Misfire at Idle when warmed up

[DTMtoDSM]

When i cold start my car it runs fine. It will run fine unitl its fully warmed up. At full operating temp, it starts to misfire at idle. The temp needle never goes past half though. I replaced the plugs with bosch coppers because my local autostore didnt have NGKs. Just ordered BPR7ES because a friend of mine who knows his way around dsms said to. The wires are Spark Transfer international-never even heard of them. Im going to change those at my next paycheck. Anyone know what could be causing the misfire? At WOT it doesnt misfire at all pulls hard and doesnt sputter. But at idle it fluctuates alot. I tested the ISC couple weeks ago and it checked out fine. I searched the problem and didnt come up with anything. Any help would be appreciated.

 

[BLINKY619]

any codes?

 

[spartan69x]

that is plug wires arching out on the VC, my car was doing the exact same thing, ran normal till warm, then you could hear a slight miss. get some wires and plugs, good to go.

 

[DTMtoDSM]

No there arent any codes. Thanks for the info man, i ordered the new plugs now im just going get new wires. Not sure what brand though. Thinking Magnacor or just regular NGKs. Any opinions?

 

[BIRDCLAWTSi]

Hi, What mod's do you have done to your car? As far as the wires being at fault, There are ways to test them. First, Spray them with water and see if the car starts to miss. Visually inspect them and look for signs of arcing. Misfires can be caused by a number of things. Vacuum leaks, Improperly gapped plugs, Sticking injector, Bad compression(burned valve,etc...), Coil on the way out, Boost leak, It is a matter of tracking it down and doing some detective work. I dont see a mod list in your profile but NGKBPR7ES's are for high output setups. I would recomend the BPR6'S The 7's need to be run at high boost levels to clean themselves properly, Daily driving will not do it on a stock setup. The 6's are hotter and therefore burn off deposits better. Have you done a Fuel filter? What did you gap the plugs to? Pull them out and see if one looks different than the others...I removed the isc, I got the block off plate. There is a mod you can do to the isc. you pop out the freez out and turn the screw in all the way so it cant move anymore, Then put the plug back in, and unplug the connector. leave the closed throttle postin wire attached though,(not sure if a 90 has that or not.) The idle will never fluctuate again. you set the biss and thats it. let us know what you have in terms of mods and what you have checked for a better idea of how to help.

 

[DTMtoDSM]

Car is basically bone stock. Didnt think the NGK 7s would have a problem but maybe I will save them and get some NGK 6s. My current plugs are gapped to .28 (read it in a thread) , and havent changed the fuel filter yet. I plan on doing higher boost so ill just save the NGK 7s. Just want to get the misfire figured out. I will look into some of the stuff you said and see if that takes me anywhere.

 

[BIRDCLAWTSi]

Car is basically bone stock. Didnt think the NGK 7s would have a problem but maybe I will save them and get some NGK 6s. My current plugs are gapped to .28 (read it in a thread) , and havent changed the fuel filter yet. I plan on doing higher boost so ill just save the NGK 7s. Just want to get the misfire figured out. I will look into some of the stuff you said and see if that takes me anywhere.

Like i said, Visually check all the vacuum lines, Check the wires, Put a long screwdriver against the injectors one at a time and listen for clicking, Make sure they are firing. You can also remove one spark plug wire at a time and stick a screwdriver into the end and ground it so you can see if you have good spark, or if it misses with the miss, You can also stick a spark plug into the end and watch it. Make sure to handle the wires with the car off though. you can also unplug one injector at a time and see if the miss smooths out. This might be a long shot but on my car, The plug that goes to the mass air flow meter had some corrosion in the plug and was making a bad connection. If none of this stuff gives you any leads i would do a compression test. Pull all the plugs and keep the throttle plate open while you crank it. Watch the first crank on th gauge and the last, Compare the numbers. Good luck.

 

[DTMtoDSM]

Someone who looked at the car before i bought it did a compression test. The results were all around 135 each. They werent very far off from each other. Drove to my girlfriends house about an hour ago and noticed it was missing while i was driving too. I guess i have some serious research to do. My fuel pump whines, which my buddy said is the characteristic of a walbro, but also said it could be dieing if its the stock so that could be a problem too. But at WOT it runs good or so i think. I cant tell because of a problem with my tach. When i hit boost on the stock boost gauge in the cluster, the rpms drop, so if i hit boost the needle on the tach falls to zero. It doesnt feel like its missing though. Thanks for the advice I will be looking into things in the next couple of days.