Need Help!

Hey guys and gals,

I have been looking at post on here for some time but this is my first. Ok on to my problem I am stumped on. I have a 2001 Jimmy 4.3L with 150k miles. It had a DTC 1345 (I think it was) where crank and cam coorelation was off. I re-timed the engine and cleared that code. Now when I hook up the air intake and the MAF it throws a code of p0306 cylinder 6 misfire. If I clear that code and leave the air intake off and MAF not hooked up it will not throw that code just the 0102 maf low circuit. Is there anyway to check the maf? Any help would be greatly appreciated! :banghead:

Hey guys and gals,

I have been looking at post on here for some time but this is my first. Ok on to my problem I am stumped on. I have a 2001 Jimmy 4.3L with 150k miles. It had a DTC 1345 (I think it was) where crank and cam coorelation was off. I re-timed the engine and cleared that code. Now when I hook up the air intake and the MAF it throws a code of p0306 cylinder 6 misfire. If I clear that code and leave the air intake off and MAF not hooked up it will not throw that code just the 0102 maf low circuit. Is there anyway to check the maf? Any help would be greatly appreciated! :banghead:

WELL YOU HAVE A MISS ON NO 6 CYLINDER.

You can not check out stuff running engine with stuff not hooked up.

Hook everything up and clear code and the run and then check for any codes?

If the only code coming back is P0306 then work on miss on no 6 cylinder.

How is tune up and fuel pressure and dist cap plugs and wires and spark?
How did you retime?
Have you checked camshaft retard seting after timing/seting dist?

The crank + cam sensors are used by the PCU for electronic signal ignition timing, the physical crank + cam timing should be good.

1) Do a visual inspection on sensors and wires.
2) Clean connections with CRC electronic cleaner and use dielectric grease for protection.
3) Goggle ''Youtube auto maf testing'' , also clean MAF connection.

WELL YOU HAVE A MISS ON NO 6 CYLINDER.

You can not check out stuff running engine with stuff not hooked up.

Hook everything up and clear code and the run and then check for any codes?

If the only code coming back is P0306 then work on miss on no 6 cylinder.

How is tune up and fuel pressure and dist cap plugs and wires and spark?
How did you retime?
Have you checked camshaft retard seting after timing/seting dist?

I did the dist cap, plugs, and wires. Waiting on the adapter to come in to test fuel pressure. I just realigned the timing marks on the crankshaft pulley and the dist pointing in the right direction with #1 at TDC. Not sure about the camshft retard, how could I test this and what should it be? thanks

I did the dist cap, plugs, and wires. Waiting on the adapter to come in to test fuel pressure. I just realigned the timing marks on the crankshaft pulley and the dist pointing in the right direction with #1 at TDC. Not sure about the camshft retard, how could I test this and what should it be? thanks

You need a scanner to check
CAMSHAFT RETARD.
IT SHOULD BE AT 0 DEGREES OR AS CLOSE TO - OR + 1-2 DEGREES AS YOU CAN GET IT.

Just an update for anyone interested. I ran a compression test and cylinder 6 (where misfire is) is about 90 PSI. The other cylinders are 170 to 190 PSI. So it looks like piston rings or valves (not sure exactly which one yet). Thanks for help and info

If your lucky, it could be a bad valve spring on cylinder 6.

One way to find out is with all the plugs outs squirt some motor oil in #6 & see if the compression comes up. If it does then good chance you have a bad or stuck ring. If it is stuck you might try pouring some marvel mystery oil in the cylinder & letting it sit. As stated maybe just a bad valve spring (weak), You can shim them or replace without pulling the head.

One way to find out is with all the plugs outs squirt some motor oil in #6 & see if the compression comes up. If it does then good chance you have a bad or stuck ring. If it is stuck you might try pouring some marvel mystery oil in the cylinder & letting it sit. As stated maybe just a bad valve spring (weak), You can shim them or replace without pulling the head.


Hey thanks for response, I did the compression test after putting oil in the cylinder and the compression came up so I am thinking bad rings! Just out of curiousity though how could I shim or or replace the valves spring without pulling the head?

Hey thanks for response, I did the compression test after putting oil in the cylinder and the compression came up so I am thinking bad rings! Just out of curiousity though how could I shim or or replace the valves spring without pulling the head?

Before you condem or blame low compression on no 6 cylinder to bad rings keep in mind that a long term miss on can wash down rings with raw fuel and cause low compression.

Make sure the secandary ign system is firing no 6 cylinder and no 6 cylinder plug and wires and cap and rotor and dist and injector is good shape.
Then run engine and see if compression comes back up on that cylinder.
Also camshaft retard and maf sensor or 02 sensor and or low fuel pressure can give you a miss.

Before you condem or blame low compression on no 6 cylinder to bad rings keep in mind that a long term miss on can wash down rings with raw fuel and cause low compression.

Make sure the secandary ign system is firing no 6 cylinder and no 6 cylinder plug and wires and cap and rotor and dist and injector is good shape.
Then run engine and see if compression comes back up on that cylinder.
Also camshaft retard and maf sensor or 02 sensor and or low fuel pressure can give you a miss.

A bad O2 sensor can cause a miss? I have checked the other stuff.

A bad O2 sensor can cause a miss? I have checked the other stuff.

Yes they can.

What is camshaft retard reading at?
What is fuel pressure on the road?

Any codes coming back after code clear and repair?

Yes they can.

What is camshaft retard reading at?
What is fuel pressure on the road?

Any codes coming back after code clear and repair?

Just getting the 306 misfire code. retard was + or -1 dont remeber which and dont remember what fuel pressure was. Sorry I know not much help

Just getting the 306 misfire code. retard was + or -1 dont remeber which and dont remember what fuel pressure was. Sorry I know not much help

If only code 306 You need to work on that.
If camshaft retard was as close as - or +_ one you are good there.
A cylinder miss can be cause by many things.
Confirm and Get good spark and spark plug to the missing cylinder.
Check compression again .
If good spark and spark plug on that cylinder and compression does not come back up find out why low compression on that cylinder.
Always make sure fuel pressure is up to par/specs at all times.
Watch spark plug for oil or gas fowl on end?
Is your spark staying plug wet or dry on end?
A fuel injector flooding or bad or bad wiring or can give a miss.
Also bad 02 sensor or 02 sensor wiring plug in can knock out a injector pulse to a cylinder.
Check and double check all these things.
Only threw proper testing will you find the problem.
Good luck.

Compressed air is used to hold the valves up on cylinder #6 while a bad, or broken valve spring is replaced.