Here is my story... Ive installed a 91 Trans Am 305 TPI in my wifes 65 Sportwagon.. It is very Cool but Im having problems with the knock sensor..
Ive hooked up a Scanner and with the key on, there is no Knock sensor being seen.. But when you start the car, The scanner says Knock YES.. The Car runs great in open loop then is goes to Close loop and it sees the Knock Sensor and runs like a turd... Ive tryed to hook a new knock sensor to the wire and Ground the sensor and raped a rag around it to try to trick the ecm. That didnt work for me.. I was just try to see if the motor had a Knock that I didnt hear.. Motor only has 66,000 Miles..
Ive checked the Wire at the knock sensor I Have 4.93 Volt.. That is Good
Ive Ohmed the sensor out it was 3.9K That is Good
Ive ohmed the wire from sensor to ECM... That is Good.
Ive replaced the ECM That didnt Help
Ive replaced the MEMCAL Chip... That didnt Help
Battery voltage at ECM with Car running is 14.3
The motor has a Good Ground...
With car running and wire on I read 2.425 volts I dont know what it should be
I Feel I've done everything I can Im very upset that I can Fix this.. If anyone has a idea Please Let me know...
there is a TSB for the problem your having which may be the fix for you.
check the code on the MEMCAL & post it up, its normally 4 letters & looks something like AXYB.
Are you sure you have the correct knock sensor for a 91? There are different types. One style for 85-89 engines and a different style for 90-92 engines, because of the ECM differences.
65 Sportwagon, what makes you think that there is a problem with the knock sensor? Code 43? Excess spark retard? As you posted your checks of the ESC system show it is correct (even the "wire on I read 2.425 volts" is correct).
Once the ECM goes closed loop what does the scan tool show for INT & BLM?
The 3.9k knock is the right one for a 5.0.. I have two memcal chips.. The first one is a AXXF and a new one of AXXB.. Ive try them both.. I think I have a knock sensor problem because the scanner with key on not running will say NO... Then I start the engine and Knock Sensor goes to Yes.. Car will run great in open loop then it changes to closed and looks at all sensors and retards tons of timing...
INT is 119-123
BLM is 128 This was in close loop
Last edited by 65 Sportwagon : 01-27-2008 at 11:02 AM.
the chip shouldn't be the problem.
AXXB shows to be the latest update for ARZC & AWFU.
AXXF shows to be the latest update for ARZU & AWFY.
both show to be fixes for driveability and/or check engine light code 43
both show to be for LB9 & auto trans, AXXB for P214/60R16 or P215/65R15
AXXF for P245/50ZR16
i show no designation for Federal or California emissions on either one.
make sure the knock sensor wire isn't near any of the plug wires. with the knock sensor disconnected, set your volt meter on the 2 volt AC scale & start the motor up & see what you get.
what is the timing set to? did you unplug the timing set connector when you set the timing?
Last edited by DENN_SHAH : 01-27-2008 at 04:45 PM.
The wire is ran under the manifold and up the firewall than inside..
I set the timing at 0 with plug off and then reconnected wire..
I disconnected Knock sensor and started engine, With a meter on wire in AC mode I have .001 I have never had a 43 Code or and codes....
Im hoping someone can HELP Im will to do anything..
. . .then it changes to closed and looks at all sensors and retards tons of timing...
So the issue is excess retard on the SA. Double check that the scan tool is also showing the knock counts increasing on a steady basis. They should be as this is what triggers the SA retard.
Couple of things that can cause this:
The Fan switch and Knock sensor connectors are switched. IOW, the fan switch connector is plugged into the knock sensor and vice-versa (this is the fan switch in the passenger cylinder head).
The scan tool is putting a 10K resistor across the ALDL A & B terminals. The ECM will ADD 8 to 10 degrees of SA to force knock to occur.
There is something that is attached to the engine that is making noise (such as a bad bearing in an accessory). Or something attached to the engine is hitting a frame or suspension member.
The Fan switch and Knock sensor connectors are switched. IOW, the fan switch connector is plugged into the knock sensor and vice-versa (this is the fan switch in the passenger cylinder head).
There is something that is attached to the engine that is making noise (such as a bad bearing in an accessory). Or something attached to the engine is hitting a frame or suspension member[/quote]
Its not the wire being switched.. Ive traced the wire from the knock sensor to the ecm and it is going to the right stud.
I took off the belt so no acc. were spinning and It still detards timing. I don't know it this would work, But I installed a new sensor to the plug and grounded the sensor (sensor not in motor) and raped the sensor in a rag to dampen and shock(sensor on wheelwell) and I still can't make it not see the knock sensor. My thinking on this is. If the motor dos have a knock, This should make the ECM not see it.. MY THINKING IS NO GOOD. It still retard timing. I fell Ive done everything..
