Need help with 4.3 tbi truck!

[BLACK6PACK]

I'm pulling my hair out and don't have a lot to spare! Been all over the s10, truck, 3rd gen sites and not getting anywhere. 1992 gmc Sonoma 2wd 4.3 Tbi z motor. Has newer plugs, wires, cap, rotor, coil , temp sensor. I've checked the egr, tested the tps, it has a new icm. It will start and idle fine, back out of driveway 50' put it in drive and it bogs down and will barely run at anything over idle. In park it will rev freely and idle smooth. After driving it 50' down the road and back it will run rough and die. Fire it back up and it will idle smooth. The fuel pump is newer, and it has a new fuel filter. Injectors give a nice smooth cone spray. There are no codes or cel showing, and if I pull something it will show a code for that sensor. I have fuel, spark and no codes. What am I missing?

 

[BLACK6PACK]

Also, truck only has 69xxx miles on it, and no major work, just regular maintenance.

 

[BuickMike]

This sounds like it has to be fuel related somehow. Is there any place where you can hook up a fuel pressure gauge?

 

[BLACK6PACK]

Thanks Mike. I checked it when I put the new pump in a couple of years ago. It was a solid 12 psi. I went to the local Napa this morning, but they don't rent tools, it seems to put the fuel out when not in gear. Guess I'll drive the 12 miles to the local AutoZone. I cut a hole in the bed, so it only takes 5 minutes to pull the pump.

 

[BLACK6PACK]

Mike, u may have called it. I basically had eliminated everything but the ecm, but assumed my 3 year old pump was still good. At best it's putting out 8 psi and when power breaking it dropped down to 4 psi and started to bog. Thanks!

 

[BuickMike]

Glad to help! This just screamed of fuel delivery issues. On low pressure systems like carburetors and TBI, the engine requires so much less fuel when idling that psi usually looks good at idle, but when volume demand is up, the pump cannot provide it. On cars like ours with high pressure systems it seems to either work or not more often.

 

[Chuck Leeper]

My NAPA guy has had so many aftermkt pumps fail, some in a day, that he sends all customers to the GM dlr for the OEM replacement. Not cheap, but they work. Sounds like you may have gotten one that falls into the short "MTBF" category..

 

[BuickMike]

My NAPA guy has had so many aftermkt pumps fail, some in a day, that he sends all customers to the GM dlr for the OEM replacement. Not cheap, but they work. Sounds like you may have gotten one that falls into the short "MTBF" category..

It's crap like this that has driven me to buy brand new cars. With all the other stress in my life, I can't handle the crappy aftermarket parts failing constantly. Most of the problems I've had are parts manufactured by A1 Cardone. They are the worst IMO. I had a '90 Honda CRX DD for a couple years. I went through and replaced quite a bit on it. Unfortunately OEM stuff was unavailable or just too high priced, so parts store items went on. I went through 4 different CV axles in that time, all under warranty. A couple were short lived joints, some were that the surface where the axle seal would come in contact were machined down and would not seal. I went through 4 distributors, 2 alternators....you get the point. I used to exchange the A1 Cardone ignition modules on my GN every 10 months just because I knew from experience that they would fail at 13 or 14 months....just out of warranty. I've been sporting an OEM one that I pulled in the junkyard for 8 years now. My "AC Delco" compressor on the GN has failed twice now. The first time was a bearing, now the clutch will not engage. It all makes me want to sell it all and just buy a Hellcat.

 

[BLACK6PACK]

Pulled the old pump, put in a new cheap (lifetime warranty) pump in 15 minutes, and now she runs perfect. My first thought was fuel, but I assumed the pump was good. Shouldn't have assumed! Thanks again guys!

 

[TurboTnZ06]

Yup, my old 88 GMC did that. Idle, plus 50 ft was fine, then barely ran. Replaced pump, good to go.

 

[turbotroy]

When I was still wrenching for a living, I finally got to the point that the only way I would replace electric fuel pumps was with oem from the dealer. Just had way too many of the aftermarkets go out, which equaled a pissed off customer, time spent changing the bad one out with no pay, and generally a full tank of gas to deal with