random lt1 issue help!

[townsend]

well today im off of work so time to go play. im gonna unplug each sensor one by one and see if the problem disappears. also im going to remove ac compressor and some other stuff to see if there is anything up with the plug wires. thinking that the ac pulley might have cut something.

[townsend]

interesting findings

disconnected maf = no change
disconnected egr vacuum solenoid electrical connector = no change
disconnected evap electrical connector at vacuum block = no change (ran worse without it)
disconnected map sensor electrical connector = doesnt act up anymore?

does anyone when the check engine light is lit for map sensor fault what sensors the 94 obd1 computer ignores?

next is disconnecting each o2 sensor one at a time with map reconnected to see if there is a change.

thank you guys for putting up with my extensive tech post with this problem. i am learning alot about this engine due to this and most of what im learning is from you guys, especially greenformula92 and LTb1ow. in a roundabout way the suggestions you have posted on other threads for lt1 issues and mine have helped me narrow this down to a sensor problem.

[townsend]

just found out all sensors are original sensors that came with the car from the previous owner. getting o2 sensors first thing tomorrow will have them replaced by 630 p.m.

[sweetbmxrider]

I would wait and see what code(s) is being thrown before changing parts personally. Unplugging a sensor doesn't necessarily mean its good or bad either in most cases. The computer is sometimes thrown into speed density mode where it relies on only a few sensors to correct for air/fuel ratio etc.

[LTb1ow]

Yea, the MAP should throw a code for it, and its simple to replace if it does throw one. Just also verify it has the donut seal on it and its not leaking air into the intake.

[greenformula92]

Originally Posted by LTb1ow

Yea, the MAP should throw a code for it, and its simple to replace if it does throw one. Just also verify it has the donut seal on it and its not leaking air into the intake.

You stole what I was gonnna say haha. MAP should throw a code, but doesn't always. I would remmove is and make sure that little donut is in good shape. Make sure you pull the MAP straight up so you don't break the little nipple. MAP could be throwing weird readings.

[townsend]

yeah im doing that now. i am just in sheer amazement that every sensor, i mean every sensor, is original according to the previous owner, even o2s. he put emphasis on them. im gonna ohm the o2s out and see what i get. thanks again guys.

[townsend]

Originally Posted by sweetbmxrider

I would wait and see what code(s) is being thrown before changing parts personally. Unplugging a sensor doesn't necessarily mean its good or bad either in most cases. The computer is sometimes thrown into speed density mode where it relies on only a few sensors to correct for air/fuel ratio etc.

that is what i was wondering when thrown into sd mode or service engine mode what sensors are kicked out of the loop. as in what sensors does it not rely on anymore. i always believed sd was using the map, so without it it is obviously running maf or off a base enrichment table.

[townsend]

well, the map sensor nipple is plugged up and dirty with crap, any way of cleaning this?

[townsend]

initial evaluation: did not reset computer, cleaned map nipple of black crap with maf cleaner, checked donut (nice tight fit), reinstalled and just did a 26 mile drive

verdict: did not act up yet, drove smoother than butter.

[LTb1ow]

This is good

[townsend]

Hmmm, besides a random service engine light that goes on for 30 seconds and shuts off, its running like a raped ape. I'm ordering the cable tomorrow so I can datalog it just in case.

Thanks again everybody. Without you guys and Google id be s.o.l.

[WildBillyT]

Originally Posted by townsend

Hmmm, besides a random service engine light that goes on for 30 seconds and shuts off, its running like a raped ape. I'm ordering the cable tomorrow so I can datalog it just in case.

Thanks again everybody. Without you guys and Google id be s.o.l.

30 seconds? Interesting. Get a scan and that will make it even easier to debug.

[townsend]

30-60 seconds its intriguing really

[sweetbmxrider]

At what speeds/driving conditions? Seems like a lame emissions related code.

[greenformula92]

goog to see its running better. I never saw one clog up but I guess if its got almost 200k on it that could happen

[townsend]

Mainly at part throttle (more like barely any throttle) cruise 50-55 mph all the roads around me are about that since I live in the twigs. No real substantial load on engine except its in od.

I have a pic of it ill put up tomorrow

[greenformula92]

you really need to get that cable lol. And your sig is right. your in LT1 hell lol

[townsend]

cable is ordered...must wait for confirmation email and tracking number....watch, this takes weeks...

[WildBillyT]

My AKM cable came in a few days, if you ordered from them.

[townsend]

didnt get from akm, he no longer offers them.

[townsend]

started reading tts datamaster user manual. all i can say is holy s*** this is why i liked carbs, much easier!

[LTb1ow]

Hardest part will be making the laptop see the cable and then making datamaster see the cable. Otherwise just plug it in, run scan, get codes.

Make some datalogs if you wanna, and then I think WBT knows how to host the file so others can view it and comment.

[greenformula92]

Originally Posted by townsend

started reading tts datamaster user manual. all i can say is holy s*** this is why i liked carbs, much easier!

yes...but little to no fuel economy

[WildBillyT]

Originally Posted by townsend

started reading tts datamaster user manual. all i can say is holy s*** this is why i liked carbs, much easier!

Not really.

Datamaster will see what's wrong and tell you what's up. If your fueling is even a little rich, or vacuum a little off, you'll see it. No more guessing with jets and accelerator pumps. If I didn't just have to buy repair parts for my exhaust I'd have bought a wideband for my Nova.