Hey guys...Im from the TBI boards Ive got a 92 rs TBI....But The other day I picked Up a 1987 Jaguar XJS that has a 350 TPI motor...Im Having a Bad Missfire problem with it...I did a Tune Up...Plugs Wires Cap Rotor and Coil....still missfires....pulled a plug to check spark....the spark is soo weak it wont if jump or arch to metal i set it next to...its very weak....what could be causing a weak spark.........it is a 5.7 i checked the back of the head...and it has block casting 14093638....which seems to be right on with it coming out of an iroc with i was told....could the distributor be bad?

 

Pull your ignition module and have it checked. Places like Autozone will test them for free.

 

can a module really cause weak spark i was told they are either good or bad and when they are bad u get no spark

 

I've seen some modules do funky things. They're not ON or OFF. Since it only takes about 5 minutes to get to it's an easy check. Most recently I had the joys of seeing a dying module cause an idle surge that had every indication of a bad IAC sensor.

 

well the motor is coming out and going into my 92 rs....if i do just go ahead and replace the distributor what do u think about the brand moroso

 

No opinion. I run stock distributors. You do know the module's under the cap, right?

 

ya hehe im just tryin to be lazzy...i had it apart many times yesterday

 

one more question...Anyone know why it is...im looking for an hei distributor upgrade....it has the coil in cap one right now....but all the performance ones alll have vaccum advance on them...mine does not

 

I'm not sure that big cap HEI (coil in cap) fits on a Tuned Port Motor, I think the plenum gets in the way, but I could be wrong. However, small cap HEI (basically whats there) works just fine.

 

actuallt i just got this...its running....and this 350 tpi is running a coil in cap distributor....would i have to butcher the wiring to get it the the hei remote coil style like my 92 rs has...becuase they have completely different plugins

 

ok update....new cap, rotor, module, coil, wires, delco plugs....these were installed yesterday and the plugs are already fouled out due to weak spark....ground to the coil is good and gettin good power at coil...what else could it be...im kidna desperate...i want the motor running good before i put it in my 92 rs

 

You replaced the module? Did it test bad?

 

no it didnt test bad..it was good...but i replaced it anyways

 

What about your pickup coil located in the center of your distributor down under the cap. You cant test it, but you also have to dissasemble the entire distributor to get to it. Its about an 11 dollar part from GM. Its wires connect to the ignition module.

 

ya i think im just gonna buy a whole new dist....this thing is pissin me off...ive gone thru everything pretty much and the spark is weak as hell

 

update.....on a cold start it runs fine for the first couple minutes...the longer its running the worse the missfire gets

 

im having a problem with my part throttle... in park i have no miss, but in drive above 2300 rpms i have a miss... i had replaced the cap and rotor with MSD, MSD blaster coil(remote) bc i have an L98, vg2 plugs gaped .035, mallory wires, accell ignition modual, 02 sensor only has 15,000 on it etc... this has all been on the car for over 3000 and longer miles with no prob but about a week ago i have this miss, really noticable in 3rd and 4th gear, exhaust note changes and sounds dead when i step on it... i think its a fuel problem, so i did this yesterday, ripped cap and rotor off and cleaned them, then ripped plenum off and adjusted fuel pressure to 48psi vacume line disconnected. was at 50psi, but when i attached the vacume line pressure dropped to 38psi at idle in park??? checked TPS voltage and its steady at .52/.54V, also added fuel injector cleaner to gas, and im throwing no codes. i run 93octane bc i have a motorvation strip chip etc. idk what it could be but its my daily driver so i need to kno wats wrong with it quick, any ideas?

only seems to happen above 2000rpms and the car will rev but hesitates/feels loss of power bc of the miss/exhaust note change, like its not getting enough fuel, fuel pump works, and pressure doesnt drop off so i think the pump is fine. but only happens when the car is in D or over Drive and when theres load on the engine....??? im stumped help me

 

mine does it all the time in park or whenever...its either way too much fuel or weak spark....the plugs are fouled pretty bad and some had gas on them when i changed them....when i check for spark its pretty weak...but ive replaced pretty much everything that has to do with spark

 

wait so the ignition modual that is found under the distributer... i replaced the one that was found under the cap, i thought there was only one... ive never had this problem and its new like only a week and a half that its been goin on for. its just that its come outa no where... i think it would have to do with fuel/spark, but idk how to test it, but it only seems to happen when the car is upder load.... i also think it could be the knock sensor since my car only missfires above 2000rpms, im thinking it has to do with the timing etc, since my distributer was fine and ive replaced all the parts.... i just need this fixed bc its my daily driver and my highway driving is crap.