random lt1 issue help!

[townsend]

hey guys so the mods are now on hold. i need to figure out what is going on with this thing.

it seems as though its randomly running out of fuel/retarding spark. right off idle pulling away from a light and when cruising barely touching the pedal then pushing it down to accelerate 5-10 mph, the motor "chugs" for a second. it only does it when the motor is warm. if i let off then push back down it smooths right out. im kinda at a loss right now considering it has good gas in it and a relatively new msd billet opti. any suggestions will be appreciated.

i have been reading about the ignition module going because of its placement on the drivers side head. anyone else had this start to go and act up?

[sweetbmxrider]

That will usually give you extended cranks, you should space the coil off the head now anyways. I would take some carb cleaner and clean the throttle body blades and opening some. Maybe reset the computer after and see how she runs after it relearns idle etc.

[townsend]

FIXED!! for now...unbelievable how a msd billet opti comes with vacuum hoses that are cheaper than the air hoses for my fishtank. 2nd broken one in a week...time to replace all vacuum hoses since p.o. said they are all original. plus the maf is oily from the air filter.

[LTb1ow]

MSD units do not come with hoses. So, odds are,their stock.

[greenformula92]

yes sir those would be stock hoses. and just as a FYI the ICM usually doesn't give you any warning, you will be driving down the road and all the sudden it will just die. then when the engine cools and the ism cools it will start and you can try to get it home.

[townsend]

yeah just got home with new hoses...they must all be original hoses because they are all cracked..

[townsend]

Well now I have an issue. It's still acting up. Put all new vacuum hoses on and cleaned maf, but it still randomly chugs off idle. I also have a nasty smell coming from underhood almost like really hot metal mixed with rotten eggs. The car has a new highflow cat so I doubt that its burning out already. I'm going to try to get a video so everyone can atleast try to see it when it acts up looking at the tach.

[greenformula92]

any codes?

[townsend]

nope no check engine light nothing....jumped out aldl and got nothing.

[townsend]

uploading video now i apologize for my complaining and your probably going to have to turn up your volume.

[greenformula92]

hmm. the rotten egg thing begs clogged cat but you said it was recently replaced. not saying that cant be it but chances are it isn't. does this only happen when warm, or is it all the time?

[townsend]

now its starting to become all the time cold or hot...it seems to be getting worse. you will see and hear when the video finally uploads to my photobucket. its like its either cutting most spark and missing all over or losing all fuel and missing all over.

[townsend]

here it is listen from 14 seconds on and ignore my talking...if you turn it up you can hear it go "pop pop pop pop" then it smooths out all of a sudden

http://i1184.photobucket.com/albums/z337/tubbytownsend/th_VIDEO0018.jpg (http://s1184.photobucket.com/albums/z337/tubbytownsend/?action=view&current=VIDEO0018.mp4)

[zraffz]

How long does it take to start when you crank it? What do your plugs look like?

Check your fuel pressure, bust out a can of ether and spray all the vacuum hoses.

[greenformula92]

check you fuel presure, check plugs and wires and look for any and all vac leaks. Whens the last time the fuel filter was changed?

[townsend]

fuel filter is questionable i asked previous owner and he said he didnt know a while maybe so im gonna change that today. also im gonna start checking every plug and wire. vacuum leaks should be nonexistent unless its a gasket mating surface

[townsend]

oh it starts right up when u crank it doesnt take more than 2 or 3 seconds cold

[JL8Jeff]

Does it still have the AIR stuff hooked up and the EVAP stuff? If the EVAP solenoid goes bad (it's on the side of the intake) it might allow air to be sucked into the intake all the time which will act like a vacuum leak. You might need someone to scan it to check the fuel trims.

[townsend]

yes all emissions are in place...i dont know anyone who could scan it..worst part about this is that there are no codes at all and its not everytime you hit the gas, although it is now doing it more and more

[zraffz]

Use a can of ether and get spraying. You'll quickly find out if you have vacuum leaks still.

