91 Lumina 3.1 no power above idle

[pizza1]

Hey guys, my 91 with 3.1 distributor ignition has been acting up for several months. At highway speeds it would suddenly stall, like turning off ignition. It would restart but would pop and faulter above idle. Then it would mysteriously come back to life and run fine for a week or two, then do it again with no warning. Well, it did it again the other day, but has not come out of it yet. It will restart and idle, but has no power. When you give it throttle it begins to bog down and smells rich out exhaust. It does not misfire, just has no power. I put timing light on it, and to my amazement, when I give it throttle, the timing actually retards....from 10 btc to as much as 4 atc. What could make it retard as rpm increases instead of advancing??? Could it be that their is a multiple problem causing the sudden stalling and the timing???

[LMP]

Originally Posted by pizza1

...from 10 btc to as much as 4 atc. ..

NOt sure of any conclusion based on this.. That does not surprise me as the knock sensor is probably acting..remember the logic is mainly oriented toward reduction of emission, not performance...
It would probably advance again when at constant throttle.
Anyway, I would first suspect the ignition module,
www.avigex.ca/xport/ignitionmodule31.gif a common failure item at that age...and, in fact, a "must" of preventive maintenance. I would not go far from home with a 17 year old ignition module.

[pizza1]

I tinkered with it a little today. I may have given wrong info on timing...it appears that the rpm actually drops when the trottle is opened, I assume this would probably cause the timing to retard. So, I advanced timing to about 20 btc, then restarted. Now when throttle is opened, timing retards to about 6 or 8 btc, but engine still bogs down ....actually loosing rpm. At idle it is fairly smooth. Soooo...I'm leaning toward a possible bad ignition module causing the sudden stalling, but, would that also cause the loss of power when trottle is opened??? There is no misfiring and the exhaust smells very rich when throttle is opened, but there is no black smoke from tailpipe. Could the oxygen sensor possibly cause that????

[LMP]

Is the Check Engine ON? If so read the codes
www.avigex.ca/xport/readingcodes.jpg
this OBD1 is quite primitive but some info might be at hand.
..in fact, I'd be somewhat suspicious of the Manifold Pressure Sensor (MAP) code 33 or the Throttle Position Sensor, 21,22, the latter being a common culprit...part 58 just at the base of the throttle body. www.avigex.ca/xport/TBI.jpg YOU can test it by measuring voltage on the sensor wiper connector (center connector) ; must sweep in a continuous manner with no jumps or misses from 0.5 V to 4.5 V as tjrottle is depressed...well...once disconnected, it would be easier to measure resistance, between wiper and one side...from near 0 to 5000 ohms (max ohm value can be different..but must vary in a seamless manner). I would also disconnecet the vacuum line from the EGR valve vacuum actuator, just to test. code 32
THe O2 sensor acts only once the engne is up to temperature..so if this behaviour shows immediately after starting, O2 is out of the loop.
...but a new ignition module is not ruled out and is at least a safety item. I would not "leave home without it". CHeck e-bay for a good price on a new one. http://cgi.ebay.com/ebaymotors/ws/eB...S%252BI%252BSS but starting at $41 on rockauto.com it is not expensive either.

..ahhh...well all options are still opened...and after all...a blocked catalyser would do something like that also....did that happen on a sudden or progressively ?

[pizza1]

No check engine light. I have changed the MAP sensor, the throttle position sensor, the ignition module in the distributor, and even tried another ECM computer, but no change...still no power. The exhaust at idle seems to strong to be a blocked converter. It starts and idles well , but, just seems to be getting too much fuel when given any throttle.

[pizza1]

It was the converter. Cut pipe ahead of converter and runs great.