FastandBlue

This only happens when I am NOT under load. I don't notice a difference when accelerating quickly. At 1200 rpms when just speeding up slowly, it hesitates and loses power for a split second before picking back up. This always happens at 1100-1400 rpms and it causes my RPMs to drop by 100 rpms when this happens (I have a video if you guys want to see it).

Fuel pressure is fine
Checked intake elbow and it's fine

94Z28LS1toLT1

I would like to see the video and probably diagnose the problem

FastandBlue

Video is right here: [URL="'s a very subtle drop, but you can see it and here a very small "rev" after the engine picks back up. Not the greatest quality, but I only had my phone.

As far as this issue goes, I found out two things:

1. When this happens, the fuel pressure is raised by 2-3psi. Doesn't say a whole lot except it is either an injector failing to fire, or a vacuum leak.

2. Another side issue that I found is when I actually took the car under load. I brought the RPMs up to 5150rpms and watched as my fuel pressure went from 34psi to about 14psi once at 5150rpms. HOWEVER, fuel pressure with the vacuum hose off reveals 42PSI of pressure. In addition, it holds pressure fine.

So, what do you guys think? The intake elbow is fine, so what else am I looking at now that is causing this stall?

Injuneer

Link?

The question is, does the fuel pressure rise, causing a problem, or does the problem (misfire) casue the MAP to rise (= vacuum drops), which causes the fuel pressure to rise. I'll bet that the MAP is increasing due to the misfire, which causes the fuel pressure to rise.

Are you saying that under load (5,150rpm/WOT) the fuel pressure drops to 14psi? If so, you have a problem. I find it hard to believe the engine wouldn't just die with the fuel pressure at 14psi.


The last sentence is confusing - did you test the fuel pressure with the vacuum line off ONLY at idle? Or did you also test it with the vacuum line off at 5,150rpm/WOT?

FastandBlue

Ugg, here is the link. Don't know why it didn't work the first time. [autostream]http://autostream.com/camaroz28/?page_type=firebirdplayerthumbnail&framepage=145&t ransactionid=1296304080-7194185244&posted_by=FastandBlue_camaroz28.com[/autostream]'m still trying to figure out if there is a misfire, but this raise in fuel pressure ONLY occurs when I am speeding up moderately and the car falls on its face. If I idle the car, the fuel pressure won't rise at all. So only under light load and at around 1400 RPMs will what you see in the video occur.

Yes, exactly. I was shocked, too. I did both the vacuum line off test and the under load test. Passed the vacuum test fine, but totally gave out at WOT. I can get a vid of it if you need to see it, but I can assure you that at WOT, the pressure was well below 20psi.

I'm just saying I did it the vacuum line off, then reattached it and drove it on the freeway under load. The vacuum line was on for the latter test.