4.3L with ALOT of issues... - (*non Vortech heads w/ Vortech intake? yay? nay?) - Great Lakes 4x4. The largest offroad forum in the Midwest

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Old May 8th, 2007, 12:53 AM   #1
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Default 4.3L with ALOT of issues... - (*non Vortech heads w/ Vortech intake? yay? nay?)

My friends friend blew up his Jimmy's engine, and I just helped my friend finish the swap. And the thing just won't run right. kind of long but I want to cover it all:

the subject is a '94 4x4 Jimmy with a running 88 4.3L from a full size swapped in.

The block and most al internals except the oil pump (read later), remained untouched. the oil pump was put back together from parts from both engines, opposite parts were worn on each oil pumps, so we combined all the good parts.

The 88 heads were reused because upon futher inspection of the vortec heads the coolant passages were very clogged.

valve covers and intake manifold swaped over from original engine.

All accessories swapped over from original engine

The issues:

Oil pressure holds a steady 60-70 psi at start up, and that actualy was where the old one was ever since they bought it. once it warms up it drops to about 20psi or less. which is not good and obviously the old one didn't do that either.

The timing keeps jumping, not as in cam timing, as in with a timing light we can't get it to stay within 15 - 10 of any mark - as in while running it jumps around that much. it's obviously running really rough

replaced rotor cap and it runs better, but stil not well at all.

Tried grounding out spark plugs to find a bad cylinder because it almost sounds like it's missing one, and there's pops from the muffler from unburnt gas. And even when we tried straight out unpluging EVERY SINGLE PLUG (one at a time, replacing the previous plug) it did not change the sound of the engine! it runs just as crappy as it did before, no changes, no difference.

pulled the oil fill cap, there's no suction, but there's also no pressure/ exhaust that we can tell.

We've gone over all the wires 5 times, there's not one loose end, or orphan connector. We're getting plenty of spark, checked that.

I'm at a loss... we cannot get this stpid thing to give any sort of consistent error or fault or issue.

I'm open to suggestions on this.

Last edited by Captain Ledd; May 9th, 2007 at 01:54 PM.
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Old May 8th, 2007, 05:50 AM   #2
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Timing there is a plug that has to be unpluged to set timing.

I didn't think you could run non Vortech heads on a Vortech motor?

fuel lines in the intake are prone to leaking causing a vac leak

Good ground ?

Rest Computer after messing with stuff .
it takes I belive 20 mins for the ECM to reset
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Old May 8th, 2007, 06:30 AM   #3
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Wires in the correct firing order?
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Old May 8th, 2007, 07:51 AM   #4
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Originally Posted by jmdzuk View Post
Timing there is a plug that has to be unpluged to set timing.

I didn't think you could run non Vortech heads on a Vortech motor?

fuel lines in the intake are prone to leaking causing a vac leak

Good ground ?

Rest Computer after messing with stuff .
it takes I belive 20 mins for the ECM to reset
Any idea where this plug is located?

heads: Thats what everyone said, but everything lined up perfectly and we couldn't find anything that one head had and the other didn't, so we ran the non vortech heads.

So how do we go about fixing this vacum leak?

that grond shouls be good as we've checked the spark against it multiple times.

I'll tell him to reset the compter, and it has ran for about 30 minutes the other day, kept running worse and worse as it heated up (the dropping oil pressure wasn't comforting either.)

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Wires in the correct firing order?
I doubt it, as wel pulled all the plugs one by one and not one of them made the engine run any different. But we'll check again.
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Old May 8th, 2007, 09:08 AM   #5
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Was the 92 a TBI motor? If so, they aren't vortec heads.
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Old May 8th, 2007, 09:11 AM   #6
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Any idea where this plug is located?

heads: Thats what everyone said, but everything lined up perfectly and we couldn't find anything that one head had and the other didn't, so we ran the non vortech heads.

So how do we go about fixing this vacum leak?

that grond shouls be good as we've checked the spark against it multiple times.

I'll tell him to reset the compter, and it has ran for about 30 minutes the other day, kept running worse and worse as it heated up (the dropping oil pressure wasn't comforting either.)



I doubt it, as wel pulled all the plugs one by one and not one of them made the engine run any different. But we'll check again.
Plug is by the distibuter .its a test plug should be able to un plug it single wire dont qoute me but I think its green ?

I would look into vortech verses non vortec this may be a issue

vac leak I use a un lit propain torch wave it over hoses and suspected leaks and the motor will rev up if it is sucking air or propain
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Old May 8th, 2007, 10:10 AM   #7
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alright, I'm heading out there tomorrow, I'll give that a shot.

