I know wrong forum but I need help!

Hey guys I just changed the plugs to ACDelco plats and I noticed that when I am crusing and punch it pretty good where it would downshift it hesitates and the engine shakes for a second. It finally downshifts and its smooth. I can get it to do it most at 1500RPM, at least that is where I notice it. Truck drives smooth and fine otherwise.

What should I do?

I dont really know what misfire is or feels like so I could be wrong in my diagnosis.

Cap, Rotor, and Wires were changed about a month ago. All genuine ACDelco.

OK guys I just went a drove the truck again. It drove awesome as usual and only gave me the shake issue one time. I can reproduce it everytime at 55MPH now when I put my foot back on the gas after coasting. Because the truck runs so good otherwise, this almost seems like a fuel issue to me. It feels like there is a flat spot in fuel or spark for a split second.

I dont even know what misfire feels or sounds like so my initial diagnoses could be completely wrong. Can someone point me to a video or sound clip of misfire?

I have reved thru most gears from 700-4000RPM and it was smooth as glass. It just this one spot at 55mph when I reapply the throttle and ask it to pick up some speed for a minute.

Any thoughts?

sounds like torque converter shudder to me.

is there anyway to tell for sure?

Feels more like the shudder is coming from the motor though.................

Anyone else?

my 97' z71 did that.... it did it only at cruise speed only not under load......it was b/c the spark plugs werent gaped how they was supposed to be......

really, maybe I will take the Platniums out and put in the extra Rapidfire plugs I have. I know the Platniums said not to gap but I did just check them anyway. Are the gaps that picky, did i mess them up by checking gap?? The rapidfires I have say to check gap.

well,i hate for you to pull the plugs out, but from my experience i have never had good luck with the platinums.......the distributor didn't like them, i have had better luck with the cheap plugs!!

Everyone told me to run the plats. I have a set of Delco Rapidfires right here on my desk.

Does what I am describing sound like misfire or fuel delivery issues? I have guys telling me its both. Would spark issues the truck run like crap?

My dad seems to think it is was spark he wouldnt be able to drive the truck. Keep in mind the truck runs like a top from idle to 4000rpm in all gears no problem.

when was the last time you changed the fuel filter??? and how old is the fuel pump?

Fuel filter was change less than 10k ago by me personally. on the 2nd fuel pump about 1 year old.

fuel pump should be good, change the filter first and see how she acts! i change my filter every 2 oil changes, you would be surprised how much trash is in these gas stations!!

I will try that, If anyone else has any other suggestions I am open.

good luck i hope you get it running!....on note, i talk to a gm mechanic a while back and he said that the 88-98 fuel filters were good for 5k in his opinion

not sure of the exact year but there is a special policy to swap out the fuel inectors to a newer SCPI style. Did you ever have this done?

it is a 97 and nope the fuel injection system is 100% stock. I have heard about the new system though but this truck does not have it.

try it again with the brake pedal applied just enough to keep the brake lights on, that will keep the converter from locking up. that will tell you if it is a TC issue or not

send me your vin.

it's something that could be causing this issue....

try it again with the brake pedal applied just enough to keep the brake lights on, that will keep the converter from locking up. that will tell you if it is a TC issue or not


I will try that tomorrow your the 3rd person who has told me to do that...

send me your vin.

it's something that could be causing this issue....


Check your PMs.

you are correct it has not had it done and unfortunatly you are out of the special policy. 10 years 200,000 miles. I would continue on with your diagnosing with the ignition system since that is when you noticed the problem originally.

The injectors you have could cause the concern as well but start with what you changed first.

Special Policy is to replace the SCPI system with an MFI system. Better injectors.

Problem with the SCPI system is the poppets start sticking. If this si the case some fuel treatment could help you out.

Could you send me policy just so I can read it? Is it something I could buy and do myself?

you should be able to do it yourself, it's not bad at all.

I will get you a price for the injector unit as well.
Parts Information

Parts required to complete this Special Policy are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering parts. Normal orders should be placed on a DRO=Daily Replenishment Order. In an emergency, parts should be ordered CSO=Customer Special Order.

