Eric Darr

I have set the base timing on my car at 10 BTDC but after plugging the EST back my timing does not advance and now when I apply the throttle it hesitates before revving and 'pops' through the intake. I have read many posts on this site about EST, setting the timing, and idle relearn but have not found anything like what I have going on.


A little history as to what I've done so far... I bought ta car a month ago with 'a bad fuel pump'. I have replaced the pump, sending unit, in-line filter, and cleaned and resealed the tank, and also took an air hose to the fuel lines to blow out any crap that might have settled as the car sat for several years.


When I tried to start the car, it would 'run' as long as I worked the throttle but would not idle and died as soon as I let of the gas. I had planned to replace the cap, rotor, wires, and plugs but I found a lot of corrosion on the pick up coil and wires going to the ICM so I bought a complete new distributor too.


I installed the distributor, plugs, and wires and got the car started. I had put 5 gal of gas and half a bottle of Sea Foam in the tank, so when it first started it smoked and idled pretty rough. After running for 30 minutes, the idle settled down and now idles around 750 RPM.


Because the car started easily and ran better and better each time I started it I left the timing alone. I finally, got around to setting the timing on Thursday. When I checked it (with EST disconnected) it was at 20 BTDC so I dropped it down to 10 BTDC. I noticed yesterday that it started hesitating when I give it gas and pops through the intake.


I have adjusted it (10,12,14,16,18,20 BTDC) and rechecked it. No matter where I set the base timing it never advances when I plug the EST back in. I 'drove' it up and down the driveway aggressively and when I hit the gas it bogs/hesitates then takes off and pops several times through the intake. I have inspected the vacuum hoses for cracks/leaks and have not heard any leaking. I checked fuel pressure with key on/engine off and it's 42 psi.


I am wondering if I have an EST problem or possibly a bad ICM (even though it's brand new) Any thoughts?


Thanks

RBob

iTrader: (1)

Did you key-off for at least ten seconds after plugging the EST/BYPASS connector back together? Need to do that to reset the ECM.

Does the SES/CEL light do a quick blink off at key-on, engine-off? Can rerun this test after 10 seconds of key-off. The blink off is important as it means that the ECM is actually running and not in limp mode.

Another test: disconnect the EST/BYPASS connector, connect the timing light to #4 cylinder (center drivers side), and start the engine.

The timing should be at 10* BTDC. Now slowly increase the RPM while watching the timing. At about 1600 - 1800 RPM the spark timing should jump advanced another 12 - 16*'s. This would be to 22 - 16*, note that this has the timing mark moving toward the passenger side of the car.

If it doesn't do that then the ICM is bad.

RBob.

Eric Darr

RBob,


Thanks for the reply.


1. Yes - key-off was for more than 10 seconds after reconnecting EST.


2. Yes - SES/CEL did blink off with key-on, engine off. I'm sure the ECM is functioning properly. There have been a few times when idling the engine the SES/CEL would come on with code 23. Sometimes the light would go out by itself and sometimes I would disconnect the battery in chasing the timing down.


3. I will check to see if the timing advances with the EST disconnected. I was under the impression that once the EST was reconnected timing would advance 10-15* at idle. I'm pretty sure I checked it before and it did advance. What made me double check the timing is that it started bogging and popping when hitting the throttle. My gut made me think ICM but I read some many threads about the EST and idle relearn I second guessed myself. I've worked on GM cars for 30 yrs but this is the first time setting the timing on a fuel injected car and dealing with the EST. I'll check what the timing does and report back later. I may go ahead and take the ICM off and go have it tested.


Thanks,


Eric

project89

iTrader: (1)

check the firing order on the plug wires , i know it sounds stupid but its happened to the best of us before

sometimes something that seems liek a big issue is really only somthing minor or stupid like that

Eric Darr

project89,


Firing order is correct. It starts easily and idles smoothly. On a cold start, it will idle @ 1000rpm and drop down to @ 800rpm within a minute. Other than the bog/hesitation when I touch the throttle it revs cleanly.


RBob,


I let the car warm up through two fans cycles then disconnected the EST and verified that the base timing is set @ 10* BTDC. I don't have a tach to check the rpm's with the EST disconnected, but 'going by ear'... I estimated 1500rpm @ 16* and 2500rpm @ 20*.