Next do the fuel filter. Check fuel pressure. Check out your plugs and mist your wires when it's running (at night) to see if it arcs anywhere. Is your MAF damaged by any chance?

[townsend]

not sure if maf is damaged i was super gentle with it and i just cleaned it last night. after reassembly it got worse. your saying to spray the connections of the vacuum lines with ether? all i have is carb cleaner and starting fluid

[greenformula92]

unplug the MAF and see if that changes anything. it will give you a code but the ECM will just use the MAP for fuel trim

[townsend]

ok trying it right now

[zraffz]

Starting fluid = ether. Don't use carb cleaner, I think that would do more bad than good to your lines. Mist it over your vacuum lines and any place you have gaskets preventing vacuum leaks (ex: throttle body) while the vehicle is running. If their is a leak the idle will raise.
It's the fastest and easiest way to find vacuum leaks without owning any special tools.

[bigz28man]

Did you check the fuel pressure at the rails? Had a similar problem a few years ago, found out I had not enough pressure at the rails. Every time I would hit the gas it would fall on its face. Let of the gas and it ran at idle fine. Also check maf sensor as stated above, anyone you know that could swap theirs out to rule that out.

[bigz28man]

One last thing does it only act up when the car is at running temp. The coil can be an issue as well, but I found in my experience that coil only acts up when it becomes heat soaked after the car is at its running temperature. I would place washers between coil and heads to fix and help prevent future issues. Bmxridder reminded me of that on my build and I realized I forgot to do that and made a quick adjustment.

[townsend]

unplugged maf and drove to advance auto parts with same problem no change. got to advance and started getting irritated at prices, then my manager buddy who works there comes outside with me and starts looking around. pulls off passenger side pcv line (the only one i didnt replace because i didnt think of it) and finds this right at throttle body:http://i1184.photobucket.com/albums/z337/tubbytownsend/Snapbucket/F2EB0A8E-orig.jpg

fixed it with a piece of fuel line that was a nice tight fit and drove around for 30 minutes with no problem...i feel like smacking myself in the face now. :facepalm: im still replacing the fuel filter and i do want to get a spare maf because i dont want this to happen again.

thanks guys. if this evil gremlin comes back even after all of this i will repost

[townsend]

One last thing does it only act up when the car is at running temp. The coil can be an issue as well, but I found in my experience that coil only acts up when it becomes heat soaked after the car is at its running temperature. I would place washers between coil and heads to fix and help prevent future issues. Bmxridder reminded me of that on my build and I realized I forgot to do that and made a quick adjustment.

i have read about this and am currently spacing it off the head in like two minutes. the coil will have to wait till payday as will the plugs and wires (ngk tr55 $$$)

[townsend]

bigz28man nice motor btw lol

[bigz28man]

I'm looking to sell my granitllie maf sensor shot me over a pm if interested.

The motor makes music next Friday, no cats, no mufflers, long tube headers, it should be a loud rock and roll concert. Thanks btw.

[townsend]

vids or can i come watch lol

[townsend]

for the granitelli dont you need a tune?

[bigz28man]

Its plug and play

[townsend]

still having the problem...im lost now. i replaced EVERY vacuum line there is and it still does it especially worse when the motor is hot. it was running ok on a short drive to a car meet. then on the way home all of a sudden at 50 mph cruising i push down a little bit on the throttle and it comes back. get home let it cool for a little bit restart it and go for another ride and i dont even get a mile from home and its back just like the video. i already unplugged the maf and map based it still did it. im really starting to think ignition problem. the coil/plugs/wires are going to have to wait a few days until i get paid though. this sucks this is my dd

[greenformula92]

Yeah I would do a total tune up. Plugs, Wires and if your feeling froggy the opti cap

[LTb1ow]

I would try swapping ICM's and see if the problem goes away at hot.

[townsend]

anybody got a spare icm? that things $90 on the cheap..

