C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

here i go again poor preformance

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Old Mar 5, 2013 | 04:13 PM
  #21  
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Originally Posted by hitmanpty
i Have no egr valve . i delite that some time ago

so to set the base idle, the ecm most be disconnected. just the get it out of the ecuation right??????

Leave the ECM connected, while doing the base idle adjust the ecm wont be able to adjust/compensate as the timing bypass connector and iac valve are disconnected while setting the 400 rpm in drive.
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Old Mar 5, 2013 | 06:08 PM
  #22  
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ok I just finish trying to set the base idle.(the engine was running into It reach normal operation temperature)
i had to disconect the brown wire at the driver side because i was going to move the distributor.

My timing was out the scale. so the most i can do was set my timing to 10* btdc. i had to play with the timming screw and the distributor to get to that point.. if I go closer to
6*btdc the car will stall and them stop. so again the best i can go was 10*btdc.

at this time the IAC was disconected also the brown wire on diver side. i check the tps the reading was 0.51 so i reset to 0.54 at idle

the car was idle much better but again only at parking gear. if i move the gear to drive or revese the car stall and engine stop. again imposible to drive.

I reconect the IAC and the brown wire. and start the car again.

the feeling the same. better idle at parking. stall and stop when go on drive and reverse.

I can not tell what is the rpm at idle. since i can not read my dash. but sound like 1000 rpm. what i meant is higher that 400 rpm

I made a video the sound is very poor quality. because is from my cell phone.

there you can see when i put the car gear.


Last edited by hitmanpty; Mar 5, 2013 at 06:32 PM.
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Old Mar 5, 2013 | 06:50 PM
  #23  
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[QUOTE=hitmanpty;1583286852]ok I just finish trying to set the base idle.(the engine was running into It reach normal operation temperature)
i had to disconect the brown wire at the driver side because i was going to move the distributor.

My timing was out the scale. so the most i can do was set my timing to 10* btdc. i had to play with the timming screw and the distributor to get to that point.. if I go closer to
6*btdc the car will stall and them stop. so again the best i can go was 10*btdc.

at this time the IAC was disconected also the brown wire on diver side. i check the tps the reading was 0.51 so i reset to 0.54 at idle

the car was idle much better but again only at parking gear. if i move the gear to drive or revese the car stall and engine stop. again imposible to drive.

I reconect the IAC and the brown wire. and start the car again.

the feeling the same. better idle at parking. stall and stop when go on drive and reverse.

I can not tell what is the rpm at idle. since i can not read my dash. but sound like 1000 rpm. what i meant is higher that 400 rpm

I made a video the sound is very poor quality. but is from my cell phone.

there you can see when i put the car gear.

Hi

I was unable to play the video on my mobile, but if your dash does not display your idle rpm you cannot set your base idle at all

You will need to connect a tacho to see what rpm you have exactly, untill then you cannot set your base idle, without that having been set the ecm will not be able to manage your engine as it needs those things to be correct first. (VERY IMPORTANT)

That is why your engine stalls when you put it in gear untill you can set your base idle, easy starting and smooth idle is not able to be achieved. And the ecm will have no idea what it is doing, that is why you are having this problem.
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Old Mar 5, 2013 | 07:26 PM
  #24  
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i will try to fix my dash. I suspect is a bad ground. because is was working before I remove may driver side heads.

Just to mantion I try to do this base idle stuff some time ago. when my dash was working ok. I recall de same problem. it was imposiblem to get to that 400 rpm. Iam sure if i fix the dash. the same thing will happend i can not set the rpm to 400.

how about the timing. I dont need to know the rpm to set my timing to 6*btdc. and is imposible to set the timing right. what is preventing me to set the coreect timing.??????
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Old Mar 5, 2013 | 08:35 PM
  #25  
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Ok Iam going crazy now. I just dont unerstand. how come I can not set my ingition timming to 6*btdc.

I have seen so many videos , post explanations. but I can not get close to that mark.
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Old Mar 5, 2013 | 09:24 PM
  #26  
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Originally Posted by hitmanpty
Ok Iam going crazy now. I just dont unerstand. how come I can not set my ingition timming to 6*btdc.

I have seen so many videos , post explanations. but I can not get close to that mark.
While setting the base idle with the timing bypass connector disconnected (the single wire connector near the windscreen wiper motor and fuel pump relay) the timing will be in a static mode and cannot be adjusted by the ecm, how close can you get it ? maybe you need to move the distributor one tooth more advanced or retarded depending on where the timing mark can be seen?

So you have the TPS set correctly and once you get the timing right and can confirm the correct 400 rpm in drive when you get your dash working it should all fall into place and start easilly hot or cold and have very little effect when a load is put on like putting the car into drive, remember any turn of the idle adjust scew will need the TPS volts to be checked again.

Looks like just your distributor needs to be moved one tooth if you cannot get it near 6 deg btdc... Almost there

Check the ground wires on block above the oil filter and there are also some on the belhousing to block bolts, driver side i think from memory

Last edited by gerardvg; Mar 5, 2013 at 09:29 PM. Reason: More info
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Old Mar 5, 2013 | 09:50 PM
  #27  
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thank you for your help. you Have giving me some pease of mine . you aré right it most be the distributor one tooth off
i will get Back to the car tomorrow
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Old Mar 5, 2013 | 10:25 PM
  #28  
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Yeah I agree the distributor is retarded one tooth that is why you are getting the backfire and stalling when putting it into drive.

Once you have the timing right and TPS volts with the 400 rpm in drive she will be good to go!

