back together and still pinging

[bigblack]

Wow,I am at my ends with this.Today I got the car back together after pulling the tpi,runners,and egr off.I found that everything was full of carbon.So i pulled it all apart and cleaned it up real good.Then put it back together and ran some sea foam through it and replaced the spark plugs.Well took it for a drive and the s.o.b is still pinging.I got alitle pissed so I stomped on it unlike i have done in the past and it pretty much pings even at wot.I then went back to shop and pulled the maf.sensor and cleanned it up.(I noticed that car dont ping half as bad with it disc.)I put the cleaned maf. back on and tried again.Same thing.Any ideas?????What do I need to check the fuel presure?Could that be it?I am lost at this point..;help

 

[Hib Halverson]

Is the EGR working on this engine?

Does it have an aftermarket calibration and if so, do you know the spark curve?

Is the base timing set properly?

Is the engine modified and, if so, what is the compression ratio and what camshaft is in the engine?

 

[bigblack]

Most of the questions you are asking I cant answer,because I just got the car two weeks agnly thing I have found that is unstock is the flowmasters,and the hypertech air foil on the tpi.Timing is set at 6 degree btdc.And it has new injectors(so the past owner told me)And they look new.Now for the egr.WOW i have gone rounds with that one.It looks new.I tested it with vacum pump with car not running and it holds vacum,however with car running at a idle it will not hold vacum no matter how hard i try.Also with car at a idle and vacum pump on it it does not change idle at all.It dont die or stumble or anything.SO i cant figure that out at all.I only have a chilton manual,and it sucks.

 

[Hib Halverson]

Use the Chilton manual to line your cat box then go buy a factory service manaual.

Typically, an engine with EGR will knock at part throttle if the EGR is disabled or defective, however, you say the enging is rattling at wide open throttle so...EGR may or maynot be the problem.

Is the check engine light on? If not, does it come on during bulb check then go off?

 

[bigblack]

no check engine light.It comes on during start up and with maf. unplugged it came on.I have checked for codes and got nothing.Pinging is at its worst at light throttle.

 

[G Winter]

Does it ping when the engine is cool? It is possible that someone was running really crappy gas and the cyl heads are full of carbon. Rough carbon gets warm and glows like a glow plug lighting the fuel. Could be EGR like Hib suggested. The EGR operation on the TPI engines is a little sophisticated, not just and open and close but almost a bleed type of operation if I understand the FSM corectly.

Glenn

 

[bigblack]

yes it pings when cool or cold .I think it pings alitle more when hot.I tried to run some sea foam through it,but didnt seem to help.

 

[John Robinson]

Try this

Just for kicks fill the tank with premium and a can of octane booster. If it does not ping then you can at least drive it and try to work out the carbon that as suggested is causing the detonation.

Also if the car was not driven much you could have a lot of water in the tank from condensation or the last fill up and driving out a tank of gas would help eliminate that problem.

Keep us posted.

 

[bigblack]

i drained the fuel already and filled it with 91 chevron and 1 bottle of 108 octane booster.then drove it for about 60 miles. that did very litle to help

 

[TedC]

You should not be pinging at WOT. Unless you can provide ECM serial data, this is going to be hit and miss. Getting a FSM is a great suggestion. Here are a few suggestions. When hot in park, force the EGR's primary valve to come unseated by pushing up inside the EGR. Use a mirror to see underneath. If idle changes than the port is not plugged (good news). Next, disconnect the EGR vacuum line and attach a gauge with a 6 foot hose. Drive the car. What happens? You may set a code if you do this too long (just disconnect the battery to reset ECM). You should only see EGR vacuum off idle. Not at idle or WOT. Some rapid needle movements will occur when vacuum appears on the gauge. This is caused by how the ECM pulses the solenoid. This type of EGR is a negative pressure valve and depends on back pressure to operate properly. When I pulled my EGR after 60K, it was not caked with carbon. Only guessing here, but I'm thinking too much timing or carbon build up in the heads that is messing up proper combustion. I have never worked on a SBC that pinged when cool. Hot yes, cool no. As I stated before, GM cranked up the timing curves on the L98 with alum heads, so it doesn't take much to cause off idle pinging. Some off idle ping is normal on light loads. WOT ping is NOT right. Disconnecting the MAF changed the fuel and timing settings. Check base timing. You tried higher octane with minimal improvement, so I'm back on the too much timing or carbon buildup idea. I worked on a 4.6L Mustang that pinged like the devil due to carbon buildup (even at WOT). It took a month to resolve by adding a bottle of techron each week in the tank. The increased use of ethanol in gasoline speeds up carbon buildup.

 

[Hib Halverson]

(snip).
Pinging is at its worst at light throttle.

Detonation at part throttle is a primary symptom of a failing or failed EGR.

Before you do other things, get the FSM and troubleshoot the EGR system per its instructions.

