the car is a 88 iroc with a 350 TPI, when I bought the car it was not running, and had a thrown rod.I have rebuilt a stock bore 350 out of an 88 suburban, that had the same casting numbers but was equipped with a hydraulic cam and I installed a cam we had just taken out of my brothers truck, I do not know the spec's on this cam though. I also had the plenum and manifold base ported while it was apart.

So the problem is my car tries but will not start,also I have gotten it to start a few times but the timing had to be WAY off, at about 20* retarded, and I couldn't get it to stay on if I set the idle lower than 1,000-1200 RPM but does react well when I give it gas.
then when I advance the timing to even 6* advance it bogs down really bad when I give it gas and it barely stays on. all the while randomly reving up and down with either timing setting.and had black markings where my turndowns were facing.

I already swapped the module, checked wiring, new coil pick-up, new spark plugs(because the others were fowled-platinium AC's), recheck distributor installation, bought some 24# lt-1 injectors, new fuel pressure regulator.

I am not getting any codes at all, before I was getting a code 23(IAT voltage high) then when I checked the sensor it wasn't even connected. it was connected to another plug in withthe same connection but was gray and pink/black that was putting out 12V into the vehicles wiring that was putting out 5V that was supposed to go to the sensor(hence the high voltage-code 23)
I so far have not founf what I should connect my mystery plug-in into the 2-pin male connector with gray and pink/blk wire coming out of it.
after I fixed wiring I also re-adjusted the TPS and installed some NGK UR5 spark plugs and then no more black deposits under turndowns(exhaust) and the car seemed to be running right and I even set timing at 8* advance and sounded perfect.

next day go to turn car on and it dies after a few secinds and makes intermittent popping noises from exhaust. Als notice that now my tach isn't reading, just stays around 7,000 RPM, and after trying for a while pull plugs and they are fouled again.

I am about to isntall a dist. cap, rotor, new wires, new set of plugs, MSD coil

is there anything I can check, does anyone know what the plug should go to?Any help and or suggestions are appreciated and and if there are any other details you need I will try my best to answer them

thanks
-Daniel

 

Daniel,

Do NOT istall the MSD coil without using a heavy-duty HEI switching module. The stock module will not switch the level of primary current at which the MSD operates, or at least, it will not switch it reliably.

As a matter of fact, if there are any aftermarket ignition devices intalled, get rid of them for now (disconnect) and restore the factory ignition system.

I'm hoping that the EST was in bypass while you were checking and adjusting the ignition timing. If so, did the idle timing change once the EST was reconnected?

The fact that the tach is pegged can indicate damage to the HEI switching module, or a shorted connector at the distributor. The small connector for the pickup coil is suspect, as are the coil and reluctor.

 

I have not yet installed the Coil, right now I have the factory one, I have switched out between 3 differnent ignition modules that I have.And all the ignition is going to be stock other than a accel cap and rotor kit.

And yes the est connector was disconnected, and when I plug it back in the car runs/idles a little rougher.

And the tach stayas at aroung 7000 rpm's when off, and when I turn ign. on it totally pegs.
as far as the small pick-up wire do you mean from the coild pick-up or the 2-wire connector between the dist. and coil?
the wire w/2- connections from dist. to coil was broken and I have already replaced it with a new one, and the coil pick-up itselsf(harness included) is new as well.

I am running a NGK UR5 spark plug and am now switching to a ac delco R43??
which are both a step colder, could this be affecting it?

Also, tonight I am going to test the IAC to make sur eit is well to make sure the idle is even properly set.
Thank you for your help
-Daniel

 

You probably should check for play in the distributor, and closely inspect the reluctor for cracking or damage. Radial play in the shaft will wreak havoc with the pickup coil signal, and can break rotors. Axial play can allow the reluctor to walk away from the pickup coil and prodice a weak and varying signal, and cause poor spark distribution between the rotor and cap.

Your new pickup coil should have resolved any problems with the suspect HEI connections on that side. Check the HEI connectors on the other end of the module, too.

The tachometer may indicate a failing HEI module, failing coil primary, or wiring problem.

If the timing wanders with the EST bypassed, the HEI module, pickup signal array, and distributor wear could be at fault. If the timing only wanders with the EST enabled, the EST or knock sensor could be a problem. For easier diagnosis, you might want to keep the EST in bypass until you resolve the problems.

The spark plug heat range is not going to be a problem until you get it running right and get some mileage accumulated on the plugs.

 

the problem acure regardless if the EST is connected or not.

the distributor does not have any play, I removed it when I did coild and took it aprt and cleaned it all then installed new parts an checked everything then reinstalled it..... actually now that you mention it the installed dist. did have a little play when it was installed, I was told that this was normal and have always ran it this way on my carb'ed cars could that be the problem?

and also withthe tach I figured it could be the coil as well and that is why I had ordered the MSD one and I figured since I was replacing it I might as well get a better one. Also, I have swapped module and I have the same tach problem, so I guess I will be hunting for another bad connection.

