More knock issues, sorry

Lhorn

Member
I"ve never been able to figure out a knock issue I have in my stock 86. Recently smogged, car is bone stock including chip currently. Boost currently at 12-13#.
On WOT runs from 0 or a slow roll I get blips on the Casper's knock gauge and KR readings (usually 2 or less) on the SM at WOT. It's all been very inconsistent however. Some runs I get nothing at all.
Tired TT chip for stock injectors and also tried 50s with a TT chip for 50s. No difference.
Usually run 91 octane, but I added equal amount 101 octane (so likely 96 octane) and still knocks no real difference.
Used stock FPR, but also tried boosting FP with an adjustable (to 45 line off) - no difference. (Has Walbro hot-wired fuel pump and confirmed that fuel pressure rises 1:1 with boost)
Exhaust not hitting, etc.
Watching the SM, the knock goes away if I stay in it. Last time I tested, I got two rounds of KR (0, 0, 0, 0, 0, 2.3, 0.7, 0, 0, 0, 0.9, 0, 0)
O2 MV reading are 750-850 when I hit the recall.

I"ve done a little testing with a WB O2 and my numbers are if anything rich. During a 0-60+ run AFR sits in the 9s, finally rising into the 10s at the end of the run.

Any thought?
Thanks.
 

Lhorn

Member
Pretty sure they are CR43s gapped to .035

Forgot to mention in my original post that SM numbers are idle are within desired ranges.
 

Mr.Spool

Well-Known Member
I"ve never been able to figure out a knock issue I have in my stock 86. Recently smogged, car is bone stock including chip currently. Boost currently at 12-13#.
On WOT runs from 0 or a slow roll I get blips on the Casper's knock gauge and KR readings (usually 2 or less) on the SM at WOT. It's all been very inconsistent however. Some runs I get nothing at all.
Tired TT chip for stock injectors and also tried 50s with a TT chip for 50s. No difference.
Usually run 91 octane, but I added equal amount 101 octane (so likely 96 octane) and still knocks no real difference.
Used stock FPR, but also tried boosting FP with an adjustable (to 45 line off) - no difference. (Has Walbro hot-wired fuel pump and confirmed that fuel pressure rises 1:1 with boost)
Exhaust not hitting, etc.
Watching the SM, the knock goes away if I stay in it. Last time I tested, I got two rounds of KR (0, 0, 0, 0, 0, 2.3, 0.7, 0, 0, 0, 0.9, 0, 0)
O2 MV reading are 750-850 when I hit the recall.

I"ve done a little testing with a WB O2 and my numbers are if anything rich. During a 0-60+ run AFR sits in the 9s, finally rising into the 10s at the end of the run.

Any thought?
Thanks.
pull 2 degrees of timing and make another run
 

Lhorn

Member
It's not hooked up currently but I have a T+. I also have an older TT chip for stock injectors (maybe version 5.5?). Would one of those allow me to retard the timing?
 

Mr.Spool

Well-Known Member
It's not hooked up currently but I have a T+. I also have an older TT chip for stock injectors (maybe version 5.5?). Would one of those allow me to retard the timing?
pull the timing out with the ttchip,it does it by gear,pull it in the gear your having knock,which in your case is the 1/2 gear
 

John Larkin

Sublime Master of Turbology
The way the knock is spaced evenly looks like it occurs when gears shift. I would guess something is banging the car - down pipe most likely. Maybe loose crossmember, torque converter bolts.
 

Pronto

You can't knock them up with spit.
They just run better with a tighter gap. Just do one thing at a time as well.
 

1986 Buick GX1

GX1 #001 [The One and Only]
Thanks for the reply. For my education, what does a narrower gap do that would lessen knock?

The spark has a harder time jumping a wider gap while under boost.
If the coil is starting to get weak, the spark will jump the tighter gap.

It seems to me this condition would result in a miss, but I'm not good at this kind of thing.
Hopefully someone will explain that part better.
 

Lhorn

Member
I retorqued the knock sensor. It might have been a little tight but nothing crazy. Torqued to 14 ftlb.

