Jas89TTA

I hooked up my Trans Am to a Tech1 and at idle when I rev it I get 20deg of Knock Retard. It only does it under hard accel and when it's above 3000 RPM's What could it be? Could it be false knock? I'm still running a hypertech 305 TPI chip, Could this be my problem? I'm planning on getting a custom chip soon. If it is false knock can it be programmed out of the chip? I set my timing from 10deg BTDC to 6deg BTDC and it still does the same. I have the AFPR at 44psi and running 93 Octane. The car has a 350 TPI stock L98 heads, Hooker Headers, LT4 HotCam, 1.6 Roller Tip rockers, Accel Intake base, AFPR, #24 SVO injectors. It's just been put back together the heads and block were just rebuilt it's only got 1400 miles on it. Thanks

e-man

Im having the same problem as you! Im using a autoXray scaner.I have my timing at 4deg BTDC and still geting 8-12deg getting pulled out.I noticed mine after I did my cam swap.Im using a hypertech chip too,tried my stock chip it pulls the same timing out with my fastchip it pulls 16-26deg out!I would really like to know whats going with our engines?

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89 350 TPI,comp cam,edelbrock intake base,SLP headers,highflo cats,flomaster cat back,accel 300+ ign,ported plenum and runners,ported maf,auto w/shiftkit,cold air induction,AFPR,Ed wright chip,3.23 posie best ET 14.011@98.72mph without cam/New best 13.926@98.27mph

Jas89TTA

Well, I took the car out with the Tech1 pluged in and under normal driving I would not get any knock retard. When I got on it It would go between 7-10 degrees of knock and it would not start until 3000 RPM's on up to about 6000 RPM's. But Why is it so high in neutral, when I rev it up I get 20 degrees? Could it be picking up false knock from valve train noise? I'm running the Comp Roller Tip 1.6 rockers on it so the lift is .525/.525 and CompCams 987 springs. It sound's noisy under there but seems to run great. BTW: It's got a new knock sensor and knock module on the car. I replaced them when I did the engine swap.

Bort62

sounds(ha) like False Knock To Me.



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Reader's ride -> My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

coach

If any of you have replaced the timing chain with a gear drive, that would also cause enough noise for the knock sensor to pick up.

e-man

Im getting my retard at 3000-5200RPM only in WOT.Reving in neutral I'll get 15-20deg pulled out.The scanner says total timing is 29deg in WOT.I used GMPP single roller timing chain.

Jas89TTA

I'm also using the GMPP timing chain. It's kit part number 12371043. If I am getting false knock how can make it less sensitive to knock? Can the chip be programed to be less sensitive?

82z

What happens if you tap on the block with a Ford tool while the engine is idling? You should see an increase in knock counts.

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82 z28 350cid, vortec heads, comp 262h cam, Holley 600cfm carb, 2in twice pipes, MSD ignition, turbo 350 trans, 3.73 posi, manly b&m megashifter

D_Amlee

With that combination, it is possible that 44 psi isn't enough. Since you have a scantool, you ought to easily be able to check your BLM values and integrators to see if you are running lean. If the BLM values show a lean condition under those WOT conditions, it is very possible that you have got real knock going on.

I'm running a 350 with a much smaller cam than you, and 42 psi in my 24 lb SVO injectors feeds me just fine. With your bigger camshaft you will need more fuel than me, and 44 psi isn't exactly a huge step up from what I run on my car. Look at your BLM values as you take a few runs. Then crank up the fuel pressure a few pounds, take another ride in the car and see if the BLM values begin to show a change. The chip might not be helping any, since it's programmed for a 305, but the scan information should be able to remove all doubt whether insufficient fuel delivery is causing this trouble.



