1g heavy misfire

[98ls1ttop]

ok so kinda new to dsm's but the buddy that helped me fix the car is not. i bought the car with busted valves, had the head totally redone and has all new gaskets all throughout. its a 90 gst. after we got it together the ecu didnt work so i bought one from a running car. my car also has a new coil pack, plugs, all that jazz. got it all together and it has a dead misfire. the injector wires have some cracking on them and a bare wire showing in a place or two but i doubt that would be the problem seeing as i think its getting too much fuel or something. brand new ngk plugs are pretty black. it will rev to redline if you barely touch the gas but still sputter. if you hammer it, it will rev to like 3k and cut out real bad and die. misses at idle also.

mods are:
cat back
2g maf and exhaust man.
k&n
550's

my buddy who helped me put it together knows these cars pretty well and i dont think its out of time, but it could be. replaced the cam sensor also. could the plugs be bad? they are black and it smells like gas when running, like its out of time or no spark. but when you pull an injector wire it almost kills it. any help would be greatly appreciated!!

 

[98ls1ttop]

also the tach does not work which the previous owner says it did....

 

[TurboT91]

Hey man....where do I start? First off, you should fix the fraying/cracked injector wires. Do you want to be revving out your car one night, an injector wire completely breaks, and fuel is cut from a cylinder? Who put the head on? Your friend? Did you guys make sure everything was timed right? Did you turn the motor over 6 times by hand and make sure all the timing marks still lined up? Do you have any way to controll the 550 injectors (AFC, DSM Link, etc..)? Does the car idle normally and at what rpm? Are your spark plug wires ok?

 

[98ls1ttop]

i have an afc but not on the car yet. the plug wires are good. i'll fix the injector wires today first thing. im thinking im gonna put the stock injectors back in and see if that does anything. what got me confused is the tach used to work....but the car sat for 8 months.

 

[anmGST]

I would fix the injector wire first, I also would not change back the injectors, I was running a 225 wally and Evo 8 injectors with not control. Ran this for a while before I got tuned on a AFC. Also make sure the Igniter is not over heating and cuting out and check the harness to it I had a problem with mine after my 1st gen engine swap.

 

[98ls1ttop]

i kinda figured i could run the 550's and be ok. a little rich is ok for a while but the way it is now is not gonna work. horrible.

 

[98ls1ttop]

Hey man....where do I start? First off, you should fix the fraying/cracked injector wires. Do you want to be revving out your car one night, an injector wire completely breaks, and fuel is cut from a cylinder? Who put the head on? Your friend? Did you guys make sure everything was timed right? Did you turn the motor over 6 times by hand and make sure all the timing marks still lined up? Do you have any way to controll the 550 injectors (AFC, DSM Link, etc..)? Does the car idle normally and at what rpm? Are your spark plug wires ok?

oh and the car does not idle normally. a tad high (tach does not work haha) and sputters and spits at idle

 

[thom2white]

Yeah man, you should fix the obvious first and then run a boost test, you would know if the motor was out of time. (1 tooth and the motor is going to be chattering pretty good, 2 teeth and your bending metal). These cars really need to be sealed up tight. Even a leaking vacuum line will give you hell! There are a ton of posts on how to make a tester or you could just grasp the concept and make your own. A boost leak will make your car rich (ie: the gassy smell on the injectors) and idle higher than normal and usually will have a hard time maintaining a steady idle.

 

[mikelv]

ok so kinda new to dsm's but the buddy that helped me fix the car is not. i bought the car with busted valves, had the head totally redone and has all new gaskets all throughout. its a 90 gst. after we got it together the ecu didnt work so i bought one from a running car. my car also has a new coil pack, plugs, all that jazz. got it all together and it has a dead misfire. the injector wires have some cracking on them and a bare wire showing in a place or two but i doubt that would be the problem seeing as i think its getting too much fuel or something. brand new ngk plugs are pretty black. it will rev to redline if you barely touch the gas but still sputter. if you hammer it, it will rev to like 3k and cut out real bad and die. misses at idle also.

mods are:
cat back
2g maf and exhaust man.
k&n
550's
my buddy who helped me put it together knows these cars pretty well and i dont think its out of time, but it could be. replaced the cam sensor also. could the plugs be bad? they are black and it smells like gas when running, like its out of time or no spark. but when you pull an injector wire it almost kills it. any help would be greatly appreciated!!

Well, the first thing I would do as someone else previously stated would be to repair those exposed wires! I think you said you already accomplished this.

Next would be to double check your timing marks, and throw a timing light on there. See what your base timing is, and set the CAS properly. If the car was 180* out or anything like that, it wouldn't run at all. You can turn the motor manually, and see where your at. If you've run the car, and run the car hard, I'm pretty sure your timing is correct. If it wasn't you would most definately know by now.

Next would be to check your Power Transistor Unit. Measure the resistance/ voltage in accordance with the Service Manual. Visually inspect all your wire connections and make sure nothing else is broken, frayed, or disconnected.

If your engine is "missing" or losing spark, it can be for a number of reasons. Check the "trouble shooting" guide in the service manual.

Remove your spark plugs one at a time and test for "arc" to make sure each plug is firing.

You said it was a bran new coil. If the coil was bran new from Mitsubishi, then I'm sure it's fine. If you bought a re-furbished one from a place like NAPA, you might have bought a bad coil pack. If all else fails, take the car to them and make them test it.

Lastly, have you messed with any of the ECU wiring at all? I know you said your going to be installing an AFC. Did the car ever haver any other "piggy-back" system installed? If so, check those "re-spliced" connection. Make sure if anything was soldered, you don't have a cold joint.