Reconnect the iac valve and reconnect the timing bypass connector and she will start instantly then have a high idle 1200 rpm for a few moments then drop to 600 rpm.
That is what my vette does every time I start her she fires up very quickly without needing to touch accelerator goes to 1200 rpm and settles down to 600 rpm.

Good luck
Hopefully good news tommorrow
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Old Mar 5, 2013 | 10:58 PM
  #29  
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I was gonna say the same thing, then I refreshed saw the page, and everyone else beat me to it. h
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Old Mar 6, 2013 | 07:42 PM
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ok i just finish moving the distributor one tooth conterclock wise. (i think only one tooth.) that is why Iam posting photos

but I try to start the car and no start condition

here is my distributor before moving.
[IMG][/IMG]

here is the distributor after moving one tooth conter clock wise.
[IMG][/IMG]
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Old Mar 6, 2013 | 07:53 PM
  #31  
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So is it pointed at the #1 wire on your cap? Your wires may be off/wrong on your cap. If your balancer is at 0, then your rotor needs to point at the #1 wire, regardless of where that wire is. Also make sure you are on #1, and not #6. h
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Old Mar 6, 2013 | 08:38 PM
  #32  
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the rotor is pointing to number 1 wire at the dist. cap
i have the number 1 cylinder at tdc. on the compression stroke. and the balancer mark on 0.
but the car have no start condition at this possition.

maybe there is a tooth between the old rotor possition and the new one. maybe i mist that tooth in between.

dont want to come back to the old possition. the car is not have good preformance on that old position.
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Old Mar 6, 2013 | 08:43 PM
  #33  
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Originally Posted by hitmanpty
ok i just finish moving the distributor one tooth conterclock wise. (i think only one tooth.) that is why Iam posting photos

but I try to start the car and no start condition

here is my distributor before moving.
[IMG][/IMG]

here is the distributor after moving one tooth conter clock wise.
[IMG][/IMG]

Hi

The distributor position at top dead center with rotor between 1 and 8 as your first picture IS CORRECT, the second picture with the distributor one tooth counter clockwise has retarded the distributor.
The distributor moves clockwise and firing order is 18436572,

With the distributor bolted in position as in the first picture, when you rotate it slightly anticlockwise (not removing repositioning). That advances the ignition and should get your 6 deg before top dead center. If you cannot get the 6 deg btdc you need to remove the whole distributor and move it one tooth CLOCKWISE to advance it one tooth. However with the distributor in your first pick if it is at tdc on compression stroke you should be able to get the 6 deg timing unless your harmonic balancer timing mark is of.
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Old Mar 6, 2013 | 09:09 PM
  #34  
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First I will try to move it one tooth clock wise this time. si if I can get a midle point between the to points if that dont work I will have to check the timming gear on front of motor.
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Old Mar 6, 2013 | 09:11 PM
  #35  
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Even with the distributor in the position of picture no 2 you should be able to start the engine, but with the adjustment you will not be able to advance it enough. Having the dist cap with the electrical connection hit the firewall, so try the distributor advanced one tooth from picture 1 and it should work. Maybe the cam timing is off as the original first picture it should be able to get the 6 dbtc.

Good luck

I have been able to run my engine with the distributor in both positions you have so you have to confirm it is on top dead center of compression stroke, maybe take the rocker cover of and confirm the exhaust valve opens when you turn your engine half a turn.

Last edited by gerardvg; Mar 6, 2013 at 09:15 PM. Reason: more info
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Old Mar 6, 2013 | 09:14 PM
  #36  
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Im starting to think your cam may be installed incorrectly, or someone thought they had a race motor, and installed it advanced. I think you're approaching the real reason to your problems. ie. your vacuum issues too. h
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Old Mar 6, 2013 | 09:55 PM
  #37  
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Originally Posted by gerardvg
Even with the distributor in the position of picture no 2 you should be able to start the engine, but with the adjustment you will not be able to advance it enough. Having the dist cap with the electrical connection hit the firewall, so try the distributor advanced one tooth from picture 1 and it should work. Maybe the cam timing is off as the original first picture it should be able to get the 6 dbtc.

Good luck

I have been able to run my engine with the distributor in both positions you have so you have to confirm it is on top dead center of compression stroke, maybe take the rocker cover of and confirm the exhaust valve opens when you turn your engine half a turn.
I just move the distributor back to position 1 photo. at list I know on this position the car fire up
when tou samove the rotor to advance. that will be clock wise or conter clock wise. getting a little confuse here. iam positive is a top death center
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To here i go again poor preformance

Old Mar 6, 2013 | 09:59 PM
  #38  
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Originally Posted by hemivett
Im starting to think your cam may be installed incorrectly, or someone thought they had a race motor, and installed it advanced. I think you're approaching the real reason to your problems. ie. your vacuum issues too. h
what is the best way to check the timming gear, I know you have to align the 2 points on tdc. but is there any way to check that with out dismanteling the hole front of the motor
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Old Mar 6, 2013 | 10:03 PM
  #39  
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Yes clockwise toward no 8 as a test if it fires up there and runs ok your cam /or timing is out
Good luck
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Old Mar 6, 2013 | 10:08 PM
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Wait a minute guys, why are you playing with the distributor teeth? Hip said when he tries to set the timing at 6*btdc the motor dies. It is not as if the distributor won't allow 6* because it is hitting the firewall. You can move the distributor rotor 5 teeth, or 10 teeth if you want. You will just have to spin the distributor in that direction and you will be back where you started. The rotor position is relative to the cap position. Hip, don't forget to move the oil pump drive so the distributor is seated before tightening the setbolt.
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