Question about 1998 GMC Jimmy

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Trouble starting but once started runs decent for most part sounds like it misses a lil but at idle back fires a lil bit and catalytic converter is making a rattling type noise

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Rattle is cat shield shaking because the engine is running rough.start with the obvious replace the sparkplugs,but problem is probably the EGR valve stuck open,buy one then look on the engine to find like part ,got mine @ orielys

Posted on Oct 22, 2013


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Posted on Jan 02, 2017

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SOURCE: starts rough

try the plugs plug wires and cap and rotor

Posted on Feb 07, 2009

  • 9 Answers

SOURCE: 1999 GMC Sierra 5.3L knocking sound around Catalytic Conerters? ?

on my gmc i have 2 knock sensors and im not possitive if you have two or not under your intake mani but when i replaced both mine i got the same code of low input so i took the small needle out and wire brushed it clean and also traced and ran a new wire just to be safe and that solved my problem. as for bank 1,2 if it helps any my bank one is located engine side driverside and bank2 is engine side passenger side and 3 and 4 are underneath bed side. but you can see the sensors if you look real close near the headers. hope this helps
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Posted on Jul 02, 2009

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SOURCE: I am having ongoing problems with the truck miss

Misfire is a common driveability problem that may or may not be easy to diagnose, depending on the cause. A misfiring cylinder in a four-cylinder engine is, pardon the pun, hard to miss. The loss of 25% of the engine's power output is the equivalent of a horse trying to run on three legs. The engine may shake so badly at idle that it causes vibrations that can be felt in the steering wheel and throughout the vehicle. The engine also may be hard to start and may even stall at idle, depending on the accessory load (air conditioning, headlights and electric rear defroster, for example).

When misfire occurs, performance suffers along with fuel economy, emissions and idle quality. And, when a misfiring vehicle is subjected to an emissions test, it will usually fail because of the unusually high levels of hydrocarbons (HC) in the exhaust.

What causes a cylinder to misfire? Basically, it's one of three things: loss of spark; the air/fuel mixture is too far out of balance to ignite; or loss of compression. Loss of spark includes anything that prevents coil voltage from jumping the electrode gap at the end of the spark plug. Causes include worn, fouled or damaged spark plugs, bad spark plug wires or even a cracked distributor cap. A weak coil or excessive rotor gas inside a distributor would affect all cylinders, not just a single cylinder.

"Lean misfire" can occur when the air/fuel mixture is too lean (not enough gasoline in the mixture) to burn. This can be caused by a dirty, clogged or inoperative fuel injector; air leaks; or low fuel pressure because of a weak pump, restricted filter or leaky pressure regulator. Low fuel pressure would affect all cylinders rather than an individual cylinder, as would most air leaks. A leaky EGR valve can also have the same effect as an air leak.

Loss of compression means the cylinder loses most of its air/fuel mixture before it can be ignited. The most likely causes here are a leaky (burned) exhaust valve or a blown head gasket. If two adjacent cylinders are misfiring, it's likely the head gasket between them has failed. Also, if an engine is overheating or losing coolant, it's likely the head gasket is the culprit.

Intermittent misfires are the worst kind to diagnose because the misfire comes and goes depending on engine load or operating conditions. They seem to occur for no apparent reason. The engine may only misfire and run rough when cold but then smooth out as it warms up. Or, it may start and idle fine but then misfire or hesitate when it comes under load. Also, it may run fine most of the time but suddenly misfire or cut out for no apparent reason. Intermittent misfires can be a real challenge to diagnose, so let's start with a steady misfire in one cylinder before moving on to intermittent misfires.

Hope this help.

Posted on Mar 25, 2010

  • 6927 Answers

SOURCE: my jimmy makes rattles in the engine is is the

No it is not,have the belts,and pulleys checked,and see if there arte any codes,spark plugs burned to a wider gap,could cause the engine to ping,make sure you are using specified oil,5 w 30

Posted on Apr 01, 2010

  • 1608 Answers

SOURCE: My 92 6.5 liter sierra has all of the suden

You probably have an injection pump going.You need to get it checked out.You could have it rebuilt or replaced.Hope this helps.Good luck.

Posted on Dec 08, 2010

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I have a 2009 Chevy Silverado 1500 2wd pickup. The check engine light along with the service stabilitrak and traction control lights also came on. It runs rough at idle or low speed. Where do I start?

Have it check for DTC'S - diagnostic trouble codes . If the check engine light starts flashing , park it . The flashing check engine light is telling you there is a catalytic converter damaging miss fire happening . An they can be damaged very easy .

