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1993 3.0L - stumble after timing chain replacement


bennie

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I've got a 1993 Ford Ranger 3.0L V6 with a manual transmission and I just got done changing the timing chain and gears (I was changing my water pump, but broke off a bolt and had to take off my timing cover to get it out).

I've got everything buttoned back up but now it stumbles really badly when I accelerate. I'm 95% certain I got the gears lined up and didn't move the crank/camshaft when I was installing them.

Is there anything else I can look at before I break it all apart again to make certain?

I used my Haynes manual for instructions, set piston #1 at TDC and the marks on the old chain were lined up before I removed them (although the chain was pretty loose).

Thanks!
 


RonD

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Check compression.

Cold engine
Remove all spark plugs, you need good crank speed
Install a screw in type compression gauge in a spark plug hole
Push gas pedal to the floor and hold it down, this turns off fuel injectors and allows more air in
Turn key to START, crank engine, you need to hear 4 or 5 "hits" of compression stroke

Read gauge, WRITE IT DOWN, release pressure in gauge

Repeat on next cylinder, test 3 cylinders at least

3.0l should be about 165-175psi at sea level to 2,000ft

If overall compression is down cam timing is 1 tooth off.

If compression is good then cam/crank timing is good

On the crank, behind the pulley is the CKP(crank position) sensor, make sure it is tight, this times spark and fuel injectors.

Check that TPS(throttle position sensor) is plugged in(upper intake)
 

bennie

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Thanks for the tip Ron, I'll check out the compression.

Also my truck doesn't have the ckp sensor, to my knowledge of never had one, or I don't remember taking it off, and it's not on there now :)

And I'll confirm the tps sensor is plugged in.

I was cleaning a lot of parts around the engine with the maf exposed, so I sprayed a little maf cleaner in there, a long shot, but I figured it wouldn't hurt (although it didn't look very dirty).
 

det107

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I used my Haynes manual for instructions, set piston #1 at TDC and the marks on the old chain were lined up before I removed them (although the chain was pretty loose).
Not sure if TDC #1 is on exhaust stroke instead of compression stroke ?
Hey Ron :icon_confused:-
 

enjr44

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The valves determine if you are on compression or exhaust stroke. Not the crank. Piston up, is piston up. Valves open or closed determines which stroke is which.

So if crank is on the mark and cam gear is on the mark, you got it right!
 

bennie

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Thanks for the info enjr44, I also had the distributor cap off and the rotor was set to fire on the #1 cylinder.

I'm not sure if I'm better off or not if I've got the timing chain installed properly, at least if it was the timing chain, I'd know what I need to do to fix it ;)
 

RonD

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Thanks for the tip Ron, I'll check out the compression.

Also my truck doesn't have the ckp sensor, to my knowledge of never had one, or I don't remember taking it off, and it's not on there now :)

And I'll confirm the tps sensor is plugged in.

I was cleaning a lot of parts around the engine with the maf exposed, so I sprayed a little maf cleaner in there, a long shot, but I figured it wouldn't hurt (although it didn't look very dirty).
CKP sensor was added when an engine design changed and it lost it's distributor, 1995 was that year for 3.0l, my mistake.
Didn't look at the year and CKP would have been in the area you were working.

If you have a distributor then it will have a TFI system and a sensor in the distributor for spark timing was used, CKP sensor replaced this function.
Distributor runs off the Cam so wouldn't help you check crank/cam timing(timing chain function).

Without actually tearing it down again and checking marks, compression test is the only way to test if it is correct.

Looking at valve positions or distributor rotor isn't precise enough.
Even with new timing chain there is slack.


Not sure if TDC #1 is on exhaust stroke instead of compression stroke ?
Hey Ron -
Crank doesn't have exhaust or compression strokes, cam does.
4 stoke engine means crank must spin 2 full revolutions(4 strokes of piston) for each 1 revolution of Cam.
Distributors are timed to cam, distributor spins at same speed as cam, 1 to 1 ratio
Crank is 2 to 1 ratio with cam/distributor, so when installing a distributor it is popular to use the #1 TDC mark on the crank, because it is really the only external position marking.
But it is a 50/50 mark, you really need to know the Cam position to set it correctly the first time.
But a no start means don't buy a lotto ticket, you guessed wrong on a 50/50 bet, lol.

When Ford switched to distributorless spark systems they used a Waste Spark system.
Waste spark fires 2 spark plugs at the same time, so a V6 engine only has 3 coils in the pack, I4 2 coils, V8 4 coils, although the last two use dual 2 coil packs.
CKP sensor doesn't ID #1 TDC compression stroke or #1 TDC exhaust stroke, just #1 TDC, because it doesn't matter, #1 gets spark at every TDC, all cylinders do with waste spark setup.
 
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bennie

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So, good news, it's working!

The results from my compression test are:

1 - 120
2 - 115
3 - 130
4 - 120
5 - 130
6 - 130

My theory is that I either didn't have the #1 spark plug boot seated or the plug itself was loose and doing the compression test meant that I put the plug and boot back on. The "observer effect" at its finest ;)

The other possibility is that cleaning the MAF sensor actually did something (although I doubt it)

RonD and enjr44, thanks for all your help, I would've been tearing back into the truck if it weren't for you guys!
 

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