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Wish I was more knowledgeable on this subject and could help as I have an ’81 as well…. However, I just pulled the body off and have headed down the road of an LS swap. If you narrow down what may be the culprit and/or want to try swapping a part(s) on from a different vette that was running fine before the body pull, PM me and I may be able to help out in that respect.
 

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I have driven 20,000 miles on the street with a Holley 770 cfm Street Avenger on my 63 Pontiac.


That E4MC Q-jet is crap next to it.


Corvette Tuned Port EFI Works Right too.
 

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In the 14 years I've owned it and 6k miles I've since put on it, I have had no problems with the carb. It now has 91K on it. The only thing I felt was a little off with it was after starting the engine cold and it running at high idle for a bit (about 5 mins maybe), it would attempt to idle down somewhat all by itself but not to low idle. Tapping the gas would let it kick all the way down to low idle like it should when warm and it would run just fine. I am not a carburetor guy so maybe that behavior is normal/expected. Paperwork that came with the car says the carb was rebuilt but there are no details on when or what was all done to it.
 

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Holley 4-bbls don't work well on Q-jet manifolds, which is what he's got. He would have to run an adapter, which are often a source of vacuum leaks.Fuel line doesn't work, need a different one. most guys and up with a rubber hose, not a step forward. various lines would have to be sorted and re-attached, including the headlight doors and A/C. Air filter won't work, hits the float adjuster front and back. vacuum line to power brake booster won't work, have to replace the distributor, it won't work without the computer. carb may hit the EGR valve. new dual feed line will hit the heater hose. have to do something with the computer and wiring harness. Fix the check engine light. Fix all the vacuum lines from the canister, re-vamp the lines as the Holley doesn't have two 3/8, actually three needed. Holley doesn't have bowl vents to plumb to the canister. power brake booster, evap and PCV. Fix the throttle linkage and TV cable. This is not a simple bolt-on change-over, I've fixed a few of these, the term that comes to mind is "butchered up mess". Did I mention the hood probably won't close with Holley on an adapter? Will it ever pass smog check again?

Have you ever done this on a nice original car? OP states he bought the car new. Think he wants it chopped up? Like I said, careful and through search for vacuum leaks hasn't even been done.
 

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Holley 4-bbls don't work well on Q-jet manifolds, which is what he's got. He would have to run an adapter, which are often a source of vacuum leaks.Fuel line doesn't work, need a different one. most guys and up with a rubber hose, not a step forward. various lines would have to be sorted and re-attached, including the headlight doors and A/C. Air filter won't work, hits the float adjuster front and back. vacuum line to power brake booster won't work, have to replace the distributor, it won't work without the computer. carb may hit the EGR valve. new dual feed line will hit the heater hose. have to do something with the computer and wiring harness. Fix the check engine light. Fix all the vacuum lines from the canister, re-vamp the lines as the Holley doesn't have two 3/8, actually three needed. Holley doesn't have bowl vents to plumb to the canister. power brake booster, evap and PCV. Fix the throttle linkage and TV cable. This is not a simple bolt-on change-over, I've fixed a few of these, the term that comes to mind is "butchered up mess". Did I mention the hood probably won't close with Holley on an adapter? Will it ever pass smog check again?

Have you ever done this on a nice original car? OP states he bought the car new. Think he wants it chopped up? Like I said, careful and through search for vacuum leaks hasn't even been done.
I noted early on he hates this Smog era E4MC Q-jet.
Its in his thread title.
I Hate this Q-jet.
He states he knows a Holley 4-bbl carb inside out.
He states he was a Mechanic in the past.
Knows all but Electronics.

So it makes Logical sense to give him what he really desires.

Its Not a 1970 LT1 or LS5 So he does not have a good factory Q-jet.
In Doug Roes Book ROCHESTOR Q-jet he states its not a good carb either a E4MC.

Why keep Ficking with it when it gives nothing but Frustration.

ITS JUNK.
Makes his Corvette Ultra slow.
Get passed by a Honda Tuner Kid with a Fart Can Muffler.
That kid that Blew by You does not care about SMOG.
 

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Discussion Starter #47
UPDATE (and a real quick response to Tom Mobley)...EGR, air pump, Cat Converter all that was removed several years ago, heat risers plugged~engine ran better with no CEL light.

I did thoroughly check for vacuum leaks...went around everything I could (headlight vacuum hoses/pods too) spraying a little 'Starting Fluid' to see 'if' Engine raised RPM's...it did not...not until the carb got a sniff.



Currently > > > Wish I could say I 'found and fixed' the problem but I did not...I removed the battery, disconnected the two large plugs and pulled the ECM out, kicked it around the garage floor, checked, cleaned the two large plugs, reinstalled it with the battery, maybe bumped some wires around and it's running like nothing ever happened however, the MCS still is not clicking at idle and I know it once did...but it's been some time.

(this Car should get better than 11 MPG around town and I baby it 140,500 pulled and rebuilt heads maybe 15 years ago, approx 3000 miles a year)

I borrowed the older Snap~On Scanner and everything from the O2 reading to Fuel Mixture and a few other readings from the Scanner were in the middle of the parameters, so it has me scratching my head...possible cracked solider joint in the ECM board? Possible funky connections at the two large ECM plugs (never touched since it was assembled in 1981)
I don't know, wish I did but, it's running just like it did prior to it running/idling bad...and especially like it seemed the ECM retarded the Timing a LOT!
Oh...and the MCS is still not 'clicking' at Idle and I know it did...because I remember it doing so, a while back.


