Help - running rough, new plugs, wires, cap and rotor

[gulleyman]

Hey folks, got a mystery I'm hoping you all can help me solve
My truck started running rough and the check engine light would come on from time to time then go back off again. It started getting more frequent so I took it to Autozone one day while the light was on, they said it needed a typical tune-up, plugs, wires, ect.

So I bought platinum plugs, cheap wires, cap and rotor and installed them with the plugs gapped at .060 as they were supposed to be...or so I thought.
After the tune-up the light went away but the truck still ran a little rough and didn't have as much power as I thought it had before.

After a while the light came back like before, then one day it started blinking and the truck started running really rough and nearly stalling. I took it in and they said I had a misfire on cylinder six.

I checked the wires for resistance with an ohmmeter and one of them was not the same as the others so I took them back out and returned them. I also noticed that the plug had fouled. I removed the rest of them and they were ALL FOULED

I returned the wires for better Bosch wires and got a whole new set of plugs. Then I posted up on here and some great folks helped me figure out how to put the wires back on right and suggested that maybe all the plugs fouled because the plug gap or maybe the wrong heat range.

So I did a little research here and on GMT400 and a couple other GM sites and found a few posts that stated GM had changed the recommended plug gap from .06 to .04 because of misfire and pinging. Some say it's only on the iridium plugs, others say all of them. The old plugs look like they may have had an even bigger gap than .06.

I gapped the new plugs to .04 and put them in with the new wires and it sounds better but still really rough.
I have an after market cold air intake and a power programmer installed. Not sure if that affects anything. I did find and repair a couple of vacuum leaks too.

What do you guys think? Sorry for the looooong post. Any help is much appreciated

 

[raptorforme93]

Yea I have heard a lot about these engines not running clean when your plug gap isnt spot on. But when your engine ran real rough and almost stall sounds like when my distributor went bad. Same thing happened, check engine light was blinking and engine ran like it was on two cylinders. but Im not sure what code it was throwing for that problem. I just know that I had everything placed and it ran like a top. (that was before I found this forum, now i do everything myself)

 

[steamroller]

So I did a little research here and on GMT400 and a couple other GM sites and found a few posts that stated GM had changed the recommended plug gap from .06 to .04 because of misfire and pinging. Some say it's only on the iridium plugs, others say all of them.

I've read the same posts before but can never find the exact GM document for it. Mine used to eat distributor caps like they were popcorn till I closed the gaps down though. People will argue you have to run .060 because that's what GM recommended when they were built.

 

[SunlitComet]

Ignition System - New Spark Plugs/Gapping

Bulletin No.: 03-06-04-060A

Date: February 12, 2007

INFORMATION
Subject:
Information on New Spark Plugs and Gapping

Models:
2004 Buick Rainier
2002-2004 Cadillac Escalade, Escalade EXT
2003-2004 Cadillac Escalade ESV
2004 Cadillac CTS-V
1997-2004 Chevrolet Corvette
1998-2002 Chevrolet Camaro
1999-2004 Chevrolet Silverado
2000-2004 Chevrolet Suburban, Tahoe
2002-2004 Chevrolet Avalanche
2003-2004 Chevrolet Express, TrailBlazer
1999-2004 GMC Sierra
2000-2004 GMC Yukon, Yukon XL
2001-2004 GMC Yukon Denali, Yukon XL Denali
2002-2004 GMC Sierra Denali
2003-2004 GMC Envoy XL
1998-2002 Pontiac Firebird
2004 Pontiac GTO
2003-2004 HUMMER H2

with 4.8L, 5.3L, 5.7L or 6.0L V-8 Engine (VINs V, P, T, Z, G, S, N, U - RPOs LR4, LM4, LM7, L59, LS1, L56, LQ9, LQ4)
Attention: Please disregard the Set Gap Per Vehicle Specification statement on the side of an ACDelco(R) Iridium Spark Plug Box. The statement will be removed from the boxes in the future.

Supercede:

This bulletin is being revised to bring attention to the Set Gap Per Vehicle Specification on the ACDelco(R) Iridium Spark Plug Boxes. Please discard Corporate Bulletin Number 03-06-04-060 (Section 06 - Engine/Propulsion System).

A new spark plug has been released for use in the above vehicles. The new spark plug has an Iridium tip instead of the current Platinum tip. Due to the different tip design, the gap of the spark plug has also changed.

The new spark plug, P/N 12571164 with AC Delco P/N 41-985, is gapped to 1.01 mm (0.040 in) when the spark plug is made.

