89bonestockiroc

Hi , I have a problem with my 89 Iroc that ive been really struggling with. I apologize in advace, I know this is going to be kind of long.
I was driving on the freeway one day when the car started jerking and popping and had no power. The tach bounced around between 0 and 1000 rpms. It did stay running but would not respond to the throttle, it just kept popping and jerking the car. I sat on the side of the freeway for a while and the car would not restart. It would not even crank. After it sat for about an hour, it started and ran great for about 5 minutes, then it did the same thing again. The car had a brand new msd gm coil, cap and rotor, plugs, taylor plug wires, and timing set at 6* btdc.
The car never gave me any error codes. I started the car a few days later without any problems and it ran great for almost 3 weeks. It then started having this same problem again. I disconnected the battery, changed the ignition module, reseated all of my plug wires, then reset the timing with the esc disconnected. After that it ran really great for the next 2 days, then bam, it started again. I got to the side of the road and had my wife bring me my timing light and some more tools. The car restarted but still popped and jerked. I then unplugged the esc wire to set the timing. It ran pretty good with the esc disconnected. I was curious so I reconnected the esc, but then the car would not start. It would not even turn over. About 10 minutes later, it started to crank but make a grinding noise instead of turning the engine. A few minutes later, it started with the esc disconnected. I set the timing to 6 degrees btdc and it drove home great, it was about 8 miles on the freeway. The problem started after about 5 minutes the next day.
I am really sorry about the length here, but I really hope someone can figure out whats going on. Im at my wits end here trying to get this car to work. I really appreciate any help I can get here.
Thanks
Mike

jdrobley

i would have to say it's your starter.
the no start and grinding noise are good indicators.
if you want to double check to make sure you don't have an elec issue with the no start, hitch up a remote switch and try using it the next time you can't get it to turn over. if it crank- electrical problem; if not- bad starter.
the rough running/ popping could be the starter not disengaging.
this can happen if it isn't shimmed enough, ie. improper clearence.
do some more checks and let us know what you find.
jess

89bonestockiroc

I thought about the starter before, but it has only done the no start thing twice for a short time. It always starts up and runs ok for a minute or so before it craps out, so I dont think the starter is getting hung up on anything. Is there anything in the ignition system that would cause it not to turn over?
Im gonna test the coil when I get home, and im thinking about getting a new pickup coil. Could the pickup coil be the cause of the really bad stumbling and popping. When the car is doing that , it doesnt even have enough power to turn a corner, but it stays running somehow. Also, how likely is it that a msd blaster gm coil would go bad after about 500 miles?

jdrobley

as far as the starter not turning over, you'll get two major responses:
heat soak, in which the starter soaks up heat from the exhaust. this raises the resistance of the starter and requires more amperage to start. the car usually starts good again when it cools down some.
starter relay, which can cause intermitent starting problems, regaurdless of the temperature.
other than that, i don't think anything in the ign system will prevent you from starting.

it is unlikely that your coil went bad.
yes, the pickup would be a good place to look.

jess

1986redbird

just a Quick thought, I have heard that if you have alot of weight on your key ring, over the years the swinging can mess up your ignition switch and cause problems similar to yours,(missing,no start,shutting off, ect.). I'm not saying that is your problem but it may be something to think about.

ChevyLuva3

Hmm interesting, might have some truth to it, but not to go blaming a car not starting cuz I wanted that nice beer bottle opener on my keyring for fun occasions.
Check out that MSD GM coil, I wanna go get, how is it?

Danno

Could be two problems, or maybe one related to both symptoms. Gotta be electrical from your description. The fact that it is intermittent rules out anything serious like timing chain. I assume charging is OK, what does voltmeter do during this? At first I would suspect fuel press. problem but your temp. fixes would rule that out. Try to tap on the ECM when it is running properly. I have seen a few act this way(stumble, no power) and they would not throw any codes. My suggestion would be to hook up your timing light and a fuel pressure guage to fuel rail, voltmeter to ignition area and try step by step to find something happening when it fails. Try to wiggle any harness and see if that affects it. This type of problem is tough, but you have to go step by step. Good Luck, Danno 89 IROC stock.

Vader

89,

Not to belabor the point, but it always helps to include the year, engine, fuel system, and modification data when you post. I presume you are talking about an '89 IROC from your login name, and you provided the ignition modifications you have done.

