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Misfire P0302 specific

Tiny
PEAR69
  • MECHANIC
  • CHEVROLET TAHOE
I have a 98 Chevy Tahoe 180,000 miles 5.7liter gas automatic trans. I have a miss in cylinder 2-- code P0302-- This all started when I started to get a P0300 code, a general engine misfire. I discovered that the distributor gear was worn out so I replaced the distributor with a new one. It ran great for a while then it started missing again. Now it's a P0302 code cylinder 2 misfire. I've changed the following the distributor cap and rotor, plugs and wires twice, ignition coil, ignition module, pcv valve, Iac valve, Egr valve, the entire upper intake manifold, switched out the injectors for the new type, crank position sensor, cam position sensor, fuel pressure sensor, fuel filter, battery, bigger size battery cable. I checked the valve lash ok. Checked compression 190 psi all around. The miss is specific to cylinder 2. I changed the lower intake manifold gasket a little while ago, with no problem, because it was leaking. I am not loosing or using any antifreeze. Spark plugs look good a light brown tint and the gap is correct. I had a crankshaft position sensor relearn and a cam shaft position procedure done at the dealer. The cam is at -3 and the cps is relearned. Please help
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Friday, November 2nd, 2007 AT 1:35 AM

21 Replies

Tiny
2CARPRO JACK
  • MECHANIC
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Will it set the code idling or does it have to be driving? What kind of injectors and tune up parts did you use?
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Friday, November 2nd, 2007 AT 7:50 AM
Tiny
PEAR69
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It set the code when I'm driving. However, once the code is set, and I get the rpms up over 2500 -which equals about 80mph in drive D or 60 mph in drive 3- the engine light stops flashing and the miss seems to go away. And-- once the code is set, and the engine is idleing- after it is at its' operating temperature, I can feel the miss more than when I first start up when Its' cold. But I can still feel the miss even when its' cold. The injectors I used were purchased on ebay. They are a conversion from SCPI (which is from the factory) to MFI. These elliminate the poppit problem on the factory units or so I think? You can look them up on ebay there called vortec spider injectors ebay Item no.290095268929.
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Friday, November 2nd, 2007 AT 11:31 AM
Tiny
2CARPRO JACK
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What you describe sounds liike a bad injector. Im not sure that I would have used those instead of the factory replacements
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Friday, November 2nd, 2007 AT 12:51 PM
Tiny
PEAR69
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Today I tested the no. 2 injector with a noid light and it pulsed perfect but I still have the mis. I then checked the spark with a Frankenstein spark tester and I noticed the spark was intermittent. So I checked another spark plug and got the same results.
All the parts I used are duralast except the distributor, cam and crank sensor which are a/c delco.
The plugs were bosch but I switched them out for autolite platinum with the regular tip.
I changed the plugs, plug wires, dist. Cap and rotor twice. Put in a new: distributor with cam position sensor. Coil. Ignition module. Is there anything else?
Before I take the upper intake manifold again I want to be sure I'm not missing anything. Thanks
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Saturday, November 3rd, 2007 AT 10:55 PM
Tiny
2CARPRO JACK
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The way you describe it, it sounds just like a bad injector. No funny noises from the engine? Trying to cover all bases. Is the spark more consistent now that you have changed all those parts again? BTW good call getting rid of the Bosch plugs, worst ever. Also try a leak down test to rule out a leaking intake valve
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Sunday, November 4th, 2007 AT 6:55 AM
Tiny
PEAR69
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If you call that laughing sound of the gremblin inside my engine that's screw'n around with cyl. 2 funny, then yes I guess there is a funny noise inside my engine. Just kidding. No funny noise.

