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Odd 1993 4.3L c1500 chevy problem!
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rtraider_88
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Jan 24, 2009, 8:11 AM
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Odd 1993 4.3L c1500 chevy problem!
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I have a 1993 Chevy C1500 TBI 4.3L V6 VIN Z pickup truck. The truck never starts in the morning hours after sitting all night however once the truck is cranked it will start up just fine once it has been warmed from the first start of the morning. On first crank of the morning the truck cranks only if I press down on the gas pedal all the way or take the air cleaner box off! Then it follows with a nasty idle once started and just dumps fuel! The truck has no power what so ever going down the road and a very poor fuel economy along with a bad hesitation in throttle response. The truck also smells like straight gasoline! I have changed the fuel pump; filter inside the tank and under the driver side door. I have also changed the MAP sensor, IAC, PCV valve, {ECM (Engine Control Management) Computer}, Spark plugs, Wires, Cap, Rotor, Spark control module, Coil, Coolant sensor, EGR, ignition module, Fuel Pressure regulator, Injectors, and have replaced all gaskets on the throttle body. The timing chain has also been replaced. Timing is good it was checked with a timing light.. And no vacuum leaks were found! I looked as the distributer and the magnets looked O.K. nothing looked out of place. No check engine (MLP) lamp on…A compression was also done reading were O.K. I’m wandering if one of the parts I put on is no good!
Any suggestions would be helpful thank you for your time in advance .I’m about to go crazy over this one!!
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Loren Champlain Sr
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Jan 24, 2009, 11:27 AM
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Re: Odd 1993 4.3L c1500 chevy problem!
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Wow; You've hit on all of the suggestions I was going to give. Have you checked for manifold vacuum to the MAP sensor and to the pressure regulator? Loss of vacuum to either, or both, will cause a full rich condition. What seems strange, is, this does it cold only? When you shut down the engine when warm, watch for 'dribbles' of fuel from the injectors. I know that you have replaced them, but the engine flooding has to be coming from somewhere.
Once the engine is warm, and running good, what kind of intake manifold vacuum are you seeing at idle? Have you changed the oil and filter since the repairs? Fuel contaminated oil (vapors) will be picked up by the PCV valve and cause a domino effect. Try pulling the PCV valve out of the valve cover and see if it makes any difference in idle quality (leave the vacuum hose connected to the valve while doing this). At what point was the timing chain replaced? Did this start happening afterwards? (I'm thinking cam timing, which would affect engine vacuum, which would affect MAP and regulator). When you replaced the ECM, did you replace the PROM? Lots of questions; Try and give us as many answers as you can.
Loren
SW Washington
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rtraider_88
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Jan 24, 2009, 11:51 AM
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Re: Odd 1993 4.3L c1500 chevy problem!
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Hello Loren I have changed the MAP sensor also i forgot to mention that. I have changed the oil and the oil filter. I changed the ECM yesterday and it didnt seem to make any difference what so ever! :( The only thing that i havent done is a fuel pressure test.. i cant seem to find a fuel pressure gauge to borrow!! Even though the fuel pump is new and the TBI is new i think there is still a problem there.. But i dont know i have been wrong so far.. ha This one has just stumped me!! I have checked for vaccum leaks with brake cleaner.. I sprayed everything down... never found anything! The plugs seem to keep fouling out on me... There is no drips coming for the injectors the both spray at a even mist! O2 sensors are also new. I have run out of things to check...??? One thing i have noticed once started at idle when i press on the gas my RPM's go up and stay up for a while.. there is a delay .. its almost as if the tps or IAC isnt doing its job.. but i dont know i have changed them... I am at a stand still I finally broke down and took it to a shop awhile back they found nothing! But im sure that its something simple but hard to find....
Thank you for helping me... any suggestions would be great mabey i have missed something..
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Loren Champlain Sr
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Jan 24, 2009, 12:00 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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We really need a vacuum reading. At this point, a vacuum leak would probably help by giving it more air. Really don't think you are dealing with a lack of fuel pressure. The fuel pressure regulator is controlled by vacuum. If it 'sees' a lack of vacuum, it will increase fuel pressure. If the MAP sensor 'sees' a drop in manifold vacuum, it 'thinks' you are accelerating, and demands more fuel. So...manifold vacuum is very important. You also mentioned that you replaced the CTS. There are two sensors. One for the temp. guage and one for the ECM. Be sure that you replaced the correct one. Do you have a scanner available so you can see what the ECM is seeing? Reread my previous questions and answer as many as you can. We'll get to the bottom of this.
