Okay here we go..I recently installed a reman smallblock in my 5.0 TPI T-5 T/A.
New bosch 3 injectors,new fuel filter,Basically took all the other stuff off the original motor cleaned it up real good and placed it on my new motor.It is also a stock 305(bored 40 over but thats irrelevant).....it runs and drives really well except every once in a while it'll kinda buck a little bit and act like its losing power and wants to die..It'll especially act up when I'm cruising at a steady speed maybe 60ish or so.I'm thinking about trying to replace the FPR or just the diaphragm and see if that clears it up...I dont know I'm just not wanting to get stuck out somewhere....Oh and the car sit for quite a while as I was gathering parts for the project if that has any relevance.Thanks for any help guys!!!

 

I'd get a fuel pressure gauge and watch it while it's acting up. IMHO, it's always better to diagnose the problem rather than throwing parts at it, hoping to get lucky. A cheap OBD1 scanner might not be a bad idea either.

 

Check for vacuum leaks. Open the hood when its black outside and look for arcing, you can even spray a little mist of water on the cap, wires and spark plug area. Don't touch anything or have someone around that knows CPR? Cheep gas can drive you nuts.

 

I hooked a gauge up to it and followed the steps in my shop manual I have for the car,The gauge would read 25psi before i cranked the car but with the key on.Then I cranked the car and it would go up to 42psi which is bout normal from what I read...then dropped bout 15psi when I connected the vacuum line.

as far as I can tell I dont have any vacuum leaks.I've tried checking it pretty good...

 

Alrighty then,I installed a holley 502-501 afpr (supposed to function 35-65psi) today after I installed it and started the car,I started out with the **** really loose but I had to crank it all the way tight to make it even close to stock..It would only go to bout 40psi all the way as tight as I could get it...took the car down the rd and it ran ok but after a min it started bucking around bout died and backfired something fierce and blew out all kinda smoke then it ran fine all the way to the house where I parked it...Getting pretty frustrated!!I guess I'm gonna take that back to advance and start over unless ya'll have any suggestions

 

Is the car running rich? I recently bought a set of bosch 3's and one of the injectors was stuck open. It was completely flooding one cylinder. Also may want to try a leak down test.

 

OHM'ing the injectors might not be a bad idea, either.

 

ok so I finally OHM'd the injectors and the are as follows cold then hot per cyl # ex...cold/hot
1=14.5cold 16.6 hot
3=14.3/16.6
5=14.6/17
7=14.5/17

2=14.4/16.8
4=14.5/16.7
6=14.3/16.6
8=14.2/16.6

it will idle perfect with maybe a little miss every once in a while(I have my timing set round 10 degrees adv,but have tried it with same result at 0),then it warms up and if I start fluttering the throttle or hold it at a steady rpm for a few seconds then tap the throttle it will backfire and go back to idle just fine....I had it in pitch black and made it do it a few times and didnt really see any arcing anywhere,now when it backfired I did see it shoot out the manifold collector but thats normal I assume when it backfires and the whole path of least resistance thing.So where to start now..I'm thinking of buying a new distributor and wires with cap and rotor obviously...maybe a coil too but I need a starting point.I can get a dizzy for bout the price I could rebuild the one I have and not have to worry with breaking something...Thanks for the help!!

 

did you flip #6?

 

nice catch..thanks for that I sure did.Gonna correct it now.

 

i just dropped in a fresh motor too, had the same problems as you. turns out the grounds for the ECM to the back of the head on the driver side came loose, and also the ground pin on the ecm bulkhead connector came partially unpinned. the cars idle would surge, i would be cruising and it would violently jerk and buck, the speedometer would jump like 5 mph when it happened too, so go check out the grounds on the back of both heads and the ecm

 

Thanks man,I'll check into that today.the car has a history of ground issues believe me it has..previous owner did an engine swap and didn't ground good which I caught hell for but oh well...when I put the engine in this time I made sure it was grounded..I made a 0 gauge ground wire for the engine to chassis ground,along with the ground straps and all that other......but I'm gonna check out the other specific grounds now before I spend lots of $$

 

okay so I've done alot more and still have the same issue so I'm gonna post fresh from the beginning here and see if starting over I forgot something.