The spark plug gap is set during manufacturing and should not be changed or damage to the spark plug may result. Any new spark plug found to not be properly gapped should not be used.

---------- Post added at 12:22 AM ---------- Previous post was at 12:20 AM ----------

I would disable your programmer and retest with a scanner.

 

[gulleyman]

I would disable your programmer and retest with a scanner.

Thanks for posting the bulletin, that's the one I saw alright! My truck doesn't seem to fit in there, it's a '97 Yukon GT, 2dr 4x4, with the Vortec engine.
I'll have to try resetting the programmer and scanning it again, maybe that will shed some light on things.
The strange thing is, the truck seems to run a little better with the plugs gaped at .04 (still really rough) and it fouled all the new plugs the first time I had them gaped at .06. The way it's running I don't doubt it will foul them all again this time. Seems like something else is not right, I'll try removing the power programming and trying the scan again.
Please keep the suggestions coming, great stuff here!

 

[gulleyman]

Well......I removed the power programming and had it scanned again. Same error code, misfire on cylinder 6. Took it to one mechanic I know to be good but pricey at times. He thought it may be a bad injector or something electrical, like a short between the computer and the injector or the computer itself, said it could take a looong time to diagnose.
I've never gotten into the injectors on any car and my other car took a poop this morning when the crank pulley fell off.
So I threw in the towel on my Yukon and dropped it off with another mechanic that's usually faster, cheaper and more honest, lol. Decided to try and do the crank pulley on the other car myself....sheez!
I'll post again and let you guys know how the story ends.

 

[SunlitComet]

Well......I removed the power programming and had it scanned again. Same error code, misfire on cylinder 6. Took it to one mechanic I know to be good but pricey at times. He thought it may be a bad injector or something electrical, like a short between the computer and the injector or the computer itself, said it could take a looong time to diagnose.

Is this code the same instant as your first scan or after you cleared active and history of codes and it came back?

Lets assume that if your plugs are fouled of fuel that you have a weak spot in your ignition but if you have eliminated that you may benefit from changing the fuel injector assy from the "Central SFI Fuel System with a new MFI (Multiport Flexible Injection) Fuel System". The shops around me just upgrade them because about about half of the customers come back later with the same problem after just cleaning them out. I have two injector that are failing their balance test so I going to convert the module to the new type which gives me all new injectors. Costing me about $400 diy. It is mostly blamed on bad quality gas causing deposits on the poppet nozles.

 

[gulleyman]

I think "sunlitcomet" is right, so does the mechanic lol.
Another member "Rebolution" had a similar issue, replaced the injector spider and still had the misfire though. He took his to the dealer and found out the distributor was bad. Someone else posted a link to a pretty good looking distributor on ebay for $60 shipped.

Sounds like I should have the mechanic check my distributor too since it's already at the shop and I can't just check it myself, then replace the injector spider if the distributor looks good. What do you guys think, sound like a good plan of action?

Also, where is the best place to pick up those new and improved injector spiders?

 

[99Yuk]

I think "sunlitcomet" is right, so does the mechanic lol.
Another member "Rebolution" had a similar issue, replaced the injector spider and still had the misfire though. He took his to the dealer and found out the distributor was bad. Someone else posted a link to a pretty good looking distributor on ebay for $60 shipped.

Sounds like I should have the mechanic check my distributor too since it's already at the shop and I can't just check it myself, then replace the injector spider if the distributor looks good. What do you guys think, sound like a good plan of action?

Also, where is the best place to pick up those new and improved injector spiders?

+1 on the where to get the mpfi to replace the spiders?

And yes, have him check the Distributer. It shouldn't take him long, and if it's good then fine, you'll have peace of mind that it's not the problem. If it's bad then change it out.

 

[Dlong30]

gmpartsdirect
part #93441235

 

[99Yuk]

gmpartsdirect
part #93441235

So, I'm interested so I go look there...here's a link 'cuz he didn't provide one. http://www.gmpartsdirect.com/results.cfm?addtocart=1&addpartnumber=19210687&singlepart=1&partnumber=93441235

Turns out that part#93441235 has been replaced with part#19210687 which just says fuel injector.....http://www.gmpartsdirect.com/results.cfm?singlepart=1&partnumber=19210687 So what gives??? What do we really want to be ordering?

 

[scottg918514]

Other things to check:

1. clean throttle body
2. Maybe seafoam gas and engine (vaccum line)
3. Maybe weezing, not getting enough air.

If you're check engine light was on, there should have been a code registered on your computer. Autozone should have told you the code and its meaning.

