RichardL

I have been trying to correct a probem with my 89 engine for some time now. It will run fine some times, but others, it will hessitate, and pop during medium or hard acceleration. The engine is not stock. It has a miniram intake, TPIS throttle bodie, AFR heads. The tune was done by Jesse Azzato. I have checked and adjusted the TPS, and IAC. Even changed the entire throttle body with a known functional one. Tried changing the timing a few degrees, experimented with spark plug gaps, the only thing I could do to get it to be better is to increase the fuel pressure up to the max of about 60psi with the vaccume connected. This lessens the problem a lot. But it is running rich then. The exhaust pipes, and the plugs show a rich condition. So I believe I am not getting enought fuel when I accelerate. I checked the fuel pressure when the throttle is opened quickly, and the pressure increases because of the lack of vacuum like it should. I disconnected the MAF sensor and the problem still existes. I get no error codes. I am new to this and would like any suggestions.

Thanks
Richard

toptechx6

I would guess one or more bad injectors. You can ohm test them to see if there is any variation, the reading will be lower if the coil is going but that only checks the electrical side. They could be partially plugged and still check good with the ohmmeter. Suppose a lazy O2 sensor is another possibility.
See the forum vendor who posted this video for some injector options.

http://forums.corvetteforum.com/show...ighlight=video

RichardL

I have replaced the O2 sensor, and the injectors are all new. I guess that does not rule out the injectors though. They were installed when I installed the heads and the miniram. It has never run correctly after the mods were installed. I will check the injectors tonight if possible.

Richard

tequilaboy

From your description its running lean during acceleration.

You need more AE or acceleration enrichment in the tune and possibly more PE or power enrichment.

This is assuming that the MAF calibration and injector sizing is in order.

JackDidley

Are you datalogging ? If so, give it about 4* more advance and a couple #s fuel pressure. Minirams like advance and FP. Only do this if you are datalogging and can see if its getting knock counts and watch the O2 and BLMs.

RichardL

No, I am not datalogging. Don't have all the tools for that.

Today I put my previous memcal in (programmed for old mods). It seems to not have the same hesitation. But it definately is running out of fuel at higher RPM. I think that does point to the program. I will see if Jesse Azzato can change the program for me.

I wish someone was close around here to dynotune my car. I would be willing to pay for that.

Thanks
Richard