Hi everyone,

I’m aware that a lot of you are possibly getting tired of being asked the same or similar question and I have viewed several posts on here regarding "pinging" & "knocking" noises but I feel my situation is a little different. So any help or advice would be greatly appreciated!!


Hi. Sorry, this will be long! I have a 1991 Trans AM, automatic, 305 5.0L V8, with 133,000kms on it. I only drive it off and on in the summers. Before last year, it was stored in a heated garage for about 2-3 years with a full take of gas and fuel stabilizer. Once and a while I would start it up and on good days, run it up and down my street. I only run premium fuel.
While in storage, I installed a functional ram air hood and upgraded to the 245 50/R16 GTA tires. Last year, when I brought it out, and shut it off for a while, it wouldn’t start. And when it did, I had to keep the peddle going to keep it running or it would stall. The next day it started and worked fine. Thought it might have been some bad fuel. Towards the end of summer I noticed the service engine light was intermittently coming on. Also, I started to hear pinging noise on acceleration once the engine was warm. Harder on fuel, maybe not as powerful as it should be but cruises around ok. I never push it too hard. Had the a/c serviced (new compressor etc), coolant flush and transmission fluid/filter changed before storage.
I went ahead and did the following maintenance through winter and this spring. New NGK platinum plugs, 8mm wires, distributor, rotor button, synthetic oil and filter. When I do see the engine service light come on, it’s intermittent and doesn’t stay in to get the code. I’m wondering if it’s one or both of the spark knock sensors malfunctioning because when, and if, the spark sensor detects a noise or vibration in the engine, it’s suppose to adjust the engine timing to compensate for it. Therefore, if the sensors are working properly, I shouldn’t hear anything.
Again, sorry for the long post but has anyone else come by this or possibly have an idea of what it could be? The ram air or tire change wouldn’t have anything to do with it?
Thanks in advance, Brian.

 

Brian, I wish I could answer this question. My 1989 Firebird Formula 350 v8 started doing the same thing, I Always run 89 octane fuel. I have replaced the spark plugs and the wires, changed oil, fuel filter. I checked all of the vacuum lines. For some reason it only knocks/pings when I hit the accelerator while driving. When the car is in park it wont knock unless I really hit the pedal. If I go slow it catches up and runs fine. when I put the car in drive/reverse and dont move the rpm's drop down to 500-400 and the car tries to stall. My next moves are to replace the Throttle position sensor, fuel pump and catalytic converter. If you figure out the problem or if anyone else does, I hope someone will answer this question.

 

Both of you should check your ignition timing and check a plug or two to see how they look. Also, you might want to go to a higher octane level or use some octane boost to see if that helps with the pinging. Brian, you should also use an additive to remove any water from the fuel in your tank, because it sounds like your car spends some time in storage. The code should be stored in the ecm for the light that you get. Let me know what you both come up with, and if either of you can pull the codes using the ALDL port.

 

We just checked the timing, the bolt under/next to the distributor was loose, maybe when I hit the, throttle a little hard once, (drag racing) it could have moved the distributor and threw the timing off?

 

Sounds like a more than reasonable conclusion. Get it set right, lock that bolt down and take her out for a spin. Let me know if that helped

 

Step one would be to pump the old fuel out and get some fresh in the tank.(maybe change the filter and check fuel psi)
step 2 is get the codes, since the light is on.
step 3 is fix those problems.
step 4 is check the timing.

 

My '91 RS LO3 started doing this, even with the timing re-set right and premium unleaded with octane booster, at 4200' elevation. It was carbon build-up in the combustion chambers. SeaFoam is the common solution, but I just filled a spray bottle with ATF, disconnected the cat, and misted the ATF into the TB with the engine running. Ya gotta get vigorous, and both hands will cramp long before the job is finished, so hire a helper. Bribe the spouse. Whatever. But that car was always daily-driven, never stored.

 

Timing off, faulty knock sensor, carbon buildup, burning a little oil, lean mixture, can all cause part throttle pinging.