The 88 was a TBI engine, the 92 is a Vortech, I think it even said Vortech on there. I'm still not sure why the non Vortech heads would be an issue. there wasn't any leftover wires, nothing went into the intake ports, nothing really special or that different about them (that we could tell).

The '92 engine has a fancy shmancy intake on it with one fuel injector and 6 lines coming off of that injector, I guess it operates on port vacum to shoot fuel in or something like that. Chevy's aren't exactly my thing so I don't the partuiculars of the system.

Oh, and I goofed on my 2nd post. when I said "I doubt it" about the plugs in the right order I meant that "I doubt they are in the wrong order. I think if they were wrong we'd gt at least a little more results when we puled the wire off the spark plug on a good cylinder. but we'll recheck that too.
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Old May 9th, 2007, 01:53 PM   #8
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Quote:
Originally Posted by friend
the truck is a 94 gmc jimmy. it originaly had a 4.3l vortec with central port injection. i bought a 4.3l that came out of a 1988 chevy scotsdale pickup. the older enjine had a throtle body. i swaped the throtle body and original intake manifold with the fuel injection and vortec intake manifold. everything else was exactly the same except that the enjine i took out of the jimmy had a balencer shaft and the one i put in does not. all sensors, bolt holes, and external accesories are the same.
Sorry, it was a '94 Jimmy not a '92. whoops. But thats pretty much everything he did and where it all came from.
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Old May 9th, 2007, 02:09 PM   #9
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alright, I'm heading out there tomorrow, I'll give that a shot.

The 88 was a TBI engine, the 92 is a Vortech, I think it even said Vortech on there. I'm still not sure why the non Vortech heads would be an issue. there wasn't any leftover wires, nothing went into the intake ports, nothing really special or that different about them (that we could tell).

The '92 engine has a fancy shmancy intake on it with one fuel injector and 6 lines coming off of that injector, I guess it operates on port vacum to shoot fuel in or something like that. Chevy's aren't exactly my thing so I don't the partuiculars of the system.

Oh, and I goofed on my 2nd post. when I said "I doubt it" about the plugs in the right order I meant that "I doubt they are in the wrong order. I think if they were wrong we'd gt at least a little more results when we puled the wire off the spark plug on a good cylinder. but we'll recheck that too.
Ok so you replaced a Vor-tec engine with a TBI engine. Then you tried to convert the TBI over to Vor-tec correct. Did you swap out the distributor when you did this. If not that is one thing I would do. Also I if you set the timing 10 degrees to 15 degrees. I would stick with one or the other. Either set it at 10 degrees or 15 degrees. Also check the computer as the TBI engine is different then the Vor-tec engine. You may be dumping to much fuel into the engine. Another thing oil pressure just because two pumps look the same if your loosing that much pressure go to a parts store and buy a new oil pump. You got a check engine light correct. You have an OBD1 scan system on the truck as it is pre OBD2 scan. I suggest you get ahold of a OBD1 scanner and plug it into the diagnostic port. Let the scanner tell you if there is anything wrong in the computer. Also it will erase any codes that maybe saved in the computer. If there are codes stored in the computer then those are considered hard codes. They need to be erased or deleted with a scan tool or diagnostic computer. Just simpily unplugging the computer or unhooking the batteries will not erase those codes. If you do scan the computer and get codes from the scan then post them on here and I can help you further along.

Are you sure then engine you installed is a good engine I would run a compression check on all the cylinders. You may have a cylinder with low compression.
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Old May 9th, 2007, 02:46 PM   #10
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Ok so you replaced a Vor-tec engine with a TBI engine. Then you tried to convert the TBI over to Vor-tec correct.
yup.

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Originally Posted by bigcountrysg View Post
Did you swap out the distributor when you did this. If not that is one thing I would do.
Will ask.

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Also I if you set the timing 10 degrees to 15 degrees. I would stick with one or the other. Either set it at 10 degrees or 15 degrees.
I'm thinking there might be a little confusion here. we hooked up a timing light and the mark on the harmonic balancer has a RANGE of 10-15 degrees. while it's running (example) it'll be jumping around anywhere between 5BTDC and 20BTDC on the balancer. It won't stay in one particular timing setting.

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Also check the computer as the TBI engine is different then the Vor-tec engine.
We re-used the Vortech computer (for fuel injection reasons). There really wasn't that many electrical components swapped over. Basically only the mechanical parts of the '88 engine were re-used and all of which had provisions to the same electrical connectors. Basically we just used the long block from the '88.

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Another thing oil pressure just because two pumps look the same if your loosing that much pressure go to a parts store and buy a new oil pump.
yeah, but we're getting excelent pressure when it's cold, and when it warms up is drops signifigantly. would wear still cause this? and would a new pump garuntee fixing it?

