L98-C4-HI

Second post on a new to me 12k mile 88 C4. I've run about three tanks of new gas thru the car now with various additives like cleaners and boosters trying to get rid of some nasty pinging with WOT. Always run premium fuel. If the car is up to speed and I nail it there's no pinging, just off the line or when it kicks down into 1st.
I figure it's been babied all it's life and never run this hard before so maybe the chambers are fouled up with deposits? Not planning on pulling the heads but maybe get a borescope at least for a looksee.
Whatcha think?

383vett

First thing, check timing before replacing pistons.

billschroeder5842

Do what 383 said.... pull back on your timing a smidge. I bet you will be good for ZERO dollars,

L98-C4-HI

clonk - knocks wooden head! troubleshooting 101 strikes again. will dig the timing light out, haven't used one in decades, heck didn't even know this one had a distributor to turn lol. will post back what it's sitting at! the PO supplied the red service manuals but we just moved so have to find that box but a couple degrees less aught to do it if out of spec?
Thanks!

L98-C4-HI

Here's my wife driving Her Car top of Haleakala, Maui, way off in background

Hot Rod Roy

If you find your timing light before you find your FSM, you'll need the know about this EST (Electronic Spark Timing) connector. Unplug it before you check your timing. It's near the lower right side of your brake booster. Most would suggest your timing be set to about 8* btdc.



After this connector is plugged back in, you'll get an error code 42. Reset the code by disconnecting your battery for about 15 sec.

GREGGPENN

If 88 and 89 are the same, 6-deg btdc is the factory setting on the balancer (with the brown EST wire disconnected...as shown above).

Low rpm factory timing can be too high. The 89 automatic BIN I have shows 10-deg more timing in the lower rpms than a manual. With cheap gas, it might ping down low.

Of course it could be a failing/bad knock sensor too. The ONLY time my stock 89 ever pinged was in low rpms on a hot day in the summer. I fixed that problem by building a 383 stroker!

IWannaKaluaInAMaDrinka!

That's the only Hawaiian I know!

Silver96ce

After checking timing, if the problem still persists, check the EGR system operation.

I had a problem on a '94 F150 with pinging which didn't set a code until about 2 years after it started. I couldn't figure it out but was able to alleviate it with premium gas until it got really bad and set the code.

L98-C4-HI

it's not timing, currently sitting around 2 degrees BTDC at 690rpm or so. somebody must've monkeyed around trying to solve this too? so I'm looking at knock sensor R&R and maybe the EGR?

got the ground strap off now was too impatient earlier and didn't clear. would the paper clip trick clear this too? (made that tool before but it's in the FSM in a box where I don't know).

anyways, fun story time I forgot to disco the brown wire at first and the timing mark was way gone like 20+ degrees Before I actually found it but before that was cursing until I remembered Hot Rod Roy's advice!

also made a steel wool on a stick tool because the timing plate was so corroded I couldn't read it! :p

Hot Rod Roy

Another possibility is that your harmonic damper may have a fractured rubber insert. This would allow the outer rim (and therefore the timing mark) to be out of its correct position in relation to the actual crankshaft position. You'll need a mirror to be able to see this rubber insert, but it's hard to determine whether this is an actual problem.

bjankuski

Reading through the posts it appears to me that you have a fuel issue or possibly timing issue. It is always good to check the basics first, before proceeding to more difficult issues. You have checked most of the basics except fuel pressure at WOT. What would be helpful to know is at what RPM does the knocking start to occur at?

-Verified timing set to 2 degrees before TDC
-What RPM does the knocking start to become audable
-What throttle position do your hear the knocking (WOT only or less)
-What is the temperature of the engine when you hear the knocking
-What is the fuel pressure at at WOT? This will require a fuel pressure gauge attached to the fuel rail and taped to the windshield so you can see it. Should be around 42 PSI at WOT.
-Is your knock sensor circuit working, can you scan the car and see if knock retard is being pulled?

-You could have a slipped balancer ring as mentioned earlier but that is difficult to troubleshoot, so verify the basics before trying to replace the balancer.
-I doubt your EGR valve has anything to do with this since EGR is only active at light throttle and does not operate at WOT. If it did operate at WOT it would reduce detonation not increase it. The EGR valve is pulled open by vacuum and at WOT their in no vacuum and the computer program turns off the EGR at moderate to high loads.
-I suspect fuel since you mention that it only happens in low gear from a launch or on a quick downshift where the RPM spikes up. This makes me think that the pinging is happening at higher RPM where a weak fuel supply cannot keep up with the engine demand and the car goes lean which has can cause knock. I suspect when you roll into the car at higher speeds the car does not downshift as far so the engine RPM may not climb as high as low gear which may reduce the fuel required so the car may not go lean.
-It could also be a failed knock sensor circuit ,incorrect timing due to a mechanical failure of the balancer, or even an engine that is running too hot.

Check all the basics and report back what you find, that will help us help you.

L98-C4-HI

That's some great info and I just happen to have a new fuel tank float with pump to install as my gauge is stuck on Full! I borrowed a pressure test kit from the local autozone but the relief button was busted so it constantly leaked fuel. No good! Will try another place.

I think your analysis is pretty spot on too it knocks under heavy load at the mid range as accelerating. If hold lower gear I played with the throttle making it knock on demand with quick throttle presses which I thought was humorous at first but not the best thing to do :p

Kinda' dovetails into my question about why the shifter doesn't go into 1st only down into 2nd, but the kickdown on WOT roll does occur which is how the pinging was discovered but one thing at a time I guess.

update: success? only had time for a short test drive with neighbor riding shotgun but it didn't ping at all with new fuel pump AND the fuel gauge now works yipee! will take it out again tonight and really test it still wish could select 1st manually but it will kick down on a roll.

the Final Final: DONE! Evidently the old pump was just too weak after 30 years. Only the barest of ping was detected once, under full load, zipping up a steep hill. Otherwise it ping is gone! I left about $35 of new, smoking and smouldering BFG burnout strips at my test spot so the HP and torque is getting down now If I can get the distributor nut to loosen I might bump the timing up to 6 or 8 as recommended to get a bit more snap but otherwise if it ain't broke don't fix it. THANKS ALL!!!
of course I found another problem that's another thread haha
yay