Stalling / CPI question

[jsgold]

My old 93 S-10 Blazer has a idle problem. A little history, it has a 4.3 Vortec "W", 98K miles on it. Had the fuel pump and ignition module replaced this past winter. Due for new plugs and wires although they look OK, (30K on them). Distributor cap replaced in January. It started stalling on me at slowdown /stopping on a very rare occasion, but would start right up. Getting more common. Idles at 650 in park, 600 in gear. Gets 21-22 mpg, runs good at normal speeds. Worse now with the A/C being run. It seems to idle "weak". I have hooked a scan tool to it and found nothing out of the ordinary except idle flutuates 30-50 rpms, but replaced the O2 (was past due for change) cleaned the EGR, IAC, and areas around, no improvement. I only got one trouble code the day after installing the O2 and it was for running rich. Nothing else before or since. The truck seems to idle well with a slight miss , then stumble and can sometimes catch itself and the idle jumps up for a few seconds, but most of the time it stalls. While I am still checking it out (going to do fuel pressure test later this week) I did pull off the Vortec plate and removed the round sensor and looked around for trouble. I notice that one of the injectors had a very small puddle around it and there looked like a very small washed area nearby, but hard to see a lot. My question is this. I have seen a lot of great information on here on the CPI and opinions as well. Seems to be people complaining at times that the system still shows signs of leaking after repairs are made. Maybe they installed wrong or rebuilt stuff? Under normal circumstances will these things leak a little, or does ANY fuel in there pose a problem? I suspect the injector nearby is leaking and if that is the case it will have to be dealt with when I get the money to fix it. There is no gas in the oil, I always check for that constantly since first getting it. Thoughts?

[wolfox]

If you haven't already torn into the upper intake on that Vortec, and fuel pressure/volume checks out; it's more than likely a regulator or a fuel/poppet injector line that's gone south on you. As for getting the right parts/revised parts, GMdirect.com's got the goods. May still have to hunt down the nut kit/injector feed and return lines at the dealership. The only reason I could see for having leaks after doing the job is not double checking all of your little o-ring seals that come in the kit. *Always* replace *all* o-rings and if you're missing one when disasembling parts, check inside the bores of tubes with a light probing with the end of a hooked pick. I *think* I am seeing a leaking regulator diaphragm myself in my truck, the idle's starting to lope and the truck has a hint of "gunpowder scent" as it sits in traffic or idles at the curb in the morning. *sigh* Rather than just replacing the seperate regulator, I am going to get all of the gaskets, seals and associated parts so everything is fresh. Check out BlazerLT's "CPI Injector Repair Day" thread in this forum if you already haven't. There is much good advice, imperical and anecdotal to be found there. Once I get my finances in order from repairing the entire cooling and lower intake fiasco of the past two months, I will be ordering my nut kit parts and a complete CPI system w/ updated, late manufacture parts. I hope it's the last time I have to look at it for another bazillion years.

[BlazerLT]

Replace the CPI and nut kit.

The pool of fuel is from the fuel pressure regulator leaking on it. replace the nut kit, the cpi injector and use a new upper plenum gasket for it all.

No one has seen a leak after replacing it other than maybe a couple.

Also, you have a vacuum leak like I had causing the idle surge. This is the IAC valve trying to compensate for the vacuum loss.

Replace all the vacuum hoses other than the PCV valve hose and the EVAP solenoid hose which probably not need replacing.

There is a hose that comes off the back of the plenum near the distributor cap and it goes to a T which then goes to the vacuum ball for the HVAC controls.

Replace all the hose. The hose is cheap and is 5/32 if memory serves me correctly.

Also, did you replace the rotor when you replaced the cap?

Also, did you replace the rotor when you replaced the cap?

[wolfox]

Originally Posted by BlazerLT

Also, did you replace the rotor when you replaced the cap?

Also, did you replace the rotor when you replaced the cap?

