Replace regulator or the whole CPI?

[shemp01]

I bought the regulator and nut kit (if I need it) at Autozone (parts 55162 and 55163) to take care of my rough idling and strong gas smell out the tailpipe after seeing an extremely clean left plenum (took off IMTV under the Vortec badge).

Once I take off the plenum to get a better look, how do I know if I only need to replace the regulator or the whole CPI spider?

Thanks

[shanes76]

does yours have a really rough idle ? I am having some trouble with me 94 Jimmy 4.3 vortec, it seems like a slight miss at idle and reving up, I cant smell any gas anywhere, could you tell me what symptoms you have? Thank you

[shemp01]

I have a rough idle. I have black soot at the end of the tailpipe.
Smells like gas at the pipe. It runs a bit rough all the time.

Been slowly getting worse over the past year or so.

Not sure what you have researched already, but look up the "Another CPI How To...." thread in the "How-to/Technical Info" forum.
http://www.automotiveforums.com/vbul...d.php?t=503238


Super common problem.

If you have extremely rough idle (almost gonna die) then that may be a stuck open EGR valve from carbon chunks. You may or may not need a new one, but definitely would need the gasket w/ a built-in screen to keep the chunks out of the EGR. Sometime works to tap on it with a heavy tool to get it to close w/o taking off the thing (Fonzy style).

[Gabe25]

Originally Posted by shemp01

I bought the regulator and nut kit (if I need it) at Autozone (parts 55162 and 55163) to take care of my rough idling and strong gas smell out the tailpipe after seeing an extremely clean left plenum (took off IMTV under the Vortec badge).

Once I take off the plenum to get a better look, how do I know if I only need to replace the regulator or the whole CPI spider?

Thanks

First of all, we need your year, Make, and the 8th digit of your VIN. Under your Plenum you should be able to see where the leak is if you turn your ignition switch to the on position to energize your fuel pump. I'm guessing that your motor is a "W" VIN. It's hard to say if you should replace the Regulator only or just the whole CPI Assembly. I Normally would just replace the whole assembly if I never had replace it before.
Just remember that you ensure that the your Pressure is within Spec's. and you don't any other leaks visible before closing up your Plenum.
Post your finding. Hope this helps.

[shemp01]

Sorry, I had that info in a recent post and didn't put it in again for this new thread. I added it to my signature as well.

$50 vs. $300 really matters to me at the moment, just wondering what fails besides the regulator on the spider that would necessitate replacement and how I would know.

[Gabe25]

Like I mentioned earlier. You need to ensure you have proper fuel pressure, and check to see exactly where the leak is. Most times its the Regulator, and or Nut Kit. The CPI Popets don't give to much trouble. Being that its a 95 and if this is the first time replacing. I would recommend replacing the whole assembly, but thats your call. The Popet tubs are plastic, and through age and heat. They do get brittle.

[Leeann94astro]

Originally Posted by Gabe25

First of all, we need your year, Make, and the 8th digit of your VIN. Under your Plenum you should be able to see where the leak is if you turn your ignition switch to the on position to energize your fuel pump.

Whatever you do, do NOT start it when you prime the system to check for leaks. If you do, you will be replacing the whole spider and nut kit, whether or not you needed to before.

Where is the clean/washed spot? Is it on the passenger side (regulator) or on the driver's side (nut kit)? In general, the spider itself is fine. Might need some Chevron Techron run through to clean the poppet valves, but the spider generally doesn't fail. Sometimes the electrical connector is a problem - you can inspect that by disconnecting the connector and checking for arcing/carbon tracing. If none exist, squirt some dielectric grease in there and reconnect it.

[shemp01]

It is under the regulator (passenger side) and I haven't taken the plenum off yet. Waiting until this weekend when I won't freeze my hands in the dark here after work.

I will have the nut kit on hand as well.

I'll take pix and will find out how to post them (I assume I just attach them).

I have been reading this really detailed post on anther forum as well w/ good info -
http://www.blazerforum.com/forum/showthread.php?t=37510
and the discussion
http://blazerforum.com/forum/showthread.php?t=8873

[Leeann94astro]

You just need the regulator, then. I got mine at Autozone (with the Torx security bit needed) for about $35. As long as you're careful and don't disturb the spider, you shouldn't need the nut kit. But if there's any indication of a leak or if they look brittle, I'd replace them while you're under there.

You have the plenum gasket, right?

[shemp01]

Leeann, thanks and yes. Probably doing it Saturday. Won't know if I need the nut kit or otherwise until I take off the plenum.

old master, done. thank you.

love this forum

[shemp01]

Well, I replaced it last Thursday and it runs a hell of a lot better. The regulator was the only thing that looked like it needed changing, so I took back the nut kit. I also changed the thermostat while I was at it since I have had some gurgling issues. I think I win the award for the most gas washed plenum. It was silver, not even coppery, on the regulator side. It started running really, really bad just that day so what luck that I had all the parts and a plan ready to go.

I also fixed a broken hood release cable (drilled a hole in the front face and crimped a ferrule) and replaced my HVAC vacuum selector switch (got it off amazon but had to take it apart and fix it since some sweat shop labor assembled it wrong....) so now my vent blows where I want it while accelerating (e.g., stays blowing on the panel vents and doesn't switch to the defrost vents on it own!).

Only issue is the blazer has had trouble starting but then runs fine????

[shanes76]

I just replaced the nut kit in mine, so my intake looks the opposite of yours! lol Clean on drivers and dirty on passenger side, but still has to roll over a few times to start