Then I connected the EST and plotted this advance curve:
(RPM's are approximated by the in-dash tach)
Idle 800 - 10*BTDC
1000 - 13*
1300 - 14*
1600 - 16*
1900 - 18*
2200 - 20*
2500 - 21*
2800 - 23*
3100 - 23*
3400 - 25*


Back when I set the timing on a carb'd V8 with HEI - let's say I set base timing with vacuum advance disconnected @ 14* BTDC and vacuum adv added 15* and mechanical advance added 15* for total advance @ 44* BTDC. Correct me if I'm wrong, but I thought when I plugged the EST back in that timing would advance a little at idle. I especially think I should have more than 15* of additional advance @ 3500 rpm.


This makes me think my ICM is bad. Again, it's brand new with 0 miles and no more than 5 hrs run time. I'm going to take it to AutoZone tomorrow and have it tested. If it is bad, what would make it fail so quickly? Is there something I may have done incorrectly when setting my timing. I did check the timing before and noticed base had increased to @ 22* with the EST plugged in. After it started bogging and 'popping' through the intake is when I noticed that the timing at idle was the same whether the EST was disconnected or plugged in. Is there anything else that could be causing the bog and 'popping'?


Thanks,


Eric

RBob

iTrader: (1)

That timing doesn't look right. As for the module, it's an aftermarket piece. Have nothing good to say about them. I've been using GM AC Delco JY pulls for a long time now.

If you have a u-pull yard nearby, stop in and look for GM ICMs. Grab one or two and try those.

RBob.

Eric Darr

I took the ICM out and had it tested. It tested good. However, when I pulled the ICM It hardly had any grease underneath. Usually there is the thick white paste but ths was clear and barely any. I'm gonna send the distributor back for a refund and rebuild the original I guess (and get an AC Delco ICM)

Eric Darr

I got to thinking about this after my ICM tested good and was wondering if there could be anything else causing my problems. Would a bad ECM cause something like what's going on? I think I'm going to return the new distributor for a replacement and then buy an AC Delco ICM to put in it. Hopefully that will take care of my ignition woes - unless anyone else has some other thoughts...


Thanks,


Eric

OrangeBird

iTrader: (1)

Hi Eric ,

I've got one thought to share with you , and one piece of advice .

First , the advise . When you set up your new ICM into whichever distributor you plan to use , take the little blister package of crap cheap thermal compound that comes with each new ICM and put it in the garbage where it belongs . Go to either your local electronic supply or local computer repair business and buy some good quality thermal compound (sometimes called thermal paste) . The stuff that comes with the ICM is really just about useless in conducting heat from the ICM to the distributor body , and I believe it's so the ICM lives just about the length of the warranty . Using the good heat sink compound (yet another name I've heard it called) on each new ICM I've installed has yielded exactly 0 repeat failures ! Yes , as a little tube of slime goes , the good stuff ain't cheap , but it's well worth it's cost in a nice cool running ICM that will last a good long time . The tiny tube of it I used to get at radio shack was like $15 , like I said kinda pricy for a tiny tube of goop , but priceless to the longevity of your new ICM

And my thought ;

I wonder just HOW well those auto store testers check the ICM for a good VS bad reading ? As in , does it only check if it can make and break the coil circuit on command or does it actually check the more sophisticated operations such as timing advance per RPM ? Because if all it's checking is whether it can make a spark or not (my suspicion here) then it would be of no help troubleshooting your timing issues . And I hate to say it , but I have seen more brand new out of the box failures of electronic devices over the past few years than I've seen in the preceding 40 or so years combined ! It's like every company fired their quality control staff , and WE are now quality control by proxy , weeding out the factory's failures as we attempt to find parts that actually work as intended

Street Lethal

iTrader: (16)

Couple of things to point out Eric, but you can take them like a grain of salt. For starters, the car has been sitting for quite awhile as you initially pointed out, so right there you may have a fuel injector issue. Did you check them yet? Fuel pressure is good you said, the wires are correct you said, and you used seafoam in the fuel tank, which I never do myself, as that has the tendency of bringing residue to the injectors and clogging them, with the result being a choppy idle until more additional seafoam is used to clean them out as well. Now, you stated that the engine had a base timing of 20* when you bought the car, as well as when it was idling better and better after the seafoam and ignition upgrades, but then you reset the timing back to 10* and this is when all of the popping issues became prevalent, correct...?

