Big backfire n pop after cam install
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Joined: Feb 2008
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From: SAN JOSE ,CA
Big backfire n pop after cam install Hey guys I just finished my cam swap two days ago. I go to fire up my car n it did a loud pop n serges to try to keep idle. I give it 15% throttle to keep it alive n it keeps poping like a loud gun shot. One thing I found wrong when I took it apart one of my rocker arms trunion was broken all the bearings had came out. I also notice the valve tip had dings. Could vale be bent due the rocker arm truenion being broken? Can that be the cause of my backfire? Any input would help me out a lot. Thanks
Did you clean out every needle bearing and swap the rocker? If not I can see why your having problems...I would pull the heads and investigate, gaskets and bolts would be cheaper than grenading the motor...good luck bro
sounds liek a cylinder isnt firing. be sure all your plug wires are in good and be sure the plugs are in tight. feel free to do a compression test also. might have one or two pushrods too long and its holding a valve open?
Thread Starter
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From: SAN JOSE ,CA
So I pulled my plugs out n the last two on the driver were just wet with a lot of gas n the others looked good. Also the ones that came out soaked were black n others had a gray look to em. What can be wrong? Can a tune fix it? It's a ms4 cam on the stock 98 tune.
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You installed a MS4 on a other wise all stock car with no tune?.....and the rocker trunion broke on just one..??? sounds like you smashed a valve on your cylinder esp. since you said that the valve tips had some damage on them. you are gonna have to pull the heads and check all the valves. sounds like the PTV was not checked.
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Brett Foote I didn't realize it was a stock tune! 98s have the worst PCM at that...I would pull heads and check for damage to the piston crown and then of that checks out get a tune...ms4 is a huge cam to try to run on a stock tune...Texas speed lists ms4 as a stock setup so I wouldn't thing your crashing valves but pulling the heads is the only way to know for sure...
Thread Starter
On The Tree
Joined: Feb 2008
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From: SAN JOSE ,CA
I did cam n valve springs. Running ms4 cam with patriot gold extreme springs with tsp 7.400 push rods on a stock tune. When I pulled the far back two plugs on driver side they were all soaked in gas. Idk what it could be. I'm sure I didn't crush a valve. The valve that had the broken trunion looked ok n plug look normal. Seems like my it's not getting spark to the two far back cylinders on the driver side
Thread Starter
On The Tree
Joined: Feb 2008
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From: SAN JOSE ,CA
all my mods:
pacesetter LT
TSP trueduals dyno max bullets
egr delete
ms4 cam
patriot gold dual extreme springs
tsp 7.400 push rods
lid
tsp replacement timing chain
like i said the far two plugs on the driver side were soaked with fuel when i pulled them. as for the valve that had the broken truenion, that spark plug checked out ok & that valve is on the passenger side head. would a tune fix the issue? i dont want to pull my heads out if thats not the problem. the car ran fine with no miss fires before the cam swap & me not knowing one of the truenion was broken.i did crank the car over with out the two main coil packs plug to make sure i was getting oil pressure, once i saw i had good oil pressure i went ahead n pluged the two main coil plugs & fired up the car, but all i got was a loud pop. the car will not idle without me giving 15% throttle. iv never ran into a problem like this on my previous cam swaps.
pacesetter LT
TSP trueduals dyno max bullets
egr delete
ms4 cam
patriot gold dual extreme springs
tsp 7.400 push rods
lid
tsp replacement timing chain
like i said the far two plugs on the driver side were soaked with fuel when i pulled them. as for the valve that had the broken truenion, that spark plug checked out ok & that valve is on the passenger side head. would a tune fix the issue? i dont want to pull my heads out if thats not the problem. the car ran fine with no miss fires before the cam swap & me not knowing one of the truenion was broken.i did crank the car over with out the two main coil packs plug to make sure i was getting oil pressure, once i saw i had good oil pressure i went ahead n pluged the two main coil plugs & fired up the car, but all i got was a loud pop. the car will not idle without me giving 15% throttle. iv never ran into a problem like this on my previous cam swaps.
I've seen this alot on 98's. Make sure your coil packs are not swapped left side and right side or front to back. They have to be correct on 98's and cannot be swapped. Check the color of the signal wire going to each coil to see if they are on the right cylinder.
1. PPL
3. LT BLU
5. BRN
7. DK GRN
2. RED
4. DK GRN/WHT
6. BRN/WHT
8. LT BLU/WHT
1. PPL
3. LT BLU
5. BRN
7. DK GRN
2. RED
4. DK GRN/WHT
6. BRN/WHT
8. LT BLU/WHT
Last edited by 2xLS1; Aug 16, 2012 at 10:59 PM.
Another thing could be you messed up a lifter. Especially of running stockers on that cam if you killed a lifter and it's not getting air that'd explain you unburnt gas and backfiring
yeah you cant put that big of a cam in and drive it right away with no tune, tow it to a shop and get a tune..
If you chewed any valve tips like you said, i would replace it because it could wipe out a rocker again..
If you chewed any valve tips like you said, i would replace it because it could wipe out a rocker again..
Why would the coil packs matter? I went from a 98 806 head to a ported 243 so had to add valve covers and brackets. My car is doing the same thing with a TV3 cam. I'm just curious because I swapped coils around on the driver side to get them to mount to the bracket and just unplugged them and ran the wires like they were before.
^I agree. The MS4 is one hell of a cam to try and run on a STOCK tune. Running a compression test is usually an easy way to tell if you bent a valve. If I were you, with a cam with that agressive of a ramp rate, I'd AT LEAST invest in the Comp Trunion upgrade while you're fiddling under the valve covers.