 

Hello everybody and thanks for the great replies. Sorry I didn’t get back sooner, and again, the long replies!
To Cuthbert, I’m not sure if my problem is exactly as yours but if there’s any pinging, knocking, rattling or engine vibration; isn’t the knock sensors (2 on mine) supposed to detect this and adjust the timing to compensate for it? Where I do hear it, once engine is warmed up, on engine load with acceleration; wouldn’t that indicate that 1 or both knock sensors could be acting up? Do you have any codes coming up when this happens with yours? I’m thinking that’s what the code could be but it’s not in the computer long enough for me to catch it yet. My car idles fine in park and seems to in gear. I’ve always used highest octane as well. As for the loose bolt, that would possibly make the timing jump around like a bad chain and sprockets; I think, wouldn’t it? Thanks Cuthbert.
To iroczracer07: I’ve checked the timing with the wire disconnected; it’s on 6 degrees and stays on 6 when revving up the engine. I put in new plugs, wires, distributor, and rotor cap. The old plugs looked ok when removed. Although they were those 4 post ones that I didn’t like. The cap and rotor button were bad when removed so I thought that might have been doing it. I only ran the highest octane fuel. You could be right on the money with the fuel additive. Before the 2-3 storage and the possible bad tank of fuel, I don’t recall having this issue. The car has been sitting too long with very little driving. I did put in a quality additive that is in the tank now. It’s full and hasn’t been run through yet. I had it out a couple of times but that wouldn’t be enough. I will be getting it out this week or next and taking it on some good runs. The weather is starting to get better here. I will jump the ALDL port when I see that code and let you know once I run it and get the code. Thanks iroczracer07
To TTOP350: I put fuel stabilizer in when I sore it but it was sitting longer than it probably should have. Last summer, I ran about 2 tanks of fresh high octane through it and started hearing the noise before I laid it up. So I didn’t pump out the old fuel but probably should have as you said. I then changed all the parts. The timing is ok. I will check the fuel psi and change the filter next because I don’t know when last the filter was changed. I’ll try to catch that code or codes too and post what I find. Thanks.
To Atilla the Fun: What you’re saying could be a possibility as well. I read on here that others have done that also. I read about the process and to be honest with you, felt a little overwhelmed by the steps. Just can’t spray it down through the barrels like I use to with the old carburetors. BTW, probably a stupid question, but how did you “disconnect the cat”? Thanks.
To Cosmik Debris: Other than the occasional small puff after sitting a while and starting, it doesn’t seem to burn much oil that I can tell. I can go quite awhile without topping up with half a liter. Sorry, I’m also not that up on how to check for proper fuel mixture but doesn’t the computer control that? Once I’m able to catch that code(s), I’ll know more. I’ll post when I have more. Thanks.

So, after all your guys help, I’m going to change the fuel filter and check the fuel psi. Then I’m going to run the tank with the additive in it and continue to run it on high octane fuel. Once I know more and or get the code(s), I’ll post with my findings. Again, thanks to everyone for all the help.

 

Let us know if it straightens out.

 

Hello, sorry for not getting back before now. I didn't really have it out much last summer and just got it out now. Since the last time i replied, I changed the fuel filter and fuel seemed to flow well. As soon as you start it, the gas was there with a full stream. I ran the treated gas out and a couple more high octane tanks through her on a couple good runs. The code was a code 24. My speedometer stops time to time and then it throughs the code. Once it starts again, the engine light goes out. There are no more codes after the code 24. I also sea foamed the engine as well.

It still pinged on acceleration last summer and is doing the same now. I took off the ram air box and installed the factory box, just to try, and it did the same. I've done everything suggested and what I could think of and i still have it. If it were the EGR valve, wouldn't i have throttle and idle issues? Injecters week? I do recall reading somewhere that there was, a while back now, an update for the EPROMs/ECM in these cars that had something to do with fuel/air mixtures. I wonder if that might have something to do with it but how would you find that out? The dealership probably wouldn't help now. Is it possible that an aftermarket performance one would do the trick? Again, sorry for the delay. If anyone has any more ideas, i'd love to hear them!

 

It looks like this thread has died. I know, it's my fault from not getting back earlier. Regardless, I'll update it for others that are having the same problems as me. Here's where I'm at with the car now.

I've changed the fuel filter, seafoamed it, changed the EGR valve and I still get the pinging noise. No new codes. The only thing I didn't do properly was check the actual fuel pressure. We only visually checked as stated previously.

**I think I'll try bumping the timing back 2 degrees but I hate because it most likely will affect performance and it's no rocket now.***

I'm pretty much fed up with this car. I think I'm going to just sell it. Had I known that this would have happened, I would never have installed the hood and the tire upgrade and air conditioning (expensive!). I would have cut my losses and sold it. I'm tired of messing with it and can't afford a part swap guessing game. IMO, there's nothing worse than putting a bunch of money into a car when the engine sounds like you store your wrenches in it!

