ok heres the deal. my car developed a misfire which i traced to the ignitor. the tach was jumping, car missing only when i leaned into it (made 5+ psi and was 50%+ throttle) so i replaced it with two KNOWN good ignitors, neither of which solved the problem. so i said screw it, and bought a new aftermarket (lifetime warrenty) one which didnt help. so i had the new one tested ( car misfired on the way to the auto parts store) and one of the used ones i had, tested bad and the new one tested good. then my car stopped missing.

it misfired on the way to the parts store and stopped missing when i left the parts store. all i changed while i was at the store was that i took the ignitor out and put it back in. it ran perfectly for 8 days, now its misfiring the same way again. can someone help? it HAS to be ignitor or ignitor wiring related right? the tach is going nuts EVERY time is misses. could it be something else?

setup is
90 LS
OBD1
Uberdata

 

and here is a pic of the car i want to set on fire (for views)

 

I had the same problem once and it was my map sensor connection. Make sure it is solid.

 

map sensor causing violent misfiring and tach going nuts? weird, ill check that. and ill go to the zone tomorrow and have the new ignitor tested again, but i REALLY doubt its that. thing is, it only happens when i lean on it. part throttle and off boost i can drive the car just fine, no missing

 

its not the connectors. i made SURE they were not coming off when i had the dizzy apart the last 15 times. and no, ignition is 100% stock. NGK7s, brand new coil

 

this might be a stupid question but what are the plugs gapped at ??? and how many pounds you running ???

 

.018 10 psi

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by I Have an STD &raquo;</TD></TR><TR><TD CLASS="quote">.018 10 psi</TD></TR></TABLE>


thats a little tight for 10 psi, thats what i run on 20+psi on a 35R, open up that gap a bit, too tite of a gap can have the same advers reactions that too large of a gap can have

also, i had some slight issues with a few distributor caps that would cause my tach to jump around, i guess it was the pickup for the cylinder on the cap, might wanna try swapping caps too

 

hmmm..... i have taken off the cap a TON of times

 

I had a similar problem a month back. Changed the ignitor a few times, coil and the whole dizzy. After I changed the dizzy, it was cool for a few days and went to misfiring again. I ended up changing the ignitor again but this time with new stock plug wires and new plugs, BKR7Es, and no problems since. Two of the plugs had cracks in em and sh*t. If youve tested the ignitor and its good, the coil is good, change the plugs & plug wires. Also check the rotor. Hope this helps. Let us know what happens.

 

thanks for the replies, bump for some more

 

how old are the plug wires? alot of cars i've tuned, have misfire issues and low and behold, we put a new set of NGKs on the car and misfire is solved...but with jumpy tach, i still think its the ignitor. find a local junkyard and salvage as many as you can, that's what i always do.

 

yeah thats what i was thinking, im gonna try to grab 5-6 of them when i go next. im just so frustrated with this car. i mean, it misfired with this ignitor, then it just stopped. now its back with a vengence, stupid car

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blazin99si &raquo;</TD></TR><TR><TD CLASS="quote">I had a similar problem a month back. Changed the ignitor a few times, coil and the whole dizzy. After I changed the dizzy, it was cool for a few days and went to misfiring again. I ended up changing the ignitor again but this time with new stock plug wires and new plugs, BKR7Es, and no problems since. Two of the plugs had cracks in em and sh*t. If youve tested the ignitor and its good, the coil is good, change the plugs & plug wires. Also check the rotor. Hope this helps. Let us know what happens.</TD></TR></TABLE>

Exactly, wealso changed the ICM on his SI and it fixed his broken tach. Also, get a friend with the same motor and swap the whole dizzy. After every thing always check the plugs as they are really sensative to all thie ****.

 

man I have a similar problem but it happen only at 4000rpm... if im past this range its okay until the red line.

I cant find what it is....

 

does the misfire happen when its hotter outside? i guess, is there anything that is common with anything when its misfiring? such as being hot outside, or rainy or plugs are old, etc?

the randomness leads me to think ignitor as well, because its just junk and that's what randomly happens with it.

 

totally random. i thought it was when the car warmed up, but now it does it when its cold too (i dont take it to 5k+ rpm when its cold, so i thought it would only do it warm). now it really wont do it on the highway, and it really only does it past 5k RPM.

everyone i know around here is either d series or OBD2 or OBD0. i cannot find another person with an OBD1 dizzy so i can swap them and see if thats the prob.

plugs look good, swapped the wires with another set i have, same prob. connections on the ignitor are good and tight, map sensor connection is good. anyone know EXACTLY where the wiring for the ignitor goes? im about to just re-wire the entire Ignitor circuit to see if thats the problem

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by I Have an STD &raquo;</TD></TR><TR><TD CLASS="quote">.018 10 psi</TD></TR></TABLE>

throw on another set. I've seen people waste a lot of time and energy because "it can't be the spark plugs!" and/or the wires.

i'd also throw in another main relay.. you can get a jumpy tach from the main relay turning off and on rapidly.

also, are you missing any of the grounding points? like valve cover to chassis? make sure the ground to the thermostat is good and clean too.

 

i DID change the plugs, no difference. changed the wires too, no diff. just changed the rotor too, no change. all the grounding points are there and clean. main relay? i really doubt it, but i guess ill check

 

I would personally be crazy and solder a wire directly from the pins on the distrib straight to the tach and nowhere else... make DAMN sure it is not shorting out somewhere, in case it is a wiring issue.

 

well, i know the blue wire goes direct to the tach, but the black/yellow one does not, and unless im mistaken, THAT is the power wire and is what causes the misfire. am i totally off? BTW, i took the ignitor out and went and tested it at the zone, tested perfect 5x in a row, so i know the ignitor isnt actually bad. im totally stumped here, someone please tell me they have had this problem before and solved it

 

did you change your ignitor fluid in the past 4000 miles?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr. Vapor &raquo;</TD></TR><TR><TD CLASS="quote">did you change your ignitor fluid in the past 4000 miles?</TD></TR></TABLE>

yup, yesterday, no change

anyway, i added a nice thick ground wire to the front of the head and grounded it well to the chassis, seems like it worked, we'll find out tomorrow when i drive it to work

 

well, im still not sure what it is. i added a bigass ground wire bolted direct from the head to the chassis, it helped, when it missed, it was MUCH less severe, but it STILL misfired. soooo, i unbolted my thermostat ground and took a razor blade and scraped it down to bare metal, and did the same to the inside of the head of the bolt and the sconnection to where it bolts to the T-housing too. hasnt misfired yet since then, we'll see

 

any other suggestions?