My guess would be an electrical problem with the ignition as well. Check the pickup coil in the base of the distributor, preferably while hot. The resistance should be between 500-1,500 ohms. Also inspect the magnetic pole piece (reluctor) for rust, cracks, and other damage. Check the distributor shaft for radial play. A worn upper bushing can cause erratic spark. Check all connections at the HEI amplifier/switch module, at the ignition coil, and to the ESC control. Inspect the distributor cap and rotor for signs of moisture, cracks, or carbon streaking.

Check the source voltage while the condition is occurring if you can, and forget about the "heavy key ring" theory - the ignition lock cylinder on GM cars is only a lock cylinder, and the ignition switch itself is mounted at the base of the steering column and is connected to the lock cylinder via linkage rods.

89bonestockiroc

Thanks a lot for the replies. I apologize for the lack of details about my car. I had just come in after pushing my car the last block home after it crapped out again and was pretty flustered.
It is an 89 iroc as you surmised.
It was the 5.7L l98, recently replaced with newly built 350 from golens engine service. It has tpi and is all stock except for my msd coil.
I will get out the old multimeter and test everything i can touch with probes when I get home tonight. I did buy a new pickup coil that im gonna put on this weekend.
And Vader, when you say to check the source voltage, do you mean at alternator? Also , is it possible to set the timing and then have it change even though the distributor hold down clamp is tight? It occured to me that I got the car to run ok for a short time after setting the timing on 2 different occasions. I wish I had checked it before loosening the distributor so I would know if it had moved. I just didnt think about it at the time, I dont think all that clearly when im that mad at the car, hehe.
Thanks again for the replies.

jdrobley

First, make sure you have the ESC (electronic spark control), a little brown wire near the heater fan, disconnected when you set the timing. Otherwise the computer could be fighting you by trying to adjust it itself.
There are a few other ways timing can change; none good.
1) Jumped a tooth on the timing chain. Replace the timing chain set.
2) The pin in the distributer shaft sheared/is missing. If it wasn't installed right or your oil pump froze up for a little bit. Repair distributer and check for other damage.
3) The distributer gear is worn and jumps a tooth. This can be caused by having the wrong cam and gear combinations. Certain types of cams require certain types of gears. ( it's a metalurgical thing) Replace the distributer gear, inspect the cam gear and check for other damage.
Verify it is really jumping time before you go ripping everything apart.
Proceed on your present course and let us know the results.
Jess

rezinn

I'd say you're definitely going in the right direction with the ignition system. That pickup coil may solve the problem. I was having a similar problem last year, sometimes as I was driving the car would completely lose all power for a second, the rpms would drop and the car would stumble, then it would rev up fine. I decided I might as well take advantage of this problem and replace my ignition system with msd. A new coil, wires, and distributor(including cap and rotor) made the car run beatifully. Those MSD distributors are expensive, but I've never seen such a difference in performance from swapping out one part(albeit some other parts were included).

87transam5.7tpi

I'd guess distributor or possibly computer. I've seen and heard of cases where the computer will mess everything up. maybe a loose connection too on one of em?

89bonestockiroc

Well, I got out there and did some testing on my car. It started the stumbling as soon as I started it. I did check the voltage from the alternator and it was 13.8V. I checked the battery with the ignition off and it was 12.7 volts.
I did inspect the cap and rotor, but im not exactly sure what carbon streaking would look like. Everything looked ok anyhow.
I unplugged the ESC wire to check my timing, and found that it started right away and seemed to run ok like that. It even revved up a little, but ran kind of rough. Is that a sign of a bad pickup coil? I hope it is. I checked and the timing has not moved from 6*btdc so I am relieved there. And the last thing that I just did was test the pickup coil. The engine had cooled quite a bit since I checked the timing, and im not positive I tested it right. I unplugged the connector that goes to the ignition module, and checked the resistance between the two contacts in the connector. What I came up with is about 0.89 ohms of resistance. I checked it over and over again. If the resistance should be 500-1500ohms, then does that indicate a short in the coil? Sorry for rambling again, im just really hoping that this is the problem.
Thanks

