i adjusted them today using the method Jake describes, going 1/4 turn after zero lash. this method worked very well. however, i believe CFI was correct in thinking that my problem had little to do with mis-adjusted lifters, as they were all pretty close.

after installing the heated O2 sensor, i drove it a few miles. when i pulled the plugs today, the insulators were bone white, indicating much too advanced timing (17* base) and a lean condition. interesting how it went from pig rich to lean like that.

i'll finally do a real time scan tomorrow, but clearly the timing needs to come down to something like 6* base, and i'll get the fuel pressure up to at least 45 - 50 psi (no vacuum). hopefully this will solve most of my problems.

 

ok - i finally did the scan. here are the results:

This is all with base timing at 17* btdc because it would stop running if I tried to retard it any more than a few degrees. is it possible that this PROM / engine combo really WAS set up for 17* base timing?

Vacuum reading at idle - 10Hg steady
Fuel Pressure set at 47psi (no vacuum hose connected, would drop to about 42 psi with vacuum)
Engine has no EGR, AIR, etc., and no catalytic converter
ECM does not throw any codes
AC Delco 41-629 plugs gapped at .040

PROM ID 102
Loop - closed
4th gear engaged?
Knock Retard 0* at idle, 5-10* when revved
Knock Sensor - first It read 0, then 242 at idle, jumps from 28-38-47 when revved
Idle air meter position 60 steps at idle, up to 100 steps when revved
coolant temp 180*
AC clutch disabled
Injector pulse 1.8-2.0 ms at idle, up to 7.0 when revved
desired idle 850 rpm
Engine load 45-50 at idle, up to 211 when revved
TPS .58 at idle, up to 4.48 when revved
1st gear engaged?
MAP 1.03 - 1.05 volts at idle, same when revved
MAT 66.2* F (yeah I have the useless relocator)
Engine RPM - 880 at idle, goes up when revved
CCP purge OFF
CCP Duty cycle 0.0%
Mass Air Flow 9 gr./sec at idle, goes up to 65 when revved
EGR duty cycle varies between 8-25%
Air diverter solenoid ON
Air switch solenoid OFF
Battery Voltage High - NO
battery voltage 14.1
O2 ready
O2 sensor - fluctuates between 68 - 796 mv
O2 cross count number continues to rise
TCC status not locked
Fuel pump sensor 13.9 volts
Learn control enabled
Blk Lrn Cell 1
Block Learn 160 at idle, goes to 128 when revved
Integrator - 132-142 at idle, 128 when revved
Rich / Lean flag - Lean at idle, Rich when revved
Spark Advance - 24-26* at idle, 39.9* when revved
Park / Neutral Detected

And after about 10 minutes of run time to record all of this, the plugs are now fouled again (the insulators on the plugs I took out prior to this were bone white - see previous post) and when i took it out for a quick ride just now, it ran a little better, but still stumbled and hesitated a bit on acceleration.

any help zeroing in on the potential problem would be GREATLY appreciated!!

thanks!!!

Dan

 

I didn't go back to refresh myself on the whole thread; modifications and chip particulars, and I don't have a scanner or scanner experience, but your MAP observation seems out of whack. With 10" Hg manifold vacuum, the voltage should be higher, and it should go higher, yet, when you rev the engine. Is the vac hose blocked, or even connected.

RACE ON!!!

 

i thought that reading was pretty weird too, especially since i believe my car (1987) doesn't have a MAP sensor, only the MAT sensor. was the MAP sensor specific to 1984 models only?

do the knock sensor and knock retard readings seem abnormal? i do have a ZF 6 speed with an aluminum flywheel and the associated "rocks in a can" that goes along with it. could this be enough to send the knock sensor into a fit?

 

The recommended preload setting differs depending on the cam and lifters being used.

Guys use all sorts of different preload settings. I've seen some as low as 1/8", all the way to 1 full turn. The lower preload settings are used to try to get a few more RPMS out of the engine before lifter pump up occurs.

I've got a file that shows the difference in power the different preload settings give and I've already sent it to a to of guys on this Forum.

My recommendation is to use the preload setting that the camshaft/lifter manufacturer recommends. GM says 1 full turn for their stock stuff, while CompCams calls for 1/2 turn on many of their offerings.

Jake

 

The '84 had a MAP and '85 up have MAFs. Somewhere near 1990, I think they went back to MAPs. Your 1987 definitely has a MAF. If your "MAP" reading really reflect the MAF output, something is wrong, because it should change when you rev the engine.

I can't comment on specific readings, because of a lack of experience, but I do know that any number of things will trigger the knock sensor. That is why mine is disconnected.

RACE ON!!!

 

Your BLM is pegged at 160, telling me that the ECM has detected a lean condition, it has tried to address that condition by adding as much fuel as it can. Once it reached 160 it ran out of adjustability and cannot add any more.

If ideally burned, the BLM reading should be 128 (+/- 4). Any number higher than that means fuel is being added and any number lower indicates fuel being pulled out.

You can try increasing fuel pressure to see if that reading will come down. My thinking is if increasing fuel pressure causes the BLM number to drop, then a PROM reburn is in order, especially if you're running a long duration cam.

Jake

 

I hope you have an adjustable fuel pressure regulator. If so, I'd try setting the fuel pressure at 48 psi WITH THE VACUUM HOSE CONNECTED. Yea, I know that's high, but what we're doing is diagnostics.

If a pressure that high causes the BLMS to drop, then you'll definitely know you need a PROM re-burn. The fuel maps in your PROM as just too lean.

BTW, I've pressure that high without any problem with my engine. All you want to do is test the BLM change at idle and at quick revs.

Keep us posted.

 

I will definitely give that a try this week (probably Wednesday, since i have off from work Wed - Fri).

Based on everything, I am probably looking at 2, maybe 3, issues that i need to sort out. The high Block Learn reading (causing a rich condition, fouled plugs, and poor throttle response), the Knock count readings (causing timing issues and poor throttle response), and a possible vacuum leak (although i checked everything pretty thoroughly today and couldn't find anything - i'll double check Wed).

CFI - were you able to simply disconnect the knock sensor without throwing any codes or did you have to have your PROM programmed accordingly?

thanks for all of your time and help - i would be ready to give up and start planting flowers in it without you guys!!