Part Number

Description

Qty/ Vehicle

12345382

Sealant, Thread, Med. Strength (6 ML)

As required

TBD*

Cleaner, Top Engine (24 ml)

If required and available

TBD*

Cleaner, Top Engine (15 oz)

24 ml (12346535 size alternative)

12345104

Cleaner, Port Fuel Injector (20 oz)

If required

15050573

Asm-Fuel Tank Fill Pipe (97-99 M/L Van)

1, if required

15747585

Asm-Fuel Tank Fill Pipe (99 C/K E63 w/o AC7)

1, if required

15747588

Asm-Fuel Tank Fill Pipe (99 C/K E62 w/o AC7)

1, if required

12568332

Assy, V6 Fuel Injector

1, if required

88894355

Bracket, V6

1, if required

17113215

Kit, V6 Seal

1, if required

93441235

Assy, V8 Fuel Injector

1, if required

93442096

Bracket, V8

1, if required

17113206

Kit, V8 Seal

1, if required

*Top engine cleaner part number 12346535 and 1050002 are no longer California compliant. California dealers will be notified via a DCS message when new alternative cleaner part numbers become available.

Important: Isuzu Parts Ordering: In order to comply with the 10-digit Isuzu part numbering system, Isuzu deaelrs must add an "8" to the beginning and a "0" to the end of the listed 8-digit part numbers when ordering parts through AIPDN.

Customer Notification

Customers will be notified of this Special Policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin-actual divisional letter may vary slightly).

Service Procedure

System Check

Use strategy-based diagnoses listed in the front of the Driveability and Emissions section of the Service Manual. If the SCPI system is operating properly, inform the customer that the vehicle does not have the condition listed in the owner letter. If poor driveability conditions persist, inform the customer that any further diagnosis and repairs will be at their expense if the vehicle is outside the parameters of the New Vehicle Warranty.

SCPI Injector Cleaning Procedure

If diagnosis leads to sticking poppet nozzles, first check GMVIS to determine if the vehicle had a previous claim for injector cleaning under labor claims J5645, T5534 or T5540. If any of these three repair claims are listed, do not clean the injectors, but rather replace the engine SCPI fuel assembly with the MFI fuel assembly. If none of these three repair claims is listed, use the service procedure from Service Bulletin 00-06-04-003B to clean the SCPI poppet nozzles. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly.

SCPI Fuel Tank Fill Pipe Assembly for 1997-99 M/L Van and 1999-some 2000 C/K Truck; with 4.3L, 5.0L, 5.7L engines and built prior to listed VIN/Production dates on Service Bulletin 00-06-04-018

If diagnosis leads to sticking poppet nozzles on these models, use the service procedure from Service Bulletin 00-06-04-018 to replace the fuel tank fill pipe assembly, if this procedure has not been performed previously. Previous service procedure can be verified by checking GMVIS for Labor Operation L1065 on M/L trucks with replacement part number 15050573; or Labor Operation L1065 on C/K trucks with replacement part numbers 15747585 or 15747588.

Correction

If, AFTER cleaning the SCPI poppet nozzles, the normal service manual diagnosis still indicates that the SCPI is the cause of the customer complaint, or if the injectors have previously been cleaned and the vehicle has again experienced sticking poppet nozzles, refer to Service Bulletin 00-06-04-003B and replace the SCPI fuel assembly with the MFI fuel assembly. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly.

I noticed in my Ford when i let of gas and hit brake and re applied throttle the TC would be unlocked, if I did not hit brake when I reapplied throttle the TC was still locked.

Is this the same operation as the Chevy should be?

Well I just drove it 20 miles and guess what. I opened the hood and can see sparks on number 1 cylinder next to spark plug and boot I believe. Is this the cable or a bad plug? Cables are brand new. I did hear a popping noise on this particular plug when I loosened it alittle bit after installing.

cracked plug or broken wire .



grab a spray bottle with water, fire up the truck and spray the sparkplugs. See which others spark. Replace as necessary.

GOOD JOB !!!

Thanks for help/.

any up date?? did you get the truck running write?

Nope dad is still out driving it somewhere in the city of Houston! ****er is pretty tough to have 200k on it, and spark plugs arcing to ground. Dad cant even tell anything is wrong with it. I hope its just the one bad plug. and luckily it is cylinder number 1.

Cracked Plug. Drove it for about 30 minutes and couldnt re-create shudder problem I was having after replacing with new plug.

I did noticed at night once my eyes adjusted to the dark I can see what I think is the blue of electricity coming from inside the porcelain in the spark plugs firing. Is this normal? And no its not sparks like what I saw last night when I discovered the plug arcing. I could hear the popping of electricty where now I cannot.

Here is the plug:
http://rtwww.reedtech.net/images/brokeplug.jpg

I did noticed at night once my eyes adjusted to the dark I can see what I think is the blue of electricity coming from inside the porcelain in the spark plugs firing. Is this normal? And no its not sparks like what I saw last night when I discovered the plug arcing. I could hear the popping of electricty where now I cannot.