detonation help

[.38 special]

As you can see, I have been having a problem with detonation. It was detonating mainly at the top of second and the bottom of third gear. Enough that I could hear it. It was registering 3-10 degrees of knock retard. At that time I noticed some bad numbers from the MAF sensor. So I figured that was the problem.
Yesterday, I replaced the MAF with a Translator Plus, and haven't had a whole lot of time to play with it, but I am still getting some detonation. You can read my modifications in the signature, but note that I have 50#injectors with a stock turbo. I have the FP set at 44line off, and my o2 millivolts are at 810 at wot. As far as I can see, there is no way that I should be running lean.
By the way, with the T+ yesterday, I could hear the detonation, but only registered like 1 degree of kr.
All of my numbers look good, but I still get kr. And the car doesn't smoke or anything--so there isn't oil blowing through.
I am out of ideas, and any ideas would be very appreciated.
Thanks.

 

[scottyb]

What boost and octane?

 

[.38 special]

sorry, I guess that would help. 93 octane and about 15 pounds of boost.

 

[scottyb]

I'm certianly no expert, but here are some random ideas:

Verify that the O2 sensor is good.

Run some Xylene as a test for octane. Maybe able to eliminate false knock from mounts, exhaust, etc.

Get the injectors tested. I've often wondered what may happen if you get a lazy injector. Even tho your O2's look good, maybe one cylinder is lean because of a faulty injector. Maybe?? I'd go here last considering the effort/expense involved.

more???

 

[JDSfastGN]

I've been with joseph (.38special) during most of his tuning, and the car is very finicky, if going from a stop or a second gear roll, it seems to knock at the top of 2nd gear and all the way through third. The 0tc is showing 0-1 degrees of retard, but you can hear a rattle that sounds exactly like spark knock. If you go from a higher speed roll third gear seems fine. My guess is to replace the 02 sensor with a new denso sensor and see what happens there. Change the fuel filter again even though it fairly new. Pull the plugs and make sure they are all gapped and look for a plug that looks like its seen some detonation and appears to be a weak or problem cylinder

 

[.38 special]

Scottyb,
Thanks, it seems we think alike. I am about to order the new o2, I got paid today, and will run some xylene as soon as it dries up and I have some time away from work (probably this weekend)
However I don't think it is false from a motor mount or exhaust, just because (like JD said) I can actually hear it detonating. But the idea about the injectors is pretty good, that makes alot of sense, that it could be just one piston and wouldn't affect the o2 numbers too much. I will try that if nothing else helps.

If anyone else has any ideas, let me know.

 

[.38 special]

By the way, the injectors are only about a year old and might have 15,000 miles on them-at the most. I don't use crappy gas, but I do let it get pretty low rather often. Does anyone else think it is possible to have one clogged?

 

[scottyb]

Don't stay stuck on the injector theory. I think it's reaching, but a possibility. I'd be curious to know if anyone has actually experienced that kind of issue.

 

[Russ Merritt]

You checked the coil pack and module with the tester? Seen that a million times

 

[.38 special]

Russ,
No, I haven't checked yet, but would that make it detonate? I know that it would make it run like crap, and miss, but it wouldn't make it detonate would it? I will check it though--I guess I could be mistaking some other noise for detonation.(especially since it showed next to no knock retard).

Also, let me make this clear: the car isn't running that bad since the translater was added. I am just hearing a noise which I am 95% sure is detonation, it probably rates a 6 on the "Oh crap, let off of it scale". I just don't want to break anything.

 

[Russ Merritt]

Yea it will. They run great till you get on it. Audible detonation! Make sure the wires are good as they will trash the new pack pretty quick if they aren't.

 

[.38 special]

How can the coil pack/module cause detonation. I'm not doubting you, I just don't know and would like to learn.
Is it because of a slow or fast signal and firing at a wrong time?

I really hope you are right. I have a spare pack.

 

[.38 special]

ttt

Don't leave me hangin' Russ

 

[Kyle F]

Yea, I would like ot know the answer to this as well

 

[Russ Merritt]

Sorry to leave you hangin, been sick. Usually it's the module when you can actually hear the detonation, but that's only if the car was running fine then all of a sudden you start hearing detonation. I don't know if it becomes a timing problem or what actually happens but I've seen it a bunch of times. You need to get the caspers tester or change it with a known good one. Keep us posted on results.

 

[Kyle F]

Autozone can test ignition modules off the car.

 

[.38 special]

Thanks Russ

I can't stand to go into Autozone. I think all they are going to do is ohm it anyway. I can do that. They won't be able to test it under load.
I will probably just swap it with a known good one this weekend. That is if JD will let me barrow one. Hell, they got turbo buicks out the wazoo.

 

[Razor]

What are BLM's at idle, whats the MAF read at WOT, have you recorded the detonation..see if someone can hook up direct scan to the car..

If you drop the boost to 12 PSI..will it knock?

If you keep the pedal steady whereas it reads like 5 PSI boost..at 5 psi does it knock?

I'll start you with these.

 

[.38 special]

I don't know where the BLM's are, it isn't something that I normally keep a close eye on. Refresh my memory--where should they be?

MAF--255-good. Just put a new LT1 and T+. I hoped to fix the problem with the addition, since the old MAF was bad. It didn't.

It does not detonate when held at part throttle.

And I was sure that the MAF would fix the problem. So when I put on the T+, due to bad weather, I didn't get a chance to play with it or turn the boost down. But according to the O2's I don't have a lean condition. Just to be sure, I ordered a new Denso that should be here tomorrow.

And as far as I know, you have to modify the computer to use Direct Scan.
What do you think Razor?

 

[Razor]

Ok..BLM's at idle should be somewhere near 128 car in park engine hot. 124-132 is ok. 105 or 150 is not.

Next, for DS yes an ecm has to be modded. I bought a spare just for that purpose. But it tells you what and when is happening.

Get your translator and add a little fuel to the WOT position. Make sure you've set the switch for the appropriate sensor..and check your blm's at idle..you may need to add fuel at idle..via the translator or FPR.

Hard to tell..if the knock is constant and doesnt go away..and the boost is reasonable.. then there are things like injectors and electrical..

If you have a spare coilpack/ign module..swap it out and see..

This tech by descript is only hit or miss.. thats why I ask for a DS recording..at least then you can see what sensors do what when the KR occurs.

Trying to help.. but these issues need data..