SlicktopS130

Hi.
So to correct a random dying issue, i had to replace my ICM. About a week after this, once the car starts to warm up (120-130F) i started noticing the tachometer jumping when i would tap the gas (or just let off the gas, and re apply), and the car has developed a heavy misfire under load.

I came to the conclusion of weak spark because 1. my dizzy has to be all the way advanced to even reach 7-8 BTDC, and instead of a blue spark at the plug, i'm getting an orange spark.

What i've done to try and fix this issue: Replaced the ICM again, replaced ignition pickup, and replaced the ignition coil. I've also checked all of my connections which are fine.

Some things to note: 5K miles on distributor - 7-9K miles on cap/rotor/wires/plugs.

Any ideas?

PredatorZ

You have replaced the Ignition module twice, and replaced the coil once. It might be highly unlikely, statistically speaking, but you might have 2 bad ICM in a row, especially if they are not Nissan parts, we have heard tales of guys swapping them out 4 or 5 times before getting a good one, would be nice to have a running donor you could swap known good parts from. Take a look at you FSM, is there any troubleshooting steps for the ICM. Also, if you have not done it yet, run a star grounding system, all that entails is running a wire from your negative terminal of your battery to a common point, from there run a wire to your ECU and to your plenum, since most of the sensors are close to that. This will give you a good ground to your critical systems, body ground is only so so when new, after years of weather and corrosion between body panels the ground weakens. A star ground set up is insurance, and eliminates a lot of possible problems.

rogerz

your thinking that a weak spark is caused by not being able to advance timing is erroneous. if the icm and coil are good you will always get a fat blue spark regardless of timing. in fact if you attached a spark plug to the coil via the wire normally going to the dizzy and then exciting the coil by hitting the primary with 12 volts (momentarily) you should get a good spark. you have to ground the plug. called make and break which is what points used to do and now they use a transistor (ICM). you can test the icm with a vom. do a google on transistor test. not always means it is good but for sure can tell if it is bad. Heat enters in to the problem for transistors on the ragged edge. doing some grounding as suggested by pdx can only improve things. do this too:
Get your battery load tested. Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen. Usually on a rainy night around Oh Dark Thirty.

Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion. DON'T USE DIELECTRIC GREASE.

87WhiteOnRed

Quote:

Originally Posted by rogerz

...Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion. DON'T USE DIELECTRIC GREASE.

Hope you don't mind me jumping in on this post gents...

I have a 1987 n/a. Having a serious running issue, that is quite sporadic. Sometimes, the car will turn over and run, maybe a little rough but at least run. Other times, it will crank like hell, I will have a slight gas odor, and it won't turn over. I'll come back to it a few days or even just a few hours later and it may turn over, may not.

Rogerz - I've seen you post this about the connectors in other threads. Do you think this could be my issue (and do you have other ideas)? On that topic, where do you purchase the cleaning stuff and CorrosionX?

Parts replaced so far: Cap, rotor, plug wires, ignition coil. Turned the distributor slightly, and thought I had it figured out when it turned over for me, then it started doing the same sh*t.

After reading this and many other threads on here, I'm worried I have an ECM issue or perhaps a poltergeist.

Happy Motoring!

SlicktopS130

Predator, The first ICM i bought was an SMP model (made in china), the current one is a Facet Electric model (Italy), but i coudn't seem to find a direct OEM E12-80 anywhere. I didn't think i would get two bad ones in a row, but i guess i'll put that into consideration. There are a couple ZX's at a few Pick 'n Pulls in the area, maybe by chance i can get a working module off of one of them. Some reccomend i switch to the GM HEI module, but this is my show car, so i'd rather not have a bunch of stray wires running all over the place. Unfortunately, the FSM only explains ICM tests done for a "no start" situation.

Roger, My theory with the timing issue was that i had to advance the timing due to weak spark. Before these issues, i could acieve 8 BTDC with the dizzy 2/3 advanced, now i am getting only 7 BTDC with the dizzy maxed out.

I will check my connections for corrision, and clean as nessicary.

rogerz

do you not know how to use google 87whiteonred?

do this stuff you will be happier:
Get your battery load tested. Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen. Usually on a rainy night around Oh Dark Thirty.

Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion. DON'T USE DIELECTRIC GREASE.

Replace outer tie rod ends, and ball joints. replace the bushings with poly (don't forget to lube them as directed unless you like squeaky things). New shocks. Get new boots for power steering. all those things will make you think you are driving a different car. doing them piece meal is a waste you won't see a great improvement until you do the complete job. You need to get the car realigned after messing with the front. Have your tires in good shape and rebalance. Rear bushings nice too but more work and you won't notice as great an improvement. Rear shocks also because if the fronts are gone so are the rears. if car squats when you jump on the gas the rears are gone. If you have the electro adjustable shocks they are DEFINITELY GONE.

get a timing light instead of randomly moving the dizzy around!
get the fsm. READ IT. xenon be free download.

replace your chts.

you can find CAIG deoxit at stores that deal with amps for bands. they always have dirty connectors. corrosion X try a locksmith.

And again. there is a whole world out there if you learn to use google

did you change plugs or just the wires? ignitiion coils generally work or not. you may find one heat affected but way out of the norm. Power transistors much more likely to be marginal.

87WhiteOnRed

Google? What is this? Never heard of such things.

Thanks. I guess.

SlicktopS130

Probably should have mentioned that the battery and terminals are new... I'll definately keep that grounding tip in mind though.

The entire suspension (except for the springs) has been replaced. KYB Struts, and 99% of the bushings have been replaced. Still need to replace the rear member mounting insulators. Trust me, this car handles like it's on rails. Will smoke anything around in the turns, if only it ran right HA! I did mention that the timing was at 8 BTDC, so obiously i have a timing light lol. Taking the car in on Wednesday to get the ignition system professionally gone though. Results are soon to come.

Literally the ENTIRE ignition system has been replaced within the last 10K miles (coil, wires, cap, rotor, ICM, condensor, plugs, pickup ignitor, whole distributor, vac advance, vac lines, ignition switch).

Oh yeah, i replaced the CHTS about 3-4K miles ago.