85 GSL-SE

straight pipe

direct fire - all new components ( I currently get spark to all 4 plugs.)

omp delete - premix, about 1oz to the gallon

new vac lines, fuel hoses (No vac leaks, or fuel leaks)


Problem:

Starts up and immediately goes into a shitty idle. If I rev it up, it chokes until about 2500 and then completely clears up and feels %100 normal. It drives fine over the 2500 mark. If it dips near 1500 it will go into the shitty feeling mode. It has no power and I practically have to go WOT to get back above 2500.

WTF???

 

Think really hard… what did you do recently to cause it? Kind of joking but kind of serious. Nothing just "starts running shitty" for no reason. It could be bad gas, bad plugs, etc. Typically, idle issues are related to vacuum leaks or Bypass Air Control Valve leak/failure.

Go in order from front to back… Air Flow Meter (is it jammed, broken?), Inlet tube from AFM to intake plenum (cracks or leaks?), Butterfly assembly (properly adjusted?), BAC, Gaskets, vacuum tubes, etc. Work all the way down to the engine.

It's running fine above 2500 so rule out spark and rule out fuel. Air is your issue. Just find out where.

There is one exception, and that is your timing. But if you are SURE you never messed with the distributor, your timing is not the problem.

 

I do a lot of work on my car. But in the past weeks, nothing.

I most recently did all the vac lines. I have no vac leaks though, I've checked three times now.

Timing has been set in the same spot for the last half a year or so.


Today I did start at the AFM, check the filter and flap. Good.

Opened the intake and sprayed all the butterfly's with cleaner. Tightened it all back down.

Same results.


I'm gonna pull the plugs again and sand blast them. I'll see what they look like after my last cleaning. It has only idled since then.

I do have injectors I am sending out tomorrow for a rebuild. Its the only part of the fuel system that isn't new or rebuilt. Just staying along the lines of Air or Fuel problems.



Thanks for the response. Anything helps, I like having some more ideas tossed my way.

 

Could be electrical - and the injectors are a culprit if the engine runs poorly at low RPM. When you rev it up, the engine has less time between injector pulses which will mask a poorly flowing injector - or a badly firing igniter. Check those, too - first by swapping the leading for the trailing, and then back to see if it fixes the issue or not. Typically a failing leading igniter will result in a poor running engine, while a failing trailing igniter will typically affect mileage and power to a lesser degree.

While you're looking at spark - check the coils to be sure you have solid spark on both leading and trailing plugs. Good luck,

 

one of the leading leads or plugs .. makes the engine run especially shitty when its DLIDFIS

 

Well I can pretty much say %100 it's not a problem with my ignition.

As I said originally. I have a direct fire setup. My trailing ignitor is good, and my leading GM ignitors are good. Spark to all 4 plugs right now.

I'm leaning towards a fuel/air problem. It runs fine over 2500.

Wtf! I'm kinda stumped!

 

My actual ignition switch is starting to go bad. That wouldn't be related would it?

 

My air intake sensor is also broken. The leads were sheared off clean.

I had been running without it for over a month and over 1000 miles though.

I'm really stumped. I'm trying to think of anything and everything.

Anyone?

 

Where do you live, smokey?

 

Sunnyvale, ca

94086

 

Working on it some more:

Bypassed ignition switch - same results. (I dont think its anything electrical at this point)

Good spark at all 4 plugs.

Good fuel pressure and flow.

No vac leaks.



Starts and dies within a few seconds when cold. When it gets warm it will hold a really unsteady, low and bad idle (may randomly stall).

If I give the pedal a quick tap, or slowly press it, It dies. I can go WOT and it bogs/misses/runs bad up to 2500 where it clears up and runs smooth.

Unplugged tps, it holds a steady idle at like 3-400 rpm. Sounds horrible, and acts the same way as the sentence above.


I'm sending out the injectors today, but I still dont have high hopes it will solve my problems.

 

What is an 'air intake sensor'? Are you talking about the Air Flow Meter? Intake Air Temp Sensor?

A non-working AFM will cause poor idle conditions because the engine can't tell how much air is coming into the system and thus, doesn't know how much fuel to mix in the injector pulse. Check that as no car will run fuel injection properly without an air metering system of some sort.

Also, could explain why at WOT it manages to limp along - the WOT computer doesn't run a fine tune map like at idle.

 

Sounds like its time to check the compression it may be blown.

 

rule 1 with rotary .... even when you swear it isnt the leads or plugs.. change the leads and plugs 1st




sparking in air when held against the body doesnt mean **** for a plug that has an arc burn across the insulator at the bottom of the plug where you cannot see it

change plugs and leads .. you describe a classic fault of DFI installs .. 1 and a 1/2 running rotors due to one of the leading leads or plugs giving up under hard conditions

 

Long duck.

Yes. AIT sensor. The 2 wire sensor under the BAC. My afm is good and in working order.

 

Bump start

Ill grab 4 new plugs today and see how they do.

 

And you are SURE you don't have the leading and trailing plugs swapped? Make sure on both rotors.

 

Please give me more credit than that.

Maybe it just doesn't show, but I do possess some competence.


To answer you, no. They are not swapped. I highly doubt they swapped themselves while driving as well.

 

I do a lot to keep my vehicle maintained. I have spent a few thousands on general maintenance in the last year. This car is not new to me, I just can't figure out what is causing this.

Pic for a little bit of reference.

 

lol, not calling you incompetent at all. I am speaking from experience. It is very easy to accidentally swap the plug wires. In my case I had the leading coil and trailing coil plugged into the wrong spots on the distributor cap. Although I suppose in your situation with direct fire, it isn't as likely. Just covering the bases.

Too bad you aren't in Cleveland, I would love to spend an afternoon looking at this thing with you.

 

I can get a bit frustrated I apologize. This is my prized possession, this car means a lot to me and to have it down for any amount of time really puts a tamper on my mood.

I've tried to be very methodical about my approach to what could possibly be the problem. Ive tried to cover all the obvious things, but we all know how easy it may be to look over something.


All that being said. I pulled the plugs a short while ago. I didnt run it today, just the bit yesterday when I was testing different things.

All four plugs are visually damp.


I have new plugs in the mail, and I have a rebuilt set of injectors. I am going to take these plugs in to work and sand blast them, then install the cleaned plugs with the new injectors.

What else would cause me to get wet plugs on a pretty much stock SE?

 

Resolved!!!



Ok. I got off work today and rushed home to toss in my clean plugs and newly rebuilt/cleaned injectors from RC engineering.

Put it all together, fired it up and!!! Crap.


WTF, I told myself. I was getting really frustrated. I checked spark again, ran through a bunch of basics all over again, and nothing was doing anything.

I started taking this video I linked to. In the video you can see how I was just trying to demonstrate its symptoms. One time when I went to start it, nothing happened.

Checked spark again and I had nothing at my trailing. I quickly ran to my storage unit and grabbed a few j-109's from my collection and ran back home.

Installed the used j-109 and!!! Vroom!

Tuned in a couple things I had played with and it was idling normally and accepting throttle input nicely. I havent driven it yet, but I would say it is good to go. I will always have a stash of j-109's with me for now on, I usually have extra GM ignitors too!!

Thanks guys!

 

What is a j109 if I may ask a dumb question

 

Awesome!!! That is the best feeling when you finally get it figured out. Glad it's running well again.

J109 is the stock ignitor, little black box (2 of them) on the side of the distributor.

 

Aren't you only using one ignitor since you are running direct fire? My SE will not start and I am running a similar setup. I am getting spark but did not consider changing the trailing ignitor.