Hey again all. I recently posted about a rebuild I did on my 97 5speed 2.7L. 19963.4lsr5 came in clutch with a great way to prime the oil pump. Now I'm actually able to start the engine. And start it does! But it doesn't last long...

It starts up strong at 2,000 RPM. Holds that and sounds great for 2 - 3 seconds, then drops down to attempt an idle. It's a real rough idle that eventually stumbles to a stall within a handful of seconds. If given gas, it will go up into the 2,000ish RPMs, but you can still feel that something is amiss.

This was a complete rebuild. New pistons, bearings, block done up, a new head (old was cracked), and I just had the injectors professionally serviced after I noted this issue (should have done that at first anyway).

I don't yet have the coolant system hooked up, but I don't believe that would be the cause. I wanted to make sure this engine wasn't coming out again before I did so, and I just noticed that I'll need to replace the radiator anyway.

TPS looks good. MAF reads about 2lbs of air moving when starting up. Ambient temp looks good. All vacuum hoses triple checked.

Any ideas on this one? Advise on what to check next would be greatly appreciated.

Check for intake vacuum leaks.. Its real easy to forgot hoses have a bad sealing and would explain the rough idle. Another option is a stuck EGR (4Cyl) only. As that is where I would start. :-)

Thanks @brillo_76 , I'll check the EGR. I didn't have any issues with it when I parked the truck a few months back though. IDK.

I find it strange how it sounds and feels good those first few seconds at 2K, but then when I press the pedal to get back up to 2k it sounds and feels awful.

We have a 4 cylinder in our fleet of vehicles.. It likes to idle rougher then it should. Do you know how to check for vacuum leaks? As that would explain it.. As it running decent at 2K. So you know its timed good..

I do. I'll just need to grab a new can of juice. One day I'll get one of those fancy fog machines LOL. Thanks for the insight.

I ended up grabbing a smoke machine off Amazon last night. It was on my doorstep when I woke up this morning. Absolute craziness. First place I noticed it was coming out of was this guy (green cap removed). I believe it to be part of the EGR, but never quite understood what it did. Not sure if this is normal or not.


Second, it started coming out from all my injectors. I put new cups from eBay in the new head, and I guess the tolerance is not what I assumed it to be. I just called the stealership and they actually have four of the cups in stock so I'm going to run out and grab those.

This machine already paid for itself. I would have never figured this out. Thanks again @brillo_76 , I hope this solved the issue.

It runs! 10 years of ownership and I finally realized where those injector insulators go 😆. Thanks for your help again @brillo_76 !