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You got a check engine light correct.
Actually never looked. I kinda already knew something was wrong with it lol

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Originally Posted by bigcountrysg View Post
You have an OBD1 scan system on the truck as it is pre OBD2 scan. I suggest you get ahold of a OBD1 scanner and plug it into the diagnostic port. Let the scanner tell you if there is anything wrong in the computer. Also it will erase any codes that maybe saved in the computer. If there are codes stored in the computer then those are considered hard codes. They need to be erased or deleted with a scan tool or diagnostic computer. Just simpily unplugging the computer or unhooking the batteries will not erase those codes. If you do scan the computer and get codes from the scan then post them on here and I can help you further along.
Allright, we'll try and track one down.

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Are you sure then engine you installed is a good engine I would run a compression check on all the cylinders. You may have a cylinder with low compression.
I have no idea if it's a good engine or not. It does start right up at least. We figured the rings were good as were not getting any pressure in the crank case - we pulled the oil fill cap and checked that. no idea on the valves though, I guess we'll have to mythodicaly check each cylinder for that and I'll post those #'s.

Thanks for your help.
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Old May 9th, 2007, 03:05 PM   #11
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yup.



Will ask.



I'm thinking there might be a little confusion here. we hooked up a timing light and the mark on the harmonic balancer has a RANGE of 10-15 degrees. while it's running (example) it'll be jumping around anywhere between 5BTDC and 20BTDC on the balancer. It won't stay in one particular timing setting.



We re-used the Vortech computer (for fuel injection reasons). There really wasn't that many electrical components swapped over. Basically only the mechanical parts of the '88 engine were re-used and all of which had provisions to the same electrical connectors. Basically we just used the long block from the '88.



yeah, but we're getting excelent pressure when it's cold, and when it warms up is drops signifigantly. would wear still cause this? and would a new pump garuntee fixing it?


Actually never looked. I kinda already knew something was wrong with it lol



Allright, we'll try and track one down.

I have no idea if it's a good engine or not. It does start right up at least. We figured the rings were good as were not getting any pressure in the crank case - we pulled the oil fill cap and checked that. no idea on the valves though, I guess we'll have to mythodicaly check each cylinder for that and I'll post those #'s.

Thanks for your help.
If your getting good oil pressure when it is cold really doesn't mean much. Cold oil is thick which means higher pressure readings. As the oil warms up and thins out the pump may not be able to pump the oil and maintain good pressure. Your engine at normal op temp should have 40psi for the oil pressure. If your engine is not capable of putting out 40 psi of oil pressure while idling at normal op temp then most likely the pump is weak and not able to pump the thin oil. Also make sure your oil pump is on the distributor shaft all the way as well. This will also cause your engine to have low oil pressure.

Just because you can get an engine to run does not mean it is good. Just because the engine does not show the typical signs of being bad does not mean it is good.

You did not mention if you reused the distributor out of the orginal engine or not. If that distributor is still laying around I suggest getting it in the engine that is in the truck. Set cylinder 1 at tdc. Then make a mark on the harmonic ballancer that will points to zero on the timing gauge on the engine. Then turn the engine back to 10 degrees btdc. Install the distributor so it is pointing at the number one cylinder. That should put you at 10 degrees btdc.

Now you also do not know if the engine you are using has jumped time or not. It would not hurt to take off the front engine cover to see if the timing gears line up or not to tell you if the engine is in time internally or not. This could also be a problem. When you are setting your timing you need to make sure that your engine is on the intake stroke as well. So you may have to remove the valve cover that is on the side of the engine that has the number one cylinder.
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Old May 9th, 2007, 05:35 PM   #12
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This vortec thing is always confusing for everyone. The pre 95 4.3 heads will swap from motor to motor no problem. Its the 96 and up ones that wont fit the older motors, so you can rule out the heads right now.

I seem to remember the timing wire being by the computer, under or around the glovebox area, and the wire color being brown. Its been a while tho.

Since its OBD1, you can do the paperclip trick for codes. Hit up one of the s10 forums for instructions on that. It involves shorting 2 pins on the ALDL connector underdash and counting the blinks on the service engine soon light. Way cheaper than a scanner.
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Old May 9th, 2007, 06:18 PM   #13
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I seem to remember the timing wire being by the computer, under or around the glovebox area, and the wire color being brown. Its been a while tho.


mines by the distributer and has to be unpluged to set time .

and the distributor will work tbi to vortech set up
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Old June 1st, 2007, 04:53 PM   #14
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took it apart just a little bit further than than we did before and found just over an INCH of play in the timing chain. Main bearings also look shot.

hopefuy after a mild rebuild things will work a tad better. I can't believe it hadn't jumped time...
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