96 GMC Jimmy Running rough. - S-10 Forum
S-10 Forum is the resource on GM S-series trucks, Suspension, engine information, Body Modifications, painting tutorials.  Modifications to suit every need, budget and whim

96 GMC Jimmy Running rough.

Go Back   S-10 Forum > Engine and Drivetrain Tech > 262ci Forum (4.3)
New User? Register Forgot Password


 
LinkBack Thread Tools
Old 05-01-2011, 07:56 PM   #1
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
96 GMC Jimmy Running rough.

I'm at my wits end with my wifes truck.

She took 3 hour round trip (hwy driving) and on the way back check engine light came on. When she stopped at a stop light it started running real rough at idle and has lost all power and is knocking and pinging

Symptoms:
Runs rough at Idle and when you put it in gear and at low RPM's
(it smooths out a bit at 3K but you can tell that it's still knocking because you can feel the ECU pulling timing)

Ecu codes
P1100 (Online says intermittent MAF signal)
-I have verified the Signal with an oscilloscope at the MAF and at the ECU the signal is a little noisey but it's there.
And I replaced the MAF with a refurbished unit.

P700 - Transmission control unit malfunction. (this one just cropped up and I think the knocking is screwing it up. it shifts fine)

and P300 Multiple misfires

What I've done
-Tune up
--New Summit Plug wires
--NGK Iridium Spark plugs gapped at .060"
--New MSD ignition Coil
--(It was due for a tune up 190K miles. This was my original diagnosis)

-Did a compression test while I had the plugs out
--#1=180psi
--#2=180psi
--#3=170psi
--#4=175psi
--#5=172psi
--#6=180psi
+ran better but didn't solve it


-Refurbished MAF from Oreilly autoparts (after getting a code for low MAF signal)
+didn't fix it

-Fuel Pressure is 50-60psi
-New revised Spider injector pack with the injectors at the end of the tube.
(I knew the Spider injectors were notorious for causing these symptoms and it still had the old revision with the poppet valves. With 190,000 miles on it it couldn't hurt to go with the upgraded unit)
+ran better but didn't fix it

-hosed down the Intake manifold with starter fluid to check for vacuum leaks.
--Note: It already has had the lower intake manifold gasket replaced at 175K miles with the Fel Pro "Problem Solving" kit
+No change in the way it ran

I've tried every thing I know to do.
at this point it's either:
A) a bad ECU (Not likely)
B) Vacuum leak

I'm going to try to call a few shops around town to see if they have the tools to do the smoke test on the intake. or see if they have the SNAP ON or GM scantool that can show the live data stream.

Any other Ideas?
Old 05-02-2011, 03:29 PM   #2
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
Re: 96 GMC Jimmy Running rough.

UPDATE:

Had a mechanic preform a smoke test on the intake manifold no leaks were found.

His scan tool picked up that cylinders #5 and #6 were the ones misfiring.

He suggested dropping the catalitic converter.
Took the exhaust off and no change

He also suggested that the Cam shaft could be worn out
I have pulled the rocker arms and push rods on 5 and 6. The push rods are straight and not bent. and they look like they are moving the same amount with the other rocker arms... I'm going to barrow a depth gauge and measure the cam lobes later this afternoon to see if they are within spec.

I May check the camshaft sensor located in the distributor.

I put a timing light on #1 yesterday and the timing mark for TDC #1 was on the other side (I think WAYYYY advanced. I know you cannot check the timing unless you have the TECH 2 scan tool though)

Any one have other ideas?
Old 05-03-2011, 02:03 AM   #3
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
Re: 96 GMC Jimmy Running rough.

-verified all fuel injector signals with an oscilloscope
(approx 5ms activation that varies with rpm)
-Verified Crank and cam sensor signals
-put the o-scope on the ignition coil - wire, Signal looks good there too.