Excuse me, Caller? Could you please turn your radio down in the background? Thanks. *Duck-n-RUNS away...*

[jsgold]

Yes, replaced both when distributor replaced. I am going to d/c it anyway as I put about 20K miles a year on it. When the distributor was replaced the vaccuum hose you spoke of fell off and I replaced some of the hoses in it then. Was causing idle issues and that cured it for a few months. I have gone over the other lines pretty well, but, it makes sense to replace them all anyway if I have to replace the other stuff. Will have to wait a little while as the old lady lost her blasted job (this kind of crap just seems to always happen when times are tough), but I won't let it go long. I have to drive it some, but with gas now at $2.65-$2.69 locally I plan to car pool several days a week. I still plan on checking the fuel pressure later this week when the weather lets up a bit. One thing I wonder, are the new cpi units improved over the old ones ? Thought I saw an ad on Ebay where someone stated these were indeed improved units. Or, are they just good for 100K? Just curious.
Also, i will check out the GMdirect.com. Thanks for the advice.

[BlazerLT]

If you have gas pooling in your plenum, your CPI needs replacing badly.

If you keep on driving it like this, you will eventually ruin your engine seeing the gask goes down into the oil, thins it out and ruins your main crank bearings.

Also, the raw fuel will destroy your cat.

[wolfox]

Just curious, but with the fuel dilution of the oil, would one readily percieve a rise in oil level on the dipstick in addition to the raw fuel smell of the oil? I am not seeing either, but that may change quickly. I haven't gone into the intake since I last replaced gaskets and seals nearly a month ago, but didn't notice washing, it was a solid black, sooty-grimy mess. Before I go "tweaking" in there, I am going to purchase a new fuel filter (it's due to have it changed again) and a pressure gague for a leak down test and a fresh plenum gasket before I do anything else. (The gasket is cheap, so looking aint going to hurt that much) I am crossing my fingers and praying she holds together for 2 more weeks when I get another paycheck in.

[BlazerLT]

Originally Posted by wolfox

Just curious, but with the fuel dilution of the oil, would one readily percieve a rise in oil level on the dipstick in addition to the raw fuel smell of the oil? I am not seeing either, but that may change quickly. I haven't gone into the intake since I last replaced gaskets and seals nearly a month ago, but didn't notice washing, it was a solid black, sooty-grimy mess. Before I go "tweaking" in there, I am going to purchase a new fuel filter (it's due to have it changed again) and a pressure gague for a leak down test and a fresh plenum gasket before I do anything else. (The gasket is cheap, so looking aint going to hurt that much) I am crossing my fingers and praying she holds together for 2 more weeks when I get another paycheck in.

Small amounts won't raise the level nor will they be detected by smelling the dipstick, but they will be doing damage internally.

[wolfox]

10-4 - I will investigate very shortly. Thanks for verifying a thought/fear.

[jsgold]

I suppose I will just park the old truck for a while and drive the wife's Intrepid when I need a vehicle until I get this fixed.(Heck she does not need it while out of work anyway). The amount of gas around the injector was so tiny that it was hard to see at first but as you say even a small amount of gas could screw it up and my plans call for me to drive this truck for a long, long time. Once I get the plenum off I may find more of a mess than I can see now too. I will study up in my manual on this procedure and revisit the shortcut to LT's CPI changing on here as well. I may have a couple of questions later as I get ready for this. It is due for front brakes and the rotors need replacing too so I guess I'd better try to borrow a few bucks from the credit union and get this all done.
One question though, on a slightly different note. I want to check the timing on this truck eventually. I do not have a timing light. I have looked at a lot of them on Ebay but see some that say inductive. Others do not. May sound stupid, but is there more than one type of timing light? Any recommended?