[LTb1ow]

Yea I got one, er prob two :lol:

[townsend]

but ur by the meadowlands correct?

[LTb1ow]

Noo, I am exit 105 area.

[townsend]

:facepalm:

[townsend]

tuesday morning/afternoon ill be in that area you going to be around? how much you want for one?

[townsend]

im gonna go pick up a coil now mine seems as though it has seen better days...try that next

[grazi]

Mine was doing basically the same exact thing as yours. I threw alot of parts at it. It ended up being that the cat was clogged. I seen yours is high flow but maybe do like I did. Shoot the front side with an IR thermometer and compare it to the back. There shouldnt be much difference in temp. I did mine and it was around 300 degrees difference . I gutted it and mine runs like a charm now for about a month.

[townsend]

the cat is 3 weeks old....in the process of changing the coil i noticed that a rediculous amount of heat is coming off of the icm/coil bracket. i dont think that it helps that the coil has the epoxy all mushy its getting so hot...ill post back in 20 minutes

[townsend]

not the coil...this sucks...must be icm/wires/opti....

[sweetbmxrider]

There is supposed to be thermal paste on the icm. Just because a part is new, doesn't mean it can't be bad. I would definitely look into the cat temps as said before.

[grazi]

After looking at the video you posted, mine wasnt doing much of that popping noise but was bogging pretty bad...I woulde still check the cat anyway, takes two seconds, dont even have to jack the car up. I dont think that the ICM would cause anything like what your having.

[sweetbmxrider]

Watched the vid, wow. Either a clogged cat (esp with the burning metal/rotten egg smell), a blown out exhaust gasket, or you're running on like 4 cylinders. I'm banking on cat. Try hitting it with your hand or something and see if you hear the honeycomb rattling.

[townsend]

it only does this once the motor enters closed loop. its especially at low rpms under load (like going up a hill) once it starts doing it though then it goes crazy and you have to keep pumping the gas and all of a sudden it will smooth out. probably doesnt help that the plugs that are in it are all gapped at .063 too.

[LTb1ow]

Def a large spark plug gap, I think stock is .050 area?

[WildBillyT]

That plug gap is way wide.

[greenformula92]

probably doesnt help that the plugs that are in it are all gapped at .063 too.

That is probobly a HUGE part of your problem. either re-gap or replace them

[townsend]

well guys it gets WAAAYYY better now....i replaced all the plugs with ngk tr55 platinums gapped at .050.. hasnt acted up yet the way it has before on a short 25 mile drive. it is cold out though. BUT, halfway on the ride the service engine light came on. when i got to where i was going i shut the car off for a minute or two literally and turned it back on, no service engine light. get halfway home and bam service engine light comes back. get home and go to flash codes and the fans turn on etc but the service engine light doesnt flash it just stays lit. this is really puzzling now.

[greenformula92]

certain codes can cause the ECM to ignore all sensors and it will kick the fans on. When I had a LT1 camaro I had a MAF code and it did that

[townsend]

yeah I just read about that and that I can't flash codes on the 94 I need a scanner or aldl cable... Lovely.

Still getting new icm though tomorrow hopefully. Anybody have the ability to scan this and live kinda close?

[greenformula92]

the jump the pins trick doesn't work on that?

[greenformula92]

do this: http://www.extreme-check-engine-light-codes.com/GM%20OBD1%20Decoder.htm

[JL8Jeff]

You should be able to get one of the parts stores like Autozone to scan the codes for you for free.

[townsend]

Already did that...doesnt work. The fans just turn on but the service engine lite stays lit no flash or nothing. I looked it up and found that 94-95 Lt1 you need a code reader or aldl cable

The local advanced and autozone don't have the obd 1 scanner to use

[sweetbmxrider]

You are correct, its obd1 and you can only read codes with a scan tool.

[townsend]

:banghead:

[WildBillyT]

http://www.ttspowersystems.com/DataMaster.html

Free for the first 20 uses.

