This question if for a buddy of mine. He has a 93 a4 TA. Vortech S-Trim (can't remember but maybe an aftercooler) Granatti (sp?) 502 cam. Stock 1.5rr's. 58mm throttle body, Crane HI6-TR ignition. Anyway after the blower his car has missed non stop. I finally rode in it today and it pulls great UNTIL about 4500 or so it varies a couple 100 rpms, but anyway it's like you hit a rev limiter it just jerks violently. No one really knows what it could be. What do you guys think? I know he would really appreciate any suggestions. Thanks guys

 

Sounds like maybe he needs bigger injectors. The stocker's may be maxed out. Could also be a tuning issue.


-Mike

 

Might want to check the spark plug gap as well... Try ~.030 and see if there's an improvement.

 

As far as I know he's running stock injectors with the FMU. Same thing I'm running and mine is fine. I would agree that it FEELS like a fuel problem. Any other suggestions?? Thanks

 

He's gapped now at .032 which is what I hear is what they should be. I thought about that too, but there are at .032. Thanks though, any suggestions are welcomed. We gotta get his car running right!!

 

Does he have a fuel pressure guage in the car?

The stock injectors will lock up at 95-100psi. My car would cut-out when this happened.

Travis

 

My car was doing the exact same thing a few days ago. I put a MSD ignition on it and threw a ton of extra fuel in the car. (Even though the wide band was saying 12.0:1) and now its still running at 12.0:1 (go fig) and pulling like crazy.


He needs to tune it ASAP. its a accident waiting to happen until he gets a chip burnt. BELIEVE ME.

BTW. my car is a 93 too.

 

It isn't working...lol...I told him I would like to see what the fuel pressure is at. I don't THINK it would be that high...but ya never know...I just thought of something...I need to find out what kinda fuel pump he has. Thanks Travis. I will tell him to get that damn guage working.

 

I agree. A chip is a must on the OBD1. We also talked about getting it tuned. He was saying he might do it very soon. Like he said he's got too much money in it to not get it tuned. Am I correct in saying getting the tune on an OBD1 is more important than OBD2 due to the whole speed density thing and needing a chip???

 

yeah, its prob not letting it spool upt 2.1 giggawatts

 

Man, this guy better get some data on his car and check the O2 mV really quick... if he is leaning out on stock pistons, he'll be singing the re-build blues before long!!!!!!!!

I would HIGHLY recommend getting in touch with PCMFORLESS.COM.

They'll work with you and get the tune right (my car is a Vortech blown stock engined '93 LT1 with headers and exhaust, and after several iterations on the tune runs about like GM put the blower on instead of me!).


Stock injectors are going to be at the teetering edge of their limit with the demands of 7psi on an otherwise stock LT1.
With those other mods, he may need more injector.
And certainly if he is not running an extra pump (at least the T-Rex inline) the factory pump won't be able to maintain adequate delivery at FMU pressure (BTW, FMU pressure is take 1/2 stock pressure and add it to the FMU ratio multiplied by the blower PSI output, so unless he is running tons of boost, shouldn't be seeing much over 75psi).

If anyone needs bigger injectors, I know a guy who gets Bosch overstock and sells them in sets of 8 for a better price than anyone else I know... he is where I got my 42#/hr injectors for my LT1 (they are "Lightning" production overrun).
wall9@juno.com if you're interested, and I'll get you his contact info.

Terry

 

Teeman,

With my FMU i can turn it up and hit near 100 psi with very little boost.

When i first put my kit on my car i didn't have the vaccum restrictor on the vaccum line going to the intake and FMU and it would lock the stock injectors up as soon i had boost.

I have a procharger kit so i dont know if the fmu raito is the same as the vortech.

Stephen i still think your friend should have a Fuel pressue guage to monitor the fuel pressure even if its not the problem.

Travis

 

TEEMAN, thanks a lot man, I really appreciate the input. I agree with the OBD1 car he really needs to get a chip. Like I said he may be going to the dyno and that would be even better. Travis, I agree about the FP guage. He will probably get it fixed soon. Thanks guys. He is gonna try some more stuff tonight with the car I will keep you updated.

 

How about this how old is the opti? I have heard problems with the crane ignition going bad as well. Try disconnecting the Crane. This is what I have experianced. I use to have a MSD 7al on the car before converting to the LS1 coils. When I had a small miss with the 7Al way up in the rpm; that same miss would be bigger and show up in the lower rpm when disconnecting the 7Al. I then open up the opti to see a green infested opti. I do a cap and rotor/ problem solved. The stronger ignitions do a good job of hiding a bad opti.

Try my suggestions, if the problem gets worse with the crane removed opti is the problem. If the problem is the same look at your fuel curve.

 

Thank you very much man. I will pass that along. He is willing to try anything. It's been running like this for a good month and half. Thanks again. I will get him to try this and keep you updated as to what we find