View Full Version : MAF sensor or what?

08-19-2004, 04:48 PM
ok well i got my AFPR hooked back up today although i broke a bolt connecting fuel rail, but ill fix once i solve this. AFPR is set perfect at 40 psi. that part seems solid. but when i start the car cold it will just die in a few seconds. once its warm it seems to stay running, but it just idles really harsh it isnt clean. i messes wish biss but it diddnt really help may have helped stalling some, but it just runs soo junk like really putt putt and if you try and rev it just hesitates soo bad. if i disconnect maf sesnsor plug it idles perfect and clean, higher like 1200 rpm ,but still really nice, then if connect it....BAM starts running horribly rough and junky again. I logged for errors, but nothing comes up when everything is connected. Just doesnt seem like a vacuum leak either. it would have to be pretty noticable i would think for it to act like this.All i want to do is get my beautiful 1g running again nicely. fuel trims are all at 100% when i logged at idle. just put keydriver chip in programmed for my 550's currently in. This is the hopefully helpfull facts i can give you to hopefully help me out with the problem to get car going strong again. thanks a lot guys. matt

08-19-2004, 05:15 PM
post your complete mod list - it'll help

08-19-2004, 05:19 PM
heres my whole car in a nutshell man.... thanks

92 AWD 6 bolt/4 bolt
20K on Engine, 10K on transmission and turbo, 100K on body

Motor Built by Thomas Automotive Developement
1991 Block bored, (.20 over), honed, and balanced
New ported and polished head with 3 angle valve job
New crankshaft
JE 9:1 pistons with Total Seal Rings and stock reconditioned rods w/ clevite bearings
ARP Bolts throughout
Clevite Bearings
HKS Metal Headgasket
Balanced Shafts, A/C, Cruise Removed
Prothane Motor Mount inserts
Fresh Timing, p/s, and Alt/water pump belts

Big 16g - Ported w/34mm flapper (10K miles) (until 50 trim goes on)
2g manifold, ported O2 housing
Fluidyne Aluminum Radiator w/catchcan
Turbo XS boost controller
Autometer Boost, Water Temp, and EGT gauges
Datalogger running mcd software
BM Tranny built to 1994 spec.
4 spider differential
bg synchro shift in tranny
syrnogen II in t-case
ACT 2600 w/street disc
Stainless steel clutch line
Symborski shift kit
Carbon fiber pedals

KYB GR2 shocks, Eibach Pro Kit Springs
Front strut tower bar, Front cross drilled rotors
Stock 1g mas unfortunately
Walboro 255LPH fuel pump
550cc RC Engineering injectors
HKS Super AFR (Air Fuel Controller) not hooked up presently
Bolt on adjustable fuel pressure regulator w/ gauge at 40 psi
Dsm chip eprom modification- has launch features and no lift shift plus mas compensation and injector sizing
Magnacore 8.5s Wires and ngk plugs
Optima Red Top battery

08-19-2004, 05:24 PM
1) When you unhooked the HKS box, did you connect the airflow signal wires back together?

2) Fuel pressure is not right

3) Chip is not for 550's

4) Injectors are not 550's


08-19-2004, 05:27 PM
i did hook it back up i will make sure it is on good though. if it wasnt hooked up right though at the harness wouldnt it throw a code on my logger? i had no codes hooked up. ill stick the stock chip back in and see if that helps. i dont know its weird doesnt seem like any of these, but i guess it should or has to be. ive checked em out tho. thanks for the help guys.

08-19-2004, 08:45 PM
i meant to say i had no codes come up. if the harness wire to ecu wasnt connected properly would it throw a code on my logger?

08-19-2004, 09:00 PM
My guess would be an intercooler pipe was left disconnected or something.

Can you see the karman count at idle with the logger? What does it read? If it says 3 Hz, than you have an open IC pipe somewhere. If it says anywhere from 30-50 Hz, than the problem lies elsewhere. If it says 0 Hz, than you have no signal to the ECU.

My money's on an intake leak somewhere.