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2.3 L crank but not starting back fire instead of start.

Hello Steve McDonald'

When a car backfires instead of starting... nobody has swapped all the firing order around... or pulled out the DISTRIBUTOR ((no make or model came through with question)...

(2.3L what? (check out your $$$ on

In my experience POINTS directly at the exhaust system.

Either your catalytic converter or muffler is in the process of completely blocking the air flow (critical to function).

This condition can be as explosive as it sounds.

There is no elegant way to test for it.

Soak up your bolts ABOVE the catalytic converter with
penetrating OIL... and open the system...

If it STARTS you know what has to be replaced before you can run it safely

Hope tis helps...

I'm given to understand MUFFLER SHOPS are excellent at finding this trouble...

(NOT my personal EXPERIENCE (I'm just saying)).

RockAuto Parts Catalog

Oct 31, 2016 | Cars & Trucks

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This issue can be related to a variety of problems. If the check engine light is on I would have the codes scanned for problamatic sensors etc. If no check engine light on, have a look at the throttle plate and bore by removing the air hose from the filter box to the throttle plate and inspecting for gumming up. ( Black/dirty) If so, use a carb cleaner spray and old tooth brush to remove any deposits that may cause base idle to be affected. Another problem could be the IAC ( idle air control ) motor not working properly

Apr 25, 2015 | 2000 Ford Mustang

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Sounds like either the fuel filter or the catalytic converter. You will need to check the back pressure of the exahust and the fuel pressure after it fails. This I say because you did not mention any trouble codes.(check engine light on or flashing)

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1988 Ford F350 460,fuel injected, Wont start,,, Coil only sends spark once per revolution of the rotor

Hello Donn,

UN-fortunately 1988 is WELL before the OBD
(on board diagnostic)... DIAGNOSTIC TROUBLE
Codes (DTC) got standardized...

So DAYS can be wasted looking for commonality...

Rather than assuming your spark, timing, fuel, ECU...
Oxygen Sensors. INJECTORS are all askew...

I would suggest that if you SATURATED YOUR

and opened you EXHAUST ahead of your catalytic
converters... ahead of your mufflers... you engine would run...

Obviously DANGEROUS to operate in that condition... at
least you would know what had to be REPLACED before
you can operate your vehicle SAFELY.

If you decide the job is a bit too much... at least
check out your PURCHASE cost of a replacement
CAT and/or MUFFLER...

Try rockauto,1988,f-350,7.5l+460cid+v8,1126437,exhaust+&+emission

1988 FORD 350 7 5L 460cid V8 Catalytic Converter RockAuto

1988 FORD 350 7 5L 460cid V8 Muffler RockAuto

Mar 16, 2017 | Cars & Trucks

1 Answer

2005 chevy silverado loss of power while down shifting up a hill at 70mph.

It's probably an accurate accessment. This is a Classic case of how one part damages another.

When the engine misfires it clogs the Catalytic converters. Sometimes the Catalytic converter can repair itself through miles of driving with a well tuned engine. But it may be damaged beyond repair and needs to be replaced after the engine is tuned up. Time will tell.

You can not expect the engine to idle smoothly when the sensors for the Catalytic converters are trying to lean out the engine. The Catalytic converters are indicating they are full of unburned fuel and are running way too rich so the engine controls set everything lean. You have poor idle and lack of power because of this.

You need to find out why the engine is misfiring. The better and more costly Scanners have a Diagnostic priority program to suggest the most probable cause of the problem, then the next, and so on. By process of elimination the problem is found. You need this type of scan.

Autozone, Oreilys, and Advance will give a free scan, but they need to use the better Scanners to prioritize your defets.

You may have dirty fuel injectors in addition to spark misfiring issues. But usually the Scan would show individual cylinders that are getting too much fuel. So be aware that once you start making repairs, the now overwhelmed onboard computer can start pinpointing more problems.

You next move is to start checking the parts the scanner says is defective.

Jan 24, 2012 | 2005 Chevrolet Silverado

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Car runs rough and exaust man gets red

You need to have your Catalytic converter checked. This sound like it is stopped up.

Mar 23, 2011 | 2003 Saturn VUE

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Runs rough,smells like not burning all the fuel/misfire

have vehicle scanned for the trouble code some thing is going and the code will give u ur starting point most auto stores will scan for free such as auto zone / advanced auto --if it smells like rotten eggs or like sulfur most likely catalytic converter going

Jan 16, 2010 | 2000 Saturn L-Series

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