If someone reads this thread and has more info on the problem or possibly a solution, anything to add, please reply and let us know. I keep checking on it and will as long as I have the car. I'll even notify if and when I do close the chapter on this money pit. Got my eyes on the new 5.0 Mustang. Maybe time to jump ship! Thanks.

 

Sorry guys, I meant to reply to thread but accidently replied within my last post so here it is again. Hope it doesn't confuse anyone!

It looks like this thread has died. I know, it's my fault from not getting back earlier. Regardless, I'll update it for others that are having the same problems as me. Here's where I'm at with the car now.

I've changed the fuel filter, seafoamed it, changed the EGR valve and I still get the pinging noise. No new codes. The only thing I didn't do properly was check the actual fuel pressure. We only visually checked as stated previously.

**I think I'll try bumping the timing back 2 degrees but I hate to because it most likely will affect performance and it's no rocket now.***

I'm pretty much fed up with this car. I think I'm going to just sell it. Had I known that this would have happened, I would never have installed the hood and the tire upgrade and air conditioning (expensive!). I would have cut my losses and sold it. I'm tired of messing with it and can't afford a part swap guessing game. IMO, there's nothing worse than putting a bunch of money into acar when the engine sounds like you store your wrenches in it!

If someone reads this thread and has more info on the problem or possibly a solution, anything to add, please reply and let us know. I keep checking on it and will as long as I have the car. I'll even notify if and when I do close the chapter on this money pit. Got my eyes on the new 5.0 Mustang. Maybe time to jump ship! Thanks.

 

Honestly, I wouldn't sell my thirdgen if the motor AND tranny blew, low mile third gens in good shape just don't appear often, especially in my area.. Everyone has a rustang of some sort now-a-days. You can find your engine fully assembled for 300-400$, and that's FULLY assembled. The junk yard sells blocks around here for 199$, buy one and build it.. Or buy the fully assembled engine. It just seems like you've covered the basis here and you've probably spent more than it would cost to replace the old small block.

 

Hi 3rdgenlewis. Thanks for taking the time to reply. Although I’m a car guy and like other brands as well, I really like these cars and looked for this particular one I have.

The problem I’m facing is that the car did not have this problem before I stored it for a couple years or so prior to my original post. Therefore, I done the tune up and changed the usual parts that could cause this problem, on my own and with help from this forum.

I still have the problem and before I start changing every sensor and replacing the computer, and or engine I’d like to contribute my findings to this problem and hear from others that may have found another solution. Outside of the pinging noise on acceleration, the engine and car works really well. I really enjoy driving it; I just can’t stand the noise.

I also thought about swapping the engine and even looked into a new engine but there’s a good chance that after all of that, it could actually still have the same pinging problem because this problem appeared after it sit for awhile. It wasn’t there before I stored it for 2-3 years. So before I spend time and money on a replacement engine, I want to exhaust all other possibilities. That’s why I’m here! I still need to adjust the timing and I’ll post my results either way for those who are having the same problem. Thanks again.

 

My 92 rs is doing the same thing. Pinging at low rpm. I got so tired of the pinging I bought new gm goodwrench motor. Put new motor in and still the same pinging at low rpm. also put new egr valve, new egr solenoid, new esc module, new knock sensor, new ignition control module, new cap, new wires, new button, new plugs, mine will set ses light but when I check for codes no codes to be found. if any one can help please do. still have not changed o2 sensor or map sensor but at this point Im tired of throwing parts at it.

 

My 92 rs is doing the same thing. Pinging at low rpm. I got so tired of the pinging I bought new gm goodwrench motor. Put new motor in and still the same pinging at low rpm. also put new egr valve, new egr solenoid, new esc module, new knock sensor, new ignition control module, new cap, new wires, new button, new plugs, mine will set ses light but when I check for codes no codes to be found. if any one can help please do. still have not changed o2 sensor or map sensor but at this point Im tired of throwing parts at it.