[LTb1ow]

If you wanna buy a cable, lemme know.

[townsend]

Thanks bill and Ltb1ow you have another pm

[LTb1ow]

Can you verify if you have a 12 or 16 pin connector?

a 94 can have either, I think, 12 pin being able to let you jump pins to flash the codes and 16 being required to use a cable.

[townsend]

12 pin still doesn't let you...and that's what I have

[LTb1ow]

Ach, that sucks, my cable is 16 pin for a 95. Sorry

[grazi]

http://www.aldlcable.com/sc/details.asp?item=aldlobd2u
Thata what you need. I had to buy one form a member on here for my 94...and I downloaded datamaster for free. You get 20 recordings for free. Its a piece of cake to install and easy to use.

[townsend]

Thanks guys I'm gonna have to wait till Wednesday to order it and then for it to get here

[townsend]

Actually that's still the wrong cable I need the 12 pin one I swear I always get the car thats special

[grazi]

http://www.obd2allinone.com/sc/details.asp?item=aldlobd1u

That one

[townsend]

yup thats the same one i found. thanks again.

[townsend]

took it for another 15 mile ride, ses light came on about 4 miles in, shut car off for 2 minutes, drove home and 4 miles into that ride ses light came back on. car seems to be running fine otherwise....

:scratch:

i gotta get that cable...

starting to think maybe a computer issue...

[townsend]

now the schizoness is back....only things i touched on the entire car tonight was i fiddled with the egr to check its operation and it checked ok, literally unplugged and plugged back in knock sensor and coolant temp sensor for computer, and touched the passenger side o2 sensor since the white wire that has the ground band that wraps around the sensor seemed fishy. now, no check engine light, tons of missing/backfiring.

[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]

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]

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]

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]

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 :rofl:

[WildBillyT]

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.

[townsend]

i started reading the datamaster manual. i see that i may have issues at first connecting like ltb1ow said. thank you again guys for the help you have given. im gonna definately need more as i start to try to figure the thing out.

[townsend]

anybody use tunercat? anybody recommend an easy to use obd1 tuner?

i want to turn my fans on earlier due to the 160 stat. they still wait till full hot and it heatsoaks.

[grazi]

Datamaster is so simpleto use. All you do is install it and plug the car in and tells you everythign you need to know.

[sweetbmxrider]

Tunercat is about it when it comes to tuning lt1s. HPtuners is actually based off of it.

[townsend]

ok thanks. another thing, is it normal to get a little fuel spray and alot of pressure release when removing the gas cap? i never got that much pressure release and never had fuel spray on my 87 tpi. just curious

[greenformula92]

fuel spray no. preasure maybe depending on how much gas is in the tank

[townsend]

ok so i got my cable and did a datalog with datamaster, anybody have the ability and look at some stuff for me? i hvae an odd open/closed loop operation going on when it warms up

[LTb1ow]

PM WBT, he is the guy to get that file stuff hosted here.

[townsend]

10-4

[WildBillyT]

Send it over dude

[WildBillyT]

http://www.njfboa.org/WBT/AutoLog_002.uni

[WildBillyT]

How new are the O2 sensors?

[townsend]

original....thats what i was starting to think that the o2s were bad

[WildBillyT]

original....thats what i was starting to think that the o2s were bad

Yeah, at one point in that scan you throw a DTC for an O2 sensor but it's also during a connection error, so I dunno. That one bank stays around 400mv a lot, might be just getting slow.

I'd replace them both. Rock Auto sells DENSO O2s for a good price. Use ACDelco or DENSO.

[townsend]

Ya know i noticed that. and then when hot idling that o2 stays at 415. Thanks I'm gonna do that first

[townsend]

Thanks again bill. My wife just looked in my initial log and there was an o2 code for the right side. I cleared it before the log that I sent you. I thought it could have been when i was messing with stuff

[WildBillyT]

No problem man.