koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-06-12 05:02 PM - Post#2199334
I have a 1994 chevy c1500 with a v6 motor and for a while it's been misfiring pretty badly. I have changed plugs, plug wires, distributor cap, rotor, tps, cts, and replace throttle body gasket. I've took it to a mechanic and he could not figure out what was wrong with it. He blocked off egr valve and it still missed. So I decided to take it to a friend's dad and he believed it was either the ignition coil or the whole distributor. Also it only happens when it hits closed loop. 
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-07-12 12:31 PM - Post#2199598
In response to koolaid2012
I would appreciate any help because I have been chasing this problem for a while. I'm to the point where I'm getting ready to sale the truck and I do not want to do that. 
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squidley63
Member
Posts: 509
Loc: NY
Reg: 09-23-04
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03-07-12 01:26 PM - Post#2199618
In response to koolaid2012
have you checked fuel pressure? vacuum gauge on it to see what it's doing when misfiring? compression test?
I would start by making sure that you have fuel, then verify that the engine is in good mechanical condition. Then start looking at electrical problems.
1963 Chevrolet C-10 Fleetside SWB
400 sbc 3 speed manual
95 Chevy Suburban 5.7TBI 4X4 |
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jimbolyo
Forum Newbie
Posts: 15
Reg: 03-02-12
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03-07-12 01:32 PM - Post#2199619
In response to koolaid2012
I would check for a dead cylinder, IE burnt valve, no compression, etc...
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-07-12 01:39 PM - Post#2199624
In response to jimbolyo
The fuel pressure has been checked and it was good.
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drifterdude
Frequent Contributor
Posts: 1282
Reg: 09-04-08
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03-07-12 02:35 PM - Post#2199637
In response to koolaid2012
on the dead cyl also check with valve cover off if the valves are not broke that they are all opening and closing fully. (IE pointing to a dead cam lobe or lifter)
92 K1500:350 bored 30 over,built 700r4,Comp extreme energy cam,double roller timing set,shaved heads,Rancho RS9000XL series shocks with wireless my ride system,35 inch Mickey Thompson Baja Claws,Relocated 4x4 switch to rocker on Dash.
Other mods.. |
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-07-12 05:37 PM - Post#2199717
In response to drifterdude
I unplugged the map sensor and it ran right. Doesn't this cause the system to go rich, doesn't more fuel= easier combustion? Could my coil pack just be breaking down when it warms up and under load?
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 someotherguy
Moderator
Posts: 23378
Age: 43
Loc: Texas
Reg: 08-01-03
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03-07-12 05:46 PM - Post#2199723
In response to koolaid2012
Unplugging the MAP generally will cause a rich condition; this doesn't mean easier combustion - in fact unplugging the MAP should make it go so rich it runs poorly. You probably have a lean condition due to a vacuum leak or low fuel pressure.
Richard
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-07-12 06:05 PM - Post#2199732
In response to someotherguy
It runs good at highway speeds. It's only at low rpm and going up hills. I've changed the throttle body gasket also.
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-07-12 06:16 PM - Post#2199739
In response to koolaid2012
The reason I'm kinda thinking my ignition coil is because I had two or more spark plug wires that had been resting on the block and got burn and began to short to the block. While it was doing this I drove in the rain, in flooded streets.
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355Cheyenne
Senior Member
Posts: 3743
Loc: Northern MN
Reg: 10-27-04
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03-08-12 07:31 AM - Post#2199935
In response to koolaid2012
Well do a proper tune up if you haven't already and get a coil. You can get a nice MSD blaster coil for around $50 that is a direct bolt on. Even if it wasn't the coil IMHO the MSD coil is a nice improvement over stock.
| 98 Silverado k1500 4x4 350 |
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-08-12 08:12 AM - Post#2199954
In response to 355Cheyenne
Ok thank you I'll update as soon as I change the coil
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-13-12 03:21 PM - Post#2202119
In response to koolaid2012
I changed the coil, and no luck.  . Any other ideas. I need help to get my truck running good again
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355Cheyenne
Senior Member
Posts: 3743
Loc: Northern MN
Reg: 10-27-04
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03-13-12 04:13 PM - Post#2202147
In response to koolaid2012
Have you changed rotor and cap and wires? I would look at the motor at night and look for arcing from the wires. After that I would run a compression test on the motor. That and a fuel pressure test.
| 98 Silverado k1500 4x4 350 |
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-13-12 04:40 PM - Post#2202165
In response to 355Cheyenne
I have changed the rotor and cap already. Plug wires were changed less than a month ago. The plugs were changed about 6 months ago.