Kingtal0n

Was the sterio on when this happened? do you have a serious system in the car? Just to be sure, this probably isnt it, so heres a question (er.. somthing)

Turn the car off like your leaving it (i.e. in park, everything off, etc..)
Close the doors so the dome light goes off.
Make sure nothing is on first, then turn on your sterio, A/C Fan, and any other electrical devices you have in your car. Mainly the sterio. Do this with the car in ACCESSORY MODE (Turn the key 1 click BACKWARDS)
Wait like this for 4-6 minutes, listen to some tunes.. whatever. open your door to catch a breeze etc....
Then, Simply try to start the car. Will it start? get back to me.
Kingtal0n@aol.com
If it doesnt start after this, I know your problem.

zroc

89 BSI,

when you where checking voltage at the altenator there was not any indication of the problem??? we are talking intermitent problem possibly multiple systems (starter, ecm, anything else???) that have some different power feeds... fun stuff...

I would back up for a moment and check some basic stuff...

remove battery terminals (ground first) and main power to the starter (it didn't happen to be loose was it???) and clean them with a wire brush...

check to make sure the grounds are in good shape (at the back of the block on pass side head and any up at the front of the intake... also the ground strap from engine to body... any thing else you can think of...

are there any other systems that seem to be affected when this happens???

this is just to add to what others have posted...

zroc

Nordbert

89bonestockiroc- I think your ECM is defective. Check e-mail.

89bonestockiroc

Well, after another round im still beat by this darn stumbling and popping problem. Im starting to run out of options though. I replaced the distributor and the spark plugs this weekend. I still have the same exact problem. Is there any way to test for sure if its the ecm? I dont have access to another one without going out and buying one. The only possibilities left that I can come up with is the ECM like you guys said, maybe the ESC module, or the msd coil. Is there any good ways of testing those things?
Thanks

jdrobley

i don't know why none of us thought of this earlier, but...
i was rereading some of the earlier posts and noticed the tpi. i don't know if they still had MAF sensors in 89, but if you have one, that would sure explain your problem. the car may be surging at idle and have some of the issues running that you have. you can test it by doing the 'tap test'. you have the car running and tap the MAF with a screwdriver. if the idle changes at all, or the engine stumbles or dies, then your MAF is bad and needs to be replaced. if that don't fix it, then you are back to the ecm. luck,
jess

Vader

89,

Eliminate all the variables you can. If you still have the stock coil, reinstall it (unless, of course, it failed). It is doubtful that you would have the same symptoms from two different coils, and we KNOW that the stock coil is matched to the HEI amplifier/switch module (we can't be sure of the MSD coil).

And before you are so quick to condemn the ECM, check it out. The ECM firmware and hardware would not likely "come and go" like that. Your condition is more likely a connection problem. It may very well be a connection at the ECM or even IN the ECM, but take it one step at a time.

Remove the passenger side lower dash panel trim and expose the ECM. You can "tap test" the ECM just as you would the MAF sensor. Start the engine, allow it to warm a bit, then gently tap on the ECM housing (front, back, and sides) and see if the symptoms change. That could indicate an internal or external connection problem. If you can create the symptoms with the tap test, you're getting closer. You can even flex the wiring harness cables slightly to check for connection problems.

Disconnect the battery, remove the ECM electrical connectors, and inspect the card edges of the ECM mainboard that are visible through the connector holes. Use a clean pencil eraser or eraser stick to clean both sides of the cards where the connectors mate.



Inspect the individual connectors in the electrical connectors on the wiring harnesses. If everything looks good, seat the connectors on the ECM mainboard and remove them several times. This wiping action can clean off the contacts in the connectors and provide a better conductive path.



When all the ECM harnesses are reconnected, reconnect the battery and try starting the engine again, watching for the symptoms. If the symptoms cannot be repeated, you may have solved your problem. If the problem persists, you may have a failing internal connection in the ECM. If you are good with a solder iron and have the time, you could search for marginal solder joints and resolder them and try it again. If you don't have the time or will, get your hands on a replacement ECM, install your PROM module, and reconnect the new ECM.

Once it is running correctly again, you can go back to experimenting with the MSD coil. If the problems persist after the ECM cleanup, we'll start looking at the ESC (the next chapter in the novel).

