I'm writing this for a good friend of mine in Daytona Beach area of FL. I'm in PA so I can't get down there to look at the car very easily..He has a 2003 A4Corvette with an LPE 383 package that was built/installed/dyno tuned by them almost 2 years ago..430rwhp and tq..with a safe 12.6:1 A/F...

Anyway, it recently developed a miss after 5600 rpm. He changed the plugs TR55 iritium, at LPEs suggestion, and magnecore wires...Still has the miss. LPE sent him a datalogger which he used and sent back...They said they detected a little knock and sent a new tune to be downloaded...Still has same miss..Changed plugs again, wires again, same miss...I know its very difficult to diagnose anything on-line, but just throw out any other suggetions...He's ready to leave to drive to LPE from Florida, which he's done before...Just trying to help him check anything else out.

The shop I use said that they have poor experience with the iritium and to use the plain TR55s or Autolite 104s and that it sound like a cracked plug which they just ran into not too long ago...This guy's pretty meticulous about plug changes so I'm giving him the benefit of the doubt that he didn't break them 2x...He also said he did wires twice, so he's thinking he doesn't have a broken wire...I dunno...bad injector? valve spring? some other ignition woes? running out of fuel? Just throw them out and I'll relay them...Thanks...

--Alan

 

36# injectors? Aftermarket fuel pump? Should at least have both of those things... Checked the rockers for valve lash and pushrod straightness? 430 rwhp is WEAK for that car (even an auto)

 

Well, LPE keeps the stock injectors and fuel pump and they use a small cam...207/220 .570/.580 on a 114...They built it and tuned it and it was apparently fine for almost a year...I would think they have built a few of these and know what they are doing when it comes to fueling the motor. It was 12.6:1 A/F all through the pull when it was built so I don't know what happened...I have one of their LT1 motors that I've run 11s with for 10 years with stock injectors and pump (have since changed things a little and run 30lb injectors now) so I wouldn't think it was a quality issue, either, BUT since John died, I dunno...I don't think he's checked the lash or push rods...knowing him he'll trek it back to LPE for that...I thought that they should have at least 30lb injectors, but since it had no initial fuel issues I thought he'd be okay...

--Alan

 

I'm not even going to comment on a 207/220 114 cam, stock injectors, and fuel pump on a 383..... Jeeze... I'm pushing near the 28# limits on my cam-only setup on a stock 346.... I couldn't imagine running the same old stuff on a "built" motor.

My 396 LT1 woke the hell up after a fuel pump/injector upgrade years ago.

Mike

 

Well, like it or hate it thats the LPE 383 LS1 package...It ran 11.50s at 120 with that miss with a way too low stall Yank 2800 with a 1.75 60' with 18" BFG DRs...LPE has always been small with their cams. Part of it is having to be totally 50 state emissions legal when it leaves the shop, another might be the 2 year warranty, etc...John knew his stuff, no doubt about it. He was a pioneer in this sport so I won't necessarily crap on his cam selections for a street car. I'm thinking he knew more about engine building and racing than anyone on this board, period. My LPE 383 ran high 11s at 115 for 10 years with no engine hiccups at all with a 211/219 cam and got 25 mpg. The cam I have now ain't much bigger and it'll go 11.20s easy with an EWP and Kooks stepped LTs. So I don't discount small cams too much...

Either way, his car still has a miss, so I guess its Indiana or bust...

--Alan

 

Guessing won't work. He needs to have a mechanic diagnose it.

Start with fuel and if that is AOk than go to electrical with mechanical last.

I would find a good local mechanic if your Bud doesn't have that kind of experience.

But 1st step would be to put a fuel pressure guage and drive around. If no fuel pressure problems. The miss should show up in the logging as to what side it is on. Than change the injectors side to side. That should isolate fuel problems.

Than put it on a scope to check the ignition and diagnose from there.

Perry

 

Yeah, I just got off the phone with him not too long ago and he's being hard headed...He's got it in his mind to go to LPE so there you have it...He's got Breathless and DaVincis (sp) about an hour from his house, but he wants LPE to look at it since its under warranty. Oh well...I've known him for 20 years, when he gets this way there's nothing anyone can say...Thanks...

--Alan

 

The warranty will cover the least likely causes (mechanical) the fuel and electrical gremlins that actuallly are causing the problems are very likely not covered.....nor should they be.

Perry

 

Well, LPE has been pretty good to him over the last 11 years...and vice versa...My current car used to be his and was built in 1995. They've done all the thru the mail stuff they can do and haven't charged him anything. He and John always had a friendly rivalry with respect to drag racing, etc, etc...I suspect if he brings it to them they'll cover it or at least take care of him a little. Thats one thing that I've always liked about LPE. They've always stood behing their stuff..I think its either ignition or fuel, but I'm not there to look at it. I can't think of it being anything too major as it runs like a raped ape to 5600...We'll soon see...I think he leaves this AM...

--Alan

 

I have a similar miss that I am working on this weekend.

So far I have found a torn in 2 plug wire (#8) and a spark plug that had the electodes touching (4). That is 2 holes on one side that were not firing. Still got the other side to check. Wonder how many holes are working over there.

Headers are hell on plugs and wires.

Perry