Loren
SW Washington
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Tom Greenleaf
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Jan 24, 2009, 12:17 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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rtraider_88 :
Like Loren said you've covered most of the suggestions already but ONE still lurks that Loren mentioned. Intake manifold vacuum reading.
To refresh on what I'd expect to see in using vacuum as a tool for daignosis. Find "actual" manifold vacuum and take reading with a "T" in a line keeping device enabled that it went to. At a normal idle you may see about 18Hg steady when all is well.
That reading should be the same at about 2,000 RPMs as well when held. Will spike higher Hg with a quick snap of throttle momentarily.
If lower at high RPM (held steady for the test) then exhaust restrictions are usually the issue. Anything that could cause a restriction but we usually think of converter(s) but could be a pipe problem - even muffler??
If low it might be telling ECM there's a hard load on engine and dump more fuel confusing it. Worth the check and easy to rule out.
With all this fuel smell and so forth along the way things already done may have been hurt like converter, o2 sensors, plugs don't behave well and again as Loren said check on the oil or just change it out as it could be thinning with gas messing things up as well.
I'm surprised a check engine light isn't on. Does the bulb even work? Should light with KOEO - pretty sure,
T
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rtraider_88
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Jan 24, 2009, 1:24 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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Hello again and thanks for working with me on this. I haven’t checked for manifold vacuum I don’t have any way of doing it. I will have to find someone how does. When the engine is shut down warm there is no drips at all. As for the rest now I’m scared to even crank the truck up.. I had it in the shop just a few days ago they changed the timing chain and the oil.. Today I just to happen to check my oil level and it was about 2 inches above the FULL LINE!!! I surprised I didn’t mess something up yesterday when I changed out the ECM because I run it pretty hard checking for a difference… I don’t know if they overfilled that much or if gas has drained down in the crank case… And no these problems were going on before the timing chain was replaced.. I didn’t replace the Prom
Tom my check engine light works…J that’s the only thing lol
Thanks again
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Tom Greenleaf
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Jan 24, 2009, 1:40 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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Funny - Loren hit "reply" before me on the last couple posts so I hadn't seen his. This gadget is handy as all get out to make vacuum for testing items AND to check vacuum "in-line" and comes with fittings. Should be available at most parts outlets.
They aren't much money and you'll use for assorted things for automotive vacuum testing,
T
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rtraider_88
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Jan 24, 2009, 1:46 PM
Post #8 of 22
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Re: Odd 1993 4.3L c1500 chevy problem!
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You know what now that yall mentioned something about back pressure i had put a new muffler on about 3 or 4 years ago and my problem starts somewhere in there! But i remember that i used to have alot of carbon coming from the pipe! i dont know that tells you anything or not?
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Loren Champlain Sr
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Jan 24, 2009, 1:52 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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 I stole this from one of Tom's previous posts. If you have an ohmmeter, you can check resistance values of the CTS, just to make sure it is reading correctly. The 'carbon' you mention, if it is black, which I'm assuming it is, is from running rich. Probably a lot of moisture, as well, if the cat is working. (The cat turns HCs and CO into CO2.
Loren
SW Washington
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Tom Greenleaf
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Jan 24, 2009, 1:53 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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Even new exhaust does count. This one is totally AFTER the sensors so my guess is unless it's plugged up wouldn't cause this issue but would show up as a restriction if vacuum tested. Some can rust or collect junk in the baffles but you usualy hear that as sounding like it's full of sand or small rocks with a rev or just tapping on them,
T
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rtraider_88
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Jan 24, 2009, 1:54 PM
Post #11 of 22
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Re: Odd 1993 4.3L c1500 chevy problem!
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Sorry what is a CTS?
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Tom Greenleaf
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Jan 24, 2009, 1:56 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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I like that Loren ----- I steal it first and you steal it again! LOL.
CTS is "Coolant Temp Sensor" in this application. It should have a yellow wire and a black wire - just the two at the thermostat,
T
(This post was edited by Tom Greenleaf on Jan 24, 2009, 1:57 PM)
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rtraider_88
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Jan 24, 2009, 1:57 PM
Post #13 of 22
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Re: Odd 1993 4.3L c1500 chevy problem!
