73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: GT1000000 on September 07, 2007, 06:58:39 pm
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:'(hERE i SIT bROKEN hEARTED, cAME TO SH.....
Hey guys,
I am truly suffering...Got an 87 V-20, 5.7L TBI 4X4. Laundry list of parts,
anyhow, here's my story; Came home runnin fine,went to start,nothing but rich black smoke, mixed with antifreeze...first thought,computer problem? Break out the scanner,nothing wrong...Check compression, all eight between 180-190 psi, check the radiator and sure enough...bubbles,millions of them...possibly blown head gasket or cracked head? Well decided to be ready for the worst possibility and decided to go whole hog...Crane cam,Trick flow heads,Roller rockers,Adjustable fuel regulator,New lifters and pushrods,plus all new Fel-pro gaskets... took everything apart and found the intake gasket sucking coolant and oil in through both back cylinders and the valve seals on 5 out of 8 cylinders cooked[must have occured about a week before when I ran very low on coolant and quite possibly overheated, honestly I just filled it up and kept going... So here I am having just spent a couple of weeks of evenings after work installing all these nice new goodies and when I finally get it running and break in the cam, it just won't idle. Let me try to explain, if I start it and immediately rev it a bit I can almost keep it running...If I disconnect the MAP vacuum, it will sort of idle for a while and then cuts off,although with the MAP disconnected it is very hard to start. On with the scanner again and after I clear the codes[by disconnecting the battery] I start it, rev it, keep it sort of running , for a little while[5-30 seconds],and let it shut off,there are NO codes...
I have adjusted the fuel pressure from one extreme to the other, re-lashed the valves,the timing,when I can measure it has been about 10-12 BTDC,not perfect but close enough for now...please ask me any questions you might need to HELP ME figure out what is going on here...
Sincerely,
???GT
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Was the cam a stock grind? If not, that will probably add to your problems. Have you modified the PROM to work with all the changes? Any changes to an ECM controlled system will require some sort of reprogramming.
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Crane Compu-Cam, Designed to work with this system...Hypertech chip,also for this application...
GT
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If it's not setting any DTC's double check your valve adjustment. If you put roller rockers remember zero lash not like steel rocker arms.
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Latest update, Figured out the fuel pressure too high... lowered to 13.5, from about 16 psi...according to crane[they recommend 13.5]. Something that has been bugging me...the MAP sensor reads 4.88v@ zero rpm and 30 In HG. Shouldn't it be the other way around? Close to zero volts and zero Vacuum at zero RPMs???
Still trying to figure this mess out...Thanks for the help so far...
PS. According to Crane, the roller rockers get zero lash plus 1/2 to 3/4 turn...
Later,gt.
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GT- my $.02-
The map readout sounds right- the 4.88 volts is a reference signal that's generated by the sensor and it goes to the ecm. Somewhere around 5 volts is correct. The ecm sees the 4.88 volts and returns a signal.
Zero rpm, of course, shows that the ecm does not see the engine running.
30 in Hg indicates total vacuum- it's the reference signal by the ecm showing that there is no pressure detected by the map sensor. And that's correct too, because your engine isn't running and there's 0 pressure being built up in the manifold where the sensor gets it's reading from. So it stands to reason that when there is no pressure, the ecm sees total vacuum .
Now Vilezamboni will see this and put us straight... :D . Hope you get it running soon
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With the engine idling Map voltage should read somewhere around 1.25 volts but if the engine isn't idling it won't read correctly. Pop the vacuum hose off of the EGR valve and make sure the egr is closed.
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Also with roller rockers zero lash is good + may cause the valve to open so adjust them very carefully. The use of a dial indicator and a leakdown gauge can help you set them just right.
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Sorry,forgot to mention, EGR non-existent,goes back to when I first dropped the crate engine and installed the Holley pro-jection intake, and I could not track down an EGR that would fit so it has been running without one for over 7 years... As for the zero lash, I will try that... Thanks for clarifying the bit about the MAP...and yeah,briefly,after the engine starts..the scanner reads the MAP voltage somewhere about 1.88-2.33V and about 13-17 IN.HG. Thanks for the input, keep 'em coming...next chance I get to mess with it is Monday,so a list of stuff to check,recheck and double check would suit me just fine...as a matter of fact if the problem persists I may be looking at replacing the TBI/CCC system with a intake,Holley,and a cd box for the ignition. Any ideas in that regard would also be appreciated...
Later,gt
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Well,here goes,
Relashed the valves to Zero, No noticable improvement, runs a few seconds,shuts off,with the MAP connected,cannot rev up engine...sputters,miisses and dies...
Disconnect the MAP, hard to start, can rev almost as much as I want, Sounds Good and strong , But reaches a moment when it just shuts down...Almost seems like something electrical or electronic???
