Greetings. I’ll try and be short as I’m driving, but I’d like some pro tips before go much further.
I bought a 90 iroc g92 5.7 tpi, and it’s 250k+ on the odometer. Fine by me as it’s a project, post upcoming deployment I’ll be rebuilding or swapping the engine... thinking 383 striker but haven’t dedicated yet, hence why I have not invested in a new Intake system. I’m a mechanic but helicopters are my forte... learning.

It stumbled on acceleration and misfired when warm. Many of the sensors have been replaced... car has no codes that I can tell by jumping the ALDL... put in Bosch iii 21 lb injectors, now it accelerates just fine, all the way up to 4-5k rpm actually, and stays there lol. New gaskets on runners/tb, did the cigar test and saw smoke from under the plenum near manifold temp sensor maybe? Or inside of runners? I suspect it is the runners that are the culprit. All vac lines are in good condition and installed I’m sure. Again, couldn’t really ID where smoke leaked. However, for out carb cleaner and sprayed away, rpm actually decreased at one point...? I did not take off the iac but could it really make such high rpm being stuck open?

so before, I couldn’t get rpm to 3k without stalling.... new Injectors= wayyyy high rpm. I did see faint white smoke coming out of the tb tho...? Plates look closed to my knowledge... also valve covers are real dirty on the seal/underside. There’s a a little bit of smoke near there like it’s leaking... but I also spilled coolant earlier again. 250k miles. If anyone has pro tips I need em!

 

I don’t think the iac even if it’s stuck can keep the idle up that high. Maybe 1500 rpm or so.
Did you notice the difference in the lower runner gaskets. Seems like a vacuum leak it’s npt and the thermistor is sealed in brass.

 

I believe you have chosen the correct replacement 21lb/hr injectors... High RPMs typically point to a vacuum leak

 

Yes I did. The one with the extra hole went to passenger side for the smaller tube on that runner. Pretty sure runners are warped as they didn’t want to line up with the plenum. Also, previous owner stripped out one of the manifold-to-plenum bolt receptacles on the inside of the runner. Just weird how cigar smoke can seep out but carb cleaner won’t reveal an rpm increase. Did not touch the thermostat. Replaced egr, new gasket and vac line too.

 

Wellll, rebuilt the runners/plenum with Felpro gaskets covered in copper seal, and furthermore used copper gasket maker on all the faces, new hardware too. One of the runners has got to have a little more bend in it as they did NOT want to go together smoothly.

However, it now idles at 750-850 rpm and the Bosch injectors fixed my bog issue. A mess of gasket maker wasn’t ideal, but it will work til I get to a full rebuild.