Thanks for the thread it has helped me out very much but I do wish i would have looked it over first LOL might have had less problems

Hi, I am new to the Forum but have been lurking for about 2 years. Very good information here. I just purchased a 2000 GMC Jimmy SLT and am very pleased with the vehicle over all. After about 3 tanks of gas I realized that the mileage is pretty bad and just started noticing a hesitation at a constant speed ~60mph and then it recovers. Immediately thought the torque converter needed help. Took it to a tranny shop and everything checks out. I am wondering if this hesitation could be a fuel delivery problem. I found this thread and am now leaning that way. Is this a known problem 2000's as well or has something changed since the mid 90's models? Any and all input very much appreciated!

Thanks a lot for these pictures and your posts. I have a '95 Safari with 170K which has had driveability ttrouble for at least two years. I was aware of this CPI problem but just didn't hit my pain thereshold until mpg dropped to 13. An inspection via the tuning valve mounting hole indicated the only trouble was a leaking regulator but consulting several techs I know convinced me to spend the extra money and replace it all since I tend to drive a vehicle "forever." Yesterday I replaced everythihng inside the plenum. My GM dealers have "crazy" prices for OEM parts even with the discount of buying through a friend business. He and most of the techs advised that GP/Sorenson CPI unit gives good results. I installed the Sorenson CPI unit PN 800-1225N and a Motormite "nut kit" PN 55163. Saved me over $100 compared to deealer AC Delco. The performance of the van improved dramatically. After only about 15 miles the tail pipe was clean of the black soot coating. Idle and driveabilty is like new. The only unexpected thing I encountered I had not seen posted here was fuel pressure. The key on engine off KOEO pressure was 75 psi with the pump running then dropped to 67 with pump off. I wondered if the pressure regulator was defective allowing the 75 psi. A call to a tech assured me that was normal. I cycled the key several times to inspect for leaks and found none. Reassembled and upon starting was missing on 2 -3 cylinders. I thought perhaps, and hoped, it was just fuel starvation on some lines and after several revs and restarts it was running on all six. Took for test drive and realized I should have done this job two years and 50K miles ago. I probably paid for the parts a couple times in wasted gasoline. So, if you came to this forum SEEKING ANSWERS to your 92 - 95 4.3 ROUGH IDLE, POOR MILEAGE, HARD START problems you found the right place.

Very useful thread. I replaced everything in the plenum yesterday on my 95 Safari. Only trouble I had was uncertainty of fuel pressure. Key On Engine Off pressure with fuel pump running was 75 PSI. I needed to consult experienced tech to learn that was normal so long as the KOEO pressure was no higher than 66 or so witth fuel pump off.

more info about cpi injector in 93 blazer

I want to know where the vacuum line from the ball on the hood is supposed to be hooked on the motor on a 95 4x4 4.3l blazer?

I also have a 94 safari with the cpi. i replaced the cpi this weekend, i istalled the poppets in a row the way the come out of the unit. from left to right. is this correct? i put the center from the unit to the ceter cyl on that side. and the one that came out the front o the front cyl and so on. is this correct? thanks joe

Hi you guys. I realize this is an older thread, but I really could use your help. I also have been about to pull out my hair. Here's the story.

I bought this '95 blazer and and it developed fuel problems. The rpm's surge up and down when it idles, poor mileage, and it misses real bad. Diagnostics at the dealer showed a bad throttle positioning sensor, a bad transmission, and the o2 sensors were going nuts. It had flowmasters on it, but they have now been replaced with stock, along with the tranny rebuilt, and a new TPS.Same problem. A new digagnostics show nothing, but the dealer says its a fuel problem. It has a recent tune-up also. I have done everything else, and had come to the conclusion it might be a computer problem? NO? Sometimes its like the throttle would stick too. Nobody has a clue about this car and its nickle and diming me to death. You think this may be the problem?

I wanted to come back on here and tell you guys my "story" with this car, and what I've been through...and what "I" did to fix it.

No, I didn't burn the darn thing..lol
Original diagnostics codes were all repaired..stupid me. It even included a transmission. Made since to me since the throttle kept taking off and it shifted from OD/D. After 4 mechanics..neither helping at all, I read these forums. Trust me, everything yours is doing, mine was doing. It almost seened electronic. Here's what I did.

I removed the positive battery cable. I unhooked the ECM and cleaned all the plug-ins with Ether.I left it unhooked for about 2 hours while I....took out all the fuses, cleaned all of them and the connections. (Some were very dirty) I cleaned every connection I could find. I threw some Lucas fuel System Cleaner in for good measure, I replaced the TPS (again) and the Idle Control Valve. And then...I hooked up the battery and started the Engine.

I"ve had this car for almost a year now, and it has NEVER EVER ran like this or had so much power. It's like a totally different car.

I also found there were several recalls on this car. My brakes and the ABS are part of the recall. Link is below. I bought myself a manual, and the best part is...I finally fixed it myself. Wish I woulda done this 6 months ago. :banghead:

http://www.carsmart.com/content/own/service/index.cfm/action/RecallsView/seriesid/5162

Quick question for anyone who may be able to help. . .

I seem to be having the same problem as most of the people in this thread, with a couple of minor differences. I have a '94 Sonoma 4x4 4.3 Vortec, BTW.

1-The rough idle is not present until the truck warms up, then it idles and drives VERY poorly.