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89 IROC with lots o' stuff

-=ICON Motorsports=-

Jas89TTA

How can i tell on the BLM values? What would be considered lean? I'm new to all this computer set up and have no idea what BLM values are. I will check for them with the tech1 and see what they are ( If I can find it in there). Thanks

D_Amlee

BLM stands for Block Learn Multiplier. It is a correction factor which the computer uses to compensate for lean or rich conditions in an effort to try and maintain a good stoichiometric air/fuel ratio. The computer uses info from the O2 sensor and determines if you are rich or lean, and calculates a modification to the fuel tables to correct this. The correction values (BLM) are stored in a table. There are sixteen BLM values stored in this table, corresponding to a range of rpm / throttle positions. If your air/fuel ratio is dead on target, the BLM values in the sixteen table positions will all be nearly equal to 128. This is the neutral position. If the computer senses that the engine is running rich, it will cut back on the fuel delivery, and the BLM value will be reduced below 128. If your engine is running lean, the computer tries to richen the mixture by adding fuel, and the resulting BLM value rises above 128. By looking at the sixteen BLM values you can tell what the computer has been trying to do lately. If the values are roughly near 128, say from 124 to 132, this is pretty normal. If the values are in the low 120s or high 110s, then you are running pretty rich and the computer is trying to compensate by cutting back on fuel. If your values are well up in the 130s, your computer is trying to add fuel to compensate for a lean condition.

Since you have access to a scanner, you ought to be able to drive your car under a variety of conditions (rpm and throttle positions) to see what the various BLM values are.

If everything is working correctly you ought to be able to make an adjustment to the fuel pressure regulator and observe the response in the changes in the BLM values stored in the computer. The BLM values don't change instantaneously, but just a few minutes of driving (after the engine is warmed up) is all it should take for the computer to calculate and store a new set of BLM values in the table.

In addition to all this computer stuff, don't forget some of the more traditional tuning techniques: pull a couple of spark plugs out and take a good look at them. They can also identify a lean or rich condition.

By the way: all the BLM data is only useful if your O2 sensor is performing correctly. If the O2 sensor is shot, or all boogered up with residue or carbon deposits, the readings may be all off. O2 sensors work by observing the unburned oxygen still present in your exhaust. Even a perfectly tuned air/fuel mixture will still have some trace amounts of oxygen left in the exhaust, and the sensor watches for this. An O2 sensor covered with thick carbon deposits has a difficult time sensing the oxygen in the exhaust and interprets this as an overly rich condition. The computer then cuts back on the BLM values in an effort to correct the perceived rich condition, which (due to a faulty reading from the O2 sensor) actually can result in a lean condition. This is why you ought to also check your spark plugs to double check the information your computer is giving you.

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89 IROC with lots o' stuff

-=ICON Motorsports=-

poncho9789

It could be your 1:6 roller rockers. They do cause a slight tick (or knock) and will cause false knock in the ecm. I have the rrs on my 97 formula and had to add the lt4 spark module to the ecm to stop the knock retard. Your roller rockers might not be set just right and causing the false knock.

just a thought.

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97 formula w/6speed,cags skipshift eleminator, hurst billet pro shifter, 30#injectors,adjustiable fuel presure regulator,Moroso cold air induction,ported mass air sensor,accell300+ ignition box, accell 9000 wires, bosch platnum4 plugs,flomaster crossflow muffler,Lingenfiter 52mm throttle body,TPIS L98 SuperProfile cam,Crane 1:6 full roller rockers,Edelbrock subframe connectors,Edelbrock strut tower brace.

Other car is a 89 GTA w/700r4w/stage 2 shift kit, corvette servo, B&M mega shifter, TPIS bigmouth intake, TPIS large tube runners, TPIS 52mm throttle body,Edelbrock ported centerbolt heads,LT1 24# injectors,GMPP LT4 hotcam,CompCams Pro magnum roller rockers,Edelbrock headers, flowmaster crossflow muffler,MSD 6A, accell coil, bosch platnum plugs, this car is currently under rebuild and restoration.

Jas89TTA

D_Amlee, I checked the BLM values and at start up and driving around it's 131 I'll have to check WOT reading later on. On the O'2 sensor I replaced it when I installed the new engine and the plugs look white.
Thanks, Jason