You have to ask yourself, why was the engine preset to a 20* base timing before you bought the car, and why was the engine able to hold a steady idle at 750-RPM after the seafoam and ignition upgrades did their thing with a 20* base? The stock prom has a 10* reference which needs to match the engine's base timing, and if your engine was already set to a 20* base when you bought the car from the previous owner, and it seemed to idle okay at 20* once the seafoam was added and ignition upgrades were installed, but only started with the popping issue when you pulled base timing back down to the stock 10*, then that would tell me that either someone before you altered the data in the prom and purposely set the base timing to 20* BTDC, or they advanced the camshaft and advanced the timing to maximize the best results possible through "feel"...

Eric Darr

OrangeBird,


Thanks for the advice and thought. I will get some thermal paste for the new ICM. As for the ICM test, they said it tests several things including advance but you're right - who knows. One thought I had, was with there being very little of any thermal paste the ICM is getting too hot to work properly but not burning out.


Street Lethal,


In trying to cover all the bases when I started this project and trying to prevent any new issues with the fuel supply. I took my tank to my friends automotive shop and he cleaned the tank and resealed it. On the supply line, I blew high air pressure forward and backward towards the in-line filter location (filter removed) to blow out any old fuel and any crap. I also did this on the return line from front to back. I spray carb cleaner in the lines and did it several times. I ran Sea Foam in the tank to help clean the injectors as well as any carbon built up in the combustion chambers, etc. I feel confident the fuel system is good.


As for the timing - the base timing of 20* BTDC came about when I first dropped in the new distributor. Because the engine was running good at the time I left it alone to give the Sea Foam time to work internally. After it ran for a couple hours over 3-4 days time I decided to set the timing. A day or two later I noticed the engine developed the bog and popping and realized it wasn't advancing. I have my doubts about the ICM being good - or it may be getting too hot because of the lack of a good thermal compound. Also I have doubts about the cheap ICM that was supplied with the new distributor. I realized yesterday that the old distributor has an AC Delco ICM in it. I'll have that one tested and get some good thermal compound.


Before I removed the ICM, I drove the car around the block and other than the initial bog and popping the car drove pretty decent. Part throttle was good with no surging. I did stomp down a couple times, trans kicked down but again it bogged and popped until I let off then cleared up and ran fine. I'm just trying to verify I have a distributor issue and not an ECM issue.


I wanted something to play with and this is fitting the bill. I just want to get it going soon and motivate my daughter to get her license. Since she's dragging her feet, I decided too tackle the front brakes and probably will replace the front struts and rear shocks too.


Thanks,


Eric

willexoIX

Aside from the timing not advancing, it sounds like its time for a new timing set.

Mine did the same, except every time I would set the timing it would jump, and any time I gave it more than roughly half throttle, bog and pop through the intake.

Changed the timing set and found a stretched chain. No problems since.

Street Lethal

iTrader: (16)

Eric, I am trying to grasp your whole scenario. Let me see if I got this right. The engine came with a base timing of 20* when you bought it. You left it like that just to run the seafoam through because it seemed to run okay with that advance, but once the seafoam did its' thing, you placed base timing back down to 10* where it belongs. Now your noticing that the advance is not advancing during idle (it stays at 10* with the EST plugged in), and when you hit the throttle... it's not that it isn't advancing at all, it's just not advancing "enough" in correlation with engine RPM. Is this correct?

This now explains why the engine was set to 20* when you bought it, as the former owner advanced it purposely to force initial idle (10*) to reflect idle state (20*) at idle so that it will have more than the 15* increase you are seeing at 3500-RPM. RBob is right, it is the ICM. When you disconnect the EST bypass make sure you disconnect the battery to reset the ECM before you check to see if it is advancing at idle...

Edit: Just so we're on the same page Eric, I keep referring to the engine coming with 20* as a base because I am assuming you marked the location of the original rotor when you removed it and then installed the new distributor in the very same spot. If this is the case, and the former owner was experiencing the same problem, then it might very well be ECM related. However if you just slapped the new distributor in there close enough without marking the original one, and the former owner didn't have it set to 20*, then yes, the ICM is suspect. Just to point out, I bought five fan relays from Advanced Auto made in India that didn't work, one by one I brought them back. Went to Napa, and the first one they gave me worked flawlessly. So yes, bad batches are most certainly a real issue...