Soooo that's my story and I'm sticking to it.
When it comes to "electronics/electrical" I'm still learning (truth is I still hate it and suck at it lol)
***All the feedback and time given doing so is greatly appreciated and I'm still reviewing all the posts :thumbsup:
 

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UPDATE (and a real quick response to Tom Mobley)...EGR, air pump, Cat Converter all that was removed several years ago, heat risers plugged~engine ran better with no CEL light.

I did thoroughly check for vacuum leaks...went around everything I could (headlight vacuum hoses/pods too) spraying a little 'Starting Fluid' to see 'if' Engine raised RPM's...it did not...not until the carb got a sniff.



Currently > > > Wish I could say I 'found and fixed' the problem but I did not...I removed the battery, disconnected the two large plugs and pulled the ECM out, kicked it around the garage floor, checked, cleaned the two large plugs, reinstalled it with the battery, maybe bumped some wires around and it's running like nothing ever happened however, the MCS still is not clicking at idle and I know it once did...but it's been some time.

(this Car should get better than 11 MPG around town and I baby it 140,500 pulled and rebuilt heads maybe 15 years ago, approx 3000 miles a year)

I borrowed the older Snap~On Scanner and everything from the O2 reading to Fuel Mixture and a few other readings from the Scanner were in the middle of the parameters, so it has me scratching my head...possible cracked solider joint in the ECM board? Possible funky connections at the two large ECM plugs (never touched since it was assembled in 1981)
I don't know, wish I did but, it's running just like it did prior to it running/idling bad...and especially like it seemed the ECM retarded the Timing a LOT!
Oh...and the MCS is still not 'clicking' at Idle and I know it did...because I remember it doing so, a while back.


Soooo that's my story and I'm sticking to it.
When it comes to "electronics/electrical" I'm still learning (truth is I still hate it and suck at it lol)
***All the feedback and time given doing so is greatly appreciated and I'm still reviewing all the posts :thumbsup:
I am going with the ECM AT FAULT . BAD COLD SOLDER JOINT ON THE CIRCUIT BOARD.
YOU KICKED IT AROUND THE GARAGE AND BEAT THE **** OUT OF IT.
SHOWED WHO IS BOSS.

See What Gunny has to say & thinks.
 

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UPDATE (and a real quick response to Tom Mobley)...EGR, air pump, Cat Converter all that was removed several years ago, heat risers plugged~engine ran better with no CEL light.

I did thoroughly check for vacuum leaks...went around everything I could (headlight vacuum hoses/pods too) spraying a little 'Starting Fluid' to see 'if' Engine raised RPM's...it did not...not until the carb got a sniff.



Currently > > > Wish I could say I 'found and fixed' the problem but I did not...I removed the battery, disconnected the two large plugs and pulled the ECM out, kicked it around the garage floor, checked, cleaned the two large plugs, reinstalled it with the battery, maybe bumped some wires around and it's running like nothing ever happened however, the MCS still is not clicking at idle and I know it once did...but it's been some time.

(this Car should get better than 11 MPG around town and I baby it 140,500 pulled and rebuilt heads maybe 15 years ago, approx 3000 miles a year)

I borrowed the older Snap~On Scanner and everything from the O2 reading to Fuel Mixture and a few other readings from the Scanner were in the middle of the parameters, so it has me scratching my head...possible cracked solider joint in the ECM board? Possible funky connections at the two large ECM plugs (never touched since it was assembled in 1981)
I don't know, wish I did but, it's running just like it did prior to it running/idling bad...and especially like it seemed the ECM retarded the Timing a LOT!
Oh...and the MCS is still not 'clicking' at Idle and I know it did...because I remember it doing so, a while back.


Soooo that's my story and I'm sticking to it.
When it comes to "electronics/electrical" I'm still learning (truth is I still hate it and suck at it lol)
***All the feedback and time given doing so is greatly appreciated and I'm still reviewing all the posts :thumbsup:


as ii answered in previous post today the e4me/e4mc is a beast, 90 percent of the computer function is to provide a smooth idle it does this by adjusting the air/fuel mixture something like 10 times a second, but once its above idle the cpu stops doing pretty much anything it does control some aspects of auto transmission function but mostly all it does is make the carb idle, and the problem is u cannot just adjust the idle higher to make it not do this because you end up with a idle of 1500 rpm or more to not have the cpu interact. the proper way to tune this is to use a combination of dwell and vacuum gauges.
start by making sure the tps sensor has the correct voltage.. then attach vacuum and adjust idle mix until the vacuum gauge is at its highest, once idle mix is set from the base screws use the dwell meter to get the proper dwell by turning the mixture screw on top of the carb until dwell is correct,, now the agonizing part of this... these adjustments must be done with the car idling at temperature... and since your issue with mostly with it not idling the start is a lot of twiddling with screws to get it to idle. (pro tip here is to ensure ur 02 sensor and map sensor are working, if one of these aint then ur pretty much sol)
 

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Discussion Starter #50 (Edited)
Been sometime since I posted (really busy taking care of my 91 year old father) but...I did ditch the OE carb, had my old junky Qjet rebuilt and the care runs great!
I can't be more pleased that E4MC is OFF my engine!:thumbsup:
 

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Good deal:thumbsup:
 
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