bgordon45

***EDIT: Problem resolved. HYDRAULIC TIMING BELT TENSIONER FAILED and passenger side cam jumped 2-3 teeth on the timing belt. Replaced timing belt, tensioner, and no. 2 idler pulley to fix. Tensioner was not replaced during previous timing belt service and failure was possibly caused by engine heat, additional heat from the A/C (which was brought back online a week prior to failure, and hot leaking coolant running down from a leak at the no. 2 idler pulley onto the tensioner)


93 Pickup/ 3VZE / 305k mi

I've been doing some summer maintenance/tune-up work and decided to set the idle speed down. The truck has been running fantastic but that idle has always been a bit high (appx 1050rpm). I made some adjustments and got it too low (600 rpm) and brought it back up to 800rpm.

I didn't notice it until driving up my steep driveway last night but there was a loss of power. Normally I idle up in first and it almost stalled out. I definitely noticed an issue today and have been looking around on YotaTech and at the truck all day.

It did get quite low on coolant this week and overheat (not into the red on the temp gauge but close). I think I have a small leak around the No. 2 idler pulley.

The truck has a definite loss of power, rougher idle, and different sounding engine and exhaust note. There is a little power above 2500rpm but still much less than previously.

Engine throws no codes.

Exhaust is running very hot and rich.

Refilled coolant and ran it for a while on an incline to get any air out. Got a couple of bubbles but nothing big.

I replaced the O-Ring on the Idle Adjustment Screw - no difference.

I took apart the air intake house and noticed a crack near the clamp. I patched it up - seemed like it ran better at first, but still same issues.

Quick visual and soapy water check of vacuum hoses for leaks - didn't find any.



I don't really know where to start with this. Maybe it was coincidence that I was adjusting the timing and this is related to the overheating - which was a very mild episode. Or I'm overlooking something??

I was thinking about taking the throttle body off and checking the coolant passages

Turtl3

Did u adjust the timing or the idle screw? If u adjusted the timing, i can c how that would change ur power and stalling issue. But if it was just the idle screw u played around with then it must be conincidental. Maybe it overheated enough to do the head gasket? That would explain rough idle, loss of coolant, and hot exhaust

bgordon45

It was just the idle adjustment screw.

I put a new belt and recharged the A/C last week and I noticed a coolant leak then. Topped it up some but it didn't overheat until the other day.

There isn't any smoke coming out of the exhaust and I don't notice any in the engine bay.

bgordon45

Coolant is clean as is oil on the dipstick - so hopefully it is not a HG issue

Janos01

Have you done a tune up lately? Plugs, wires, cap & rotor, oil change?

A few signs of a Head Gasket issue consist of:

• Water in oil (Milky Oil)
• Loss of coolant or having to add coolant often
• Excessive white smoke out of the exhaust pipe
• Water in cylinder #6 (definite sign of a bad or blown HG)

Rich fuel smell could be from dirty/bad injectors, bad EGR valve, cheap gas to name a few. I would run some B12 or Chevron w Techron in the gas and drive the car for a bit.



If its time for a tune up, I would replace what I mentioned along with a PCV as they get clogged up over time.

bgordon45

Not seeing HG signs.

It has been tuned up. Went on a 3000 mi road trip a few months ago.

This is a sudden and dramatic change in performance. It has never run like this before. The truck will be barely get up to 55mph.

I was planning on changing the air filter and looking at the plugs anyway so will continue with that but it seems like something in the ECU is way off but it's not throwing any codes

bgordon45

The PCV was replaced with a Toyota part last year when I did the valve cover gaskets. I've been thinking about doing the injectors and am not sure of their health. But like I said, the truck has been running great

bgordon45

I think I've got a head gasket issue.

All the plugs on the passenger side are fouled heavily with carbon
Driver's side plugs are ashy and show normal wear

Compression test as follows:

Driver's----passengers
2 - 140-----70 - 1
4 - 135-----70 - 3
6 - 120-----70 - 5


also noticed oil around the lower left corner of the timing belt cover - near cylinder 1

bgordon45

The mystery gets more mysterious

I was thinking over those compression numbers and realizing the truck still runs (albeit at half power) and the fact that I don't see any smoke out of the tailpipe, coolant in the oil, or oil in the radiator.

It's seemed like a timing issue and so I thought that maybe the timing belt jumped a tooth or two. I was suspecting a FAILED TIMING BELT TENSIONER. I started stripping it down this morning and sure enough it looks like the TIMING BELT ON THE PASSENGER CAM JUMPED 2 OR 3 TEETH.

To back up the overheating started with some pinholes in the radiator a few weeks ago. Even though there was coolant in the overflow tank, coolant in the system got down pretty low and it overheated. At this point I believe a leak started behind the No. 2 idler pulley. I have always had trouble tightening over those bolts, but have done 2 timing belts on this truck and thought I had. I also find that bearing wears very quickly - being under tension from the timing belt. I couldn't see this leak but could hear it and saw some steam coming from nearby a few weeks ago.

There is coolant residue down the face of the engine from the leak at the No. 2 idler pulley. There is also oil around the hydraulic belt tensioner. There is also oil on top of the A/C unit near the tensioner. There is a slight drop of oil on one of the bolts near the passenger side camshaft seal. The seal looks good. Both camshaft seals were replaced at a 190k timing belt change. Engine has 305k on it now.

I did a timing belt change last fall - about 15k ago. My plan is to replace the belt, hydraulic tensioner, and probably the no. 2 idler pulley. The bearing already has a little play although it does slow down to a stop after spinning. The previous idler pulley I replaced (15k ago) continued to spin.

I'm not sure what the cause of the jump was - maybe adjusting the timing and having the engine bog down a bit and/or coolant leaking down into the hydraulic tensioner causing it to fail. It was not replaced during the last timing belt change. During that timing belt service (15k ago) I replaced timing belt, water pump, thermostat, and no. 2 idler pulley, and crankshaft bolt seal. During a previous timing belt service (at 190k) I replaced both crankshaft seals, no. 2 idler pulley, hydraulic tensioner, no. 1 idler pulley, timing belt, and water pump.

ANY THOUGHTS ON WHAT CAUSED THE BELT TO JUMP? Would a failed tensioner be the sole cause - on top of a coolant leak from the no. 2 idler pulley passing water onto it. I recently got the A/C back in service a week before this started. Would that have any effect? It had a bad bearing in the clutch which was replaced by pulling the clutch plate - compressor stayed on the vehicle.

bgordon45

Replaced timing belt, tensioner, and no. 2 idler pulley.

Truck is back together and running well.


I hope I don't have to do another timing belt for 90,000 more miles. I did two last year. I kept having to get back in there because of coolant leaks from the no. 2 idler pulley. This time I scraped the gasket that comes pre-installed on it and went with a fresh bead of Toyota FPIG.