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-13-12 11:27 PM - Post#2202320
In response to koolaid2012
Any thoughts on a bad 02 because the exhaust smells super rich
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355Cheyenne
Senior Member
Posts: 3743
Loc: Northern MN
Reg: 10-27-04
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03-14-12 04:38 AM - Post#2202347
In response to koolaid2012
Any thoughts on a bad 02 because the exhaust smells super rich
Could be but more likely there is a bad coolant temp sensor than o2 sensor. Also new parts don't mean good parts, was it skipping before the new parts?
| 98 Silverado k1500 4x4 350 |
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 jham0077
"2nd Year" Silver Supporting Member
Posts: 320
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Loc: Greenville, Il.
Reg: 11-04-11
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03-14-12 08:05 AM - Post#2202410
In response to koolaid2012
So you've changed wires since they've been burned and wet? You can ohm your CTS. The ranges are in the FAQs. 355 is right and this is sad to say but, new parts don't mean good parts.
Keep throwing money at it, it'll get better...
95 Tahoe 5.7 w/5 spd
Gone but not forgotten,
87 LWB 4x4 5.0 w/3 spd granny,
84 SWB 4x4 5.7 w/3 spd granny,
93 Full Size Blazer 5.7 w/5 spd,
97 Step-side Vortec w/5 spd.
I like shifting gears. |
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-14-12 09:20 AM - Post#2202433
In response to jham0077
I have changed the wires. I'll get on testing the cts. I really appreciate all the help.
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someotherguy
Moderator
Posts: 23378
Age: 43
Loc: Texas
Reg: 08-01-03
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03-14-12 09:25 AM - Post#2202435
In response to koolaid2012
The O2 sensor doesn't have near the power over the fuel mixture that your CTS does. If the CTS is suspect in any way - you can't remember the last time it's been changed, or it looks cruddy/greenish at all, just replace it. They're not expensive, even for a good brand, and they do need occasional replacement to stay in top working order. I've been pushing the school of thought that it should be a semi-regular maintenance item (like tune-up parts) because I've seen way too many rich mixture problems caused by an old CTS.
Richard
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Timothys Chevy
Valued Contributor
Posts: 3651
Loc: Fredericton, New Brunswic...
Reg: 09-24-03
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03-14-12 04:56 PM - Post#2202627
In response to someotherguy
A compression tester is cheap, found at most auto parts stores, and should be the first thing that is checked before throwing parts at a motor.
Have you got results from the test?
Tailpipe smoke blue or black?
~~Timothy~~
1984 Chevy Citation 2.5
2009 Pontiac Vibe AWD
1993 Buick Park Avenue
2001 Pontiac Sunfire GTX
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-14-12 07:31 PM - Post#2202712
In response to Timothys Chevy
I don't see any smoke, but I do have my exhaust dumped before the back bumper under the bed. You can smell the richness even when getting out of the truck.
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350whip
Contributor
Posts: 116
Reg: 02-24-12
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03-15-12 08:08 AM - Post#2202915
In response to koolaid2012
yep 20 bucks for a cts try that then move on. unplug your bypass wire set it to TDC and pug it back in. i had the exact same problem 3 weeks ago code 22 and 24 i think after i give it gas she would die unless i let off really lightly. all i did was reset my timing to TDC#1 and pluged that wire back in it fixed it. it started as a coil/ICM problem but after i got it back together it worked but the same way your truck seems to be working. just a thought, easy and free to try.