Wasn't able to verify the camshaft, I could not obtain a proper depth gauge within the allotted time.
Old 05-03-2011, 12:39 PM   #4
General L33
 
Hotwire's Avatar
 
Join Date: Jul 2001
Posts: 1,561
Location: Summerfield, NC
User is: OffLine
Re: 96 GMC Jimmy Running rough.

replace your distributor cap and the distributor gear. Look at the teeth on the bottom of the dist, probably worn out. I've had two blazers do this, cold it runs fine, but once it's warmed up or heat soaks from long trips I get p0300 and rough running.

Autozone sells the gear for $32

http://www.autozone.com/autozone/par...mString=search
Old 05-03-2011, 02:33 PM   #5
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
Re: 96 GMC Jimmy Running rough.

Thanks for the suggestion

Pulling the Distributor and seeing if that gear was cracked or damaged was going to be my next step.

I dropped it off at a different shop this morning that has the Snap On scan tool that can issue the diagnostic commands but if they can't find any thing that will be my next step.

My cheap Harbor Freight vacuum gauge has a green mark where the needle is supposed to sit and below that it has a red zone that reads "late ignition timing" and the needle reads right where the red meets the green. So I could easily see why a bad distributor gear could cause these problems by retarding the ignition timing.

If that doesn't work I have a friend who has a fiber optic bore scope I can barrow and inspect the combustion chambers for a fried piston or something

I think the hardest problem right now is trying to deal with my wife who is
stuck at home with two small children (2yo and 3yo)
Old 05-03-2011, 03:03 PM   #6
Registered User
 
Join Date: Dec 2010
Posts: 350
Location:
User is: OffLine
Re: 96 GMC Jimmy Running rough.

Have you checked your EGR Valve? If it is stuck it will throw misfire codes! Misfiring engine will not pull proper amount of air through MAF sensor and can cause transmission to shift wrong triggering transmission codes. After replacing all ignition components and it still did this....

Runs rough at Idle and when you put it in gear and at low RPM's
(it smooths out a bit at 3K but you can tell that it's still knocking because you can feel the ECU pulling timing)

EGR is the very first thing that comes to my mind.
Old 05-03-2011, 05:35 PM   #7
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
Re: 96 GMC Jimmy Running rough.

I blocked off the EGR valve with a piece of an aluminum can sandwiched in between the EGR and Intake... No change.
Old 05-03-2011, 08:14 PM   #8
Registered User
 
Join Date: Dec 2010
Posts: 350
Location:
User is: OffLine
Re: 96 GMC Jimmy Running rough.

Quote: Originally Posted by pk386
I blocked off the EGR valve with a piece of an aluminum can sandwiched in between the EGR and Intake... No change.
I would find someone with a scanner that shows live data stream now...might have to break down and spend $100 and take it to a dealer and have it diagnosed unless you have a friend with a TechII or equivalent.
Old 05-04-2011, 12:06 AM   #9
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
Re: 96 GMC Jimmy Running rough.

I took it to a local mechanic that had the MAC-DADDY Snap-On MODIS scan tool.
He told me that the ignition timing was -17° Retarded.

He also preformed a head gasket test with the coolant and the DYE that will turn a different color if exhaust gas is found in the coolant. Head gaskets are good.

He didn't have time to pull the distributor and check the distributor drive gear, it was 5:30pm and closing time. So I took it home and pulled it.





I didn't notice any where on the gear... there are some shiny spots as seen in the second picture. But no knife edges or any thing significant. I just put it back in as all of the parts stores were closed by now. When I bolted it back in, the rotor button will move approximately 7° (I measured it with a plastic protractor)

I saw this article which suggested that it may be the distributor too.

I wasn't able to do an official test to see if the timing chain has stretched but I was able to put a finger in the distributor hole and feel the balance shaft. I turned the crank with a ratchet while I felt the balance shaft with my finger. I didn't sense any slack in the chain. (When the crank moved the balance shaft moved.) Now that I think about it I didn't do two full revolutions of the crank. so there still could be a stretched portion of the chain. Se La Vi.

