Upgrading ECS module on 85-89 L98?

[TedC]

Has anyone upgraded their 1985-89 ECS Module to the ECS used on a 1990-96 using part number 16038331? I've read several positive articles on this upgrade. Net net is that the knock sensor is very sensitive on all years, but the ECS used on 1985-89 L98s generates way too many knock counts, causing ECM to retard timing (even at WOT).

 

[tonylong]

BTT I'd like to follow this thinking too.

 

[TedC]

I'm trying to find a picture of this recommended ECS. When I looked at the Corvette Central catalog, it looks like the ECS design was physically changed and would not be a simple plug in replacement.

 

[Hib Halverson]

Are you talking about the sensitivity of the KS or how the ECM processes the KS data?

Also, where are these articles you've read whichy are favorable on updating the ECS module. I'd like to read them.

 

[TedC]

Hib, Sure would like your input on this. Here are some of the details available when seaching by ECS and 16038331 on Yahoo.

Background The '85-'89 L98 uses an Electronic Spark Control (ECS) module to listen to the Knock Sensor and report ping to the ECM (on '90-'96 Corvette motors the ECM listenes directly to the Knock Sensor). When the ECM detects knock counts it pulls timing till no knock is reported and then gradually increases timing to the current setpoint. Problem Even with base timing at +6deg and running the stock MemCal chip, my '88 L98 was plagued with false knock counts under WOT operation (seen on my AutoXray scan tool). These were causing timing to be pulled, which I felt was hurting 1/4mi performance. Solution When I discussed this issue with Gordon Kilebrew, at Corvettes at Carlisle 2001, he told me to replace my stock ECS module with the upgraded unit: GM P/N 16038331. Verification After doing this upgrade a short WOT run on the highway showed no knock counts on my AutoXray. Subsequent testing at the local drag strip showed an improvement in trap speed of about 1 mph. No other changes had been made and trap speed data was normalized for weather conditions to provide a valid comparison with prior time slip data. Equipment Safety This upgrade is safe for the motor since the ECM checks the ECS module occasionally by advancing timing till a knock count is registered; if no knock, the ECM would record a code 43. Just to be sure all was well, I advanced my base timing to about +12deg and made a WOT run on the highway; 7 knock counts had registered on my AutoXray.

 

[Hib Halverson]

I know all about how EST works.

I just wanted to read those articles.

From your post, it sounds like the change worked well on your engine.

False knock can be a tough problem to solve. No doubt that the later ECS processes the KS signal differently.

Lastly, I'll add that when confronted with false knock, another useful strategy is to find out what's causing it. Some possibillities are: noisy valve train, headers, piston knock or defective KSes.

 

[TedC]

Hib, I have not yet performed this upgrade. I can't find the part recommended. The positive info I posted was from the net. Can you help locate the ECS part they are referring (GM P/N 16038331)? What year does this part belong to? When I was monitoring IAC steps (different project), I noticed a number of knock counts, even at idle. Then I uncovered this article when researching.

 

[vetteoz]

I can't find the part recommended..... would not be a simple plug in replacement.

ELECTRONIC SPARK CONTROL MODULE GM# 16038331 - $61 : Auto Engine Parts Warehouse & Automotive Accessories | Engine Parts R Us

This is identical to the 882407 ESC I have in my '87 and the one in my '89 that has no label left.I think the 1603331 is an upgraded module for our earlier models; not from a later model
I believe the ESC on the later models is part of the ECM circuitry so there is no external ESC module.The knock sensors themselves are different ; 84-89 v 90-91 because as you note the KS signal goes direct to the ECM on 90-91 cars.

I have the same problem with false knock counts.This might fix the problem.

 

[topless82vette]

desensitize your knock sensor

 

[TedC]

vetteoz, Excellent information. This really helps. I suspect this issue impacts numerous early L98s. Looks like an easy 10 minute project.

 

[KANE]

Old thread... but a good one of you have an 82 or an 84.

Yes, you can absolutely swap in an 85 - 89 knock sensor. however... you will need the matching ESC that goes with it. Otherwise, you will get false knocks. It took a lot of data logging to figure out it was false knock, but the best I can guess is the OEM ESC is looking fo a slightly different signal than the 85 - 89 knock sensor delivers.

Wiring is easy- blue harness wire goes to E, brown goes to D, black goes to C, and pink black goes to B. You will need a Delphi 5 Way 4 Usable Black Metri-Pack 280 Sealed Female Connector and then four Delphi Metri-Pack 280 Female Sealed 18-16ga Terminals.

NOTE: In the attached image I have a pigtail shown to illustrate how much smaller the late model ESC is. I went ahead and cut the card reader connector off the harness and crimped on the 280 series terminals. I don’t like butt connectors- replacing the terminals is way to do this properly.