Lean Conditions...

this one has got me stumped...
Last night driveing my car... wasnt even raging on it or nothing... just cruising nice and easy when my car got very rough... my check engine light came on, I HAVE OBD1 SYSTEM!!! when does the check engine light ever come on with obd1... well anyones i look at the AFR and IT WAS AT 30!!!!!!!!! so i killed it... looked for any posible fuel leaks... none... just the MAF harness... still plug in... so i started it up... didnt do it... took of it kicked back on agian... so I very gently keep the car under 500 rpms and eased it home... check this morning in light for any possible leak or sensor undone... checked the fuel pump everything... i cant seem to find the problem... I have after maket fuel pump and complete fuel system... the FPR seams to be great... injectors are recently new... i have been running it on new turbos for hte last week and have had no problems... ive got 20g turbos with 550cc injectors... and all week it has been running rich... has anyone ever ran accross this very odd problem?

What are you boosting at, and on what octane?
Did you try pulling the codes?

http://www.stealth316.com/2-diagcodes91-93.htm

Are you datalogging?

No I did not read codes, due to the difficulties of geting them being OBD1.
I'm currently boosting at 25 lbs (Main thing is the CFMS im flowing...)
Im running on 93 Octane... Most of this is irralivant due to the fact I've been running these turbos for about a week and a half... I upgraded from my old 13gs... and for a week i was running on the rich side to keep it safe... i believe around 11 afr... that doesnt explain the 28-30 afr... I run a piggy back that my freind from Power House racing had mad known as the MAP-Ecu... it is very sufficient, not like those peice of crap AEMs... the map ecu is a data loger and of course a tunable piggy back that the Inavate Motorsports Wideban hooks up too to allow good tunning and better data logging... there has to be another explination for this due to the fact it ran beutiful for over a week... Im going to replace the O2 sensors for starts... fuel filter and what not... all the small stuff... so ill see how this goes... ive just never seen such a drastic change in AFR in my life... Im a mechanic at MVP Motor Sports, and im haveing to ask qeustions on a forum... I was just wondering if anyone has ever ran accross this problems and see what they did... because i know this has nothing to do with the performance parts...

ok, fair enough. But why not pulled the codes? I posted the link above....it can't hurt. Replacing hte fuel filter can't hurt, but what kinda knock counts and pulled timing are you seeing? Also what is your fuel pressure at idle?

How rich? Do you have a cat?

My guess is something got fouled downstream of the engine (oxygen sensor or cat)...

so you're running the MAP ecu? i thought you had the AEM ems? but your MAP ecu has datalog capability? can it read the codes from the ecu? i would HIGHLY recommend you get a datalogger. simply get a palm pilot, load software on it, get datalogger cable, voila. do a search, you'll find many threads.

as for your ems, you might want to have someone look at its tune.

2old, Im not running rich... I running lean (to much air) the AFR was at 30.
And I found out the problem! It just was killing me because of how quick the change was... when a o2 sensor goes out it goes over time so you can tell if its in the process of going bad... and it would have to be one hell of a clog it was the filter... but from perfect running to really really lean in almost a instant didnt sound right... untill my freind car did the identical thing...
but both made a relization that it happen within a hour after geting gas, and it was a suddent change within seconds... we figured out the Exxon is now mixing their gas with water ans sometimes can over do it... we pul gas out to see that it was very hazzy like a water gas mix... this would explain the quick change... due to the fact that the fuel lines can hold up to 2 - 3 gallons of gas and we where able to make it about 10 - 20 miles down the road... then the bad gas hit... so after syphoning out my gas tank and going through the long process of cleaning out my lines it ran perfect... and i even look on the internet and this has been a very common problem here lately due to the "new Formula Gas" I would advise that you tell every one that you know to be very picky about where they get their gas... for as they might run into the problems i did... I am now currently in the proccess of geting reprocutions back from the station i got the gas... though it will be a while I should get back money for gas - $50, money for spark plugs $20 - and just so fortunate I am a mechanic i can process a recipte for labor ;) ;) ;) and get back 5 hours worth of labor at $80 an hour ;) ;) though I wont be the mechanic but my partner will ;)
But the bran dgas station i got my gas was at Exxon... so if i where yall stray away from exxon for a while, i would buy shell.
so now i have to go syphone gas out of my freinds recently new Ferrari 360 Modeana... and trust me he is more pissed than i am...

watering down gas and still charging $3 plus?!!!?!!!

:flipa: :chair: :twak: :swear: :wtf: :thumbsdow :nutkick: :slap: to Exxon... that really pisses me off by the way... I hate corperations sometimes..

wow, that is screwed up. Hope you avoided damage to the engine.

For the most part it seams ok... Like i said the main damage was done to the spark plugs... Of course there was always the chance of me blowing a hole in the pistion but nothing that serious happened haha... but yeah like I said avoid this happening to you and be carefull on where you get your gas...
for now on I'm only puting 118 octane in mine haha... I already bout a berale of rocket brand feul 118 octane its beutifull stuff allows great boost haha.

wtf...im guessing they dont do that in winter??? Gas and water will seperate before too long at all wont they? That seems like a major lawsuit waiting to happen to me. Its nothing less than false advertizing.

I will definitely spread the word to stay away from Exxon.

EDIT: ....Exxon and Mobil are the same company, arent they?.....hmmm...should i stay away from Mobil?

Honestly, with all hte rain we got in July, excess water in the tanks could have been an accident. Granted it is something they are still responsible for, but I have my doubts on many gas stations doing anything they 'should' without a little governmental kick in the behind. With all the price-gouging going on around here, I'd be willing to be most places had more than the regulated amount of water in their underground tanks...and probably didn't mind the extra profits too much. A friend of mine who used to work at a Wawa always said their gas was a bit cheaper due to the fact that they were always right on the line of legally allowed amounts of water in their tanks...so...yeah. Good luck, I hope you get money out of them.

Honestly, with all hte rain we got in July, excess water in the tanks could have been an accident.

92VR4red is out of Bridgeport, TX around Ft. Worth. there hasn't been rain in north texas in the last few months. [actually, there was a brief storm this past sunday for a few hours.] so i don't think ground water from excess rain in the NE would have trickled down to TX. but still, i'll stay away from Exxon Mobil gas stations. Shell is a good brand. Texaco too.

I just think they put water in it to get more money...

^our minivan had a horrible problem from Citgo watering down their gas. We had to replace the fuel filter and the plugs I think, but I've never gone there again...

So only shell?? Hmm, that's it, I'm just gonna' drive 45min each way to the southside to get sunnoco race gas :evillol:

Im now Buying berals of 118 octane from RocketBrand Fuel, ;) so I just desginated my car a Weekend driver... :(

Well let's try to figure out hte problem.

What kind of timing counts are you looking at, is the ECU pulling ridiculous timing, if so when and how much?

I know you mentioned 550cc injectors, but what fuel pump and what fuel pressure are you seeing at idle with vacuum?

Also are 20Gs TD04 or TD05? Either way 550ccs maybe entirely too small. What kind of IDCs are you seeing? I know you said you were running these for a week and a half on the rich side, but it sounds to me like there maybe a shortcoming on the fuel side of this...ie, like you maxed out the fuel the injectors can flow.