Something tells me it's a combination of something electrical, and possible boost/vacum leak.

Can you descirbe in better detail out the car "misses"? Is it something that happens real quick, like a "pop" noise, or is it something that surges the idle, and makes the car "chug" out? When you try to go WOT, does the car "hit a brick wall"??

Just make a good visual inspection and ensure nothing looks suspicious. Sometimes we can over-look something small.

Good Luck, let us know!

 

[90 tsi awd]

what year do you get the ecu from

 

[98ls1ttop]

the ecu is a 90 ecu....the right one. im currently getting all the old gas out (about 8 months of old gas) putting new in and new plugs and fuel filter in it. the injector clips were a little corroded so i cleaned them up. i found that out by pulling a plug and it was white . but still has a bad miss. it hesitates while idling bad, and when you get it out on the road its hell to drive. it takes 2 miles to get to 55 mph. if you give it any amount of gas it just "hits a brick wall". you can hold it WOT at 55 and it will just sputter and spit and not gain any ground. actually slows the car down. timing is correct, all cylinders sparking, getting fuel (plugs are black). tomorrow i will get good gas and run it through a new filter. also it sounds like the CAS is kinda loud and chattery. dont know if its supposed to be like that or what. i had an extra laying around and swaped it and it doesnt do anything different to the car. im gonna try to build a boost leak tester tomorrow if i have time also. we checked it a while back and it had a small crack in the intercooler and i had it fixed, but thats the only leak we could hear. that was on my buddies tester. im gonna build one for myself

 

[mikelv]

the ecu is a 90 ecu....the right one. im currently getting all the old gas out (about 8 months of old gas) putting new in and new plugs and fuel filter in it. the injector clips were a little corroded so i cleaned them up. i found that out by pulling a plug and it was white . but still has a bad miss. it hesitates while idling bad, and when you get it out on the road its hell to drive. it takes 2 miles to get to 55 mph. if you give it any amount of gas it just "hits a brick wall". you can hold it WOT at 55 and it will just sputter and spit and not gain any ground. actually slows the car down. timing is correct, all cylinders sparking, getting fuel (plugs are black). tomorrow i will get good gas and run it through a new filter. also it sounds like the CAS is kinda loud and chattery. dont know if its supposed to be like that or what. i had an extra laying around and swaped it and it doesnt do anything different to the car. im gonna try to build a boost leak tester tomorrow if i have time also. we checked it a while back and it had a small crack in the intercooler and i had it fixed, but thats the only leak we could hear. that was on my buddies tester. im gonna build one for myself

Unless you have an intercooler pipe completly blown off, which the car will wouldn't drive anyway, boost leaking isn't going to make the car THAT bad. You would have to have some serious boost leaking, obvious enough to fix it.

A car needs three things to run...... right?

Air, Fuel, and Spark.

Fuel: Ok, so you said the plugs were white, and you also sais the plugs were black? Which is it? If the plugs are black as hell, then we most definately know your getting fuel. You can probably even smell the gas down in the spark plug wells, and even on the plug. Yeah, bad gas will give you bad performace, but there would have to be a ton of water in there for that to be a serious problem at the moment. And it probably wouldn't even run.

Air: Well, let's make sure everything is good here. You said you'll run a leak test. Make sure there are no pipes almost off, or busted. Injector seals, Manifold, TB, Gaskets, everything. Back out the BISS some, check the seal.... let air in there some.

Spark: This is most likely your problem by a long shot. How do you know you have spark? Did you take the plugs out one at a time to "arc" test them, and to make sure your sparking like I told you to? Did you set your base timing with a timing light? Did you test the coil pack, and fix the damaged plug wires? Are you sure you routed the plug wires correctly? (Really the car shouldn't even run like this, but you never know, check it)
Did you check the Power Transistor Unit? This could be the problem. The wires were frayed on mine one time, and the car would not pull past 4,000 rpm, bottom line. Not sure, but the car missing in open loop could be from this. My car ran fine closed- loop with this, so not so sure. Look anyway. Check it out, test the voltage to the coil pack, and to the Power Transistor. Check the ECU wiring, make sure nothing has been tampered with.
Find someone with another 1990 ECU, and make sure you didn't get a bad one. If your not fimiliar with Prined Circuit Boards, or basic electronics, I DO NOT recommend testing the ECU on your own! But the easy way is to find one, and eliminate that possibility.

Now, a timing issue. How do you know your timing is right? What did you do to check it? If your timing was completly wrong, and you've driven the car for any length of time, you would most definately know it by now. Most likely you would have bent every valve you have, the car wouldn't hold compression. It just plain wouldn't run. Check it anyway!

Turn the crank by hand, clockwise and line up your timing marks. Now, if everything is lined up okay, turn the entire rotating assembly SIX TIMES CLOCK-WISE to ensure everything lines back up. It would be best to pull your accessories, and remove the timing cover to see the Crank Disc & Sprocket. This isn't necessary, but if your going to re-time the car do it anyway. Make sure your belt tension is evenly distributed on both the intake side and exhaust side of the cam gears. Ensure nothing has "jumped" a tooth or the belt isn't damaged. 1 tooth off will cause a lot of chatter, if nothing else, check that. Read the timing belt FAQ's.

Here is the link on Ignition Timing Adjustment:

Engine Timing

Once you verify that the mechanical timing is correct, we can eliminate that, and work on the big three. Just make sure that is good first. Then base timing, then connections, then plug spark, then air testing. See the pattern here?

Alright man, good luck, let us know.