 

Hi jk92, Thanks for replying. Sorry for this long reply. I feel the same way. I was afraid of replacing my motor as well for the same reason because I feared that it may still ping. My car seemed fine before the 2-3 year storage. Just before I put it back on the road, I installed the larger GTA size tires (not sure if that would put more strain on engine and cause it to ping?) on it and did the tune up with ngk platinum plugs, 8mm wires, cap, button, oil change and trans flush & filter,etc. Then once I started driving it again, I noticed the pinging.

Where it did seem like a fuel/air mixture and timing issue, I was looking at the knock sensors but was getting no codes for them. I then noticed the “lean mixture” in the CosmikDebris reply and searched about that.

I found out that the o2 sensor could cause the engine to ping as well so I unplugged the o2 sensor and noticed more power and little to no pinging; because it wasn’t pulling the timing back now. With it unplugged, the SES light will come on once the computer checks for the o2 sensor reading (once it warms up enough)but where it gets no reading it will use the default setting that is stored in the computer and go by that. The only problem with this is that I find it’s not always accurate, it doesn’t get the real time reading and still pings as result. I have the new o2 sensor but couldn’t get the old one out yet.

Also, in my research, I found that there was flash update for the computer in my car. This was quite some time ago and I’m not sure how to go about having it done. The flash was to fix some of the fuel/air mixture issues as well. I tried to find it on line again but couldn’t. My next step is to replace the o2 sensor and check on how to update the computer. I thought about buying a slight performance upgrade chip thinking that that would be like updating the computer as well. I'm thinking of going back to the GM wires, cap & button and plugs as well.

See where the engine seemed to work fine before, has more power at times with o2 sensor unplugged and started doing this quickly, I’m not convinced that the motor is bad. Again, PLEASE, anyone that has an idea or solution; let us know and thank you all for your help and replies.

 

By unplugging the O2 sensor, you are causing the engine to go into open loop. This means that the PCM is not adjusting the fuel control based on feedback it receives from the O2 sensor, and it is defaulting to the pre-programmed fuel map. If the engine is running much better with the O2 sensor unplugged, then there is likely nothing wrong mechanically with the engine. All that is happening is that one or more of the sensors on the engine is giving an incorrect reading to the PCM and causing the engine to run poorly.

To start with, I would recommend that you validate that the O2 sensor is working properly and giving correct information to the PCM, or if you don't have the equipment to do that just replace it since there is only 1 and they are cheap on these cars. Definitely get an AC Delco one, don't buy an aftermarket one. Once you have a known good O2 sensor in there, make sure to disconnect the battery for a while so that the PCM forgets all the incorrect adaptive strategy it learned. If the O2 doesn't fix the problem, at least you now know that it is providing an accurate signal to the PCM. At this point I would strongly recommend that you get yourself a scan tool so that you can view the fuel trims. I use one I got from moates.net for $80 and you can use it with tunerpro software which is free. Not only will you be able to monitor the fuel trims but you can see all of the voltages and waveforms generated by every sensor on the engine so you can identify if you have a problem without throwing parts at it.

 

PROBLEM SOLVED!

Hello everyone. Sorry for the cold thread. I hate it when threads go cold. Either the poster didn't figure it out and gave up or they did and din't bother to fill us in. In my defense though, I only really had the car for one good run last summer and only brought it out this past 2 weeks to burn the old gas out of it to prepare for storage.

I ended up doing pretty much what everyone suggested but still had the problem so figured it was just where i wasn't driving it much. Made sense because after the long run and pushing WOT a couple times, the pinging was near gone but as I putted around, it returned. The intermittent service light was just for the speedometer where it stops time to time.

I had it out for a drive and noticed something that i previously didn't pay attention to. When i would use the passing gear, kick down, it would quickly kick in and out before it really did anything. So, when checking on that, I ran into the TV cable proper setting that i previously adjusted back before it came out of long storage, using the Haynes Repair Manual, because it was limp. The Haynes manual does not explain it properly and I didn't have it set properly. I moved the throttle by hand and did not get the proper WOT setting. So this time, I had someone push the pedal hard to the floor and it set correctly.

The car works much better with more power and doesn't lug back on hills. I wasn't expecting the pinging to be gone as well but it makes sense now. Where the car was laboring on load due to the improper pressure in the transmission, the computer was fully advancing the timing to compensate for it, i guess, and therefore pinging as result. Thanks again to everyone and this site.

So, sorry for the long explanation but I hope it can and will help others. This link below was the best one I found:

http://www.tvmadeez.com/article/