskets (fun story there...), new pcv & breather hoses. spraying intake cleaner (externally) doesn't raise idle = no more leaks!

no exhaust just downstream of oxy sensor
no filter, just a rubber coupler on maf.

I doubt the last 2 are causing major issues that im having, should just yield slight mixture issues, those are to be fixed once it moves.

last test that has me thrown a bit.. power balance test (not the first time doing this..odd results this time)

removing ign wires 1, 3, 5, yielded no drop in idle speed. REALLY? its running on 3 cyls? disconnected injector connector for 1,3,5, again no drop. 2,4,6 drops properly. if I add fuel via a vacuum line it smooths out and runs great. I have 12 v at injectors(key on, eng off) feed wire, 10.2v on 'ground' (manual states 12 on all...). I HAVE not checked with noid/test light yet, but plan to do so. things pointing to a bum ecm/injector drivers for 1,3,5?? suspect not getting fuel. btw, this car has not had the recall for injector wiring repair.

Offline Wonderingraven

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Re: Idles Great! No power under load
« Reply #7 on: 10:36:05 PM / 02-Aug-15 »
Sounds to me, there has to be a vacuum leak or your ecu is toast.
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Offline Jsvob03

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Re: Idles Great! No power under load
« Reply #8 on: 08:11:07 PM / 14-Aug-15 »
So things are progressing smoothly (unlike the forums here...wth happened??)

Found a couple problems.

1.)My new (2-3 years old, but probably less than 2 hours, 10 miles run time) Timing belt had stretched. Replaced it.

Spark plug wires shit out. Those were also replaced with the previous timing belt. Got new ones on.

Completed the egr delete (made a plug for the exhaust manifold.)

Did the PRW2 swap. It's temp wired for now, but it's in.

The results? It starts, and RUNS top notch. Then it gets warm the ecu under what hey who misfire 37 ohms confused pip pop.

Yeah. Basically once it gets warmed up, it seems confused. it steadily loses power,I know it's low on fuel and I'm going to address that tomorrow. If it's still present I'll double check fuel pressure/volume. Beyond that...I'll cross that bridge when i get there. It's nice tho..this is by far the best it's run. I'm actually excited to get fuel in it and see how it does now.
« Last Edit: 08:12:22 PM / 14-Aug-15 by Jsvob03 »

Offline Charlie S12

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Re: Idles Great! No power under load
« Reply #9 on: 01:49:15 AM / 27-Aug-15 »
I had the same issue as you. Would idle great but after warms up it would bog and not run properly i replaced the maf with a z31 YELLOW TAG MAF (yellow tag is federal blue tag is cali yes it makes a difference) and a 84 na z31 ecu then unplugged the 02 till I can find a 86 ecu. It ran better all around turned out to be the ecu
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Vgs are picky ngk wires ngk plugs and buy quality parts. They will never fail you if you take care of them
« Last Edit: 01:50:53 AM / 27-Aug-15 by Charlie S12 »
1984 z31: hy35, 450cc injectors, act 6 puck clutch, obx hlsd, 17x9, 275 rears 245 fronts, q45 brake calipers, coilovers, catchcan, nistune and too much to list

1987 S12 SE: stock for now.

Offline Ju_S12_Turbo

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Re: Idles Great! No power under load
« Reply #10 on: 02:14:41 AM / 25-Oct-15 »
I had something like that happen to me, My fuel pump wiring was shot. It would randomly have issues. Once I replaced with with a heavy gauge, a lot of weird issues went away.

Offline sideways_s12

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Re: Idles Great! No power under load
« Reply #11 on: 02:03:46 AM / 26-Oct-15 »
Check CTS sensor and the wiring to it in my experience (although with ca's not VG's) The CTS when bad or not plugged in shuts the car down as the ecu doesn't know it's no longer in closed loop. since your yours isn't shutting completely down I'd check the wiring and the sensor itself...

Offline Jsvob03

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Re: Idles Great! No power under load
« Reply #12 on: 08:33:35 PM / 27-Aug-16 »
Update.

Put in a used, but good working ecu. Has an extended crank (exhaust not present past the ypjpe so no back pressurel, but once it fires, it's happy to be alive. Idle is smooth as ever, better than my last VG.  Hits 70 mph without blinking, and can light the tires on fire.

So I'm certain the bulk of the issues were caused by exposed/misrouted wiring that played hell with the drivers in the old computer. Just too much strain for too long.

I know it's an old post, but I cannot stand it when I cruise through other forums and find dead ends.

Offline Wonderingraven

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Re: Idles Great! No power under load
« Reply #13 on: 08:45:43 PM / 27-Aug-16 »
Good to hear.
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