::k here we go,it's a .40 over 305 crate engine tuned port 5 speed 91 Trans Am convertible.
When it warms up and I take off down the road when I get in third gear I can feel it starting to act up(jerk around and stuff)when I get into 4th gear at low rpm it'll start really acting up,it'll start acting like its going dead,if I push the gas it'll just stall then act like it wants to backfire and it'll just buck around and act all kinda stupid!!

What I did-heads are rebuilt by local machine shop.all other parts were cleaned and dried and new gaskets were installed upon rebuild.it has stock manifolds on it,all the smog/emissions stuff has been removed including the egr and blocked off.
I have replaced the distributor with a brand new one not a reman.It included the pickup coil and the module,I set the timing at stock,10 degrees advance then 5 degrees retard just to see if it made a difference which it did not except for changing the timing like its supposed to.
I have checked the fuel pressure,it has a guage on the schrader valve so I am keep an eye on it.The pressure stays between 45 and 50 steady except for when I accelerate obviously..but all that seems to be functioning properly and has from day one even when the car is acting up.
Has new cap rotor coil plugs wires and I have checked for and repaired all the vacuum leaks I found.i have check and replaced ground straps and even made a 0 guage ground strap and grounded the engine to the chassis with it also.i checked the grounds at the ECM too,from the plug to the chassis and it had good continuity.
I've replaced the map sensor,o2 sensor,iac and tps,knock sensor and temp sensor.
It also has new Bosch 3 injectors I got from the fuel injector connection which I have ohmed out hot and cold and they are well within spec.i can also physically tell each one is firing by touching them one at a time.i replaced the fuel filter too
Lastly I replaced the ECM today with no change,I took it back and got my $$ back because I didn't really have another hundred to throw at it but I did anyway....ok so there we go,if I think of anything else I'll post it,Thanks again guys for all the help.This is really frustrating as I'm sure you all know oh so well!

 

Have you checked the fuel tank for trash or rust. I had the same issue and went thru about 5 fuel filters and before it cleared up.

 

dwillis, I feel your pain. Looks like you've replaced practically everything that could possibly cause this problem. Since the motor and heads are new/rebuilt, have you looked at the possibility that the cam my have been installed advanced or retarded? Are you sure the rockers were adjusted properly?

 

were you able to figure out what was going on dwillis ?

 

I have not and I've been so busy I haven't had a chance to do anything with it.Maybe one day after the holidays I'll have a chance again to look it more :{

 

will stay tuned

 

Are the rockers adjusted properly?
Fuel PSI check while driving???
Sounds like bad plug wires, cap, rotor or weak coil.

 

Dwillis, I think you should check your Holley AFPR to be sure it not contributing to or masking the problem. I had the same Holley AFPR you have and found that it was leaking, there was fuel in the vacuum line.

 

rockers have been double checked,brand new distributor,module,cap,rotor plugs,wires,computer,chip(that tuned hooked me up with...Thx again and I havent forgot about ya)...I have ohm checked the injectors cold and hot,tested the tps with an ohm meter..fuel pressure is correct running,cold,warm and driving down the road and I no longer have the holly afpr its back stock now....Thanks guys

 

Did you check the ground wires on both side in back of the engine? What about the ground wire from the battery to the head? And the small ground wire from the battery to the fender? Set the timing 6 degrees before top dead center. What size injectors are you using? They should be 18lbs injectors. Are all the sensors hook up including the one under the plenum?

 

I replaced all ground straps with brand new ones.Heads to firewall,batt to fender and batt to head..I even made an extra gornd out of some 0 gauge wire that goes from the frame to the engine block.I also checked the ground from the computer through the harness.I am running some yellow Bosch 3 injectors I ordered from fuel inj connection.I believe they are 21lb but i dont know for sure right now.all the sensors are connected and %90 of the sensors are new the rest have been tested by me and are within specs i am getting from the shop manual.Thanks for the help and as soon as I get my timing light back from eho borrowed it I will double and triple check the timing

 

Well if you have 21lb injectors with a 19lb injector chip that's part of your problem. It's dumping too much fuel. You have to change in the chip or get 19lb Injectors.

