Bob1985z51

Hey guys, it's been awhile I've really been wrenching hard lately. So I got my vette to run and drive with it's new top end revamp. It idles very nicely but under load at anything off idle it just dies out and if I hold the gas down to much for to long it's just dies. I did get a chip from ed wright and I'm wondering if the timing curve is off, any ideas? Thanks guys

Cliff Harris

I would think (based on your symptoms) that it's more likely to be a fuel problem. Put a fuel pressure gauge on it and monitor the pressure.

Bob1985z51

Something that makes me think it's timing related is that my idle increases at random times after it starts to warm up and I lose more power, I think it's advancing itself.

bjankuski

Bob1985z51

Ok I checked with a gauge and it was 50 at idle and higher than normal throughout the rpms

Kevova

You should be able to watch timing with timing light. Timing light with advance would be best. What happens with set timing connector disconnected? Vacuum routing? Restricted exhaust(cat. conv)? Balancer wobble?...ring moved.

Bob1985z51

It's not exhaust, I need to check the timing while it runs, I've set it to 8 degrees but haven't checked total timing

Bob1985z51

So I talked it over with my buddy who builds tpi and lt motors, we discussed that my bad fpr is causing a very rich condition and it shoots black smoke like a diesel so I ordered a new one from summit, hopefully that's just the problem. I'll let you guys know how it comes out👍

Bob1985z51

Ok well I replaced the fpr with an adjustable one and set it to 40 psi and still same problem, it seems once it's in closed loop the plugs are set to .045 with 10.5-1 compression could that be wiping out the spark?
The injectors are almost new so I'm really stumped

Carbd84

Hey Bob, I'm unaware of what type of top end mods you have, but I too run 10.5:1 CR. I personally use an MSD HEI distributor with both vac and mechanical advance. I use accel "header" spark plugs to clear the long tubes I have and I'm not sure on the exact plug gap that I use (can't check, I'm at work right now), but I know its smaller than the stock gap setting. PM me with the details on your top end build or just post a link to a build thread if you have one and once I get home from work I can measure my spark plug gap and give you my 2 cents.

bjankuski

You need to see if the car is going lean or rich, I do not believe the spark is being wiped out. It sounds like it is very rich from your black smoke comment. It appears to me that the chip has the wrong injector values entered in.

Bob1985z51

I'm going to try and data log my buddy has a cable so I'm going to see if anything is out of the norm or if something's not working, thanks guys I'll keep you posted on my adventure into tpi land haha

Vett1990

Bob, I installed a performance chip in my 90 vett several years ago and I recall this same issue. It idled OK... sounded like it had a mild cam however, during acceleration or load it would stall, miss and barely run. The fault I had when I installing the new chip I removed the original (light blue) chip and replaced it with the new performance chip. In my case to fix the drivability issues I had to leave the original chip (light blue) installed and attach the performance chip onto the side terminals of the circuit card, where the original chip is located.

playsdixie

lots of threads on these performance chips....I don't believe they work all that well...I had one....went back to stock...car runs much better...lots more power on acceleration......

Cliff Harris

The ECM controls the spark advance, so it's highly unlikely that it is somehow changing by itself or is "off".

The ECM could think the coolant is cold. In that case it will richen the mixture. A bad (corroded connector contacts) or open connection to the CTS can cause that.

Bob1985z51

It's not a performance chip it's a tuned chip due to the fact it's heavily modified and a stock chip would probably not run.

Bob1985z51

Ok guys tried everything and am going to order the obd to USB cable but I did check my cts and it was all over the place never one steady number so I'm going to replace it tomorrow, would anything else cause it to run rich without a code? I checked with ed wright and he said the tune should work fine

Bob1985z51

Any ideas?

MrWillys

What injector (number would be helpful), and what fuel pressure without vacuum to regulator?

Bob1985z51

bosch 30 lbs and fuel pressure started at 55 so I swapped the regulator for an adjustable and set it to 43psi and tried everything in between 55 and 43