hey guys I have a '87 Trans Am 5.7L 350 mostly stock. I've been having this problem for some time and have replaced/checked many things. the most recent thing I did was replace spark plugs. now when I set EST in bypass and am checking timing, I set it to about 6* BTDC like the label says and it sounds fine idleing, then if I blip the throttle it takes a sec and revs some but mostly sounds like crap. I observed the timing while accelerating and it goes to about 5 or 4 deg BTDC. plug wires are new, cap and rotor are fairly new, dizzy is fairly new autozone junk. coil tested good and is fairly new. thought maybe TPS and swapped with a new one no difference. now I did mess with the min idle screw a long time ago and I think I have it set about right now. can anyone determine how many full turns on the screw from all the way back position (not touching lever) is the factory setting? I put the trans in D and set it to about 450 RPM and it seems to be close. IAC is fairly new. I read this in another post and have the same problem: sometimes when going in reverse from a full stop engine dies. starts right back up. I tested fuel pressure and during 2 sec prime I get build up to 31 PSI then drop to 0, then while cranking maintains 31 PSI same when running. I know this is low but can the 10 or so PSI loss make the car buck and miss while accelerating but idle fine and sometimes drive fine thru speed ranges. sometimes it acts like it's fixed runs perfect, then I come to a stop and when I try to take off, put put. but it does seem somewhat intermintent. maybe the pump dying??

also it seems like when it is "missing" or whatever that if I floor it, nothin.. but if i just barely give it throttle it will start to catch and I can get up to 45-50 mph. one conditon has been I get up to 30 MPH then loss of power, I try to rev up engine tach reads same rpm but engine feels like, well like a miss or a slip in tranny can't really tell. I just want ti to be something else easy b4 I take it to the shop and pay out my A$$ for something really dumb.. or a fuel pump.

 

well tried again and this time replaced dizzy with new one from autozone (gotta love lifetime warranty pieces of crap) and well at first I set timing to 6 deg BTDC and blip throttle and it sounded really good.. then tightened down the bolt checked timing was the same so I blip throttle again and put put backfire through TB. wtf i don't understand this. well only thing I can assume now is it's not getting enough fuel pressure (31 PSI0 and it will idle but when i try to accelerate the psi just isn't there.. but it will run good sometimes then i'll stop.. put put bog down again. i'm breaking down and prob taking it into the shop tomorrow. any last minute ideas first? anyone know how to check a EST sensor. or whatever it's called.

 

when my ESC thing went bad it felt like something was slipping when I tried to accelerate. the way I checked for it was by running the error codes (per chilton's manual directions) I think it was code 43. I think the timing at idle after everything is connected back up and the car is restarted should be closer to 20 deg BTDC. Did the new distributor come with a new ESC, If not that would be something to look into.
Bucking is a sign of a lean condition. I've had loud pops from the exhaust while running too lean and also while running too rich. I've only had a backfire when my distributor was 180 out when I changed my intake, but the engine won't run like that. When my fuel pump went bad it did so without warning, one day my car just would not start.
my fuel pressure during priming goes up to 43psi and holds for 5 to 10 minutes at least. maybe you need to replace the fuel pressure regulator. I think what you actually get is more of a rebuild kit for the regulator rather than a new one.

Oh, and my dads astro van was bucking, missing and felt like the transmission was slipping. It was the FUEL FILTER.

 

just to add I also broke the pipe comming out of my cat for the A.I.R. system so could this cause a lean condition? well only other thing I think i've tracked down is my ESC Module. I found a kick *** test chart for it . I am going to test it tomorrow and will repost with my findings..

Test Chart for ESC


EDIT: well the test seemed to say replace the ESC so I did but no change. now the only things left really are fuel pump and tranny rebuild. only 2 things left from 1987 on my car.

