PT Ray

My SE won't hold an idle speed and surges from 200 to 750 rpms, where do I start?

Just kidding, that would be too easy of question to do a seach. My actual question is more specific. I came up with a theory to help diagnose if it is an ignition or an intake issue and looking for some validation.

If it is an ignition issue should I not be able to see this using a timing light? Right now when I check the timing it is erratic although I do need to repeat this with the advance vacuum diaphragms disabled to keep from skewing the readings. If it is an intake issue causing the surging idle I have to believe in being able to still get a steady timing reading with a good ignition system. I have been brainstorming this today and sounds good in theory but I tend to overlook things.

Manntis

surging idle could be something as simple as dirty throttle valves. or even a clogged air filter.

trochoid

iTrader: (6)

Ignition is not usually a cause but can give erratic readings through the timing light due to the variance in rpms.

Start with cleaning the bac and checking the tps. There are some good trouble shooting links for the SEs in the FAQs. Other than that, Doc will probably pop in and point you in the right direction.

PT Ray

That's what I want to know and why. If the vacuum advance diaphragms are disabled then your timing should hit at the same degree regardless of changing rpms. I can see getting a slightly distorted reading but don't see why it should be any more than that. When I get some time, I'll use my other seven as a test subject to see how my logic really works.

PT Ray

It took me over a month to trouble shoot my idle issue and should have just stayed with my hunch on it being a problem with the ignition. Went through all the steps to address a vacuum/air leak, no luck. Decided to just drive it as is and kept thinking, the car is telling me what the problem is.

I recently noticed the headers glowing red at idle, the exhaust smelling of fuel and the tach would twitch. Today I swapped dizzys with my GSL to see if it was an ignitor, mainly the trailing, easier to just swap the whole dist. then to pull the ignitors off. Started her up and waited for the fast idle to drop, as soon as it did it was rock solid. Just to clearify things, I wired the SE with GM modules and is what was giving me idle issues but otherwise ran fine.

linexrandy

You have a hypothesis. A theory is several hypothesis's tested and proven to be a fact.

Manntis

Not in his case; theory also means abstract reasoning, speculation, or an assumption based on limited information or knowledge.

linexrandy

Per Wikpedia:
The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion.

In common usage, people often use the word theory to signify a conjecture, an opinion, or a speculation. In this usage, a theory is not necessarily based on facts, in other words, it is not required to be consistent with true descriptions of reality. True descriptions of reality are more reflectively understood as statements that would be true independently of what people think about them.

In science, a theory is a proposed description, explanation, or model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through experiment or otherwise falsified through empirical observation. It follows from this that for scientists "theory" and "fact" do not necessarily stand in opposition. For example, it is a fact that an apple dropped on earth has been observed to fall towards the center of the planet, and the theory which explains why the apple behaves so is the current theory of gravitation.

Ok no more thread jacks. But he asked for it!

PT Ray

O.K., "tentative theory".

linexrandy

LOL I don't give a crap! I've just been studying 5 chapter of biology all day for a lab practical tomorrow. My brain is fried!

linexrandy

I'm sorry, I meant "chapter's". I tink i can spel if i tri heard enuff.

John64

Ok techno guys get a room!

trochoid

iTrader: (6)

Maybe, maybe not. If the surging is sharp enough, it may be moving the mechanical advance. I've also found that at really low rpms, timing lights don't always give a consistant reading. I've also seen similiar problems with badly worn dizzys.

cdrad51

hey n00b don't cha know you need at least 1000 posts or being for a year in the forum to have the right to thread jack every now and then? don't make me open a can!

Manntis

yeah, in science. And in other uses it has the aforementioned definitions differing from the very narrow and specific one that you cherrypicked to unneccessarily and pedantically criticize him. Dig?

linexrandy

I give up lol.

linexrandy

Aint sceered