 

[SunlitComet]

Also, where is the best place to pick up those new and improved injector spiders?

the ones i am getting are from kragen. They have the spider assy new bracket and gasket set seperately for less then $400

 

[gulleyman]

Other things to check:

1. clean throttle body
2. Maybe seafoam gas and engine (vaccum line)
3. Maybe weezing, not getting enough air.

If you're check engine light was on, there should have been a code registered on your computer. Autozone should have told you the code and its meaning.

Thanks scottg918514, was gonna try the Seafoam. Before I did the tune up there was a misfire code, they told me I probably needed to change the plugs, wires, cap and rotor. Didn't solve the problem though...

So what gives??? What do we really want to be ordering?

I couldn't make any sense out of it either. One of these is less than $300 though. I sent an email to their customer service department to try and sort it out. They said I needed GM PART # 93441235, $313.46....wonder what the difference is?
Anyone else have a better, or more cost effective idea?

 

[SunlitComet]

This may help.
They were revised for californians. Attachment with file name that ends in 942 is for bottom bulletin.



Bulletin No.: 00-06-04-003B

Date: February, 2003

TECHNICAL
Subject:
Rough Idle After Start, And/Or A Service Engine Soon (SES) Light
(Unstick And Clean Central Sequential Fuel Injection (CSFI) Poppet
Valves or Convert to MFI)

Models:
1995-2002 Chevrolet and GMC S/T Models
1996-2002 Chevrolet and GMC C/K, M/L, G, P Models
1996-2001 Oldsmobile Bravada
1999-2000 Cadillac Escalade
with 4.3L, 5.0L or 5.7L Engine (VINS W, X, M, R - RPOs L35, LF6, L30, L31)
Except 2002 VIN X - RPO LU3 Models

This bulletin is being revised to update the Warranty Information. Please discard previous copies of Corporate Bulletin Number 00-06-04-003B with warranty chart (Section 06 - Engine). This copy is for Dealers in the state of CALIFORNIA ONLY.

Condition

Some customers may comment on rough idle after start-up, especially if the vehicle has sat overnight. These symptoms may be intermittent. The Service Engine Soon (SES) light may also be illuminated. Current misfire or history misfire codes may be detected with the Tech 2 scan tool.

Cause

A deposit build-up on the CSFI poppet valve ball and/or seat may cause the poppet ball to stick open or closed. In either case, the specific cylinder will be mis-fueled, resulting in a cylinder mis-fire condition.

Correction

A new injector unsticking and cleaning process has proven to be effective in restoring poppet valves to an "as new" condition. CSFI injector replacement should NOT be considered as a correction for this customer concern.

Check the vehicle history to determine if the vehicle is returning for a second fuel system repair for this condition. If the fuel system has been repaired for this condition previously, then inform the customer that an alternate fix is available. A new MFI fuel system has been developed that will back service the CSFI fuel system. The MFI fuel system eliminates the CSFI poppet valve ball and seat. The CSFI fuel system will need to be replaced as a unit. Refer to Central SFI to MFI Conversion instructions in this bulletin.
Notice : Individual CSFI injectors can not be replaced with MFI injectors. The entire CSFI fuel meter body will need to be replaced. The bracket used to retain the injectors in the fuel meter body is different between the CSFI and MFI unit. The unit may not seal if you mix injectors. Severe engine damage could result.

Cleaning the CSFI injectors is the preferred repair. The CSFI unit should not be replaced until cleaning has been attempted. If the vehicle should return for the same repair, then the CSFI unit can be replaced with an MFI unit. If the vehicle is out of warranty, the customer should be given the option of which fix to pursue.
Important : "GM of Canada" dealers require District Service Manager approval prior to replacing the CSFI unit with a MFI unit under warranty.

The first step of this process is to use the J 41413 Evap Pressure/Purge Station, in conjunction with the J 44466-10 pressure regulator/hose assembly, to provide the required high pressure (150 psi) source to perform the unsticking procedure. The J 39021 fuel injector tester and accessories provide the means to "energize" the injector. Some later model-year vehicles may utilize the Tech 2(R) to "energize" the injectors.

The second step of this process is to run the engine on a solution of 10% Top Engine Cleaner and 90% gasoline. This will effectively clean any deposits from the ball and seats of the poppets. It is very important that the engine fuel system is separated from the vehicle fuel system. Top Engine Cleaner may have detrimental effects on the fuel pump.

Parts Information



Cleaning Procedure Parts



CSFI to MFI Conversion Parts



Parts are currently available from GMSPO.

Warranty Information
Important : Some California vehicles may be covered by Special Policy 99066E if built with California Emissions RPO YF5. If the vehicle is covered by the special policy, then that warranty information should be used.

