emergency - on road repair

[gordo999]

Don't know which category to put this in but it seems engine related.

On the road and camped out in a motel. For the past few hundred km, I've had a gradually worsening noise I can only hear when the vehicle is over 80 kph (50 mph) with a slight vibration above 100 kph (60 mph).

It began on a freeway. I was using cruise control and had not used it for some time. As I approached a town I kicked it off with the brake but the motor seemed to keep racing. Pulled into a rest area and the motor was racing, as if on a really high idle of around 3000 RPM or higher.

Remembering how to get out of high idle in the old days, I kicked the accelerator and it went back to normal. Before it did, I popped the hood to check an accompanying noise, which sounded like a bad lifter, or maybe a bad timing chain. I flipped off the AC to exclude it but the noise was still there, appearing to come from the power steering pump area.

It's a rattling sound like lifters make or a loose chain drive. Might be similar to the rattle some water pump's make when the pump is going but not a bearing squeal. Had the belt off the other day to check the AC compressor and the PS pump did not seem to have play in it.

When I kicked the accelerator and normal idle returned the noise was gone. However, it has been on and off for the past 400 km above 80 kph. I have tried revving the engine while in Park but can't reproduce the noise.

I am not noticing anything in the steering although it may have become a bit jerky.

The only other thing that comes to mind is the drive shaft. However, my experiences with drive shafts was always a shuddering that shook the dashboard as the car accelerated from a stand still. That would not explain the vibration I noticed initially when the van was running on high idle. That seems to suggest it is internal to the engine or to the power steering pump.

[chevymaher]

Vibration check the driveshaft input on the trans.
ticking like that after higher speed operation sounds like a lifter collapsing. It just isn't pumping up correctly.

[SilverBullet1997]

I would install a new TPS sensor to start, it is a cheap part, every autopart store should have one, can be done in less than 30 minutes through the doghouse, it's cheap enough that your not really throwing money down the drain replacing it, like 15$, and only two screws.

Good luck.

[gordo999]

Vibration check the driveshaft input on the trans.
ticking like that after higher speed operation sounds like a lifter collapsing. It just isn't pumping up correctly.

Thanks for the tips chevymaher.

I realize it could be due to several problems and I will check out what you say. However, the ticking was rather severe in Park with the engine running by itself at high idle, and that was my initial problem.. Obviously something else was causing the high idle with the ticking accompanying it. I was not able to reproduce the ticking by revving the engine high on several occasions.

[gordo999]

I would install a new TPS sensor to start....

Thanks for the idea SilverBullet1997.

I did experience issues with a sudden rough idle while playing with the AC. It was almost like the compressor was jamming and really loading down the motor. The TPS sensor makes far more sense than the AC compressor..

I saw two tests for the sensor. One was a reference voltage check with ignition on and motor off checking for +5 volts at one lead. The sensor harness was removed to access the harness sockets. The other was with sensor installed checking the harness wire sockets from behind with a DVM. The were looking for a smooth variation in the 5 volts as the throttle was opened and closed.

That could pose a problem if it was affecting the timing and causing detonation. I had wondered if maybe what I was hearing at 80 - 100 kph was knocking, but when I heard it at first with the high idle it sounded more like a rattle of some kind. Not sure if a fuel mixture could cause a rattling sound.

[SilverBullet1997]

I would install a new TPS sensor to start....

Thanks for the idea SilverBullet1997.

I did experience issues with a sudden rough idle while playing with the AC. It was almost like the compressor was jamming and really loading down the motor. The TPS sensor makes far more sense than the AC compressor..

I saw two tests for the sensor. One was a reference voltage check with ignition on and motor off checking for +5 volts at one lead. The sensor harness was removed to access the harness sockets. The other was with sensor installed checking the harness wire sockets from behind with a DVM. The were looking for a smooth variation in the 5 volts as the throttle was opened and closed.

That could pose a problem if it was affecting the timing and causing detonation. I had wondered if maybe what I was hearing at 80 - 100 kph was knocking, but when I heard it at first with the high idle it sounded more like a rattle of some kind. Not sure if a fuel mixture could cause a rattling sound.

Yea, I'd just buy the cheapest one and try it out, if it isn't the problem you at least have a spare lying around. I fowled a TPS sensor with moisture one time, van was running all sorts of weird, bad shifting, high idle, stuck the new one in and everything was right as rain(minus the rain)...

[gordo999]

Yea, I'd just buy the cheapest one [TPS sensor] and try it out, if it isn't the problem you at least have a spare lying around.

I picked one up but have yet to install it. I need to do plugs and distributor so I'll wait till the dog house is out to do the sensor.

I replaced the belt tensioner and idler pulley on spec. The tensioner was bouncing noticeably as the belt turned. When I got it out, the belt wheel could be spun easily and it kept going and going with a bit of a dry rattle, typical of a dry bearing. The new one spun freely but quit within a revolution or so.

The idler pulley spun freely but when I tried to remove the rubber backing guide, powdered stuff came out. The bearing had play in it and seemed dry. May have gotten it just in time.

The new tensioner had no apparent movement in it with the belt turning and the spring tension was a lot greater than in the old one.

Changed the fan clutch as well since it looked rusted and grotty. I learned my lesson in a previous car when the water pump began leaking and I tried to drive it back to town while refilling the rad. Blew a head gasket. Not taking a chance with the fan failing.

I road tested the van afterward and it was pretty quiet, however, a couple of days ago I went 80 km before the noise started up. It was intermittent and would disappear after stopping and letting the motor cool down for a few minutes.

Suspected it might be an oil issue so I had the oil changed after a flush with Exel product.