I have a 1991 Aerostar XL- 121,000 miles. It is in excellent shape, runs great except it is pinging or knocking. It is not noticeable when the gas tank is full, but when it is empty, you can really hear it. A mechanic heard it and said it sounds as if it is running on 5 out of the 6 cylinders. Also the gas guage always reads full, every once in a while it will go in the correct position? Any suggestions? Aerocolorado, help if you are nearby as I am in Westminster, CO.

Thanks!

 

Welcome to FTE.

A little more information would be helpful. Is this a 3.0 engine or a 4.0 engine? Also, when the pinging/knocking occurs are there associated driveability problems or just noise from the fuel tank area? I'm unsure if you are asking about an engine problem or a noise condition. Please post back.

 

Sorry, It is a 4.0 and the noise is coming from the engine, sounds like on the right side of the engine

 

it drives great, has power and idles fine

 

In reverse order, the gas gauge fluctuation could be either a sticking float (sending unit) in the tank (most likely) or a poor connection between the fuel pump and the dash gauge. Replacing the sending unit involves dropping the fuel tank and removing the entire pump assembly. It is more of a question of whether you can live this nuisance problem or not.

The engine noise associated with varying fuel tank levels is a bit of a puzzle. There have no reports to date of others having this problem, so all is guesswork at this point. The only engine mounted item that would make noise that is associated with the fuel tank is the fuel pressue regulator. This should not be making noise unless the fuel pump is acting up. Since you have no driveability problems this is unlikely and furthermore, varying fuel levels should not have an affect on pump output.

I am more intriqued by the mechanic's comment that it sounds like an engine misfire. This makes more sense, as pinging sounds are common from bad plugs and wires. Your current mileage also makes me suspect this plug/wire scenario. Do you hear this pinging/knocking noise at idle as well as on the road? How long have you owned the van and has the engine been serviced regularly?

 

I have owned this since 1995, it had 24,000 mi when I bought it. It has been great to us, we have gone everywhere in it with little or no problems. We do have it serviced regularly. oil changes every 5k and air filter about every 6mo to a year. I had the plugs changed last fall, but not the wires. Give an example, last night I drove it, you could hear it ping,ping,ping,etc. in idle and faster when you accellerate. I filled it up with gas last night and today at lunch i started it up and we are in aparking garage, you could not even hear a tick, even when you pushed on the gas. I know it 's not magically healed? but any suggestions?

 

Backround: It started about 2-14-03, I had the oil changed, right after that I heard the pinging. I checked the oil level to make sure they filled it up and it was filled but they overfilled it. I took it to them and it was a 1/2 qt high, they said it would not have any effect on this noise, to them it sounded like the valves. I went right to a mechanic and thats when he said it sounded like it was running on 5of 6 cylinders, said He could fix the top part of the engine for 850 but if I was to keep the car getting a new engine would be a better deal for 3k. I thought maybe If I filled up with high octane gas and added injecer cleaner it would help. right after that, things went nuts it was idling badlyflet like the engine would die at any moment, always had to shift it to neutral to keep it going at a stop. I took it back to mechanic who put a diagnostic machine on it and said, I needed a major tune up an O2 sensor for about $400. So we decided to donate the car and we bought a windstar, while I hadn't donated it I really didn't want to part with it. SO I read on this forum about the 02sensor and replaced it myself. I them replaced the MAF. Still idled badly, but an acquantenice hooked it up to a diagnotic machine and said everything checked out, but then put his hand inside the engine while it was running an touched something and it smoothed right out, their was a vacuum hose not connected. But now i just have that pinging. I don't have the tools or the knowhow to fix anything major, so hopefully it is not too bad!! Sorry soo long!

 

Well, I have to admit, you've got me stumped as to what this could be. I can't fathom any connection between engine noise and fuel load. I tried to conjure up some relationship between the evaporative emissions system but, being a passive system with no moving parts, it was stretch.

(Whiff, whiff, whiff)

Three strikes and I'm out. Next batter please.

 

The only thing I can think of is, is it possible that with a full tank of fuel that the evaporative system is picking up enough fuel in conjunction with a partially blocked vent to make it run correct, no pinging. But when the fuel load is low and the evaporative system has bled down the ping starts due to low fuel amount due to a plugged vent? Just a stretch otherwise I'm trying to fiqure why it would change with more rear weight with a full load vs less rear weight. I have read where some vehicles will run too rich if a gas tank is filled too full as it can run actual fuel into the evaporative system.
Just an .02 for thought.

68torino

 

Thanks for the thoughts! I just don't know! Over the weekend I noticed it really is pinging when the engine is cold, but once it warms up, you can't hear it. It is running good, although I think I ought to change the spark plug wires, since I don't think they have ever been done! Thanks again!

 

Does it soung like a pinging(marbles in a tin can) or lifter chatter? Just curious as it pings cold but not so much when warm. Possibly lifter noise till the oil pumps up the lifters? There have been comments about Fram filters inducing lifter noise in 3.8s.
If it were true pinging-spark knock this would make me think poor fuel, lean running condition, high carbon buildup. So many possiblities to think of without being able to hear your motor.
The greatest addtion to the internet would be being able to add sound to these sites so we all could listen. Nine times out of ten this would help find the problem fast.
"Oh yeah I know that sound, did it on my rig this is what I found."
I am leaning towrds the lifter noise as when re-reading your posts, you said it started after you changed oil.

 

I am leaning that way also, I am not sure what lifters are, but it seems like chatter. Should I change the oil again with a different filter, to see if that makes a difference?

 

It's a possibilty, I've read other places that the Motorcraft is a better filter than a Fram. Could be personal preference. However, I put a Fram on my son's 68 Torino and it has lifter noise(tapping chatter) and when warm the oil light stays on at idle. When I can get past all my other vehicle repairs-maintenance, I'm changing to a Motorcraft first to see if this helps. If not with an original pump and 140K showing it may just be the pump. But like I tell my sons, do the cheap easy stuff first, if you don't know, the expensive stuff will still be there and you would feel bad 'fixing something expensive' to find out it was the buck three ninety eight item.
Wish I could loan you my 'ears' but hope the best and easiest for you.