I did not test the spark with the old set of wires and stuff but I did save them so I'll put them on and let you know. I just picked up the frankenstine spark tester---it was cheap and cool

I'll do the dreaded leak down test too.
I know what it means if the test is bad. Blown head gasket. Bad valve. Either way. Heads come off
Thanks for your patience. Please everyone cross your fingers.
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Sunday, November 4th, 2007 AT 11:22 PM
Tiny
PEAR69
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I did the leakdown test and there was no air escaping anywhere. The valves are sealed and there are no bubbles in the coolant and no hissing in the oil pan. So I took the upper intake manifold off again. I switched no.2 injector with no.3 injector. I cleared the code, drove around, and the code came back p0302 mis in cylinder 2. I talked to a friend at the local dealer and he got me a new set of a/c delco wires--a/c delco cap and rotor real cheap, he said this may be the problem-- however it wasn't, same thing.
I pulled off no. 2 wire and hooked up an old spark plug to it. The spark remained constant so I hooked the wire to my tester and found I didn't have a good ground before, sorry.
This has really got me stumped. Is it possible that the computer is screwed up?
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Tuesday, November 6th, 2007 AT 9:07 PM
Tiny
2CARPRO JACK
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Ive never heard of the PCM reading the wrong cyl on a misfire. Maybe have your friend talk to one of the techs and have the PCM flashed? That is a good one. Are the injectors in their correct holes in the intake? Wondering if it might have a bad lower intake gasket at cyl 2
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Wednesday, November 7th, 2007 AT 7:26 AM
Tiny
PEAR69
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Hello again I had the computer flashed nothing
yes the injectors are in the right spots
I changed the intake gasket a little over 2 years ago no leaks
however I did this I draped a rag a little out from the exaust and watched it blow in the breeze and guess what. The rag sucked in every time the motor misses. I think it's a sticking exaust valve.
What do you think?
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Saturday, November 10th, 2007 AT 12:22 PM
Tiny
2CARPRO JACK
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Could very well be, they take the brunt of the abuse
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Saturday, November 10th, 2007 AT 1:38 PM
Tiny
PEAR69
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Well, just wanted to let you know I got done changing my heads- and sure enough - the exaust valve was sticking. Thanks for your help.

BTW Gm performance vortec heads are cheap and with a little -back yard home garadge porting- they run better than the 906 head! In case anyone was wondering.
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Saturday, November 24th, 2007 AT 6:13 PM
Tiny
2CARPRO JACK
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Installed a set of ZZ4 heads on a CPI engine, made it run much better, way crisper
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Sunday, November 25th, 2007 AT 7:23 AM
Tiny
GREEN1
  • MEMBER
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I have a tahoe that acts up to I did all the wire change and cap and rotor ect to I kept asking around one guy told me thier is a ball bearing in the injector that gets stuck often and to use a injector cleaner two or three bottol the bran is red line from checkers the other brans dont work as well it work for me. Just another info for you late
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Tuesday, September 15th, 2009 AT 10:12 PM
Tiny
PEAR69
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Thanks for the info, but I changed out the injectors for the type without the ball bearing inside of them. The best type of injector cleaner for these engines is Tectron made by Cheveron. IMO
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Friday, September 18th, 2009 AT 12:40 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Hey,

Did you ever get the problem fixed?

Cheers, Ken
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Wednesday, May 31st, 2017 AT 4:11 PM
Tiny
HORTA
  • MEMBER
  • 2 POSTS
  • 1998 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 165,000 MILES
Engine Performance problem
1998 Chevy Tahoe V8 Four Wheel Drive Automatic 165000 miles

I have a P0302 misfire #2 cyclinder.
Replaced plugs, wires, cap. Same code. Fuel injectorOK
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Wednesday, May 31st, 2017 AT 4:12 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
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Hi horta, Welcome to 2carpros and TY for the donation.

Check compression on #2, wet and dry test. And comeback with the result.
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Wednesday, May 31st, 2017 AT 4:12 PM (Merged)
Tiny
HORTA
  • MEMBER
  • 2 POSTS
Thanks for coming back.
150 lbs compression
All cylinders compression seems OK.
Does this engine have some common failure problem regarding cylinder #2?
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Wednesday, May 31st, 2017 AT 4:12 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
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Not that am aware of-additional causes could be:

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
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Wednesday, May 31st, 2017 AT 4:12 PM (Merged)
Tiny
DEENELI
  • MEMBER
  • 6 POSTS
  • 1996 CHEVROLET TAHOE
1996 Chevy Tahoe

what cause an p0302 and if the sprak plug and wires or good what else would be.
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Wednesday, May 31st, 2017 AT 4:12 PM (Merged)

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