Car: '87 GTA with 5.7 TPI and 700r4
Mods: Stage 3 Port&polish, 3 angle valve job, cold air intake, headers, 3in exhaust, high flow cat, stand alone coolant relay, art car strip shift kit.

I completely rebuilt this engine and maybe only has 40 miles on it. But the acceleration keeps getting worse until now when you put your foot down on the gas it has absolutely nothing there. In "park" the engine will rev up no problem, without any delay. Its when you try to drive it that everything falls asleep on you. Also a couple times when swithching into "reverse" or "Drive" it will stall. I have fuel pressure and a new dizzy along with all new plugs and wires. The spark isnt as strong as id like so im going to buy a coil too, however i believe there is something else going on here. Any advise?

 

Any help or even a hunch is greatly appreciated guys.

 

at first, it sounds like a vacuum leak but i'm not so sure because you say it will perk right up in park. but there's no power.

weak spark is a possibility, so your new coil may help.

air restrictions - i.e. filter new? Any way to check air flow thru the maf?

fuel flow? injector condition? try putting a noid light on each connector. those are old injectors right? the bad ones came in '89 -91. yours may be fine, but need a good cleaning.

and again - check wire condition and spark after the new coil goes in.

one other - check vacuum!

 

Thanks for the advice, i installed the new coil and it did help a little, i also checked for and found 2 small vacuum leaks that i fixed then timed the engine again. It has acceleration again but still lacks power. Im still going to check a few more things with my fuel delivery. also ill buy a cleaning kit for my cold air intake to try and get my power back. Do you know how much vacume the plenum should read at idol. Thanks for the advice

 

one thing to try - unplug the o2 sensor then unscrew it, you may have an exhaust restriction.

But does the engine rev? I'm wondering if i'm hearing you right. No acceleration, but does the engine sound right? If you blip the throttle by hand at idle, does the engine respond immediately? I'm wondering if it does, then your problem might be the transmission.

also, check the fuel pressure by gauge while standing at park revving the engine and if possible, by driving the car. Sometimes a pump is just fine in a static situation, but under a demand scenario, they cant deliver the goods. then it could be a clogged fuel filter, restricted fuel lines, leaky pressure regulator, or your worst nightmare, a dying fuel pump.

depending where you are located, you should have around 15psi vacuum for a healthy engine, but they will idle pretty well as low as 10, again, depending what elevation you are at.

 

Part of me is scared that this is a trans problem

I have acceleration again, just not much power. Also it has a searching idol, fluctuates between 400-600 rpm when in drive( in park it idols smooth). The engine revs up if you blip the throttle in park, but is slow to rev up in drive and shifts late.

A few weeks ago i replaced the fuel pump and filter then blew compressed air in the lines. This raised my pressure to 46psi

Ill check vacuum pressure tomorrow (im at sea level). Also is it possible for the smog system to be causing any of these problems.

 

idle should be around 6-700 if the stock chip is used. assuming thats the case, the surging idle in D is a clue. Is the surging taking place after the engine is warm, i mean close to 200? What were looking for here is the case where the ECM has entered closed loop and is relying on the o2 sensor to close the feedback loop. If the o2 goes above a certain value, the ECM will lean out the mix i.e. shorten the injector pulses. vice versa if the o2 voltage is low. Is the ECM the originally supplied unit for an '89? Is it a stock chip? are the injectors clean and not broken? Do a search for "multec" and read up on the problems those injectors had, especially in the 1989 time frame.

 

sorry, but the stock multec injectors are junk. They are SO problematic and prone to coil failure. Check the resistance on them when they are hot and cold. If you get any readings below 12ohm then you need to replace the injectors.

www.southbayfuelinjectors.com
516-442-4707

 

Luckily I don't have the multec injectors. I have an 87 gta with stock ecu and chip. My injectors were cleaned and fully tested (leak down test, ohm test hot and cold, and noid light).

I tested to see if the car still surged in D at idol when warm, and it did. It also has more of a tendency to stal at idol when warmed up. I checked for codes and it came up with a 42 this time (42. Fault at electronic spark timing circuit OR Fault at direct ignition system OR Fault at fuel cutoff relay circuit) I'm thinking this code could be thrown from timing my engine?
I have to wait till my next pay check to buy a vac gauge and filter cleaning kit but ill keep you all posted

 

Doing some research I found that there should be an air temp sensor on the rear of the plenum for all tpi engines 87-89. Is this true? When I bought the car, my engine was in a million pieces so I don't have anything to compare it to. I just have a bolt where they show a sensor... And then I have the 2 sensors below the throttle body

 

Here is a photo of my plenum if it helps

 

all Tpi engine use the mat, these is a extension from the harness to connect it.
gm 15326386 or acdelco 213-928 it is the same as your cts.

 

Sorry I'm a little confused. So are saying that I should get one of those parts and install it in my plenum then look for a plug to attach to it?

 

Okay I found the sensor on my plenum. Its hidden on the bottom side next to the egr. I was wondering if I could test it with a simple resistance test to see if its working...

 

Have you hooked a scanner , to lok at the tps, cts and mat , maf readings ? Does this happen when the engine is cold and at operating temperature ? If just warm have you verified CL operation ?

 

I figured out that my engine seems to run better and be far more responsive at 20-30deg of advance..which makes me think that the charge is burning slow? Any input guys?

 

 

is that advance with the EST unplugged and at idle?

 

Thats with est unpluged

 

thats wrong, thats just wrong.

seriously, your balancer may have slipped on its hub. but i'm glad youre finally able to get it to run right.

 

There are 2 different balancers for these motors. make sure yours is correct and also make sure your balancer didn't slip.