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General Car wont go past 10 hg of vacuum. Please Help

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DsmDanielson

Proven Member
104
0
Jul 13, 2016
Peoria, Arizona
So i did dome research and couldnt find much to touch on my particular scenario. Shout out to Michael Hensel for helping me get my car startwd and idling normally! seems i found a friend. In other news, heres the facts. 1g block, 2g head, 1g cas, 560 evo injectors, stock fpr for now, 190lph fuel pump, fmic, and big 16g turbo. Problem goes as follows. The car goes really lean when i get past 10hg of vacuum. Ill cold start it, and it will idle at 800 rpm on 16hg of vacuum till it warms up, then it will go to 20hg of vacuum and 1000 rpm. ( I made the idle high to compensate for my exhaust leak at the flex pipe because at low rpm it will make my car go lean) I verified an issue at my ecu with the alternator as it was outputting a low voltsge (12.2) at idle, so i clipped ecu pin 33 and sure enough, volts at idle went to 14.0. So now my car will stay on, the low voltage on my alternaotr wasnt enough to supply the fuel pump no matter what i did on my safc2. So i stsrt driving my car and i can get my car to 10 hg of vacuum before it starts going waaaaay lean and bucking. Heres whats strange: I already put +20 all the way across to make my car stoich at idle and a little higher for high rpms. this bothers me because the baseline correction for 560 injectors is -18, and i know every car is different but my maf is untouched, no vacuum leaks (strong 20hg vacuum) and a boost leak would make my car rich not lean. So i dont know if my fuel pump is going bye bye, its not crazy loud or anything. if my injectors were clogged it would be lean at idle too. i have 3/4 tank of gas, although its been in there for 3 months, i wouldnt say its bad yet. Could it be my fuel pump relay? Fuel pressure regulator ? Im soooo close to my car running perfect and this is the last issue
 
Also, i tune off a narrowband for now and i read the 02 sensor voltsge off my safc. I also have a bluetooth obd2 datalogger and im able to see every reading i can think of so its not like im blind. Any thoughts?
 
Before you get any more serious you need to invest in a wideband and a better way to make fueling and timing adjustments and a way to monitor knock if your datalogger is'nt capable.
 
Yes. I understand that. i can monitor knock and timing through the datalogger. And while im sure you mean well by telling me i need a wideband. Remember something; we make do with what we have, and there was a point where widebands werent available so it is possible without it. My a/f gauge still reads lean and rich values, so i know what my car is outputting. The problem is my car is lean. So if you have a way of diagnosing my situation then I would appreciate it. No other information is useful to me. No sarcasm or disrespect intended. But Ive done nothing but try and figure out whats wrong with my car, and a wideband is not whats wrong with my car. Id like more relevant information please. Thats all im asking. You have no idea how much my car means to me, so if i thought i coukdnt do it without a wideband, that car wouldnt even be turned on without a wideband. Thank you
 
Do you have an adjustable fuel pressure regulator? and what is your fuel pressure at idle and under load?
 
No my afpr broke. Im not able to log fuel pressure for some reason. All i know is that my o2 sensor cycles between. 0.02 and .8 volts at idle every second or so. under 2000 rpm the car shows an advance of +17 whike cruising in first and second gear. At this time my vacuum shows around 15 hg. When it gets to 12-10hg, it goes really lean.
 
Or, because its going lean its showing 12hg, the ecu opening the isc to keep the engine running due to any other problem will cause the vacuum to drop.
 
Check your fuel trims. Get a real wideband and sell that narrow band to a Honda guy.

Next post better say you fixed your flex pipe and added a wideband. what ecu are you using?
 
I dont have 150 for a wideband so umless somebody wants to be a savior thats going to have to wait. it will take me 20 bucks to fix a flex pipe. what does a leak at the flex pipe have to dp with going lean while accelerating? Im using a 98 flashable ecu. Im going the ceddymods route, im not going ecmlink. Maybe one day but not right now
 
I use a scg-1 to read vacuum, I'm running BC 272s, the compression, blt, and vacuum lines are all 100%, and I only get -12ish. I have the idle turned up to 950, I just where it seems most comfortable.
 
Lose the safc and put in stock injector. Find the problem and fix that first. You're chasing a ghost and modifying around it. Bad plan and it makes it 10 times harder to find the problem.
 
It runs perfect at idle. Ive had to bump the safc setting to +20 so it would idle and even at idle the fuel trim hovers around 20%. and this is with a 190 lph fuel pump and stock fpr and 560 evo injectors. Something is failing.
 
Put in stock injectors and remove the safc. That is probably your best bet to find the root cause.
 
Okay well i dont have stock injectors laying around and i woukd love to get rid of the safc for a tactrix 2.0 cable so i can tune my ecu. Maybe somebody has some stock injectors they can lend? I dont kniw but but i do know its not my ecu cause i changed out with my buddies ecu and its still the same problem
 
Did this start out of the blue or since a build or since a part install etc. ?
Has the car ever run correctly In its current configuration?
 
I bought the car not running right but it would boost to 5 psi but it had a blown sensor ground so it was pig rich. I changed the turbo, and fized some frayed wiring in odd places and pkugs and wires but that was pretty much it. Quick question: What causes the car to up the fuel pressure while accelerating? That might be the issue. its stoich at idle but goes lean on acceleration which makes the car act like i didnt hit the gas at all
 
The biggest thing I see is youre adding fuel with the safc. Check fuel pressure maybe? There arent many things that get fuel that far out of whack.
 
I have it narrowed down to my fuel pump or my fuel pressure regulator. but considering thst i have a stock regulator on right now it wouldnt be making my car lean, but rich if it failed so im guessing my fuel pump is going bye bye. Thing is, its not loud? I thought walbros were supposed to be loud when they were giving out, mine actually sounds more quiet than normal. but before the sucker was pretty loud.
If i get another fuel pump im going to have to another afpr. But agsin, what causes fuel pressure to rise during acceleration? The afpr?
 
Yes FPR regulates fuel pressure via the vacuum line going from it to the intake manifold.
 
Update: Car is now running perfectly after 3 months. The fuel pump was dead, switched it out for a walbro 255 and car started right up, and i did a nice 12 psi pull a little bit ago. Such a relief! I put so much time into this car and its finally done. I changed everything you can think of and thought my engine just took a crap but everything is just fine now. Fuel trims are at 0, no coolant or oil loss or leaks, car doesnt overheat as i rewired it and put a switch in the console. Timing advance was 35° during my pull. We did everybody thank you so much!
 
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