After header install, miss developed...
Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 6,692
Likes: 56
From: Troutman, NC
After header install, miss developed...
after about 5 or 6 minutes of hard running and engine hot.
Seems to begin during right turn, and clears up under full throttle until throttle is reduced for next turn. When idling in off track there's a terrible miss. When things cool off, it good to go again until it gets hot.
I replaced the spark plugs and wires.
Any ideas?
Seems to begin during right turn, and clears up under full throttle until throttle is reduced for next turn. When idling in off track there's a terrible miss. When things cool off, it good to go again until it gets hot.
I replaced the spark plugs and wires.
Any ideas?
Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 6,692
Likes: 56
From: Troutman, NC
Burning Brakes
Joined: Dec 2003
Posts: 1,243
Likes: 5
From: Loveland CO
not sure if they would but i can tell you its a common mistake.. after the engine gets hot the ECU goes from Open loop to Closed.. then your O2's will cause issues if they are reversed. Also, did you do any other mods? have you cleaned the MAF? Do you have a MAF screen? Did you do any sort of tune after the headers?
What plugs/wires did you use? (Brand, type (plat, copper, irridium) and temp of plugs) Did you gap them (some plugs are supposed not to be gapped). If you have a scan tool you can scan to see if its a miss and what cyl has the miss. Did you use plug wire grease between the plugs and wires and did you check the connections between the wires, plugs and coils? did you try the old wires on the car and see if it changes?
S
What plugs/wires did you use? (Brand, type (plat, copper, irridium) and temp of plugs) Did you gap them (some plugs are supposed not to be gapped). If you have a scan tool you can scan to see if its a miss and what cyl has the miss. Did you use plug wire grease between the plugs and wires and did you check the connections between the wires, plugs and coils? did you try the old wires on the car and see if it changes?
S
Racer
Joined: Jan 2013
Posts: 377
Likes: 0
From: Jasper Texas
St. Jude Donor '13
This may or may not help but many years ago I had a '72 F-100 with a 302. It ran great but off and on it would have a miss. I tried everything and couldn't figure it out. One day while it was missing I got fed up and just punched it and ran it hard when I heard a pop and then an intermittent hissing sound, I thought I had a flat. When I pulled into the driveway and stopped with the engine running the intermittent hissing continued. When I opened the hood I found the porcelain part of a spark plug hanging on the plug wire. I found my miss. Krappy Champion Plugs.
Le Mans Master
Joined: May 2007
Posts: 5,393
Likes: 17
From: Belleville Mich.
Some times the new boots will cause (trapped) air to eventually pull the wire away from where they make connect onto the coil, not making a proper/direct contact.
Also when the 02 sensor wires get crossed, it will create a pronounced miss at all levels of RPM.
Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 6,692
Likes: 56
From: Troutman, NC
That's when I shrugged.
It only misses when coming off throttle and when the engine is hot (after a few hot laps). When I go back to full throttle the miss goes away, but after it's occurred, it stumbles bad at idle.
After it's cooled down, it's good to go, again.
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Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 6,692
Likes: 56
From: Troutman, NC
Tune didn't make any difference. Miss was there before and after.
New GM Performance (the red ones) plug wires. I have the nomex boots over the ends.
I checked the resistance on all the new wires before installation.
I installed the new wires because I suspected the old wire as being the problem, but the same issue returned.
I'm thinking it might be a coil, since most other electrics have been eliminated, but since I don't want to buy 8, I'll have to get the engine to the temp to create the miss (it's a race car so on the street doesn't work), and change each coil to a new one until it doesn't miss.
Getting it to temp is the hard part.
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Just wonder if there's something directly related to physical engine movement that may be worth checking out. By that, I mean a wire, or wire harness bundle (either coil or injector) that is in close proximity to a bracket or some other component that either a.) gets grounded when engine torque moves the engine upon hard throttle application, or b.) cause enough flex in a harness that a broken/damaged wire "opens" preventing current flow. Same for anything close to an exhaust component.
It's the relationship to hard throttle application that's making me think in this direction.
HTH
It's the relationship to hard throttle application that's making me think in this direction.
HTH
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Have you checked the ground wire on the back of the drivers cylinder head and make sure that the two wires and the ground eyelet are properly secured to the head?
The harness on the drivers side of the intake manifold is known to rub thru near the back of the fuel rail. on the black bracket behind the fuel rail.
BC
The harness on the drivers side of the intake manifold is known to rub thru near the back of the fuel rail. on the black bracket behind the fuel rail.
BC
Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 6,692
Likes: 56
From: Troutman, NC
Have you checked the ground wire on the back of the drivers cylinder head and make sure that the two wires and the ground eyelet are properly secured to the head?
The harness on the drivers side of the intake manifold is known to rub thru near the back of the fuel rail. on the black bracket behind the fuel rail.
BC
The harness on the drivers side of the intake manifold is known to rub thru near the back of the fuel rail. on the black bracket behind the fuel rail.
BC
Thanks!
Racer
Joined: Dec 2005
Posts: 287
Likes: 2
From: Bay Area California
After header install, miss developed...
I chased a closed-loop miss for more than several weeks. No codes and scanner only logged a random spark miss. Replaced sensors and O2's one at a time. Last sensor replaced was the MAP and low and behold the problem was fixed!
BTW, engine is a H/C/H setup and moved to Champion copper plugs in one colder heat range. Have worked excellent and do last many miles in my daily driver. Reduce gap to .035 and you are good to go. Oh, and the best part is they are sold at Kragen's for under two bucks each! Trust this is helpful...
A1
BTW, engine is a H/C/H setup and moved to Champion copper plugs in one colder heat range. Have worked excellent and do last many miles in my daily driver. Reduce gap to .035 and you are good to go. Oh, and the best part is they are sold at Kragen's for under two bucks each! Trust this is helpful...
A1
Race Director
Joined: Sep 2005
Posts: 11,060
Likes: 291
From: Pasco WA
I just remembered that when I installed my LGs, the heat burned the insulation off a starter wire, and damaged one O2 bundle. Depending on brand; some guys have had problems crimping the back O2s because the bungs are angled toward the underbody too much.