i didnt have time to read the entire thread. but heres common problems that cause these symptoms on TBI motors. first check the TBI gasket for vacuum leaks. get a can of carb spray and spray the base of the tbi. if the revs change you have a vacuum leak. spray the intake gaskets too. next is the coolant temp sensor to test this, you need a digital ohm meter, when the car is running use the meter to test resistance. you are looking for variances of 200 ohms. if it is not varying 200 or more ohms, replace the coolant temp sensor. next, is Idle Air Control or IAC. the only way to test these unfortunately is with a tech1. you can try cleaning it with carb spray or replacing it. i hate to recommend throwing a part at a car. but if you dont have access to a tech1, you have no other choice. next, is the fuel pump. you need greater than 13 psi with a tbi i believe, i cant remember everything off the top of my head. i have seen countless times where people have replaced laundry lists of parts yet still have the problem. be smart. dont just go replacing things. these are the most typical problems when plugs and rotor/cap dont fix it. also, invest in some sea foam. carbon build up will also cause a very rough idle...

 

I am having a similar problem with my 92 5.7 k2500. I posted looking for help a while back under a different user name, but found no good suggestions, or at least any that fixed the problem. Mine will not idle well after warm up, usually around 400 to 500 rpm, and if driving for a while it will go lower. My biggest problem is when the idle drops that low the oil pressure also drops. The engine was just rebuilt in May and nearly everything is new. Since then I have tested and replaced almost everything on the truck including the 02 sensor, ECM, TPS, MAP, IAC, distributor, rotor, plugs, wires, oil pump, cam, timing set, lifters, ECT sensor, Temp. switch, tested the knock sensor, exhaust system, PCV valve, cleaned throttle body, compression tested, cyl. power balance tested, stall speed test, Trans VSS (both), tested tach, thermostat, water pump, tested ignition primary and secondary system, installed positive and umbrella valve stem seals, turned crank, new cam bearings, new oil pressure sending unit, manually tested oil pressure with guage, tested every individual wire from engine sensors to ECM, new radiator cap, ran 15w40 oil to boost oil pressure, exchanged oil filter head gasket for an un-restricted gasket, new serpintine belt, new piston rings, new thermostat, vacuume tested, replaced engine ground straps, tested fuel pressure, checked injector pulse width, tested injector resistance, and recently took it to a dealer to diagnose which revealed no problems they could find in two days of diagnosis. I know that is a lot to read, but if anyone has any suggestions on where to go from here I am all ears. I have also tested the EGR system, checked timing, and re set the overhead multiple times.

 

I just purchased a used 1999 Chevy Silverado 1500 LS. It ran pretty good on test drive and the next day for part of the day, I drove about 50 miles. I then noticed the service engine light on and it running rough, a miss in the engine. Took it back to the dealer, they replaced plugs and plug wires. Got it back drove about 8 miles this time, woke up this morning, service engine light is on, again, with same miss in the engine. I bought the truck "as is" only has a 114,700 miles on it. Now i have read this blog, seems, I could have a lil trouble diagnosing this problem anybody have anymore tips than what I have read. Appears to me to be some when it trips the service engine light??

 

I had a 1995 2500 350 ci . It was only a year old when the truck would stall every once in a while. Dealer couldn't find anything wrong but the symptoms got worse. I wound up tuning it up myself and changed little, until I replaced the coil and cap. I still have the truck today with only 54,000 miles and fires up in Chi town weather.

 

Hello new to thread but I have been having this same problem with mine the miss at idle and steady throttle well I replaced the dist, dist cap, rotor button, plugs ,plug wires ,alt, tps, idle air, coolant temp sen, egr valve sol, map sen, and it turned out to be the stupid thermostat it had a 160 in it so I put a oem 195 degree and walaa fixed after 500 plus dollars in new parts all along it was the thermostat letting the motor run colder then the oem reading so no more miss no more surging just thought I would tell my story thanks

 

Hello my name is Dan I've got a 78 gmc with a 350 and a big cam at part throttle runs rough and not much power fells like it running out of gas and yes theirs gas in it and I've checked the filters any ideas

 

I scanned my 96 Tahoe looking for why it was having starting problems. The only code it sets is P1345 crank/cam sensor correlation. In checking the sensors electrical readings the ac volts were 1.8 and not 5v. Since the ac volts appear to be sent from the PCM I thought it may be the problem. I removed the PCM and installed it on a friends 96 and their vehicle started and ran fine. I put my PCM back on my Tahoe and it starts fine now but after clearing the code it still sets the code within 5 seconds of restart. I notice the rpms at idle fluctuate between 650 and 750. The scanner shows the ignition advance to fluctuate between -18.5/-22.5. Does anybody know what a normal ign adv reading is at idle on the 1996 5.7? From what I understand there is a tan wire with a black strip somewhere to disconnect to check with a light. I have looked everywhere for this wire but cannot find it.

 

1999 Suburban number 2 cylinder miss fire. I had this problem for 1 year.
replaced the spark plugs, HD plug wires, voltage regulator, gas filter fuel pump (2 times), gas lines, and replaced the fuel injectors with electronic injectors' also replaced the distributor shaft, rotor cap, and rotor (twice)!
Still reading number 2 cylinder miss fire!!
Are you ready for this! I took my car to a 24 year old mechanic and he found that both of the distributor caps were defective. It seems that the wire in the ceramic going from the spark plug input to the electrode was broken inside.
Problem fixed with a new rotor cap (the new one was made in USA!)

 

hey guys im not sure if my problem is the same
I had to replace my intake manifold and along the way we had to set the distributer and do the timing
now when im driving I get a random miss. its pretty jarring
its mostly at low rpms. it doesn't send any codes.
it starts fine, drive fine, idles fine
the miss only happens randomly
any clues

 

[QUOTE=re_boot1;4404]OK, ran a full diagnostic on the truck. narrowed it down to the in-tank feul pump. The computer reads that all of the electronic components of the pump are running at optimal, but a pressure guage connected to the feul rail on the intake showed the pressure was 58psi at an idle and it dropped to 45@ 2000 rpms. 58psi is minimal for a big block, 60 is optimal. The book shows the small block should be around 50 to 55 psi for optimal pressure. The drop in feul pressure causes the engine to lean out under a load such as accelerating and pulling and could cause the engine to burn a piston from the increased cyllinder temp. The pump for mine is $150 at the dealership and it's easier to lift the bed and slide it back than to drop the tank. Hope this helps.[/an easy way I use is two ratchet straps. They are the easiest for me to take down and lift back up right into place. ]