Here we go again. Engine in sig ARAP bin modified by me. Drove 70 miles to a friend's house. Ran great. Warmed up the engine the next morning and shut it off to get something from inside.

Came back out, tried to start it... it fired, flared up as usual and died immediatly. Tried 10 more times same thing, throttle seemed to make no difference.

Checked fuel, check spark... getting both.
Unplug the maf sensor... engine runs rough for 2 seconds then the MAF ses light comes on and it idles and drives pretty good minus the being rich.

-Tried two other chips, and burnt another one just to see, no change.
-Tried another ECM (Theory it might be bad), no change.
-Tried two other mafs (disconnecting the battery between each one Wells and Bosch style) No change.
-Went through all the steps to check MAF ses codes 33/34, all checked out good.
-Tested all the grounds in the engine bay, all are good.
-TPS voltage good
-Cleaned IAC, no change.
-Checked for obvious things (Plug wires, connectors, vacuum leaks, burnt wires) nothing.



Where do I go from here? Why does it run with the ses light on maf unplugged, but wont run when its plugged in.

When the maf is plugged in, I can get it to sort of run by pumping the throttle. It tries to pop and studder and sounds kind of like its back firing, or coughing or kicking back.

Ignition Module? If so, why only when the maf is plugged in? I'm so lost.

Help PLEASEEEEEEEE!

 

The EST link might not be active, with the SES light on, MAF unplugged.

I had a DIS module that wouldn't work when the EST line wasn't active. So it wouldn't run at less then 400 RPM.

EST/on/off/module problems can be fun.......

 

When she drives around, it doesn't seem to heat up like if it was only stuck at 6deg. Am I correct in that with the EST not active, you don't get spark advance? My scanner also reads a commanded timing advance...


Just got a new distributor/module and all... the old one was starting to strip one of the cap threads so the parts store swapped it out for me.

Still a no go.

What else could be bypassed with the ses light on? Or is the EST still a possability? Does the fuel pump relay act differently? It get's it's initial fire up real nice, but its like nothing keeps it going...

 

Did you happen to check your TPS voltage? A bad TPS will exhibit the same symptoms.

 

TPS is good on the scanner and verified with the DVOM at the connector.

 

Oxygen Sensor Toggling?

Problem I had, did same as yours. If I could get it to go in to failsoft it would run fine. But getting it there was a pain. The SES would kick on after 5 minutes of driving and it was awesome from there.

Replaced O2 and now its golden right from the get go.

 

Does the ECM make up O2 values when the ses light is on? Though I can't really get it to run with everything plugged in. With the maf unplugged the scanner has o2 readings and shows the computer correcting which all seem to be about where I was running before. Though it could just be default stuff, I'm not sure.

The o2 is about a month old. I can take it back and say its defective. I still have the receipt. Good Idea, I'll give it a try! Desperation sucks. First nice weather here in weeks and the car is out of commission!

 

Does the O2 move at all?? When mine went bad it went to the stock default of being lean so that it would dump more fuel into the motor. i.e., wont run lean and pop the motor but will run rich and keep it in line.

If the O2 value moves over .450 back and forth you're good. If it stays at 1 value then its bad. Get a Bosch, they're like $30 where I'm from. Make sure to get the one that already has the connector attached as you cannot reliably splice one on.

 

Yeah the o2 moves according to the scanner. Bounced back and forth of the swing point.

 

Update: If I let the car warm up with the ses light on...

--Wells maf... I get the flare and die.
--Bosch maf... will idle, rough, maf values bouncing 5-9gm/sec If I put my foot on the throttle a little(.54tps to 1.0tps), the engine doesn't speed up and the maf values don't change... it will only rev up if I romp on it.

According to the scanner my IAC is at 160 steps, and I've got the throttle blades open now almost as far as they will go with the set screw.

Got a burnoff and power relay ordered from the parts store, should be here in an hour. Inspected all the maf wiring I could and found nothing. Also found no obvious vacuum leaks, starter fluid in the valvecover and around the intake revealed nothing.

More ideas?

Edit: Tried the new relays, nothin. Wells maf this time seemed to be about the same as the bosch one.

 

Maybe check the temp sensors. might be getting pegged signals causing calculating errors.
Something to look into.

 

You said you have fuel but do you have fuel while its trying to run? Im thinking the fuel pump contact on the oil pressure switch. If it is bad you will still get your 2 second run of the fuel pump when you turn on the ignition but it wont go after the engine starts and it will die.

Steve

 

Whoops, that was dumb on my part. I didnt notice that you could get it to run by unplugging stuff. Disregard previous post.

Steve

 

Hehe its okay. Went through last night and started testing voltage at the ecm and found a few wrong ones so I'm gonna start disecting that now. Damn 17 year old electrical.