The only time any DTC's is when I physically disconnect any sensor,otherwise ECM seems to be functioning normally...
Feeling Quite Dumb and Numb,gt.
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one more update...After checking and rechecking everything I found what I thought was the answer... the distributor was one tooth off...made the necessary correction and now,with the MAP unplugged,it starts eventually, and seems to run just fine as long as it stays well above 1200 rpm...as soon as I let it fall below that...it almost seems like it is going to idle, but then speeds up just a little bit and cuts off...
At my wits end,almost ready for a gallon of gas and a match,gt.
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Did you set the timing? Put the EST in bypass and set it to 0°
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Cannot keep it running long enough at idle to make that setting...gt.
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With a liittle help from an extra pair of hands and eyes, I was able to start it with the timing light at the ready and...Yes, with the EST unplugged I got it set to between 0 and 2 degrees before TDC, I would imagine thats close enough for now, but I still CANNOT get this crazy thing to idle...My Head Feels Like Ghost Rider's...gt.
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Is the throttle body sealing off to the intake? My truck acted like that and I changed the gasket on the throttle body and it is running fine.
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Yeah. Somebody else on here had a similar problem and found the Throttle Body gasket bad. It sounds like a bad idle air control too.
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Thanks again,but unfortunately both the gasket and the IAC are new...had to try...also tried NEW computer,temp sensor,EST module...got a friend at the parts house...None have made any difference...
Still tryin',gt.
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What are your IAC counts? If you take off the oil cap does it make a difference? Are you sure you have no vacuum leaks? Brake booster is hooked up?
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Last count noticed approximately 53-55,Haven't tried the oil cap...Booster is hooked up and the check valve is working, haven't actually checked for leaks, cause with the air cleaner off, the opening leading to the IAC in the throttle body almost sounds like a vacuum cleaner on steroids...besides spraying some brake clean around the intake and trying a long screwdriver like a stethoscope,nope,don't seem to have any leaks, also when I disconnect the MAP vacuum signal to the MAP sensor and I keep the engine running, I also hooked up a vacuum gauge and at about a fast idle,1500-2000 rpm, I would get a nice steady vacuum reading, no bouncing or jitter... I'm the one getting bouncy and jittery,gt.
PS-Gonna tow it to a friends shop tomorrow,maybe he'll see something I'm not...
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A screwdriver to your ear will help pinpoint a mechanical noise not a vacuum leak. Sounds to me like that's your problem either internal or external somethings way off...
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Are the injectors firing consistently?
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Sorry,I meant a screwdriver with a piece of wd40 soaked paper towel on the end, have found a few vac leaks when the wet towel gets near or on makes a significant change in sound,sometimes whistles, sometimes kinda snores...as for the injectors,they are firing with a nice cone all the way to shut down...gt.
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Is there any way the wiring might be bad at the coolant temp sensor? I read where you installed a new one, but can't understand why the temp gauge didn't let you know the engine was overheating to the point where it fried all those valve seals and blew the head gasket originally. The reason I ask about the temp sensor wiring is because the computer gets a signal from that sensor and adjusts the idle air motor so there's a proper idle.
I read once where a guy couldn't get his car to idle properly unless he took off the gas cap! I guess the gas tank wasn't vented correctly or something.
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All good points, but the original overheat was a completely dumba.. move on my part...you know middle of the highway and you really don't want to stop till you get home and I used to have a coolant leak from what I found out to be the t-stat housing was warped at the base[since been replaced], and this was one of those times when the water level got below the sensor an it indicated everything was OK, I had forgotten to top up the rad before I hit the road,mind on other stuff, never glanced at the gauge...
Any how my buddy at the shop I took the truck to, checked and rechecked all prior and found everything to be in order, except one thing...Seems to be getting too much fuel and its loading up...since everything with the computer seems to be OK, we are now going to try a used TBI from the salvage yard. Didn't realize the TBI's were getting scarce,finally tracked one down at Cars-R Us, in Illinois. They are shipping one out to me...should get it by Mon or Tues. Hope that's the problem,Will let you guys know...
Meanwhile THANKS again for all the ideas and inputs,gt.
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Most auto parts stores carry these rebuilt. They are easy to rebuild though. I just went through chasing down problems on my Suburban. I would guess the regulator on the back is probably shot if you are getting to much gas.
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I thought you had a Holley throttle body?
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You being GT1000000, right...
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hey guys,
Just answering the Holley Question, No And Yes...No, I did not have a Holley TBI,it was just the Holley Pro-jection Intake...when I first installed it I had my eye toward someday putting a Holley TBI on it...And...Yes,we tried getting a used TBI,thinking that might be the problem,could'nt find a good one and have had bad memories with rebuilts,so I ordered the Holley Unit and I am back to nowhere...So...
