Well, after changing just about everything with the new motor...Opti, plugs, wires, coil, Jet Hot LT's, 36lbs injectiors, as&m 58mm TB...and a few other things... the car is stumbling and missing very badly. I checked the plugs and wires, everything seems to be fine there. It is a brand new 95+ opti, and it is installed right.

It seems that when the car is cold, it will miss badly, put once it warms up, seems to clear almost up. It is also not going into closed loop. Car is throwing no codes...

I have tried everything i can think of...what do you guys think?

 

Bad temp sensor?

 

I'm with eye, bad temp sensor in the water pump.

Check the o2's with a voltmeter and disconnect a vacuum line. When theyre hot should shoot in one sec to 0.2 volts.

I'm curious why do you have 36# injectors. Do you have other mods to use the high flow?

If the injectors are too large it is hard to control the flow even with a very short pulse width and leads to idle problems and the like. Just curious.

Also a 58mm TB without other mods like stroking and high lift cams is useless and again leads to drivability issues.

 

the heads were ported from advanced induction, and i think the cam is a pretty good sized cam. Phil knows the cam spes... This set up should make about 420 at the wheels tuned. thats why i got the 58mm TB and the 36 pound injectors. both the TB and the injectors where recommended by phil. A similar set up making 400 rw had 30 pound injectors and the pulse width was around 90%... so thats why i have the 36's. I now that a tune is in order... might be the reason it is running so bad at this point. I have a tune out of a similar car as well, so i thought it might run ok with that in it, but i guess i was wrong.

 

I had a real bad stumble in my motor and PCMFORLESS scanned my computer for me and burnt me a chip (I was local). All the stumble is finaly gone now after a new motor/opti/all sensors/cam/ blah, blah, blah. I still have a very small torque convertor shudder but my miss/stumble is gone. Get a custom program for your car, tuning is the key.

 

If you've got 36lb injectors installed on the stock tune, you're going to have issues. The PCM thinks your stock injectors are still in there so it is most likely firing the 36# longer than needed. Once you hit closed loop, the PCM can compensate for this to a point (BLMs can only remove fuel to a certain point ~108).

Once you hit closed loop is probably where you notice the better performance. You won't know if the PCM can adequately control things until you get a scanner on there and see if it's within its bounds.

Rob
95Z28

 

You need a custom tune alright. At a minimum you need to adjust it for that size injectors and raise the idle just a little.

Hal

 

the tune that i flashed in was from a similar heads cam car. I thiought it might be close to what i needed, but i do not think it is. I did compensate for the larger injectors, and for the TB and everything else. I looked at the tune, it is an open loop tune, so that is why it will not go into open loop.

I just can't stop thinking it is a miss somewhere. I have scanned it many many times and nothing is out of the ordinary. So, i guess it is to the tuner she goes. also, it is only really bad when the motor is cold. as soon as it warms up, it runs ok. But still not in open loop....

 

I'm a bit confused by your post. You're running an open loop program meaning it won't ever got into CLOSED loop, right?

Is the stumbling only at idle or all over?

Do you have any idea how the fueling looks? I would run a closed loop program and watch your BLMs to sniff out your stumbling problems.

What injector constant did you use?
What injector offsets did you use?

Rob
95Z28

 

CHECK THE PLUGS AGAIN!!! Pull them out, and you might think you have dropped one... say it's closing in on itself. I had a plug drop from .055 to .015 after around 500 miles. Check the plugs again. It was a Delco platinum tip, also.

I put 2 optis on, timing chain, WP, everything, 02 sensors... and it turned out to be the damned plug I THOUGHT I dropped.

CHECK THEM AGAIN!

 

well after talking to the tuner..he seems to think it has to do with the injector constaint I used. I am going to flash another tune in with the corrected numbers and see if it helps.

I also found out that the tune is an open loop tune. so it will never see closed loop. that has to go..I like all my sensor and such. I replaced all the spark plugs..still no go.

Here is a funny twist. I had a crane coil on it, thought it might be the problem, so i took it off and put the stocker back on. it would hardly run with the TR6 plugs. So, i put the stock plugs back in with the stock coil, ran OK..then i stuck the crane coil back on with the stock plugs..it ran a little better, but still like crap when it is cold. I am pretty sure it is loading up due to the wrong injector settings. I am going to fix them this weekend and see if that helps. EVERYTHING else is new...from the bottom of the engine to the top, with the exception of the intake and fuel rail, everything has been replaced. So, i either have something messed up there, or it is in the tune. I have checked and doulbe check the wires...they are fine.

thanks guys
Buss