Marcus Martinez

08-19-2004, 09:23 PM
is it sufficient to hook up intake tester to turbo and try it. is there any other place i should hook up to get other or full results for all leaks that are possible? my mafs is ok reading in the 30's hz. any thing else i should check on the logger tho? thanks for the help. matt

08-19-2004, 10:03 PM
would 1 broken manifold to head bolt that is broken off just behond the gasket cause all this? it doesnt seem like it but i do hear funny popping noise from that precise area. figured i ask. heres a log incase anyone can find anything abnormal from it. im new to the logger.please dont worry about my zip file there is definately nothing harmful. it is on spreadsheet. thanks soo much you guys. matt

08-20-2004, 01:28 PM
anybody see anything with my log that may be a sign of whats going on with my car? please anyone? thanks. matt

08-20-2004, 01:37 PM
You need to work on your language skills. There are certain parts of your initial post that barely make sense. Anyway, I'll digress. First take us through the steps of when it WAS running up until now. Anything you've changed or added.

Also, have you done a test for leaks? If you are unsure how to do it, go check the vfaq.

08-20-2004, 03:33 PM
Is the only way to test for leaks to hook it up to turbo? would an exhaust leak of some sort cause the rough junky idle and loud putt putt noise out the tailpipe? thanks. matt

08-20-2004, 09:19 PM
checked for leaks... can hear very faint one at throttlebody someplace, tried to drive car and it hesitates soo bad its not even driveable at all. guess i may have to get it towed in which sucks. i am just really stumped this time. no idea what it could be hopefully technicians will.... thanks. matt

08-20-2004, 09:48 PM
under revving is it normal for the maf sensor to go up to like 175 hz or so?

08-22-2004, 02:37 AM
yup that's normal... under wot my hz go to 2300.....


08-22-2004, 12:27 PM
hey i just took off my mas to check and see if maybe it was modified and causing the problems.... well apprently the genius that i bought the car from had completely hacked the lower section honey comb. it was removed and all plastic inner part was cut out along with the screw. resulting in one huge gaping hole!!! since removing the fuel controller and putting on AFPR i have not tried to start car till now and this happens. before the afr was set too compensate for the severely hacked mas.... now no af controller, just a chip and AFPR. could this be the cause to my horrible idle and not driveability problems?!?!?!?!

08-22-2004, 12:40 PM
That will be the problem. Find an unhacked 1g mas and put that in. I've got one if you need one.

Having a severly hacked 1g maf will cause you to run very lean at idle and lower engine speeds.

I'll bet that is your problem.

Marcus Martinez

08-22-2004, 12:44 PM
SWEET im soo glad i may have found out what is wrong!! thanks for backing my theory up man. i was hoping youd respond :-) I think im just going to go ahead and buy the nice gm maft set up that i was planning on getting in the future anyway, but since it looks like i need it now... why the heck not!! I am pretty sure that this is my problem with the car although the fuel trims say 100% at idle. is that lean or rich? i hope this solves it!! thanks again. matt

08-22-2004, 03:26 PM
is having all fuel trims at 100% mean that im rich or lean at idle?

08-23-2004, 12:12 AM
100% means your perfect, they are only usually like that after you reset the ECU or your a perfect tuner...

anything higher means leaner then 100%
lower is rich


08-23-2004, 12:16 AM
ok soo like if they said 139% that would mean really lean then? im thinking my hacked maf that i just realized was hacked today when i pullled it is causing the horrible idle and driveability issues considering this is the first time ive tried to run car without the af controller in. just using custom chip and AFPR. sound like that could be it?

08-23-2004, 12:28 AM
ok soo like if they said 139% that would mean really lean then? im thinking my hacked maf that i just realized was hacked today when i pullled it is causing the horrible idle and driveability issues considering this is the first time ive tried to run car without the af controller in. just using custom chip and AFPR. sound like that could be it?

Very lean.

100% certain that it will run worlds better when you install an unhacked MAF or just richen it up.

Marcus Martinez

08-23-2004, 12:34 AM
my fuel trims are actually at !00% at idle, i was using the 139% as an example to verify that i understand the concept of reading the trims. sorry if i confused you. still seem like it could be the cause though? right?

08-23-2004, 07:39 AM
Oops. Getting a little ahead of myself.

I thought that when you were asking about it that your trims were there.

Marcus Martinez

08-23-2004, 09:36 AM
naww man sorry that was confusing there really all at 100% im gonna borrow a maf set up today and see if it fixes it.thanks