[wolfox]

There are some inline timing lights that are merely a fancy flash-tube device that fits between the plug and the spark boot. However, given the sensitive nature of the ignition systems and timing in these trucks it's best to use an inductive pick-up light. Just about any one that says it's inductive will do... clip the red and black terminals to the battery and then clip the pick-up on cylinder 1's spark wire. Make sure the engine is fully warmed up and that there is no Service Engine Soon light on. Pull the passenger side carpeting up just to the side of the front kick-panel and you will find a tan wire with a black stripe with a little connector in the middle of it. Disconnect this wire from the in-line connector, this removes the computer's control of the engine timing so you may set the base timing of the engine. Now for the fun part - you're going to need a wrench to loosen the distributor bracket so it can be rotated if timing needs to be adjusted, but not so loose that you completely loose timing. You want it to turn only when firm pressure is applied to the distributor. Start the engine and keep the transmission in park with the brake on and wheels chocked; hopefully keeping the timing light wires out of your fan and belt - aim it at the front of the engine on the main crank pulley. It's easiest from the driver's side of the engine. At the 2 o'clock position behnd the harmonic balancer, you will find the timing marks. Adjust the distributor in very slight movements as needed until you get it dead on 0 degrees of TCD on those marks. Cut the engine, tighten the distributor bracket, remove the light and plug your timing wire back in and lay the apholstery back in place. You're done. If timing jumps randomly a few degrees here and there, suspect valvetrain/timing chain backlash that's way out of tollerance or a loose/worn timing chain. Hopefully, she just simply works and behaves well for you. *crosses fingers*

[BlazerLT]

Originally Posted by jsgold

I suppose I will just park the old truck for a while and drive the wife's Intrepid when I need a vehicle until I get this fixed.(Heck she does not need it while out of work anyway). The amount of gas around the injector was so tiny that it was hard to see at first but as you say even a small amount of gas could screw it up and my plans call for me to drive this truck for a long, long time. Once I get the plenum off I may find more of a mess than I can see now too. I will study up in my manual on this procedure and revisit the shortcut to LT's CPI changing on here as well. I may have a couple of questions later as I get ready for this. It is due for front brakes and the rotors need replacing too so I guess I'd better try to borrow a few bucks from the credit union and get this all done.
One question though, on a slightly different note. I want to check the timing on this truck eventually. I do not have a timing light. I have looked at a lot of them on Ebay but see some that say inductive. Others do not. May sound stupid, but is there more than one type of timing light? Any recommended?

You won't see a lot of fuel seeing there are drain holes that drain anything in the upper plenum down into the two middle cylinders.

[jsgold]

Fuel pressure tested out this way. When the switch turned on, shoots to 60lbs, then zero. I assumed it would hold presssure with key on, but, so much for assuming. When started it hits 60lbs for a second then drops to 54 lbs where it stays. Plugs turned out to be very worn,(thought I put platinums in, but did not) cap/rotor are OK but show signs of age. Plug wires are OK as I thought, but I am debating changing them anyway... They are < 2 years old, but have 34K on them. I plan some major duty work for the old truck in the next 2-4 weeks, including a total tune up including fuel filter, CPI assy, and brakes. Just a thought, does the pressure seem OK as I have listed it? With the pump being 8 months old I thought it would be better.

[BlazerLT]

It should never drop like that.

Replace the CPI and the nut kit and use a fresh upper plenum gasket. also clean your EGR hole which will be exposed when you remove the upper plenum.

Replace the fuel filter, air filter , PCV valve along with the plugs, cap and rotor, wires etc..

Make sure the coil plug wire connection is clean and tidy and remember to transfer the wires to the new cap one at a time.

[jsgold]

This is addition to my original post. I am trying to d/c the fuel pump to be sure it is not also a problem here. I have been working on the old truck as I get money to work with, new brakes, tune up parts, etc. I have put ut the CPI on hold until early October as I still am still saving money for it. Been making due with old ladies car. I am suspect of the fuel pump that was installed in this truck in Dec/Jan. Noisy as hell, but I see many are so I have ignored it until now.
I know there is a fuel pressure issue here and most likley the regulator, HOWEVER, would apprciate feedback on the fuel pressure tests I have done to it to be sure it is not BOTH.
When ignition switch turned on, pressure goes to 60lbs for the 2 sec the relay allows it to run without starting. then drops to 58lbs and stays there. No bleed off that I see after 5-6 minutes. When you start the truck it drops to 54lbs. Will go up when you give it the gas to around 60lbs and drops back again to 50-54 then settles at 54. How can I be sure of the fuel pump with these readings?