Jeep Grand Cherokee check engine light

I think I would be first looking at the distributor cap under a strong light for a small white spider web looking mark around the post for that cylinder.

I next would take an ohm meter and check the plug wire. I would compare it to the ohms for #2 or #6 depending on the engine. I believe one of those wires are the same length as #1, so they should read the 'same'. It is measured in "X" ohms per foot, so a 2' wire measures double the "X" of a 1' wire.

I next would spend 2 or 3 bucks and change the damn spark plug, then pull the battery cables to reset the computer. When I did that, I would pull another plug to see if #1 looks fouled or really clean in comparison. (electric misfire vs coolant/compression leak)

'Then' if all else failed I would get a ten dollar compression tester and check the compression to compare all to #1.

Then I might change the head gasket....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

I would change dealers anyone who said that is about as much of a mechanic as a rock, it takes a lot more than a misfire code to determine you need a new head. Coasty

Mike Romain did pass the time by typing:

Also if that's a coil on plug setup, 1 and 3 fire at the same time. A leaky injector on #1 (or a fowled plug) can cause a misfire.

I'd take a look at the plug first.

Is it a I-6 or the V-8?

The '01s have no distributor cap or wires. They do have coil packs (I-6) or coil on wire (V-8)

On an I-6 a coil problem would show up on cylinders 1 & 6 as that same coil pack fires both.

A close examination of the sparkplug may reveal if a plug is oil fouled, contaminated by coolant, or damaged. If the misfire occurs only occasionally (but enough to set off the code) it may appear 'normal'

If the plugs are more than a year old go ahead and change them all, if less you might try just one plug in cylinder #1

I personally prefer the Bosch Platinum plugs but if you have a preference for copper then I would suggest Bosch Supers.

In article , Firebird wrote: #I have a 2001 Jeep Grand Cherokee Laredo. My check engine light was on and #the code being displayed is P0301, which is misfire in cylinder 1. I finally #brought it to the Jeep dealer, they could not find any issues with the #plugs, wires etc.. What engine do you have? The i6, the v8, or the High Output v8?

/herb

I would change dealers anyone who said that is about as much of a mechanic as a rock, it takes a lot more than a misfire code to determine you need a new head.

I brought it to the dealer, there was no problem with a plug or wire. The engine runs smoothly, there is no missing.

It is a I-6. I had it at the dealer, they found no problem with the plugs. The engine runs smoothly, it does not misfire or shake or anything like that, the code just came on...One thing however, I had been using Premium unleaded gas for about 3 weeks. Thats the only thing that was different.

In article , Firebird wrote: #The I-6.

As someone said earlier, the I-6 fires two chambers at the same time so it could be either 1 or 6.

It could have been a slightly loose wire, or the the coil pack might be headded south.

How old are the spark plugs? While they are probably still good, it can't hurt to re-gap or replace them if the maint schedule says to do so.

/herb

Sorry.... from your original post I was assuming this was an ongoing not a one time problem.

Well..... That is probably not the problem directly and there is always the possibility of bad gas but may I ask why you use premium?

Back-in-the-day the oil companies actively promoted Premium gasoline as having 'more power'.

The real story is that high compression gasoline engines begin to act similarly to Bill Hughes beloved diesels. The way they compensated for this tendency for detonation was to make the gasoline burn slower.... yes I say BURN SLOWER..... the higher the compression the higher the needed octane to prevent engine damage.

It is more correct to say that Premium gasoline has 'less power' than 'more power' in a standard engine.

Why do we 30 years after the last 'real' engines cling to this myth? If you are my age or older you received daily propaganda about Sunoco 260, Union

76's 105 Racing gasoline, and my personal favorite Humble (Esso-Exon, Exxon) 'Put a tiger in your tank'. For a while unscrupulous companies only put adequate detergents, etc in their premium grades but that is rarely the case now..

Hopefully you get this in time... Before you dip into your pocket. CHANGE THE GAS CAP....

Firebird wrote:

That usually throws a P0456 code

Hi....

I don't have to do any repairs. The Jeep runs fine. WHat is the issue with the gas cap... Can it cause this problem...I will replace it tomorrow.