Occasional Severe Driving Problems
10-27-06, 05:14 PM
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Occasional Severe Driving Problems
I'm almost at the step where I want to take my 91 LS to the dealer and have them diagnose and fix it. Any ideas on where to start looking for problems would help.
2 months ago, I changed the timing belt myself. After the timing belt change, CEL error codes 13, 25 and 26 would show up occasionally. It didn't affect driving at all so I just ignored it. I noticed that sometimes driving on the highway, my foot would be in the same position, but for a second it felt like i lifted my foot off the gas pedal and placed it back on.
Fast forward to now. The car still has the cel error codes. There seems to be two problems. Are they related?
Problem 1:
It starts fine and most of the time it's perfect. When the temperature is normal, sometimes all of the sudden the engine would act up. When the car is idling, all of the sudden as if the engine was no longer getting any air and was suffocating, the rpms will drop to 200 and stay that way for a second. Then the car will act as if the gas pedal was being pressed. It will rev up to about 1300 and then drop down to 600.
Problem 2:
While driving, all of the suddenly I loose power. Keeping my foot on the gas, there are periods when the engine seems to pick up and move and periods where nothing happens at all. Stepping and letting go of the gas pedal rapidly is very jerky but it seems to make the car move.
I've looked around the engine and noticed the following:
Spark plug wires are all under 25k resistance.
The spark plugs on the passenger side bank all had a slightly damp black (carbon?) stuff on it. They do look a little old.
The radiator cap has cracks in the rubber
The transmission fluid is about .75 inches higher than the hot limit when the transmission is hot.
I changed the rotor and the distributor a while back so they are fine.
Resistance of the MAF is normal (according to the repair manual)
The throttle position sensor's closed and .4mm open are normal. When it's fully open, it's an infinite resistance
Engine coolant sensor is fine
Using a timing gun and attaching it to spark plug wire 6, I see a 5 btdc which I know it's suppose to be higher than that
ICV has a resistance of 50
So any ideas on what to look at next or replace? ECU? Fuel pump? TPS? ICV? changing the timing?
2 months ago, I changed the timing belt myself. After the timing belt change, CEL error codes 13, 25 and 26 would show up occasionally. It didn't affect driving at all so I just ignored it. I noticed that sometimes driving on the highway, my foot would be in the same position, but for a second it felt like i lifted my foot off the gas pedal and placed it back on.
Fast forward to now. The car still has the cel error codes. There seems to be two problems. Are they related?
Problem 1:
It starts fine and most of the time it's perfect. When the temperature is normal, sometimes all of the sudden the engine would act up. When the car is idling, all of the sudden as if the engine was no longer getting any air and was suffocating, the rpms will drop to 200 and stay that way for a second. Then the car will act as if the gas pedal was being pressed. It will rev up to about 1300 and then drop down to 600.
Problem 2:
While driving, all of the suddenly I loose power. Keeping my foot on the gas, there are periods when the engine seems to pick up and move and periods where nothing happens at all. Stepping and letting go of the gas pedal rapidly is very jerky but it seems to make the car move.
I've looked around the engine and noticed the following:
Spark plug wires are all under 25k resistance.
The spark plugs on the passenger side bank all had a slightly damp black (carbon?) stuff on it. They do look a little old.
The radiator cap has cracks in the rubber
The transmission fluid is about .75 inches higher than the hot limit when the transmission is hot.
I changed the rotor and the distributor a while back so they are fine.
Resistance of the MAF is normal (according to the repair manual)
The throttle position sensor's closed and .4mm open are normal. When it's fully open, it's an infinite resistance
Engine coolant sensor is fine
Using a timing gun and attaching it to spark plug wire 6, I see a 5 btdc which I know it's suppose to be higher than that
ICV has a resistance of 50
So any ideas on what to look at next or replace? ECU? Fuel pump? TPS? ICV? changing the timing?
10-28-06, 01:13 AM
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My 91 repair manual states that the idle control valve should be up to 30k. I measured mine and it is at 50k. However, looking through the forum and at the repair manual for a different year, 50k seems ok also. Is this the case? Or is my idle control valve going bad?
I'll check the fuel pump tomorrow, but i'm a little nervous about working in the gas tank area.
Would a faulty tps cause this type of problems?
I'll check the fuel pump tomorrow, but i'm a little nervous about working in the gas tank area.
Would a faulty tps cause this type of problems?
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