 

okay so after some more digging and studying on this and focusing on the injectors I believe that could be my issue all along.The ones I got from FIC are Bosh 3's the part number on the inj itself reads that its a 19lb but the flow sheet they sent me state that they are 22lb injectors( I assume they rebuild them to flow more if they want to..I don't know)I am going to call them and see if they will send me some 19lb inj in place of these I have now...Its kinda my last resort because as youve seen I have pretty much covered all the bases in my opinion.thanks again for all the help guys

 

heres the sheet that was sent along with the injectors

 

Its not the injs unless they are all stuck shut or all stuck open.

 

Talked to Jon at fuel inj connection where I got the injectors and he agreed that with my fuel pressure where it is the injectors are probably putting out to much fuel and flooding and causing the bucking around so he's going to send me some 19lb injectors and I'll go from there.so we shall see...thanks again for y'alls help

 

well I replaced the injectors with the new 19lb ons and rechecked the timing and ignition componets this weekend with no avail.It continues to do the same thing so at this point in my frustration I'm considering one of two things,I'm either going to sell it and put the money towards my other project(77 Trans Am)or put a carbed smallblock in it.But for now I'm done with it.thank you guys for all your help and I may be back some day but for now adios amigos and Happy New year!

 

-

 

It's a 305.

 

okay,I still need help with this same issue..I'm looking into possible internal issues now.I was thinking that the only two things that I changed when I put the crate motor in was I deleted the EGR and removed all the stuff with it including the A.I.R tubes and the egr relay or valve-whatever that thing called that the vacuum lines are connected to..haha .I have checked for vacuum leaks vigorously and replaced lines and blocked off all unnecessary vacuum ports.
I say all that to say the second difference is I used the cam that come with the crate engine.The motor is an 87-93 5.0L 8cyl according to the tag that come with it.I don't know if the cam is a tbi cam or if there is even a difference.When I run the numbers on the block it come back to be a later model vortec engine,probably a truck one but I don't know.I cant find any info on the freaking cam though that makes sense to me anyway as compared to a stock tpi cam.I will post a couple pix of the numbers on the cam that come in the short block that and see if you guys maybe can help me out...if all it is is the cam thats an easy fix though I'll hate myself for not changing it out on the rebuild...Thanks for any help guys

 

Did you scan the qr tag ?

 

I tried but I couldnt get a result

 

The E.I may stand for Elgin industries

 

well just in your opinion do you think the cam could be my issue all along?Thanks for your continued assistance by the way

 

I'm really not sure, but if its made bye Elgin I would toss it in the trash. I just look at there online catalog and didnt see any part numbers that even looked close.

 

I may just take the chance and replace it with a stock one if I can come up with a good one thats pretty affordable.You know anyone who may have one?lol

 

is the block setup for a roller cam ? If so you might put a ad in the wanted section of the classifieds here. You will need shorter pushrods and the lifters and retaine ect..

 

yeah its a stock hydraulic roller 305 block as far as I know.it has the provisions for the lifter retainer hold down

 

Comp cams 7808-16
A used lt1 cam
http://www.skipwhiteperformance.com/...px?Item=J-2079

 

thanks bro,I'll check into those...Those are some good prices too!!!

 

You can use a used cam retainer and spider retainer and the dog bone links.

 

Are you having any issues with the engine wanting to die when you put it in gear? and also when you check the timing did you disconnect the brown advance timing wire on the passenger side of the car?

 

It's a T-5 and yea I disconnected the brown wire..I readjusted the valves yesterday too lol..I bout to just sell it I think and use the cash to work on my '77

 

Did you ever figure out what that cam was ?

 

All I can find from the numbers is that it's a late model vortec cam.most likely for a truck and one would assume it'd be a tbi truck engine..so in short no not really..I've been having to work so much I haven't undertook the process of removing it yet

 

well another chapter in my long drawn out story...I'll make it short and to the point...When I disconnected the brown wire to adjust the ignition timing I forgot to plug it back in when I took the car for a spin(I got distracted)...so when I was driving with the brown wire disconnected the car did not act up one single time...seemed to run just fine,Then I noticed the check engine light on and it made me remember I needed to plug the wire back together..When I reconnected the wire and took it out again it started running crappy again just like it was before...so I tried it again and with the wire apart it runs fine and with the wire connected it runs just like it did before...What the heck it up?any clues?Thanks guys

 

Have you put a timing light back on it with the est connected to see if the timing goes retarded ?

 

It stays the same regardless if the est is connected or not.