RickT.
- 1989 chevy k1500
- regular cab, shortbox
- chevy SB350tbi (little piggie!)
- L60E Automatic 4speed
- corvette servo
- 30"BFG AT's
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N8sToolz
Very Senior Member
Posts: 2314
Age: 27
Loc: N 42° 53.290' W71° 34.1...
Reg: 10-23-03
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03-15-12 09:25 PM - Post#2203233
In response to 350whip
Sounds like we should go back to basics with this.
Misfire is a cylinder not contributing the same power as the others, What is missing, fuel spark and ignition. Fuel, this is a wet intake setup so most likely not the case, but is something contaminating the mixture like coolant?. Compression. is a valve not opening as it should, exhaust valve not closing as it should? Leaking head gasket.
Ignition, most likely bad plugs, wires, cap or rotor ( A coil feeds all cylinders so no likely to cause a misfire.) A plug can carbon track outside of the porcelin, a wire can cross spark to another cylinder, carbon tracking inside of a cap.
To test; At night hose down the engine while its running, if its plugs carbon tracking (misfire from a used car dealer showed up for this, they put 3 sets of plug wires on an impala for this and failed to notice a plug with carbon tracking) or bad wires it will show up now. Verify a correct firing order 18436572 (am I right? Been working on so many cars not sure anymore). A cap may be crossing internally (Vortec style distributors are famous for this). Plugs may be bad, or even a gap that is too small. (Had a no start after a tune up towed in from another garage for this).
Sensors rarely cause a misfire, but may make a misfire more apparent. You can test a Map sensor easy with a voltmeter and a needle. Stick the needle along the wire on the backside of a connector its called backprobing. One wire will read 5v, the middle will read 4.7v at key on engine off, and the last wire will be close to 0v.
Maybe its time to check compression, All cylinders should be within 20% regardless of pressure. (doesn't matter we are looking for a misfire) OR you can do a cylinder leakdown test it can show you more information. It requires more work and a leakdown tester tool.
1982 Chevy K20 Converted from C20.
355/700R4
2002 Yamaha XVS1100CL VStar
2002 S10 2WD |
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-26-12 06:36 PM - Post#2207837
In response to N8sToolz
Sorry to bring this back to the top, but I retested the fuel pressure and at idle it was 12 p.S.i I forgot to check the pressure under load. What did catch my eye was when I turned ignition on engine off the pressure went to 12 then fell. Could that mean a bad fuel pressure regulator? I did not change it when I rebuilt throttle body.
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 CowboyTrukr
"2nd Year" Silver Supporting Member
Posts: 698
Loc: Salt Lake City
Reg: 06-20-09
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03-26-12 07:02 PM - Post#2207858
In response to koolaid2012
Not necessarily. The pressure will bleed down when you shut it off.
'94 Silverado K2500 4X4 5.7 5spd Xcab LB
RV cam, Pace Setter Headers, TBI spacer, Flow Tech air cleaner adapter, Hypertech street chip
"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke |
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-26-12 07:37 PM - Post#2207880
In response to CowboyTrukr
It bled down while the key was still forward. As soon as it hit 12 p.s.i. it bled down to zero. Before I turned the ignition off
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someotherguy
Moderator
Posts: 23378
Age: 43
Loc: Texas
Reg: 08-01-03
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03-26-12 08:32 PM - Post#2207914
In response to koolaid2012
The pump only primes for a couple seconds then shuts off, if you don't start the engine. The TBI system generally bleeds pressure off immediately but there have been mentions of a few of them that are designed not to; all the ones I have seen do.
Richard
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-27-12 11:52 AM - Post#2208097
In response to someotherguy
So what are signs of a bad fuel pressure regulator?
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koolaid2012
Forum Newbie
Posts: 75
Reg: 05-05-11
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03-27-12 06:06 PM - Post#2208234
In response to koolaid2012
I found someone who had a similar problem on another website.
http://www.gminsidenews.com/forums/f53/hesitation -...
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