Thanks for the replies. I'll try putting on the T+ and LS1 MAF so I can retard the timing. And later try gapping them tighter, one change at a time.
I tried to get to the gas station that sells the race gas and they were out. said it might be a few days until they got more. At this point, I've pretty much got mainly 91 in the tank. I'd like to test with a bit higher octane to give myself some safety cushion.

I took it for 4 runs today on 91 at 14# boost. 3 runs I got no knock up to 60-80 MPH. Once I got around 1 KR that went away. Couldn't tell if it occurred on the 2-3 shift or not.

Any thoughts on the WB reading? Would it be reasonable to pull some fuel with the chip and see what happens? Guess what I'm asking is, is 9-10 AFR too rich that it would cause issues, or not that bad?

Thanks for the replies. I"ll report back when I get to work on the car and do some testing.
 

RUQWKNF

KEEPER OF SECRETS
Staff member
Here's an obvious question.
When was the last time the factory fuel filter was changed?
Reason I ask is, if the car is slightly leaning out between shifts and causing some slight knock, this could be a sign of a clogged/semi clogged fuel filter. I would change it for good measure before you go out and make anymore test runs.

Next time you go out for a test run, when you hit the recall button, hit the other button as well. That will tell you the MPH that each event occurred on the Scanmaster. For example, if say you had .760 O2 Mv and 2.3 knock retard, and then you hit the other button while holding the recall button at the same time and it says 80 on the left side and 75 on the right side, that means your .760 O2 Mv happened at 80mph and your 2.3* of knock retard happened at 75mph. If you know exactly what mph the car shifts at, you can better pin point a lean spike during the shift. Lean spikes during the shift are almost always fuel related.

KR or knock retard of less than 2.0 is manageable, so long as it goes away during a pull. You gotta remember, the ECM is pulling timing when it sees KR. Once the KR goes away during WOT, it will slowly add the timing it pulled, back in. If it keeps seeing the KR, it will keep pulling timing. It's the sustained KR that blows head gaskets. And you definitely don't want that. Especially if you are running high boost levels.

When everything is worked out, you should be able to run 14-16psi with 91 octane and either a octane booster or a splash of 101 octane unleaded fuel. Typically, with good 93 octane, and a TT chip burned for your combo, with the hot wire kit, adj reg and a good 255 lph fuel pump, there' s no reason why you couldn't run 17-18psi of boost and 18-20* timing in all gears. But that is optimum conditions and state of tune on an "86 - "87 intercooled car.

Also, pull timing out as previously mentioned with your TT chip burned for the stock injectors. If you are running 91 octane with some 101 splashed in, you should be able to run 18* in all gears at your low boost levels.
It's also a good idea to tighten up the plug gaps to at least .030. Some are a little skiddish of tightening them down to .028, but .030 won't fail you.

I would not recommend running a stock GM "86 - "87 chip with today's ethanol blended 91/93 pump gas. The timing tables are/were programmed for pure 91/93 non ethanol blended Premium unleaded used back when the cars were new.
And one last thing to remember, the stock 12" D5 torque converter puts a huge, HUGE strain on the factory fuel system under WOT on a bone stock car. If the fuel system is not upgraded, it will / can also cause knock between shifts. Over the years, I've witnessed this first hand on friends cars that were original / unmodified examples. And as they slowly started to upgrade, this KR went away. Especially when the stock D5 converter was swapped out to a 10" or smaller and the fuel system and chip was upgraded.
Hope some of this helps.

-Patrick-
 

Lhorn

Member
Regarding the fuel filter, there are not many miles on it, but a lot of years (10ish?). I'll replace it. Considering how much the car has sat, sometimes with fuel stabilizer, sometimes not, it's probably due.
 

Mr.Spool

Well-Known Member
is 9-10 AFR too rich that it would cause issues, or not that bad?
thats too much volume,but your light on octane inmo and thats why i said to pull a few degrees of timing.this ghost knock is what happens when you run light on octane,afr looks good but knock is present.i could be a list of other things that guys have posted up as well.
 

TurboBuRick

Moderator
Staff member
Should be doing 3rd gear pulls with no shifts to get accurate data. Put the gear shifter in regular drive. Get the car up to 55mph then lay into it. Bring it to 75-80mph and let off. Hit the recall and see what you got.

If it shows no knock and the o2 millivolts are 780-800 you can disregard knock in lower gears. It's false.
 
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