If the EGR troubleshoot comes up zeros, then consider the carbon build-up issue discussed above by "TedC"

 

[topless82vette]

I've heard a punched cat on TPI motors can make the egr rattle and sound like detonation. However my friends 1990 with a plugged cat used to detonate alot as well. Like this hibhalverson said check the prom chip see if it is some custom chip that was never burned correctly and certain things are disabled like egr function.

 

[TedC]

Topless82vette, What is a punched cat? Removal of the converter honeycombs? Never heard the term. Did your friends 1990 ping when the engine was cool? Interesting idea with the plugged cats, causing the heads to overheat.

 

[topless82vette]

Topless82vette, What is a punched cat? Removal of the converter honeycombs? Never heard the term. Did your friends 1990 ping when the engine was cool? Interesting idea with the plugged cats, causing the heads to overheat.

the things his car did was this, fans would run all the time, engine sounded like a vacuum cleaner (sound of injesting tons of air) temperature would always be in the 220 degree range, higher then normal oil temps, car also got quieter (he has muffler eliminators).

turned out the cat wasn't plugged but the honey combs or whatever you call them were loose inside the main cat. The car also never got the glowing exhaust that you would expect. I drove the car for about a week so I would say yes it did it whether hot or cold but was much worse as it got hotter and more noticeable as the engine was lugged in a higher gear (six speed car). It definately didn't like full throttle driving the car would surge heavily like engine shutting off a cylinder. (probably the knock sensor retarding) but medium driving it even did the same thing just not as bad.

The car even passed an emmisions test in this condition and did it with ease which is why the cat was never suspected by anyone as being the problem. No codes were in the ecm either, after a new main cat was installed the rusted remains of his muffler eliminator baffles started coming out the tailpipes and car got very noisy however, all other problems went away.

 

[bigblack]

I have tried to open egr(unseat) at a idle and still got no change.I didnt get a chance to work on it today.I started to check the compression yesterday before i got called away due to a friends daughter blowing her toyota up.Anyway the two cyl that i did check where both 185-190 lbs.My car runs at about 175- 180 degree going down the road.I have yet to see it go over 202.temp hear has been about 74-80 degree here where i live.I will try the gauge trick while driving car and check and see if the chip looks stock or not too.

 

[TedC]

bigblack, When you say you tried to unseat the EGR, what method did you use? Vacuum or physical? The key here is to verify that the valve does indeed move using a mirror. This test is critcal to verify that the ports to/from the EGR are not all plugged up. Another way to test the EGR is to plug the vacuum line to the EGR. Does the pinging condition get worse?

 

[bigblack]

tomorrow I plan on rechecking with a mirror to make sure it is unseating.I will report back with what i find.Just want to tell everyone thaks so much for all the input.

 

[bigblack]

Ok did some testing today and yes the egr will hold vac with car not running,but it takes like 10 in.hg just to crack it open and I cant get it to pump up any higher.I started the car and could not get it to hold any vac.I then put a mirror under it to see if it was opening and with me pumping the vac pump nothing,so i opened it up manually and the car almost died.So i think my egr is bad.I will try and get some hose to check vac to egr when driving tomorrow.Well what do you thing???

 

[TedC]

We are now getting somewhere!!! You validated that the EGR ports are open. Great news. The next key test is vacuum readings off idle while driving. Do NOT use a tee connection. Directly plug in the gauge to the EGR vacuum line (no EGR) with a hose long enough to watch while you drive (don't fully close hood). So far, early indications are pointing towards a leaking EGR valve.

Here is post I made several months ago when I was having EGR issues.
I received a new AC Delco EGR today. When testing it, it started to open between 2-3 Hg-In. The 19 year old EGR on my 1989 L98 was not as responsive. I also noticed full open occurs at a much lower vacuum with the new EGR. These negative pressure EGRs have two diaphragms and two springs. The lower EGR diaphragm and spring play a critical role is sealing a vent hole that the upper diaphragm depends on. So my guess is that the lower spring had weakened with age, or the seal was failing, or both. I experimented by adding the vacuum pump in-line with the EGR vacuum line, manually forcing EGR operation (open/close) while driving. If I forced the EGR to stay closed, after a few minutes I could hear engine ping under light acceleration with a fully warmed up engine. Really appreciate you sharing your L81 EGR findings which helped me determine that my EGR required my attention.

 

[bigblack]

I did the vacum line into the car with the vac gauge today and Once car was up to temp it started reading when I gave it some gas it Moved around from 3-10 hg.So next just for the heck of it I wedged the egr partialy open and took it up the road.It still sounded like it was pinging.It didnt want to idle smooth with the egr cracked open.I just cant figure out why the car sounds like it wants to ping even with it cracked open.I am really afraid of spending 100.00+ on a egr and have it still ping.Even though it must not be working.I may try a used one before spending the cash for a new one,just to see if it changes anything.