Hey guys, as the title says I am getting an 88 GTA back on the road and it has a 305 TPI. When driving the car it idles well, revs fine in neutral, but has very low power when driving. If I floor it on level road it gives a slight increase in power for the first half inch of pedal movement, and then barely any more until it's all the way down. If I'm going up a hill then I have to shift into 2nd and floor it to even maintain my speed.

I've ruled out the engine coolant temp sensor, MAF seems to be working well, TPS reads the exact voltage range it should. Intake is good, exhaust and cat are clear, it has spark, compression and the fuel rail reads 43psi with vacuum line plugged, around 36-38 when revving in neutral. Replaced the fuel pump and it runs strong. Brand new bosch injectors and all new gaskets down to and including the intake manifold gasket. Instrument panel numbers look good. Timing is about 6.5 degrees advanced and vacuum lines all look good and are routed correctly. I'm pretty much out of ideas on what could be limiting my engine this much and I've done everything I can think of or find on here to test. Any help would be appreciated.

 

I am no expert but it sounds like the ECM is in "limp home mode" or "open Loop". This is a common symptom of power loss. Also did you tune the ECM for the Bosh injectors? Did this problem occur after the injector change? Did you use 19lbs injectors? Bosh injectors are notorious for causing fits with these engines and more times than not the ECM need to be programed for these injectors to operate properly.

 

The fuel pressure numbers look reasonable. The lack of MAF codes is an indication it is working properly. The TPS voltage check was worthwhile.

Timing is 6½° BTDC when set, but where is the timing with the EST active?

What is idle vacuum reading?

Has a compression test and/or cylinder leakage test been performed?

 

Thanks for the reply. As far as EST i watched it change from 20 something to mid 30s as it goes up in rpm (I might be remembering the numbers wrong) but it is advancing the timing. I did compression tests on I think the 1, 2, and 4 cylinders as those are the only ones I could get my gauge onto and they were all good, no leakage either. The engine is in excellent mechanical condition, no shavings in the oil filter, no lifter tick, runs like a clock. And I don't have a number for the vacuum but it does have significant pull when I felt it by hand. I even put an oscilloscope on the injector plugs and watched it supply pulses with my own eyes.

 

Thank you for the reply, from what I've seen about limp mode, it would give me the SES light if that were the case and i have no codes whatsoever. And the reason for changing the injectors was because I was getting no combustion in 2 and 4 so I thought the only culprit would be dead injectors. I bought a set of 8 bosch 19lbs from southbay, so they should be about the best drop in fit for this engine.

You know what? Before I wrote this reply I pulled the 2 spark plug and it was completely clean just like before I swapped injectors! No combustion at all and I'd expect to see that from the 4 as well. no idea what could cause this, I have spark, compression, fuel pressure, injector pulse, and new injectors in those cylinders (inside of fuel rail isn't clogged, looks like it was machined yesterday) but it's as if nothing is happening in them. The car behaves exactly as it did with the stock injectors, with maybe a little more torque, but that doesn't surprise me because I didn't gain those cylinders! This really has me stumped as to what could prevent them from burning.

 

Did you test for injector pulse on 2 and 4 with a noid light? These ECMs uses a batch fire where each bank of 4 fire at once, If you get pulse on 6 & 8 and not 2 &4 check the connection in the harness for those 2.

 

Yes, tested 2 and 4 with a light and it flashes in greater frequency when you rev the engine. I even watched the square wave on an oscilloscope. After looking closer it almost seems like none of the 4 cylinders on the passenger side work. Spark plugs looked brand new when I pulled them. They are getting spark, compression, signal to injectors and good fuel pressure, but when I touch the exhaust manifold anywhere on that side it's totally cold when the driver side is hot as you'd expect.

 

It sure does sound like the whole bank is out. I would say check the fuses in the box as there is a fuse for each bank but the light shouldn't lie. I can't think of anything else that would tie those 4 cylinders together.
Crossover on the fuel rail clogged?

 

The fuel rail is a possibility, although the Schrader valve is on that side and it reads the exact pressure it should. I was very diligent to ensure that the inside of the rail was clean before installation too. I even speculated that the new intake manifold gasket was obstructing the injectors, but it was doing the same thing before I replaced it.