I am in the process of towing the truck back to my shop and seriously considering a complete removal of the CCC/TBI system, but first I need some answers...
Q1-Q-jet carb best?
Q2-Do I need to replace the Ignition system with a 1-wire HEI?
Q3-The Transmission, what does the computer monitor there? Shift position?,and By completely eliminating the computer system, is that going to affect the tranny in any way?
Q4-Do I run power to the fuel pump relay from an Ignition On source?
Q5-Anything else?
I am going to install an adjustable Fuel pressure regulator with return.
I am getting a spread bore intake manifold,dual plane, good from idle -6000rpm.
Thanks again for all your help,gt.
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It would be SO much easier to rebuild a TBI yourself. They are the simplest setup as far as fuel systems go. The only thing to them are gaskets, and the injector pod with consists of a diaphram a spring and 2 injectors.
1) I think Q-jets are best, right behind TBI's
2) You need a non computer controlled HEI.
3)700R4's are not computer controlled.
4)If you are keeping it, it needs to have power when the ignition is on. Techincally you don't have to change it
5)Sure, why not fix what is wrong with the TBI, you are going backwards putting a carb on it...
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Thanks Capt.
It is a TH400 and I just want to make sure it wont get fried if I go this route...
And yes I would love to fix what's wrong, but we[meaning the four "mechanics" who have looked at it] are a bunch of Dumba----s,cause we can't seem to figure it out...
One thing that continues to bother me is why??? if I connect the Map sensor vac hose correctly, the engine starts right away, idles for a moment, then dies...If I disconnect the vac signal to the map sensor, the engine cranks for a while before starting then seems too idlle pretty good, can even rev it and hold it at whatever rpms,but then after a little bit[30 seconds to well over a couple of minutes] it just seems to shut down,,, This I can do over and over again,thinking maybe the computer needs to wake up and re calibrate itself,but this doesn't seem to be the case...
If you can think of anything that might be causing this, besides everything we've already tried, I am open to suggestions,PLEASE...I would much rather keep the TBI, but I can't afford to be without my truck much longer,Thanks again,gt.
PS- as to rebuilding the TBI, it shouldn't be necessary now with the NEW Holley TBI,which I have on there NOW...
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The Holley TBI is a 2" bore, it is never going to run correctly on a stock 350, you will be getting to much air for the ECM to compensate. You will have to burn a chip to make the Holley TBI operate correctly.
I am reading over this again to see if anything is there I missed...
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If I disconnect the vac signal to the map sensor, the engine cranks for a while before starting then seems too idlle pretty good, can even rev it and hold it at whatever rpms,but then after a little bit[30 seconds to well over a couple of minutes] it just seems to shut down,,, This I can do over and over again,thinking maybe the computer needs to wake up and re calibrate itself,but this doesn't seem to be the case...
Mine was giving symptoms like this. What happens if you hook everything up and pull the IAC connector off? Mine ended up being a bad fuel regulator diaphram and a faulty injector. It would idle and run fine right until I put a load on it and it would die immediately.
To get our stories straight this is what we are working with:
Old motor with previous blow head gasket, intake gasket and bad seals
Crane cam - for TBI right?
Trick flow heads - what kind of flow/compression we talking about?
Roller rockers - (adjusted properly)
Adjustable fuel regulator - (set to 13.5lbs)
New lifters and pushrods - broken in with the cam?
new Fel-pro gaskets
Timing set to 0 with bypass (10-12 while running)
No EGR
Injectors are firing ok
No vacuum leaks
All with stock TBI...
Now we are working on the same setup, but you changed to the Holley TBI right? 670cfm?
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Crate motor with about 40K miles, overheated which caused initial problems
Crane for TBI,http://store.summitracing.com/partdetail.asp?part=CRN%2D114122&autoview=sku
Trick flows,http://store.summitracing.com/partdetail.asp?autofilter=1&part=TFS%2D30400005&N=700+115&autoview=sku
Roller Rockers,http://store.summitracing.com/partdetail.asp?part=SUM%2DG6905&autoview=sku,adj properly
Adjustable Regulator,NO,No,not any more...Installed Holley 670 cfm TB Complete,New,part#502-6
New Lifters & Pushrods,Yes,Lifters come with cam,Push rods are stock 7.90" long
New Fel-Pros
Timing @ 0 degrees
No EGR
New throttle body[Holley}
No vac leaks
No longer stock TBI[Holley]
If everything is hooked up and I discionnect the IAC, I Honestly forgot what happens...
It[the truck] is currently waiting to be towed to another shop...and I don't have immediate access to it.
gt.