I'm going to go for the distributor and pray.
Old 05-04-2011, 01:26 AM   #10
Vig Pimpin
 
viggy58's Avatar
 
Age: 31
Join Date: Apr 2011
Posts: 724
Location: Lawrenceville, GA
User is: OffLine
Re: 96 GMC Jimmy Running rough.

how'd the cap look?

what's your vin code? w? x? or whatever? should be 8th "digit"
have you run any fuel/TB cleaner through it?
may have a bad cap or a couple stick injectors.
have you tested fuel pressure?
Old 05-10-2011, 12:37 PM   #11
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
Re: 96 GMC Jimmy Running rough.

Update: Replaced the distributor. It ran better but didn't solve the problem.
I have it at a shop right now and they are diagnosing it now.

I will post updates when I finally figure out what it is.

I'm at the point were it's either:
A) stretched timing chain
B) bad cam shaft
C) hot spot on one of the pistons or combustion chamber causing preignition

Also
W code engine with the top mounted TB
New injectors and fuel filter was replaced not too long ago
Fuel Pressure is 50-60PSI (within factory specs)
Old 05-13-2011, 07:36 PM   #12
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
Re: 96 GMC Jimmy Running rough.

Update from the shop.

They did a leak down test and discovered that the intake valve on #5 was burned.

They did the drivers side bank first and he told me two cylinders were leaking on the passenger side. (note above that the compression test was showing 170-180psi. But when he preformed the leakdown test he heard a hissing noise coming out of the intake. You could feel air coming out of the throttle body with the leakdown tester on #5)

Long story short it needs a head job. My wife needs a baby hauler now so we will be taking out a small loan and getting her a minivan (what she wanted any way) and I'm going to shift Jimmy to the back yard and work on it in my spare time. I've got 2 other projects besides this one so I'm going to be wrenching a lot in my spare time 0_o

The mechanic told me I could pull the rocker arms and valve springs and spin the valves with a drill with compressed air in the cylinders to get the valves to re-seat. Much like lapping the valves with the head off the car. Not a permanent fix but enough to fix and sell it. (I will give full disclosure before I sell it.)

Long story short: Don't go replacing parts with out doing a full diagnosis. Don't guess, KNOW!
But this failure has taught me an important lesson that will make me better in the future.
Old 05-13-2011, 09:41 PM   #13
General L33
 
Hotwire's Avatar
 
Join Date: Jul 2001
Posts: 1,561
Location: Summerfield, NC
User is: OffLine
Re: 96 GMC Jimmy Running rough.

Dayum man, sorry to hear that, I would have never of picked that. Did your vacuum gauge flutter when you had it hooked up? Do you think # 5 injector is clogged and leaned it out?
Old 05-14-2011, 07:55 AM   #14
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
Re: 96 GMC Jimmy Running rough.

Yea the vacuum gauge would flutter but not by much. Not enough for me to suspect a burned valve but a different vacuum port may have shown different results.

Yea the old spider injectors could have leaned out that cylinder.
Old 10-17-2011, 11:12 PM   #15
Registered User
 
pk386's Avatar
 
Join Date: Apr 2007
Posts: 72
Location: Ridgeland MS,
User is: OffLine
Re: 96 GMC Jimmy Running rough.

Finally found the problem. It was the DISTRIBUTOR CAP!!!

I thought it was leaking intake valves but the EDI distributor cap was burned on the inside causing the spark for #5 to arc over and fire #4 on the intake stroke causing the motor to knock on #4 but since the ECU was firing #5 it thought the misfire was caused on #5

Unfortunaltly this was after I had pulled the heads and had a machine shop work them

See this thread:
http://www.s10forum.com/forum/f107/4...colors-478686/

Oh well the intake valves were Burned on #3 and #5 according to the machine shop. So instead of having a truck that will last another 20K miles I have one that will last another 200K

I'm too lazy to post pics to Photobucket so here's a link to my Facebook album (Don't worry it's public so you can see it)

http://www.facebook.com/media/set/?s...1&l=218d93363f
Sponsored Links
Advertisement
 

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the S-10 Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 05:40 AM.

Powered by vBulletin® Copyright ©2000 - 2011, Jelsoft Enterprises Ltd. SEO by vBSEO 3.2.0
SEO by vBSEO
vBulletin Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.