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  #1  
Old 05-03-2006, 10:00 AM
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1990 4.9L Straight Six (Missing Head Gasket)

Greetings,

I posted this in the V6 section, but thought I might be able to get more info here.

I'm new here, and need advice/suggestions on how to resolve an issue with my truck.

About a week and a half ago, I was heading home, and I lost all oil pressure/truck died. Started truck up again, ran fine for about 5 minutes, died again. So, I had the truck towed home.

I checked the oil, and to my dismay, I found a bunch of burnt antifreeze. Blown Head Gasket, right? Wrong.

Pulled the head off, and guess what? I didn't have a head gasket (seriously). It was obvious someone had rebuilt the engine in the past, and deliberately left the head gasket off. The really odd part is, that I'd had this truck for 2 1/2 years, with no problems at all.

So, I replace the head gasket, put it all back together, and it starts/runs like a champ.

The problem is, now when I put the truck into gear (it's an automatic tranny) and leave my foot on the break, it shakes the bejesus out of the truck, especially in reverse.

Once the truck gets up over about 5mph, the shaking goes away and it drives fine.

I've checked the plug wires to make sure they were all connected well. I've made sure the motor mounts are very secure.

I'm going to do some checking of the fuel system (maybe 1 cylinder isn't getting fuel?), but I made sure to check that really well when I put everything back together.

The truck also seems idle at a higher RPM than before, and I've wondered if this is contributing to the shaking problem.

Maybe my torque converter is having problems and sporatically locking/unlocking?

Or is it possible that before, since I had no head gasket, that my compression was horrible, and that now I'm just feeling the extra power/torque that was being lost?

Any help/suggestions would be appreciated.

Thanks,
Todd
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  #2  
Old 05-03-2006, 01:03 PM
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Well, all i can say is you would have had more compression without a head gasket, therefore conceiveably more power. maybe you left off a vacuum line(lot of the problems you mentioned can be traced back to a vacuum leak.

I purchased a grooms 258 6cyl jeep once that had NO piston rings in it, and the replacement they sent had NO rod bearings!
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  #3  
Old 05-03-2006, 01:15 PM
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Also, the spark timing may be too far advanced.
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  #4  
Old 05-03-2006, 01:34 PM
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Thanks for the replies.

I don't think it would be the timing. I never touched anything to do with that. Although, the previous owner may have advanced it to compensate for the loss of compression. I guess that would have made sense.

I think I have all the vacuum lines in place or plugged, but I'll double check again to make sure.

Maybe a line was split/cracked while doing the head gasket replacement.
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  #5  
Old 05-03-2006, 10:22 PM
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Quote:
Originally Posted by StupidTodd
I don't think it would be the timing. I never touched anything to do with that. Although, the previous owner may have advanced it to compensate for the loss of compression. I guess that would have made sense.
As mentioned, having no head gasket would increase compression, not lower it.

I'd look into the tranny, esp. the fluid level, and make sure the filter hasn't come loose.
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  #6  
Old 05-04-2006, 09:51 AM
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I've had problems with the tranny in the past, and keep a VERY close eye on the fluid level. I've had several leak problems in the past. I still have a couple small leaks, and when I can find them, I fix them.

I think if anything my tranny fluid may be high, although I suppose that if it is too high, it could be the problem. (not allowing the torque converter to spin completely freely under no load)

Last night I changed the plugs and wires, and inspected for a vacuum leak (which I couldn't find).

I think I'm going to start looking into the tranny tonight. I flushed/cleaned it last year, and maybe the filter came loose/is clogged. Or maybe I just have too much tranny fluid.

Oh, and another question. I checked my motor mounts. Both are fine, except 1 of the dampeners is white and the other 1 is black. They are similar in shape, but not quite the same. Both appear to be doing the dampening job quite well, but I was wondering if them being slightly different might be part of the issue?
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  #7  
Old 05-05-2006, 08:48 AM
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ok, checked drained some excess tranny fluid last night. That seemed to help a little bit, but not 'enough'.

So, I took a closer inspection of my distributor. I tried pulling the cap off, and the front screw head snapped off. Lucky for me the back screw was held on with a plastic pull tie as the distributor assembly has been broken.

Am I going to need an entire new distributor, or is there any way to just replace the part that the cap screws into? (I don't think there is, but not sure)

So, once I change out the distributor, any suggestions on timing the truck?
Am I going to need to buy a timing light? And if so, any special kind I'll need?
Should I go ahead and replace the cap/rotor while I'm at it?

Thanks for all the info thus far!
Todd
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  #8  
Old 05-05-2006, 09:07 AM
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I would put a different distributor with a new cap and rotor. You may want to check your EGR valve to make sure it isn't stuck open. You will need to check the timing.
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  #9  
Old 05-05-2006, 11:58 AM
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I use the "old school" timing method:
At idle, advance it until the revs stop speeding up, then retard it until the revs just start to slow down.
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  #10  
Old 05-05-2006, 03:40 PM
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Did you pull the pan and check the tranny filter?

Replace the dizzy, cap and rotor, and pick up a timing light (one with a dial on the end is preferred, but not mandatory). When you check the timing, don't forget to pull the spout connector first.
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  #11  
Old 05-07-2006, 12:34 PM
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Find the vacuum hose diagram under the hood and double check the hoses. That will definatley give you low rpm vibrations like you describe.
Lotsaluck
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  #12  
Old 05-08-2006, 03:08 PM
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Well, I think I have the issue mostly resolved.

I didn't pull the tranny pan, but I checked the fluid and I was about a quart/quart and a half too full. Drained that. From what I remember of having the tranny pan out, I don't see how the filter could just fall out. It's kinda forced up in, and the pan prevents it from moving.

There's really not a lot of vaccum lines left to check. A LOT has been removed from the truck, and a LOT has been plugged up. I've double checked the remaining lines, and I can't find any type of leak.

I was about to check the timing, I noticed that the back of my distributor cap was held in place via a plastic pull tie. Pulling the cap off showed me that the distributor frame was actually cracked, and needed to be fully replaced.

I was going to get a timing light, but stopped at my neighbors to see if I could borrow theirs. (my next door 'neighbor' is a high po performance shop)

Talked to the guy there, and he said with as old / rusty as my truck was, he wouldn't trust the timing marks anyhow, and he'd just tune it by ear.

So, back to the truck, set cylinider 1 to TDC, pointed at plug 1 and it started. A bit more fine tuning, and now the truck is running better than ever.

There is still a very small vibration at low idle and only while in gear (but there was b4 the head leak). I'm not sure if I mind enough now to pull the tranny pan or not. We'll see how she runs when I take her for longer than a 5 minute test drive.

Thanks everyone for helping me get my truck back together!
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  #13  
Old 05-08-2006, 10:12 PM
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Balance test and getting codes with a paper clip



www.troublecodes.net/Ford/
http://www.mustangworks.com/articles...-iv_codes.html

Warm the engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 99 for everything OK, or the number of the failing cylinder such as 22 for cylinder #2. Quickly pressing the throttle again up to 2500 RPMís will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isnít putting out power like it should.
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Old 05-08-2006, 10:12 PM


 
 
 
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