Hey, im having some problems with my -91 chevy pickup with 4.3 v6 tbi engine. I understand this is not blazer but afaik they have same engine. So here we go...

First of all with cold engine, Rpm goes up and down so bad that when its going down it goes so low that engine has about 50/50 chance stayi g running. Half the time ita able to rev up itself to stay running. Happens about every 15 - 30 seconds, lowering little by little. As warm it idles fine at about 1000rpm.

But when i present load, gear on and raising clutch, it starts to stall, then few seconds later it starts going better, at higher revs. This it does warm and cold. Also on highway at 80km/h on overdrive, it stutters bad, with occasional misfires.

It first started month ago when i bought it and did full service on it, first it only seemed line it didnt want to go when pushing full throttle, progressively getting worse.

What ive done so far:
*Changed all liquids and oils
*Changed spark plugs
*Changed air filter
*Changed fuel filter
*Measured map, ect and tps sensors (all good)
*Cleaned EGR
*Checked for vacuum leaks multiple times
*Cleaned cap and rotor in diatributor
*Took off sparkplug wires and measured them, was between *11,5 - 12,5 all of em (too much i guess but those were higher ohm cables, stamped on side)
*Used injector cleaning solution, one you add into tank
*Changed fuel, from different pump
*Cleaned IAC
Also, when i bought it, it had been sitting in barn for 7years, so it has low mileage, only 130 000km.

I will post winaldl log for my test run: https://aijaa.com/AqRymJ

Thanks in advance

 

As with all these engines Check fuel pressure - top of second gen section and follow sticky step by step

 

Ok thanks. Only problem is, where i live, fittings like these are really nowhere. Have to order them further away (across borders), but those are on my list. But i guess looking into fuel delivery system is better place to continue. I will probably then take tbi out and clean it. Fpr is easy to check and clean also, then atleast that is checked. If it wont start running then i will take out fuel pump

Thanks again

 

Ok i tried pinching fuel systems return side hose (close to transmission) and recorded o2 for a while. O2 went towards rich side (jumped between 0.4 to 0.9) so i guess pump and fuel filter are okey. I will take tbi out this weekend, clean it and install with new gaskets and new fpr.

 

Ok i were able to loan a pressure gauge from my workmate and were avle to connect it instead fuel filter. Pressure was only 0.4 bars (6psi) so i dropped tank and behold, small rubber hose after pump (inside tank) had small rupture on it.

During removal, pipes connecting to fuel pump unit above tank broke when i tried opening "couplings" so i had to order new pump unit. With any luck they arrive before end of next week.

 

I had something similar happen once. I was assembling the pump and sending unit assembly, and my wife came in the garage and distracted me. I forgot to put the clamp on the piece of rubber hose that connects the pump to sending unit. Ran halfway ok, but under any extra load, just fell on its face