For vehicles repaired under warranty, use information contained in Special Policy 99066E.



-----------------

And Another:

Bulletin No.: 99066F

Date: March, 2003

SPECIAL POLICY
SUBJECT:
99066F - SPECIAL POLICY ADJUSTMENT - SEQUENTIAL CENTRAL PORT
FUEL INJECTION (SCPI) FAILURES IN CALIFORNIA ONLY (YF5
EMISSION EQUIPPED)

MODELS:
CERTAIN 1996, 1997, 1998, 1999, 2000, 2001, 2002 S/T, M/L, C/K, G,
P, W4/NPR TRUCKS AND 2003 NPR TRUCKS EQUIPPED WITH 4.3L
(RPO L35 - VIN CODE W OR RPO LF6 - VIN CODE X), 5.0L (RPO L30
- VIN CODE M) OR 5.7L (RPO L31 - VIN CODE R) ENGINE AND
CALIFORNIA EMISSION EQUIPPED (RPO YF5)

This bulletin is being revised to add the 2002 and 2003 model years to the SCPI Special Policy on certain S/T, M/L, C/K, G, P and W4/NPR truck models. Please discard Special Policy Bulletin Number 99066E, dated February, 2003.

CONDITION

Some customers of 1996, 1997, 1998, 1999, 2000, 2001, 2002 model year S/T, M/L, C/K, G, P, W4/NPR trucks and 2003 NPR trucks, that are registered in California, equipped with 4.3L (RPO L35 and VIN Code W, or RPO LF6 and VIN Code X), 5.0L (RPO L30 and VIN Code M) or 5.7L (RPO L31 and VIN Code R) engine, and California emissions (RPO YF5), may experience a "Service Engine Soon" light, misfire, rough idle or hard start due to a deposit build-up on the Sequential Central Port Fuel Injector (SCPI) poppet valve(s). The deposit build-up may cause injector poppets to stick closed. Certain fuels have been found to interact with the SCPI system to cause the deposits.

SPECIAL POLICY ADJUSTMENT

This special policy covers the SCPI failure condition described above for a period of ten (10) years or 200,000 miles, whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership.

The repairs will be made at no charge to the owner. This special policy applies ONLY to repairs requiring SCPI system servicing, injector cleaning and/or MFI assembly replacement of the SCPI system. The customer should not be charged for performing a system check when it is determined that the SCPI system is not the cause of a customer complaint (labor operation T5532 is provided to submit claims for such system checks). Any additional necessary diagnosis and repairs that are not related to the SCPI condition are not covered by this special policy. The customer should be informed that any further service that is not covered by new vehicle warranty will not be covered by this policy.

VEHICLES INVOLVED

Involved are certain 1996,1997,1998,1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR and 2003 NPR model vehicles, registered in California, equipped with 4.3L (RPO L35 - VIN Code W, or RPO LF6 - VIN Code X), 5.0L (RPO L30 - VIN Code M) or 5.7L (RPO L31 - VIN Code R) engine; and California emissions (RPO YF5). This Special Policy covers all vehicles within these model years, with these engine and emissions RPO's.

PARTS INFORMATION

 

[gulleyman]

Wow, I think that about sums it up...
Thanks sunlitcomet, now let's figure out if GMpartsdirect is the best place to buy the MFI and we've got this licked

Come on guys, I know this is something that a BUNCH of us have had or will have to replace.

 

[Mcoffey24]

I also had a misfire problem that I was fighting for about a year. I replaced 3 injectors before I finally got a new spider in MFI. Never had a problem since.
I was able to get mine from Autozone for $300 but it was on a company discount.

 

[SunlitComet]

I will be getting mine from kragen for less then $373 w/tax.

Includes spider and new bracket made by BWD and felpro gasket set.

add 113 for delphi parts(oem).

or you can try http://www.gmpartsgiant.com/

A dealership in Ca. with good prices and ships.

$352 for the v8 module which is cheaper then kragens oem price.

just verify part number applicability.

On second thought I am going to use giant instead for oem parts.

 

[gulleyman]

One of the other members, 99YUK, found the MFI Upgrade on Amazon for $217 shipped, check out my other thread

http://www.tahoeyukonforum.com/forum/showthread.php?t=19346

 

[gulleyman]

Oookay, so the new MFI is in place and it's STILL running rough
So I have them checking the distributor now too, haven't heard back from them yet. Guess I'll start going through the list scottg918514 gave me. Anyone else got some insight on this one? Need all the help I can get...