2-I have a bad exhaust "donut" gasket, and I haven't found time to change it yet, so there's a rather large exhaust leak.

3-The hesitation isn't consistent. When the truck's idle starts becoming more and more rough, the engine just loses all power and it will pop and rattle when I attempt to accelerate.

Any help is much appreciated, and I hope you all can help me resolve my problem quickly!

This is a very fine post and I wanted to add something of an update.
NAPA carries a OEM sourced NUT kit #CRB218477 =$72.49,
http://partimages2.genpt.com/partimages/545667.jpg
The lines without the Braket and screw #BK 7002370 +$44.99
http://partimages2.genpt.com/partimages/379305.jpg

pressure regulator #BK 7002368 $45.49http://partimages2.genpt.com/partimages/232760.jpg

I know this is an old thread But it has helped me beyond belief and deserved a BUMP! (i promise to try and not do it again...:( )

I'm another who was helped by this thread. My lower intake had fuel accumulated under the feed lines that was about .5 - .75" deep. For the longest time my blazer would idle up while braking from speed and I couldnt figure out what was causing it. There is a drain hole that goes into the #3 intake runner, every time I hit the brakes hard enough it would pour fuel into #3.:eek7:

There was a large crack (.10" huge) that I found on the return side while I was fixing this. What brought me here was that another leak finally got bad enought in the feed side to affect the idling and starting of the engine (fuel pressure) and a search on google led me to this thread.

Thanks to everyone who contributed to this thread!! My auto blazer will spin the tires going into 2nd again!!:):)


Can't wait to see the fuel economy gains.:biggrin:

i am a beginner when it comes to auto repair but tired of shady repair shops so i try to research and do as much as i can on my own. so...thanks for all your threads and picts. it has really helped.

my issue: 95 jimmy will not start after sitting. it took 40 cranks this morning to start! longer it sits, more cranks to start. with help of this site, i changed fuel regulator today ($43). it did not help at all- seems a bit worse to be honest. i had entire spyder system changed 15-20k miles ago (ac delco part plus labor $500- i dont know if they changed nut kit).

when i opened manifold today there was gas sitting on left side (regulator side) and oil and a bit of gas mixed on right side (nut kit side). is this normal or should it be completely clean? also, is it possible that entire fuel injector system is bad again with less than 20K?!?!

this truck is killing me. any suggestions apppreciated.

If it looks anything like the picture below, then They never replaced your spider assembly or regulator. This is a picture of my leaking fuel pressure regulator. The look of the "nut" kit side is normal, this engine has 160,00 miles on it. The regulator side was cleaned by the leaking fuel. The regulator can be replaced by itself. Also if your spider assemly is dirty like this..it was never changed.

http://i154.photobucket.com/albums/s242/volfan4/IMAG0360-1.jpg

when i opened manifold today there was gas sitting on left side (regulator side) and oil and a bit of gas mixed on right side (nut kit side). is this normal or should it be completely clean? also, is it possible that entire fuel injector system is bad again with less than 20K?!?!

Have you tested your fuel pressure? Your fuel pump might not be putting out enough pressure. You need something like 60-64 psi for a cold start.

Also, when is the last time you replaced your fuel filter? It could be clogged, not allowing enough fuel through to the engine.

The oil under your manifold is normal. Gas pooling is not. With the manifold off, did you pressurize the system (KOEO) and check for leaks? That would tell you if the nut kit was cracked anywhere.

the pictures dont show up when i view this page...there is just and X...any solution?

the pictures dont show up when i view this page...there is just and X...any solution?

They do when I look at it. Your browser must have a setting that blocks pics from opening.

no picture her either

http://i154.photobucket.com/albums/s242/volfan4/IMAG0360-1.jpg



Thisis a test post.

Do you see it now?

http://i154.photobucket.com/albums/s242/volfan4/IMAG0360-1.jpg


Thisis a test post.

Do you see it now?

Yup, that one works here.

I believe those ports are for your EGR valve gas circulation and not your exhaust and that would explain the carbon buildup from a rich running engine. I wouldn't cause too much of a problem but it will be limiting the EGR gas going into the cylinders. No biggie but make sure you clean it out good. Been noticing any pinging lately?

I know this is late but I just noticed your note about the exhaust ports leading from the head to the intake manifold.

Those are to allow exhaust gas to heat the intake manifold to allow for better atomization of fuel in the intake, otherwize the intake would freeze up and fuel would condense in the manifold and not reach each cylinder.

This method has been used forever on v-engines. Later on they also tapped these ports for the EGR.

It is important that the passage be clean, and the new intake gaskets should have one small and one larger opening for these ports. this allows flow, otherwize the exhaust just comes up and sits in the manifold, condensing and hardening into what you see in the pics.
http://i15.photobucket.com/albums/a358/Cailen/LowerManifold2.jpghttp://i15.photobucket.com/albums/a358/Cailen/UpperManifold.jpg

what injectors and nut kit are recommended?

what injectors and nut kit are recommended?

You need to be more specific, or possibly start a new thread, this one is really old.

The injectors and nut kit for your vehicle are very specific as with all the parts to fit your application.

the last few pictures work but not the original ones

You need to read the entire thread.
Then start a new one for your issue...

You need to read the entire thread.
Then start a new one for your issue...

Why would he start a new thread to say the early pictures in this thread don't work? :screwy:

how do you get the pictures up to see them ?