I have also been told that lack of back prerssure would throw off my timing, I currently have edelbrock headers going to dual 2.5" both dumped near rear of tranny, I have already ordered a flowmaster american thungder cat-back, and it should be here thurs. could this be ADDING to my problem?

And how can I check pickup signal array, I have a fluke meter that measures AC or Hz if that would help in finding the bad signal wire possibly checking for either along tach signal wires should help , just I don't know all of the wires I should check-So could this help?

And thank you once again I appreciate someone taking time to help/answer my question
-Daniel

 

Exhaust restrictiuon/backpressure will have no effect on ignition timing.

As for the distributor, how much play was there and in which direction(s)?

A frequency counter scale on your Fluke probably won't help much, since it will ignore missing pulses and only count what it sees. A scopemeter would be handy, or a plain old lab oscilloscope could detect missing/random pickup coil pulses, but you'd have to turn the distributor at a constant speed.

 

i had the same issues when i first put my 383 in and it after 3 months of messing with it i was like ahh screw it lest wap out the distributer with this extra one i have and what do ya know it work! runs like a champ now!

 

the dist. has maybe 1-2* play counterclockiwse and clockwise, I figured that this was normal, but just to be on the safe side, I tried anothe dist, and same thing-so I figure it is normal(right?)

And, I don't have a scope of anykind I just figured that either the Hz or AC would verify that I am infact getting a signal at all, possibly test at ECU wiring to further check for wiring issues. my reosoning was in AC or Hz signal should go up when cranking as well as higher per RPM.

I did try another Distributor and same thing.

right now I have already ordered
MSD Coil
MSD cap
MSD rotor
Delco Module
MSD wires
and coil pick-up and wiring are already new
and am also getting new spark plugs(again), and then hopefully find out some way if I have a definate wiring issue, basically all of the ignition system will be new, So if it doesn't work it should be the wiring right?
I know that even it being the wiring I am still going to have ALOT of work to do to figure out where my problem is but this should really help isolate my problem, right? Is there anything I am forgetting?Other thigs I shoudl check while waiting for my new parts?
and once again I appreciate the help and advice
-Daniel

 

A few degrees of rotational lash should not be causing a problem. I was more concerned with radial (side-to-side) and axial (up and down) play in the distributor shaft itself. You are allows about 0.004" of radial play, and 0.040" of axial play before you need to shim the shaft, although I've seen them run with almost 1/8" of axial play.

You can use the AC voltage scale to test for pickup coil signal, but will have to turn the distributor at a fixed speed to have any meaningful indication. The signal level is very low, and might be at about 25 Hz or so at cranking speed, so make sure your Fluke is true RMS.

The second distributor shuold have eliminated that possibility, however, since the pickup coil and reluctor would have been different.

Since the tachometer is exhibiting strange behavior. I'd suggest ejecting/removing the white wire from the ignition coil clip to eliminate the tach from the circuit and see what happens. The tach itself may be shunting coil primary power, or it may only be displaying oddly because of a different problem in the coil primary system.

Whic MSD coil did you acquire? If it is a stock replacement, it should be safe to use. If it is a "Blaster" coil, it should only be used with the high-current HEI modules.

 

the dist. seems fine,and it acually has a really good fit, not really any radial or axial play.

And yes my Fluke is a true RMS meter, on the distributor I do not have a new reluctor, is this something that I should replace as well, I am just rying to get the car running and have as little problems down the road as possible.And also if all these parts go in new it really doesn't leave anything other than the wiring or ECU that could be causing the problem right?

Also, the previous owner had an aftermarket tach on the dash and all the wiring is routed through a hole he had made on the dash, but when I bought car it did not come with the tach. Is there a way I can make sure that there is no wiring that is being shorted, should any of the coil/dist wires other than the one on the four pin to module have continuity to groud when everything is disconnected? that way I could check that as well.

And on the coil, it is listed as a "blaster GM" coil, but has same connectors and they(MSD) say it should work with stock system.

hopefully all my other replacement parts will be here thursday from summit.

 

OT: Vader i also have the MSD-8226 Blaster and it says to be used as a replacement for stock system,although not yet installed does this mean something can be broken if i not install a new MSD module and if so what module should i have is it the MSD-83645 4pin module,this is scary to say the least with such problems as u have 88iroc-Z makes me whana go back to carbs and simple ingition systems again.....almost.
I have an 89 350tpi stock distributor.

 

jsut to let you know, I have not installed parts yet, I am still waiting for them to get here.....but I will update as soon as I get them here and in.

and BADCAM70 this was really making me want to go to a carb, but I have too much cash into the TPI to not use it.And I think all these problems that I am having aren't that common, so I wouldn't be worried

well I will update soon and thanks again for all your help
-Daniel

 

just to update:
I received all my new parts exept instead of sending me my ignition module I received a coil-pickup, I already sent it back and I ordered the Petronix ignition module, should be here by friday.Until then I have alot of other work to get done anyways.
Also I was looking at my distributor, and was wondering how much space should there be between the reluctor gears, on my current one there is like .060", I have another that has about .020-.030", I am going to possibly swap disributors and install when I get my module, but could this hacve been a cause of my problems?????
thanks again
-Daniel