4th Gen swap ignition break up at higher boost/rpm

J

JRWperformance

Member
I have an 88 ST165 with a 4th gen swap (stock coil on plug ignition). Its been running great for the last few months. It feels like the ignition is breaking up when I get it over 10 psi of boost. First thing I did was pull the spark plugs (proper stock NGK copper plugs) and gap them down to 25 thousanths (.63mm). Didnt seem to make a difference. Then I looked up codes in the ECU. (Wiregap did my harness and added the OBD connector for JOBD.) The only codes are from the lack of automatic transmission. Im pretty sure its not fueling as my wideband is showing the normal AFRs. I know Im not going lean.

My next plan of attack is to improve grounding. I put the battery in the back and maybe my grounding isnt good enough. Anyone else have similar issues? Maybe using 1ZZFE coils could improve things?
 
U

UtahSleeper

Active member
Has it always felt like it was breaking up after 10 psi? Or did that start some time after? I guess the question for me is, what is the feeling of ignition breaking up? Like timing being retarded?

How many miles are estimated on the engine? Did you drop the engine in straight, or rebuild/reseal?

I haven't had any issues with mine, but I have my MBC set to about 13 psi and it pulls great till than. The coils on mine have been great, except when 1 started dying when the car was at full operating temp. I doubt the need for new coils cause I can't imagine all of them being bad at around the same time.

Did all the plugs look the same?
 
J

JRWperformance

Member
Just started doing it the past couple weeks. Engine is rebuilt with rods/pistons to stock specs. It makes a sound similar to the popping antilag systems you hear on WRC cars, but usually past 5k rpm at around 10 psi. Still hauls ass though. Does not seem like a hard misfire. Was thinking it was the octane booster I was using. (Our fuel in Alaska sucks, only 90 octane for premium. Thats why I run water/meth or octane boosters)

Spark plugs are all even. Nice brown color. Less than 10k miles on it so far.
 
D

dbucks2k

Member
I don't have any issues running 20 psi on stock setup. Maybe the COPs are going bad. What heat range are your spark plugs?
 
D

dbucks2k

Member
Yeah I've used bkr7e in both my engines and never had a problem. The 6s are supposed to work. But maybe because of the 4th gens compression they're too hot. Idk. But for $10 it's worth a shot
 
T

Tecker185

Member
Check the connector on the coils. I had a similar issue with my gen4. It wasn’t getting a good connection and i was getting break up. I ended up bending the tabs on the coils down a little so when i plugged in the coil it got a good connection.


Sent from my iPhone using Tapatalk
 
C

CTechBlueDragon

Member
I had a misfire issue that ended up being the same thing as Tecker. Mine was evident at idle so easier to diagnose by moving wires and plugs around... yours may be more problematic. Better grounding would not hurt.
 
J

JRWperformance

Member
Ill look close at the coil connectors this weekend. I added a decent size ground to the side of the head. Also re-crimped the battery leads. No difference.
 
J

JRWperformance

Member
Looked at the connectors. They look good and still contact tabs in the coils. I changed out the coils to another set I have in my Gen 4 spares. Made no change at all. It still pops and sputters with around 9 or 10 psi. I do know, this problem is load dependent. I am able to rev the engine out to near redline and Its OK as long as boost is under 9 or 10psi. So I doubt very much Im loosing a crank or cam sensor signal. Then only thing that has always concerned me is the super rich AFRs. Im dipping into the low 10 to 1 AFRs. But, Im using a stock ECU,so no good way to change fueling...I would like to fix it before I go with an ATS racing ECU set up.
 
underscore

underscore

Well-known member
Maybe run a boost leak test? Make sure you're not losing air and causing it to run too rich under pressure.
 
J

JRWperformance

Member
Figured it out...bad fuel. It was actually bad fuel. Or at least it does not like the Octane booster I was using. I finally ran my tank super low and filled with about 11 gallons of fresh premium. Turned off the water/meth snd boost to stock. Runs great now. Runs great with meth and 18 pounds of boost! Now my tires spin REALLY fast on the icy/snowy roads.

Thanks to you guys that responded with suggestions. Your help was appreciated.
 
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