Can I have a new chip burned to not see the knock sensor..
this is kind of strange, you shouldn't see any knock counts with the resistor in place of the knock sensor. it sounds like your getting AC voltage induced into the knock sensor wire.
with the 3.9K resistor still in place, ground the negative lead of your DVMM & with the positive lead tap into the knock sensor wire, set the DVMM on the 2 volt AC scale & start the motor and see what the AC voltage looks like. let it run long enough to go into closed loop & watch your scanner for knock counts. when you see knock counts, look at the DVMM.
Ok, I installed a 3.9 resistor were the knock sensor goes and hooked up a DVMM (on AC volt) to the resistor and grounded other meter end. I ran car in closed loop and it still pulls timing and I show no AC volts on wire..
If you do a brake stand (just off idle 900rpm) It pulls 10 Deg timing out..
With the resistor installed scan still says Yes to knock..
It also pulls timing, I saw Knock retard Jumping for 8 to 12 well in gear and foot on brake around 900RPM.
I did see the INT go down to 80 well this was going on..
I thought it was to stay at 128.. I dont know why it was doing this.
There got to be something retarding timing besides the knock sensor..
I'm REAL GREATFUL for the help trying to fix my problem.. I will try anything...
With the 3.9K resistor and no A/C on the knock line, then it is either:
1) the ECM is bad
2) the scan tool is bad
3) there are bad grounds between the ECM & engine block
Note that having the INT drop to 80 isn't good either. That is pulling a lot of fuel out. Did the engine start to stumble or want to die when the INT went that low?
How did you make out with the knock sensor problem? I'm having very similiar problems in my 91 Z28 L98. I tried putting the knock sensor in insulation, but still have same problem. Just started diagnosing recently, but seems to happen more often under hot conditions, and I lose all advance, and timing goes into retard under accel. The more I accel, the more it retards. Is there an Electronic spark module like the older tpi's or is it built into ECM? Please let me know if you fixed it or not. Thanks.
subscribe.I`m having similar problem.On acceleration getting alot of retard.20 degrees is not uncommon.Pulling out most of my advance.Sensor is new,was installed with new engine which has about 11,000 miles on it.No knocking or pinging heard.Plugs look perfect.No signs of detenation.I`m going to try to insulate the sensor and see what that does.I was running lean and thought that was the problem,but had that fixed and no change in retard.I know I prolly shouldnt have done this but I kinda had to see.I disconnected the knock sensor and went for a drive,only differance I noticed was the car seemed to have a good bit more power.I wasnt dattalogging when I did this.Will do soon.Gonna pull sensor and check part number and get a new one.That things a PITA to get at.
__________________ Completly rebuilt front end with all moog chasis parts.Formerly a 305 LB9.Now it`s an all new L98 block with nodular iron crank,PM connecting rods and hyperutectic pistons.10.1;1CR.Stock TPI.LT4 production cam,summit alluminum 1.6 roller rockers,7/16" screw in studs,Isky adjustable guide plates,with a few other mods and bolt ons.ZZ4(113) D-port heads,LT4 springs and retainers. crappy flowtech headers,3" flowmaster cat back.msd coil & digital 6,UMI lcarb`s,panhard bar,lca`s,Alluminum driveshaft,J42 alluminum rear drums.Built 700r4,performabuilt 2500 stall,trans cooler,3.42 gears.No porting to heads or intake yet.No cat,non emissions,a/c delete.Old Best with stock stall and 2.73 gear,1/8th 8.787@79.24 mph 1.968 60`street tires on a hot and humid day.No times with new set up.
Completly rebuilt front end with all moog chasis parts.Formerly a 305 LB9.Now it`s an all new L98 block with nodular iron crank,PM connecting rods and hyperutectic pistons.10.1;1CR.Stock TPI.LT4 production cam,summit alluminum 1.6 roller rockers,7/16" screw in studs,Isky adjustable guide plates,with a few other mods and bolt ons.ZZ4(113) D-port heads,LT4 springs and retainers. crappy flowtech headers,3" flowmaster cat back.msd coil & digital 6,UMI lcarb`s,panhard bar,lca`s,Alluminum driveshaft,J42 alluminum rear drums.Built 700r4,performabuilt 2500 stall,trans cooler,3.42 gears.No porting to heads or intake yet.No cat,non emissions,a/c delete.Old Best with stock stall and 2.73 gear,1/8th 8.787@79.24 mph 1.968 60`street tires on a hot and humid day.No times with new set up. 
