Need help with backfire issue
#1
07-24-2017, 08:25 PM
Need help with backfire issue
I'm having an issue with cold engine backfiring. I have a 1982 xjs he 5.3l with 46k on the odometer.
Engine starts and idles fine at 650 RPMs but backfires threw intakes if i stab the throttle when the engine is cold the problem goes a way as soon as engine is at normal temp. Here is what I have done to the engine so far.
replaced fuel filter, fuel pump, all fuel lines, Replaced plugs gaped to 25 thousandth, Replaced plug wires, cap and rotor, Gaped distributor pickup, Static timed to 10 BTDC Checked vacuum and centrifugal advance, check distributor shaft play replaced air and water sensors, Replaced both O2 sensors, Checked Fuel regulators witch hold 50 psi no vacuum and 25 psi full vacuum. I've bypassed inlet regulator Then back of timing 5 degrees but no change. I have also replaced radiator and thermostats. swopped out dis pickup and amp with ones from good running car. I run four tanks of 100+ octane gas with injector cleaner. I've pulled each fuel injector connector to see if one injector is not fueling. I am now at a loss help
Oh ya running 2 1/2 Borla exhaust and large bore air intakes with K&N filters
Engine starts and idles fine at 650 RPMs but backfires threw intakes if i stab the throttle when the engine is cold the problem goes a way as soon as engine is at normal temp. Here is what I have done to the engine so far.
replaced fuel filter, fuel pump, all fuel lines, Replaced plugs gaped to 25 thousandth, Replaced plug wires, cap and rotor, Gaped distributor pickup, Static timed to 10 BTDC Checked vacuum and centrifugal advance, check distributor shaft play replaced air and water sensors, Replaced both O2 sensors, Checked Fuel regulators witch hold 50 psi no vacuum and 25 psi full vacuum. I've bypassed inlet regulator Then back of timing 5 degrees but no change. I have also replaced radiator and thermostats. swopped out dis pickup and amp with ones from good running car. I run four tanks of 100+ octane gas with injector cleaner. I've pulled each fuel injector connector to see if one injector is not fueling. I am now at a loss help
Oh ya running 2 1/2 Borla exhaust and large bore air intakes with K&N filters
#2
07-24-2017, 10:02 PM
OK,
650 Cold, is NOT good, so the AAV is jammed. Should be around 1000+/- and gradually drop to the 650 when nearing operating temp.
10deg is always a base I use, and then advance from there by drive timing it, BUT, the engine must be at operating temp. I reckon I am at about 15 on most of the V12's maybe more on the PreHE. No timing plates, another oil leak fixed.
The ECU fuel "pot" needs a tickle.
The vacuam fuel enrichment valve is not working, missing, not connected even.
Attachment 149923
Attachment 149924
Attachment 149925
Attachment 149926
My spare fuel enrichment vac valve/switch, so you know what to look for. It is usually located near 5A inlet track, and has a clamp with a bolt. Some early HE engines are running the early PreHE switch. I will find a parts drawing of that sucker and edit this later, just in case.
Found it, #1 in this parts drawing.
What ECU are you running?????, being an early HE, I reckon a 6CU, which is a tad slow for big throttles. You need to find a 16CU that suits your market, and simply plug it in. ?bay has them mostly.
650 Cold, is NOT good, so the AAV is jammed. Should be around 1000+/- and gradually drop to the 650 when nearing operating temp.
10deg is always a base I use, and then advance from there by drive timing it, BUT, the engine must be at operating temp. I reckon I am at about 15 on most of the V12's maybe more on the PreHE. No timing plates, another oil leak fixed.
The ECU fuel "pot" needs a tickle.
The vacuam fuel enrichment valve is not working, missing, not connected even.
Attachment 149923
Attachment 149924
Attachment 149925
Attachment 149926
My spare fuel enrichment vac valve/switch, so you know what to look for. It is usually located near 5A inlet track, and has a clamp with a bolt. Some early HE engines are running the early PreHE switch. I will find a parts drawing of that sucker and edit this later, just in case.
Found it, #1 in this parts drawing.
What ECU are you running?????, being an early HE, I reckon a 6CU, which is a tad slow for big throttles. You need to find a 16CU that suits your market, and simply plug it in. ?bay has them mostly.
Last edited by Grant Francis; 07-25-2017 at 08:19 AM.
#3
07-25-2017, 06:43 AM
Thanks Grant
OK,
650 Cold, is NOT good, so the AAV is jammed. Should be around 1000=/- and gradually drop to the 650 when nearing operating temp.
10deg is always a base I use, and then advance from there by drive timing it, BUT, the engine must be at operating temp. I reckon I am at about 15 on most of the V12's maybe more on the PreHE. No timing plates, another oil leak fixed.
The ECU fuel "pot" needs a tickle.
The vacuam fuel enrichment valve is not working, missing, not connected even.
Attachment 149923
Attachment 149924
Attachment 149925
Attachment 149926
My spare fuel enrichment vac valve/switch, so you know what to look for. It is usually located near 5A inlet track, and has a clamp with a bolt. Some early HE engines are running the early PreHE switch. I will find a parts drawing of that sucker and edit this later, just in case.
Found it, #1 in this parts drawing.
Attachment 149927
What ECU are you running?????, being an early HE, I reckon a 6CU, which is a tad slow for big throttles. You need to find a 16CU that suits your market, and simply plug it in. ?bay has them mostly.
650 Cold, is NOT good, so the AAV is jammed. Should be around 1000=/- and gradually drop to the 650 when nearing operating temp.
10deg is always a base I use, and then advance from there by drive timing it, BUT, the engine must be at operating temp. I reckon I am at about 15 on most of the V12's maybe more on the PreHE. No timing plates, another oil leak fixed.
The ECU fuel "pot" needs a tickle.
The vacuam fuel enrichment valve is not working, missing, not connected even.
Attachment 149923
Attachment 149924
Attachment 149925
Attachment 149926
My spare fuel enrichment vac valve/switch, so you know what to look for. It is usually located near 5A inlet track, and has a clamp with a bolt. Some early HE engines are running the early PreHE switch. I will find a parts drawing of that sucker and edit this later, just in case.
Found it, #1 in this parts drawing.
Attachment 149927
What ECU are you running?????, being an early HE, I reckon a 6CU, which is a tad slow for big throttles. You need to find a 16CU that suits your market, and simply plug it in. ?bay has them mostly.
The following users liked this post:
Grant Francis (07-25-2017)
#4
07-25-2017, 08:45 AM
Problem solved
Thanks for the info. AAV is working engine idles at 1000 rpm's for a minute or so before dropping to 650 rpm's. I'm running a CU16 ECU but have tried running a CU6 with same issue. The voltage on the ECU enrichment plug in the trunk runs at 1.9v with plug removed or in Drive and it should be closer to 2.5v. I don't see any change in voltage if I adjust the switch on the ECU whether I run CU6 or CU16. I think the enrichment valve you pointed out is working but I will re-check that today.
[/QUOTE]Problem solved advanced timing to 18 BTDC with advance disconnected car has come alive [/QUOTE]
[/QUOTE]Problem solved advanced timing to 18 BTDC with advance disconnected car has come alive [/QUOTE]
#5
07-25-2017, 09:16 AM