 

just in case anyone reads this some of the things I have fixed/tested since: when I unplugged my MAF sensor the car returned to normal performance. no bog during acceleration, can peel the tires again, just has a hard time idling. so I check the MAF power and burnoff relays, replace power and now got code 33. suspect bad MAF sensor and replaced it. seems to run good now. then problem came back. no codes. bog during acceleration. so I tried disc canister purge solenoid and reset ecm. seems to run better indefinatley. I suspect the solenoid is bad and sticking open or something, I can hear hissing comming from it now. I ohmed it out and it read like 38 ohms so I guess that's good? I know one of the solenods on the Air Management Valve thing is bad, one reads open other reads 38 ohms. seems wierd to me tho that even with canister purge solenoid hooked up car will run great with maf sensor disc. I did find one vacuum leak maybe there are more. my int and blm go up to 180 during accleration after closed loop not sure if that's cuz of low fuel pressure (31 PSI) or a vac leak. also is 180 deg high for intake Air temp sensor @ idle and 195 deg engine temp?

 

REPLACE YOUR FUEL PUMP AND FILTER NOW! That's the problem with the acceleration. It's a pain to do the pump, but it IS the problem, unless the wiring to the pump is shatty.

 

when I disconnect my MAF Sensor my car runs great. if I have it plugged in the car bogs/misfires during acceleration. I replaced the MAF sensor itself, and checked/replaced the 3 relays ( MAF power, burnoff, and fuel pump). checked connectors and get 12V on oranges, 5V signal on C of MAF sensor, 12V on red while engine running, and my black/whites read good to ground with ignition off, but with ign on or running they read 350 ohms. is this wierd or normal? my pump 2 sec primes no matter what relay I put it in. I do have a fuel pressue issue it reads 31 PSI always but I flow tested the pump and it put out 3/4 a quart in 15 sec. also my burn off circuit works. just a bad ground? or could tripping the MAF code by disc it make the car run good with bad fuel psi?!??

 

fuel pump!!!! 31 is way low. While you are at it put an afpr and open the power band

 

alright so per the advice here and my own assumptions I went ahead replaced my fuel pump myself. was a little tough but all in all not too bad. well I get it all back together and still does same thing. pressure goes to 30 then drops when pump isn't running. and that's when testing at the fuel rail and directly at the pump. so WTF!!! all that work and it does the same thing, bogs during acceleration. on my scan tool the only value I can see that changes while it bogs ( besides it always saying lean and INT & BLM at 180 during acceleration) is spark advance is up in the 27-30 range then when it's doing the bog/stumble drops to 16-18 and when it goes again it's back up to 27-30. only thing I can think of is I noticed when I had the pump sender out that the two vent lines were kinda loose and I could see a small crack around them where they connect to the sender. but I figured since they are just vent it wouldn't hurt anything. the two lines that carry fuel were solid and attached good at the sender. so could small cracks at the solder joint of the vent lines on the sender cause low fuel pressure and for it not to hold? remember I tested it before the fuel rail.

 

Its been a while since I read this so I skimmed through and didn't notice if you've tried the fuel pressure regulator. The FPR went bad on my moms 97 transam ramair when it was brand new and it started running like crap (still under warrenty then, luckily).

 

no one ever tells you howto check things out. with a fuel preasure gauge conected to the fuel rail disconnect the the vaccum line that connects to the fuel preasure regulator. the preasure sould go up 8-10 psi. if it doesnt then put a vacuum tester on the fpr, it sould hold ten pounds. check the vacuum at the vaccum line it sould be about 10 pounds. if the fpr does not hold ten pounds and there is ten at the vacuum line repace the fpr. then turm the key on let the fuel pump cycle and put a vise grip on the main fuel line.
if it looses preasure right away then you replace the fpr.


BUY THE HELMS MANUAL, not chilton not haynes HELMS or you are going to repace parts based on the advise of people with the same experience level as you. put the phone up to the car and start it and maybe I can figure it out or use the books that were issued to the dealership if you are serious about owning a high performance fuel injected car that will break your heart from time to time

 

OK so my car finally runs good and all the problems I listed here are gone now!!! my problem was I did not replace the fuel pump pulsator when I did the pump the first time. did the same problem so I took it all back apart and replaced that damn $20 part and now my fuel pressure goes to 43-44 and holds steady even when pump is not running. so like others have said here about replacing the pump, it's too much work to be a cheapskate. if the pulsator is in there replace it, especially if you weren't holding pressure or getting good pressure before and your replacing the pump. well hope this helps anyone who has similar problems and they only have to do the work once!!