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TOM.... when in going down the road or something i can hear something under the truck when i open my door but i dont what it is ... it kind of sounds like something loose...rattel noise
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rtraider_88
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Jan 24, 2009, 1:58 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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Oh ok i changed the one on the top ... I didnt changed the one on the side of the block
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Tom Greenleaf
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Jan 24, 2009, 1:59 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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This is going so fast we're crossing swords here! Look above I added what a CTS is.
Rattle - Take a rubber hammer and tap on exhaust and other things with everything off and it may show itself,
T
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Tom Greenleaf
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Jan 24, 2009, 2:00 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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Ok: Side one is probably for the gauge not the puter control. Try unplugging it and see that the gauge doesn't work,
T
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rtraider_88
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Jan 24, 2009, 2:05 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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What about my oil level being so high what do you think that is from? So do you seem to think that all my problem is a plugged pipe or muffler thats makes sense..! I also know when i mash on my brake peddle my rpms change slightly...
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Loren Champlain Sr
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Jan 24, 2009, 2:13 PM
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Re: Odd 1993 4.3L c1500 chevy problem!
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Pull the dipstick and take a sniff. If it smells like gas.... The RPMs changing when the brakes applied goes hand in hand with low manifold vacuum, or you've got a leaky power brake booster. You really need to get a vacuum guage and take some readings.
Loren
SW Washington
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rtraider_88
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Jan 27, 2009, 4:31 AM
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Re: Odd 1993 4.3L c1500 chevy problem!
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……. UPDATE
Hello sorry it took me so long to respond I done a vacuum test on a constant vacuum and it read a steady 20! As for the Compression test results
CLY 1 180 PSI
CLY2 160 PSI
CLY3 170PSI
CLY4 180PSI
CLY5 165PSI
CLY6 160PSI
I will check the fuel pressure today and let you know..
Thanks!!
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Tom Greenleaf
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Jan 27, 2009, 5:43 AM
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Re: Odd 1993 4.3L c1500 chevy problem!
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Looking back to top post - this has no power and dumps fuel. I'm still looking for a vacuum test with two results and at what RPM taken. One at idle and another with a steady 2,000+ RPM. I'm looking for an exhaust restriction not just a plain #.
Vac of 20Hg is a tad high - suggests gauge error or wrong port. Not even concerned with a couple off - just uniform readings for now.
Compression results indicate that it's not the upfront issue at least to me so far,
T
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rtraider_88
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Jan 31, 2009, 4:47 AM
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Re: Odd 1993 4.3L c1500 chevy problem!
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I done a fuel pressure test and the tested showed a steady 15... i read where the Min should be 9 so im good there..... I have no idea about this problem and im getting to where i dont have time to look ...... there just so much to do..... Im thinking about ripping that motor out and just replacing it with a v8 350 or a 305... because i think its something in the motor.... As for the vacuum test that was the only place to test it!! my truck only have about 3 vacuum lines... one going to that black coal cleaing box one going to MAP and the other one going to the egr solenoid i think.... anyway mine have the electrical linear EGR valve... As for the compression there was a 20 PSI drop for cly 2 to 4 and also a 20PSI drop from 4 to 6 .... 135 seemed to look ok.... Thanks for your time let me know what you think... mabey its a distributor
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Tom Greenleaf
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Jan 31, 2009, 5:38 AM
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Re: Odd 1993 4.3L c1500 chevy problem!
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VACUUM TEST! I'm looking for an exhaust restriction and one test at one speed isn't helping. Put a "T" in line to MAP sensor and check vacuum. MAP = Manifold Actual Pressure (vacuum) not any "venturi" created vacuum which can be purposeful for just air speed going thru air horn/throttle body.
Need to rule exhaust problems. If a lower vacuum reading was had when held steady at say 2,200 RPM +/- than at idle than it suggests exhaust problems. That info is telling the controls the vehile in under load and would normally dump fuel under higher loads.
Again with compression. I don't see anything there that's the upfront issue. Seems some are high which might be an overoad of liquid - oil, gas and depending on how much time it took to go from one to the next for a reading.
If running rich it would trash converter and the problem just get worse. Need to rule out exhaust restriction - if you don't like a vacuum test try another way,
T
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