85 Trans Am,won't accelerate,backfires,no power

[coachcoffy]

I have an 85 T/A ,305 TPI, the motors been rebuilt,has 2000 miles on it,all sensors on motor are new,we've checked timing,it's exact,it starts,run a little rich and rough,but it smoothes out a little.you can drive it slow as long as you don't accelerate, You try to accelerate it cuts out,back fires. I've tested the ignition module & pick up coil,& as I said the knock sensor,map sensor are new, I'm at a stand still,all new plugs,wires,distributor cap & rotor,Please does anyone have any advice or ideas,

[j cAT]

Originally Posted by coachcoffy

I have an 85 T/A ,305 TPI, the motors been rebuilt,has 2000 miles on it,all sensors on motor are new,we've checked timing,it's exact,it starts,run a little rich and rough,but it smoothes out a little.you can drive it slow as long as you don't accelerate, You try to accelerate it cuts out,back fires. I've tested the ignition module & pick up coil,& as I said the knock sensor,map sensor are new, I'm at a stand still,all new plugs,wires,distributor cap & rotor,Please does anyone have any advice or ideas,

what is the back pressure ? I would open the exhaust up stream of the cat converter see if it runs better. what about the heat riser that open ?

fuel evap valves working properly these can suck extra fuel into the engine and melt down the converters.

EGR replaced the last 10 yrs ?

[coachcoffy]

[quote=j cAT;7173004]what is the back pressure ? I would open the exhaust up stream of the cat converter see if it runs better. what about the heat riser that open ?

fuel evap valves working properly these can suck extra fuel into the engine and melt down the converters.

EGR replaced the last 10 yrs ?[/QUOTE Thank you for your quick reply,EGR was replaced when we put the engine back in,2000 miles ago,my son put headers on it so I'm not sure about the heat riser,or the back pressure,I will go out and check it in a few minutes & check the cat converter,I forgot if we replaced it with everything else or not.I know all of the sensors & modules were replaced,& I just checked pick up coil & had ignition module checked,I really appreciate the info,also we didn't replace the electronic spark control module,could that be it,no way to test them that I know of, thanks again,I'll let you know results in a while.

[coachcoffy]

O'k, I checked EGR valve,cat converter and evap valves,there aren't any.exhaust has headers into 2 1/2 pipe back to mufflers,EGR valve was taken out before engine rebuild,and I look for the evap canister & it was taken out also. The car was running good and then just started acting up.So I replaced,plugs,wires,rotopr cap & distributor cap,ignition module, & still doing the same thing,runs but no power and backfires on acceleration. I do thank you for your information,any other ideas are greatly apprecited

[777stickman]

I would be inclined to look at valve timing. Do a compression test on all holes. Check cam timing. Check valve adjustment.

Another issue could be a way too lean A/F ratio.

Good Luck.

[coachcoffy]

Originally Posted by 777stickman

I would be inclined to look at valve timing. Do a compression test on all holes. Check cam timing. Check valve adjustment.

Another issue could be a way too lean A/F ratio.

Good Luck.

Thank you for your information,I will check the valve adjustment and compression this evening & let you know. I'm not sure how to check valve & cam timing if its different than just checking the timing,I have checked the timimg,even tried it a little advanced. but one thing I didn't mention,the timing mark on the crank is kind of jumpy, it moves up & down 5-10 degrees at idle,I'll check the valves tonight,thanks again.

[brcidd]

Backfires on acceleration-- is usually lack of fuel- or more commonly fuel pressure- have you tested fuel pump pressure?

[coachcoffy]

Originally Posted by brcidd

Backfires on acceleration-- is usually lack of fuel- or more commonly fuel pressure- have you tested fuel pump pressure?

Yes actually,it's right at 40lbs which is what it calls for I think thats what it said,it's definitely running rich & backfiring,black smoke out both exhaust pipes ,& backfire when you accelerate, thank you for your info though,

[j cAT]

Originally Posted by coachcoffy

Thank you for your information,I will check the valve adjustment and compression this evening & let you know. I'm not sure how to check valve & cam timing if its different than just checking the timing,I have checked the timimg,even tried it a little advanced. but one thing I didn't mention,the timing mark on the crank is kind of jumpy, it moves up & down 5-10 degrees at idle,I'll check the valves tonight,thanks again.

to change the timing you need to disconnect the EST connector. this when disconnected removes all spark advance. then I think its 700 RPM you set the timing to like 7deg BTDC...

I still have a 1984 305 berlinetta.. timing if too retarded could do it..

another tool to use would be a vacuum gauge.. vacuum should be 17-21 inches and hold steady .. if the reading is jumping around that would be bad valves.. a bad valve will do it.. so then you do compression check compare all cylinders..

good luck..

[coachcoffy]

Originally Posted by j cAT

to change the timing you need to disconnect the EST connector. this when disconnected removes all spark advance. then I think its 700 RPM you set the timing to like 7deg BTDC...

I still have a 1984 305 berlinetta.. timing if too retarded could do it..

another tool to use would be a vacuum gauge.. vacuum should be 17-21 inches and hold steady .. if the reading is jumping around that would be bad valves.. a bad valve will do it.. so then you do compression check compare all cylinders..

good luck..

thank you, We're going to start on that tonight, I appreciate your help,thanks again, Mike

[Blue Bowtie]

Is it still running the stock (Bosch) injectors?

[coachcoffy]

Originally Posted by Blue Bowtie

Is it still running the stock (Bosch) injectors?

No we put new ones in when the motor was rebuilt,has 2000 miles on it,and fuel pressure is 40lbs,and it is blowing black smoke ideing,& backfires when accelerating,even in park,

[Magnum01]

If this problem persists, Or is even going on.. For what it's worth. The timing chain could've slipped.. It's one of those things no one really checks but it does happen. If the problems resolved then carry on.

[coachcoffy]

Originally Posted by Magnum01

If this problem persists, Or is even going on.. For what it's worth. The timing chain could've slipped.. It's one of those things no one really checks but it does happen. If the problems resolved then carry on.

Thank you,I thought about that,but really didn't want to face it,LOL,I kind of wonder if it's worth keeping it all original or switch motors to a newer one,this is the first year for TPI and I know why it didn't last.Any how thanks for the advice,I guess reality is I'm going to have to go that route.thanks

[Blue Bowtie]

What flow rate injectors were installed?