Ignition timming!!!

[00bluegtp]

If the timming isnt at exactly o* is it possible that the engine would run rough somtimes, especially when hot? Explain!!!

[00bluegtp]

TTT. No one has any ideas. I have a truck that runs rough once in a while and I cant figure out what is wrong with it. Could an ICM cause it. It sounds like it goes out of timming once in a while. Its really weird. It only does this when it is running for a while.

[Crew Cab Sonoma]

if its intermittent, its probably not the base timing, if the
dist. is locked down well.
faults with the ign. module or the knock sensor module
or circuit can potentially cause intermittent problems.

[00bluegtp]

I know the icm is under the cap but where are the knock modules? Are those what they call the knock sensors them selves? How would I diagnose a these parts to be faulty?

[Crew Cab Sonoma]

the ign. module can usually be tested at parts stores.

is your truck TBI or CPI?

not sure about the knock module on 94's.
it may be "piggy back" on the ECM, or even
integrated if its PCM (uhderhood) equipped.

check knock sensor wiring to make sure it has a
good connection to the sensor, and isnt
shorting to ground anywhere.

[00bluegtp]

It is a 94 cpi. Sometimes when I am sitting at a light it will start to shake and then all of a sudden it will run smooth again. But then some days I will drive it 80 miles or so and it will run like a clock the hole time. Maybe one of the popets on the cpi getting stuck?

[01cherryreds10]

Probably a random misfiring cylinder. Usually cap and rotor, set of wires, and plugs will take care of that problem. You can't adjust the timing on the distributor so yes it's perfectly fine where it is. You can turn it all you want it has no effect on engine performance.

[01x.joyride]

Quote: Originally Posted by 01cherryreds10

Probably a random misfiring cylinder. Usually cap and rotor, set of wires, and plugs will take care of that problem. You can't adjust the timing on the distributor so yes it's perfectly fine where it is. You can turn it all you want it has no effect on engine performance.

so how do we go about adjusting the timing on our newer vehicles...is it timing light only..? one of the nicer and more expensive timing lights...?

[01cherryreds10]

Nope there is no control over timing. The PCM takes care of all of that. You can put the distributor in bass ackwards, but you'll notice when trying to find a place for the coil wire. You don't adjust timing anymore because everything is set up via fuel trim parameters based by either the tuner, or based on the fuel learn enable mode which is on all of our trucks. Basically over time it will adjust fuel trim according to altitude and engine RPM.

[01x.joyride]

wtf damn man, that blows...so if we send in our pcm to get a tune, is that the only way to get the timing changed..?

[01cherryreds10]

Yup that's exactly the case

[00bluegtp]

well I replaced the cap, rotor and plugs, and wires. It is still doing the same thing. I opened up the plenum and found fuel puddling up in there. I just repaced the cpi about 3 months ago, along with the nut kit. Well I brought it back and got a new one and now it runs like a clock. Just thought I would post what I found.

[01x.joyride]

nice job, so that bitch was leaking or something..?

[00bluegtp]

yea I think one of the plastic lines going to the popets was leaking on the drivers side, and beleive it or not i think the fpr was leaking a lil too. I cant beleive these things are made soo shitty. You would think somone would design one that actually lasts.

[lesterl]

If you keep having issues with the CPI going bad, might switch to a cooler thermostat that wont cook the plastic as much.....

[SpiderDallas]

You can change your timing using a msd box I believe. I really don't know but have heard this before.