Ok,
Just bought an 89 GTA, and it has a wierd low speed (30-45mph) cruising surge condition - any guesses? I've hooked up an AutoXray to watch the Block Learn, and the cell it works in, and for the same cell, it seems to learn drastically different numbers depending on a slight load difference, i.e. the Block Learn for the same cell never stays the same. I can watch the Block Learn learning, and it never seems to stabilize.
What could be causing this surging? It isn't horrible, but it's annoying. If you weren't in the car you wouldn't be able to see the car surging or anything, but from the inside, you can feel it and hear it. It doesn't go away in Drive either, as opposed to Overdrive.
Anyone got any ideas?

1989 350 GTA, TPI, MAF, auto, 3.27, 100,000miles.

 

My 91 Camaro did the same thing. Rpms drop for a sec...you can hear, and then return to normal...about 4 seconds of normal, 4 seconds of bog or so?

All I can say is, every ignition part I replaced, it got better and better...almost gone now with just a new cap and rotor, spark plugs, and wires.

 

Fuel filter getting plugged?
Weak fuel pump?

 

If it is using the stock EPROM, the TCC lockup point is right around 41 MPH. It could be the clutch locking and releasing.

 

Yeah but between 30 and 45? If the TCC was locking at 30....you would be able to tell for sure.... I've done it before, I know!

 

Well, I doubt it's the Torque converter, mainly because now I notice it at lower speeds also. I've hooked up an AutoXray and drove it around and watched things. At idle, Block Learn goes to 108, which is as lean as it is allowed to go, and the Integrator hovers around 122. When slightly revved into BL Cell 1, then that Block learn starts dropping to 108, same when revved even higher. Then when driving slowly, the Block learn starts climbing for cell 1, and that is when I notice the surging. That leads me to believe the surging is lean surging. OR something in the ignition, BECAUSE now there is a trouble code (and has been since I bought it Thursday, but it wasn't there when I first checked the car out) for 42 EST Spark timing monitor error. I'm hoping this was just from the emissions test, where they probably had to disconnect the bypass wire and check the timing. It doesn't set off the SES light, it just shows up in the AutoXRay scan tool. I haven't cleared the codes by disconnecting the battery yet, and the scan tool isn't able to clear the codes for this car (but it can for other cars).
The previous owner said he had a problem with one of the spark plug wires and had it replaced, so I checked it out, and sure enough, there was a different colored wire. I also thought maybe there was some arcing somewhere, so I took some slit loom and covered the wires just to test it out real quick - problem remained.
I'm pretty sure the cause is too much fuel at idle and low load, but why? The scan tool says the MAF is reading what appear to be normal numbers, and it changes with load and all that, could there still be a problem with the MAF sensor? Also, the guy that I bought it from hadn't had it very long, and got it from a dealer, so he couldn't verify the stockness of the motor, but since there are no obvious external modifications (headers, runners, whatever), then I'm assuming the cam is stock.

Anyone have any ideas as to why the Block Learn for the same cell is changing?

I guess it could be leaky injectors, but I'm not about to tear it apart and send them off quite yet. I'd like to be sure first. Ditto for the MAF.

Another thing: When I was digging around on the passenger side head checking to see if the spark plug wire boots were all on firmly, I noticed that I had found an unconnected connector (not sure if I had just knocked it off, or whether it had been off the whole time). It was a one wire connector, and connected to something in the area of the #8 cylinder (had to do it blind - AC and junk in the way. What could that be for? Knock sensor? It felt like it was up in the head area. Could it be a temp sensor for the gauges?

Any help is appreciated.
I'm kinda new to the TPI hands on scene.

 

Yeah, you have to disconnect the EST to check base timing or else it goes way out of whack...so that's your code right there... As far as the rest, I can't help you any man..sorry..never owned or been around a TPI, and I don't know what in the hell block learn is or any of this cell stuff...sounds like something straight out of a sci-fi flick.

 

As long as you have the means to test it, what are the injector pulse width timings at idle?

 

Well, when at idle, the Injected Pulsewidth is 1.3 to 1.4 ms. That's with a MAF of 6 g/sec.
Thing is, when not moving, no load, I can rev the engine and allow the Block Learn to do its thing there, through all the cells at no load, and then when cruising, the same cells that it was using during the whole no load revving are being used to cruise, and since at no load, the BLM went to 108, it now is too lean, and causes surging as it learns the other right BLM, in the same cell.

Vader, or anyone who might know: What is/are the right IAC counts for a properly working, and clean IAC. I'm reading numbers up in the 80's, but I'm not sure if that is referenced to zero, or some other number, or backwards.

I'm going to try to do a leakdown test, if I have time, and can find the right connectors in our pos fuel pressure kit.

 

At hot idle and with a properly adjusted minimum air, the IAC counts I'd expect to see are more like 10-30. You might try just a little more throttle air at idle, but I doubt that is going to make any real difference at part throttle cruise. Then again, it can't hurt.