ignition advance?

[1996pmt]

i have a 1996 z71 5.7l. it started jerking and it only does it when i reach highway speeds and try to maintain speed. it also starts perfect then immediately sputters or stalls. i have replaced the distributor,rotor button,dist cap,wires,plugs, and coil. need to know if ignition advance is the same thing as cam retard? if so should the ign advance be -18 @ 630 rpm?

[jyount]

Originally Posted by 1996pmt

i have a 1996 z71 5.7l. it started jerking and it only does it when i reach highway speeds and try to maintain speed. it also starts perfect then immediately sputters or stalls. i have replaced the distributor,rotor button,dist cap,wires,plugs, and coil. need to know if ignition advance is the same thing as cam retard? if so should the ign advance be -18 @ 630 rpm?

No, ign timing and cam timing are completely different. Cam timing is the timing of the valves, ignition timing is the timing of the spark. Cam timing is set with the chain and cam gear, not adjustable stock, and ignition timing is set by the ecm. I don't know what the pcm is gonna show at given rpms, but -18 @ 630 doesn't sound way off. That is a number of what the computer is doing to the timing from base timing. When you set the distributor in you set it at 0 degrees. The computer controls what the timing actually is, cause it controls the spark.

[jyount]

Originally Posted by 1996pmt

i have a 1996 z71 5.7l. it started jerking and it only does it when i reach highway speeds and try to maintain speed. it also starts perfect then immediately sputters or stalls. i have replaced the distributor,rotor button,dist cap,wires,plugs, and coil. need to know if ignition advance is the same thing as cam retard? if so should the ign advance be -18 @ 630 rpm?

No, ign timing and cam timing are completely different. Cam timing is the timing of the valves, ignition timing is the timing of the spark. Cam timing is set with the chain and cam gear, not adjustable stock, and ignition timing is set by the ecm. I don't know what the pcm is gonna show at given rpms, but -18 @ 630 doesn't sound way off. That is a number of what the computer is doing to the timing from base timing. When you set the distributor in you set it at 0 degrees. The computer controls what the timing actually is, cause it controls the spark.

Honestly it sounds to me like you have a fuel problem. You have tbi though don't you? They don't require much fuel pressure. Never have any start problems? Just dyes after start sometimes.?

[1996pmt]

actually i just replaced the coil yesterday because it decided not to start at all. so now im back where i started. it starts perfect then it sputters and stalls. i can play with the throttle and it helps keep it running. it also jerks say around 45mph i try to maintain speed it will jerk when u ease off the throttle. fuel pressure reads fine but my spark is almost non existent after start up maybe a spark every three seconds or so.

[1996pmt]

showing cam position sensor A bank1 ckt malfunction? p0340 also MAF or VAF ckt low input but i replaced the MAF.

[Jeremy-WI]

Is there some play in your distributor(side to side)? You could also have a worn distributor gear. Cam retard is the difference the PCM detects between pulses from the crankshaft position sensor and the cam position sensor(in the distributor) and it helps to set the distributor correctly after removal. The cmp code may indicate a worn distributor housing

[ctwright]

Check your throttle cable and make sure it's adjusted right, I agree with whoever it was who said it was a fuel problem.

Your getting fuel at idle seems to be the problem, like you said it starts fine, sputters and dies, then if you reach speeds and let off gas to coast, it jerks, I had a vehicle do that and the problem was the throttle cable adjustment. Also are you showing any codes for your tps, could also be a problem there or could be something completely different?

[ctwright]

I just wanted to come back and add that I would be leaning more toward the throttle position sensor than the throttle cable adjustment now that I think about it.

My problem was it idling too high after start, but would also jerk back and forth when letting off to coast going down the road. The problem was the cable adjustment, I looked under the hood the throttle was pulled up a little bit somehow the adjustment worked its way in that position I fixed it back and the car then ran perfect.

Your problem though being similar is still different in that it is too low, with the throttle all the way down the car should idle, and a cable out of adjustment can't make it go any lower. There might be an idle adjustsing screw however that you can turn to purposely move the throttle up a little bit.

The tps tells the computer where the throttle is at so it can send the pulses to your fuel injectors, if that is bad then you will have problems like you are describing. The sensor should have three wires, it should be located near the throttle. One wire should be a reference voltage from the ecm, the other a ground, and one wire should be the wire going back to the ecm telling it where the throttle is at. I'm not familiar with your vehicle maybe someone already knows that can tell you this, but the reference wire should have approximately 5 volts, and the other wire besides the ground should range from a low voltage up to about 5 volts. I don't know which color wires would be which for your vehicle though. If someone here can give you the specs for the sensor and it checks out of range you should replace it. You may be able to temporarily fix by taking the sensor bolts a little loose and turning the sensor counterclockwise(should be but it's whatever way you turn it that it has tension on it) and tighten it back down, that might up the voltage signal to the ecm at idle a little bit if the sensor isn't completely damaged.

[jtmarten]

I had a similar issue years ago with a Jeep Cherokee. Throttle worked fine except in that one spot where you just maintain speed.
Bad TPS.

[1996pmt]

ok i'll check the tps again. but still does not explain the slow spark. loose as in i can turn the distributor?

[1996pmt]

also if it were a fuel problem would it not give me more trouble when i increased the gas?

[MT-2500]

Originally Posted by jyount

No, ign timing and cam timing are completely different. Cam timing is the timing of the valves, ignition timing is the timing of the spark. Cam timing is set with the chain and cam gear, not adjustable stock, and ignition timing is set by the ecm. I don't know what the pcm is gonna show at given rpms, but -18 @ 630 doesn't sound way off. That is a number of what the computer is doing to the timing from base timing. When you set the distributor in you set it at 0 degrees. The computer controls what the timing actually is, cause it controls the spark.

The engine timing is preset by crankshaft sensor.
The VCM contols timing advance.

Camshaft retard reading in scanner has nothing to do with engine timing advance or camshaft timing/advance.

Camshaft retard setting is the position of dist rotor to spark plug terminal.
Which is adjusted by turning the dist on ones that can be turned.

Camshaft retard setting should read ut as close to - or + 0 degrees as you cam get it.

If over -or + 2 degrees reset it with scanner.
If way off like 15/25 - or + your dist needs reset or camshaft sensor is dead.

Basic dist setting setup is in link below.
http://files.automotiveforums.com/ga...hp?photo=51302

[ctwright]

Originally Posted by 1996pmt

also if it were a fuel problem would it not give me more trouble when i increased the gas?

No it wouldn't give you that problem while giving it gas if it was your idle adjustment or TPS. We already explained that, and that your problem was only getting enough fuel at low rpms(idling),keep playing around with the timing though if it makes you happy.

[1996pmt]

MT would the distributor being off center slow the spark down to nothing almost? also i have been testing everything i find and anything else that is brought to my attention

[1996pmt]

i just want it right. i just had the idle and tps checked again told me its fine. he also mentioned the ignition module could be bad and may not be saturating the coil properly?