Eric Darr

Street Lethal,


No and Yes... I don't know where the timing was at when I got the car - the car did not run. I replaced the fuel pump, sending unit, fuel filter, and cleaned and resealed the tank. After I got my fuel issue sorted I found out I had an ignition issue. I could get the car to start, but I had to constantly adjust the throttle or it would die. Upon inspecting the original distributor, I found it to be less expensive to purchase a new distributor than to rebuild. I have dropped in many distributors and usually get them in right the first or second try so, No, I did not make any marks - especially since I was switching distributors. I just brought #1 piston to TDC and pulled the original out and installed the new distributor. When I fired it up, it ran fine so I left it alone until I set the timing a few days later. Then, a few days later is when the bogging and popping and no started. (The 20* BTDC came about from when I first checked the timing after dropping in the new distributor.)


As for the advance issue, it's my understanding that when you set the timing with the EST unplugged then it should advance once the EST is plugged in. It doesn't matter where I set my base timing at, when I plug the EST in the timing stays the same. As for advancing enough with the EST plugged in when I raise the RPM's, No, I don't think it advances enough either. I know it advanced before with the EST plugged in because I checked - base went from 10* BTDC to 22* with EST plugged in and when I raised the RPM it went to 41* (don't know what RPM - one hand on the throttle and timing light in the other - talented, I know. lol) I use a dial back timing light, btw. Also, I have checked the timing on #1 and #4 as RBob suggested and all the above is still the same.


On Friday, I took the ICM off the original distributor and had it tested and it tested good so I'll use it when my replacement distributor comes in.


willexolX,


I have wondered about the timing chain being stretched. I do not know the car's history and assume it is probably the original - the car has 159,000 miles. I did notice a slight movement in the timing whenever I checked it. For example, if I set the base @ 10* I would notice the timing fluctuate a couple degrees to 12* while idling - but I noticed the tach would fluctuate up and down too. I could never determine if the fluctuation in RPM was causing the fluctuation in timing or vice versa. Or, was the Sea Foam or something else causing the RPM to fluctuate, etc. A lot of variables running in a vicious circle. That's one of the reasons I wanted to tackle my advance issue then see if something else needs addressing. When I get my distributor back, I will check if there is play in the chain by watching the rotor when I move the balancer back and forth.


I really appreciate the feedback from you guys.

Eric Darr

Well, I FINALLY got my replacement distributor today... the problem is the box was all beat up, had a 3/4 inch hole in the side, and a corner of the top of the box was caved in. When I picked up the box, there was a rattle inside and I thought "Uh-Ohhh!" I opened the box and found 2 of the towers on the distributor cap were broken off and floating around the bottom of the box. UGH!!! I will go ahead and install the distributor and use my old cap until the new one comes in.


I'm going to replace the cheap control module with an AC Delco unit and see if that solves my timing issue. In the mean time, I got the front brakes rebuilt and new KYB socks and struts installed. Once I get it running again I'll go get it aligned.

Eric Darr

I have several things to report in my saga...


After finally getting the replacement distributor and finding the cap broken to pieces, I went to install the distributor and found it had been damaged in shipping too. There was zero endplay between the gear and body and it would not turn freely. So I'm sending it back for a refund. I'm finished trying to save a few bucks off the internet. I got one from AutoZone for twice the money but I found the construction to be quite a bit better than the cheap one off of ebay. Lesson learned. I removed the cheap ICM and installed my AC Delco ICM.


I installed the distributor Wednesday and although it ran better I still had no advance... or so I thought. Saturday night I was on here again and read this posting again about someone else having a timing issue... https://www.thirdgen.org/forums/v6/7...ng-timing.html


In post #1 they showed a picture with 2 connectors asking which was the EST. In post #2 someone edited the picture and circled one of the connectors in red and that was the one I thought was the EST. Upon looking farther down the post the was another picture and said both connectors were wrong, it's the one above the blower motor. I went out to my car and sure enough there it is sticking out of the loom!Needless to say, but when I set my timing at 10* BTDC I was actually a couple of degrees retarded. My timing is now working properly and the car runs great.


One last thing, someone mentioned the possibility of a stretched timing chain. When I installed the distributor, I moved the balancer back and forth and could feel when the chain would tighten and move the distributor. There is about 3* play in the chain - is that too much. Like I said the car seems to run great for almost 160k miles.


Thanks for all your help.


Eric

willexoIX

Beware the parts store dizzy's for our V6's. I have encountered my 2nd bent dizzy shaft.... Though if you aren't going to put a turbo on it you may be fine.

You are better off finding a really good unit, from a well known company, that will ship you a free replacement if it gets damaged in transit. And Cardone is crap anymore, steer far, far away from them.

Also, if you need to ask about the play in the timing set, just replace it with a single tooth unit, not the double. The double will stretch in half the time it would take the single tooth set.