wabrand

I have a 93 T-100 4WD with 131K miles that I bought new. I know, it never has had much power, but I still like the truck, so no jokes please.

About a year ago I noticed that the truck is down on power, with engine ping while climbing hills at highway speeds. After this started, I left it out in the tall grass for a couple of weeks, and a mouse moved in, chewing up the air filter. I noticed this after I started the truck, so I suspect that some of the air filter and/or mouse got sucked into the intake. The truck would start, but would barely idle. I finally got around to working on it this month, replaced the fuel pump, took the intake plenum off to look for the mouse (nothing found), had the fuel injectors ultrasonically cleaned, replaced the fuel pressure regulator, fuel pressure damper, cleaned the throttle body, and removed a mouse tail from the idle air control valve passage. After I put it back together, it runs exactly the same. I checked the timing, and I can't even see the timing notch with the timing light. I have a junk T-100 of the same year that I bought for parts, so I swapped the distributors, and now I have the timing set, but the distributor is at its limit of rotation, which is different from normal. I tried moving it one tooth either direction, but can't seem to find a better spot. The engine runs smoother now, but still has no power. I checked the compression, and all are 190-200. The passenger side spark plugs are clean and light brown, the drivers side are dry but black and sooty.

This truck had the head gaskets recalled at about 80K, and I had the valves and timing belt done at the same time (at least I paid to have them done).

It seems to me that the drivers side cam has slipped the timing belt. Is this possible? Any other ideas?

Thanks,
Warren.

skypilot

iTrader: (1)

Black and sooty means RICH. Compression says the cam timing is Ok. Slipping a tooth is remote. O2 sensor more likely.

Start with the basic tunup, plugs wires, cap, & rotor.

TNRabbit

If you have 200 psi compression, you are off a tooth on the timing belt, probably at the crankshaft.

wabrand

Plugs, wires, cap and rotor are all new. If its the O2 sensor, wouldn't all the plugs be black, not just one bank?

I will probably be pulling the timing cover this week.

wabrand

Here's what I found:
http://www.madtel.net\~wabrand\timing.jpg

The marks on the belt that help align the crank and cams are not aligned with the timing marks at all. Does this only happen when initially installed?

The belt doesn't look worn, and isn't missing any teeth. Do I have a bad tensioner?

Thanks.

skypilot

iTrader: (1)

A bad tentioner can only cause a jump. It needs to be pretty stiff.

I would use the timing marks on the pulley's not the belt. Belts stretch over time and the marks are imherantly unreliable.

Set the crank first, then passenger side cam, then have someone hold the tensioner while you place the driver side cam. Then release and see if you are on the marks. The most you can move them is one tooth so they might not be exact. The tensioner will pull the cam marks inward so you may have to put one cam a tooth too far so the tensioner can bring it in.

TNRabbit

You're link is bad.

skypilot

iTrader: (1)

The belt is supposed to be replaced every 100k miles. I would not trust any marks that are not in hard steel. Now my 91 has 200k and is still Ok. YMMV

TNRabbit

The FSM calls for belt replacement every 60k miles, but you can easily get at least 100k out of them. That said, it's a PITA to get in there, so many folks replace the water pump, belt, idler pulleys, and maybe even the oil pump while they're in there.

wabrand

For those who can't see the picture, it shows that the driver's cam is 4 teeth too far clockwise, and the passenger cam is 3 teeth too far clockwise.

After I took some more parts off the engine to expose the rest of the belt, I found that a mouse was living in the space under the intake manifold, and the remains of a shredded mouse body near the crankshaft. I wonder if this is the reason the timing is off.

Andy A

That is allot of slippage, are the cam pins intact? Cannot tell from the pic.

wabrand

As far as I can tell, the cam pins look intact. I'll be able to see them better when the tools arrive to hold the cam while I remove the bolt.

TNRabbit

That much slippage almost certainly indicates a failing idler pulley tensioner.

skypilot

iTrader: (1)

It jumped, there fore the belt and the tensioner both need to go. I do not remeber if this is an interference engine or not. If it is, check for bent valves.

wabrand

Just finished replacing the timing belt, water pump, idlers, and tensioner. Running smooth again! Thanks for the help.