initial full throttle hesitation

[Golgo13]

Probably wrong section, tried to move to swap area but couldnt delete original post, sorry mod.



96 GP, 03 3400, I have been running my original 3100 high mileage injectors with a 3400 fuel regulator and just recently swapped in a set of 3100 low mileage injectors and fuel regulator which did seem to fix some other quirks.

Questions,
from a dead stop if i launch the car at full throttle the car sits for a second then decides to take off. What would cause this? No CEL or anything of the sort. I am running the 3400 cam sensor on my 3100 harness (the 3100 sensor didnt like the new motor), a 3400 MAF and a open cone on the end of the factory accordion intake.(factory airbox being put back on soon.)


Around town cruising at 30 mph or less, the exhaust sounds like its pulsating, like an erratic idle or a vaccum leak. The tach barely moves if at all. I have checked and checked, i have no vacuum leaks to speak of.


with the old injector setup, gaining speed with half throttle @4500rpms the engine would almost get a second wind so to speak, throwing you back in the seat, louder intake noise and exhaust. With the new setup, it does it around 3500 rpms. I'm not manually shifting or anything, just letting the gear wind up slowly on its own.

any help appreciated, thanks in advance

[Canyonero]

Why did you change from 3400 injectors to 3100, was there a problem with the old ones? I would think they'd have different flow rates, the 3100 being lesser of course. I would put your 3400 injectors back in, maybe after being cleaned and flowmatched.

[Golgo13]

rephrase, was running original high mileage 3100 injectors w/ 3400 regulator, swapped in another set of low mileage 3100 injectors and 3100 regulator.

[IsaacHayes]

You want to run whatever injectors and FPR the ECM is calibrated for, or it will run overly rich unless you have tuned the ECM for the different flow rate and pressure.

Running old 3100 Injectors and FPR is the right thing to do if you can't tune for larger ones.

Two things probably:
1) The WAI. When I run a WAI the throttle response goes out the window cause it's sucking in hot air. Hot air as you know is way less dense. When it's cold out on my car throttle response is awesome. Going back to the stock air box with a K&N drop in and modify it to breathe more air is what I run.

2) If your O2 sensor is old time to replace. My car always bogged off the line like that until I replaced the O2 sensor. Now it will just tear out. When they get old the report lean so your car ends up running rich all the time. Go for an AC Delco or a Denso (sparkplugs.com has them for good prices). Avoid bosch.

All of your "new" injectors are firing correctly too right? If they've sat for a while some might be a bit clogged. Doing the two things above and running some fuel injector cleaner should solve your problem.

[Golgo13]

thanks isaachayes,

im sure the "new" used part approach might not be the proper way to do things but I plan on getting rid of the car soon and I'm not too wild about dumping too much more money in it. I'd just like it to run proper for whoever buys it. Cant beat 25$ for all 6 injectors and the regulator all still on the rails.

Any idea on the pulsating exhaust? Replace both up and downstream o2 sensors or just the front one?

The injectors seem to be running fine, but you're absolutely right, I'll go buy a can of seafoam later tonight.

[IsaacHayes]

Rear one is only to tell the computer if your catalytic converter is working or not for emissions. Has no affect on engine operation at all.

[Golgo13]

thats what I thought, thanks again.

[Golgo13]

just changed the upstream, no change as of yet. Car still hesitates like before but now will break the tires loose for a distance. But car was definately running on the lean side judging from the coloring on it. I'll put a few miles on the car and see what happens.

But while testing some other things I found that my battery has half the cold cranking amps it should which means replacement. Hopefully this will solve a few things. Maybe even having the battery disconnected for a while wont hurt.

But as a warning in case no one knows, dont buy the cheap "never" everstarts from walmart, I have to replace these batteries every year but due to the 3 year warranty I get them for free...oh well.

[Superdave]

Duralast gold batteries from Autozone are the best i've found..


the 3400 will run leaner on the small port 3100 tune but the computer should be able to compensate for that pretty good... daily driving will be fine but PE mode above 5K RPM is where i'd worry a little..

[Golgo13]

Yeah Im pretty sure I'm running a duralast in my truck, my buddy just started selling optima yellow tops at his shop, I'd love to throw one of those in.

that much of a difference in tune? I should be fine, the car hardly ever sees high rpms. Plugs look good though. If I remember right, I think thats why I was running the 3400 fpr with the 3100 injectors, hoping for a good balance. I was wrong, lol.

I'm just hoping I can get more than 2k out of the car when I'm ready to sell it. Great car, I've just outgrown it I guess.

[PCGUY112887]

Red Bud eh? Your not too far from me!

You said you used a 3400 FPR on there? What year? I am running a 3400 FPR too, but because it's 55psi vs the 45psi stock pressure for a 96 3100.

If that is true then you were running richer than expected... I am running the higher pressure since I need the fuel but my PCM knows about it, yours doesn't!

I would pull the battery and let the PCM reset, since it's probably adjusted (or tried at least) for more fuel. Then drive it around for a week or 2, and see if your throttle response changes. I would reset the PCM after you change your intake as well, since your intake will skew MAF numbers... may as well have it rebuild your tables for your proper injectors and intake at the same time.

[IsaacHayes]

Yeah reset the ECM and then drive it for a while. It took a bit before my car adjusted to the new O2 sensor but after a few days all of a sudden I was like WOW!

[Golgo13]

yeah did everything, got the new battery car sat without power for a day or so. Took it out last night and car seemed to have much better road manners than before.

But it seems the new battery I just got may be bad already, headlights were dimming again at full throttle.

I woke up with a migraine this morning so I took off work. Its starting to rain as well. I'll have my buddy do another load test on it and see what the amps look like again.

Anyone going to the new relocated riverport swap meet at Gateway this weekend?

[pocket-rocket]

But it seems the new battery I just got may be bad already, headlights were dimming again at full throttle.

Mine did that once. It turned out to be a bad connection from a loose nut for the cable on the starter from the battery. It was from the previous owner. Mine wasn't really only WOT, it was more like high RPMs. BTW, I remember the game which you got your name from, lol. Does that date me now?

[Golgo13]

Thats funny, lol. If it makes ya feel better, I'm 25.

The game sucked, I picked up the movie on vhs somewhere, early anime. Pretty good actually.