89bonestockiroc

Wow, Vader you always make such great posts with pictures and diagrams. Im gonna try cleaning up the contacts on the ecm when I get home today. I have tried the maf tap test and the its ok. I also inspected the wiring harness and moved it around to look for a loose connection but didnt find anything there either, but that was just in the engine bay. I did check the resistance of my msd coil as per the haynes manual. Test 1 was for the primary and it tested really low, like .06 ohms. Test 2 on the secondary part at the coil wire post was supposed to show really high resistance but not infinite, but it only showed about 5.20 ohms. Is that considered high? What does it mean if the resistance is to low? I really appreciate all of the replies and info that ive gotten from everyone. Im starting to think that I might actually figure out whats going on with this thing.
Thanks

Vader

89,

If the coil primary resistance is too low, the HEI amplifier/switching module output transistor may not be able to effectively and sharply cut off the current to the coil. The transistor is sized to switch a coil with a given primary current, and the biasing of the transistor in the module is based partially on the resistance of the load (coil). Secondary resistance is less of an issue in this case, but could be indicative of coil insulation breakdown or a turn-to-turn winding failure. I'd still go back to the stock coil for now, since some high-output coils can also create RF interference that can "confuse" the HEI module into false triggering.

MIG-29

before you change anything,
follow the positive wire from the batt to the starter, once you're there notice two or three red wires going up (from the same point at the starter)
follow those wires and you'll notice in each one a black plastic cilindrical shape thing,
that's the current limiter, wich in the event of a short circuit (a big one) will prevent your car from frying.
typical problem with those is...vibration tends to cut the wire right at the place were it becomes the limiter.
so, start your car and play with those wires and you'll see, those are the wires powering the whole car (all systems)
remember, wire long and then...ooopppsss!!! what's this black thing cylindrical shape around the wire about 3/4"long ?
that's the current limiter and it happened to me.
i just cut the suckers off, spliced, made sure that it wont corrode and must important, kept it FAR from the heat of the exhaust manifold.
i hope it helps.
Fernando.

89bonestockiroc

Well, ive gone and tried some more things. The stock coil did not make any difference. I tried the tap test on the computer, but it didnt seem to have any effect. I took it apart and cleaned the contacts and stuff anyway, and I tried wiggling around the wires under the dash. It just seems to randomly start missing really bad still. I am going out when I get home today to wiggle around all of the wiring under the hood and see if that effects it at all. Is there anything else that could cause such an intermittent problem? When it starts messing up it looses almost all of the spark I think, because it barely stays running.
Is it time to look at the ESC module? Is there any way to test that?
Oh, and I did check all of the starter wires, they are all in great shape.
Thanks

Vader

89,

There are a few more things to check before you get out the checkbook.

Are you still using the original pickup coil and reluctor? Either one can cause your symptoms, especially with the wandering timing. Check the pickup coil for signs of heating and cracks, and closely inspect the reluctor for rust, cracks, and any looseness on the shaft. The resistance of the coil should be between 500-1,500 ohns with a high-current ohmmeter, like an old Simpson analog meter, or a digital meter with a high-current capability (like a Fluke 80-series or lab meter). I'm not sure what the resistance might be like with another DMM, but 0.89 ohms sounds like a real problem. Make sure the leads are disconnected from the HEI module for the test (or at least one of the leads). You should also test the coil resistance to ground on a high resistance scale. Any reading means that the coil insulation is breaking down and the coil should be replaced.

Check for wear in the distributor shaft and mounting plate for the pickup coil. There should be no radial play in the shaft, and no movement of the mounting plate. Any wear will require removal of the distributor and replacement of the bushings (or a remanufactured distributor).

Make sure the detonation (knock) sensor is connected, and the ESC module connections are clean and tight, including the set-timing bypass connectors.

I hope one of these gets you closer to the problem.

89bonestockiroc

I think the readings I was getting were not right ( aka - I didnt know how to properly use the the resistance settings on the multimeter, hehe).
Anyhow, I replaced the whole distributor. The old one looked a bit worn and I wasnt sure if I damaged anything trying to get that pin out bottom. It came with all new parts on it including the pickup coil. It did improve my things a little during normal operation, but the same problems keep occuring.
The timing is staying at 6* where I set it and its running great when its not crapping out. The problem is so intermittent its really hard to test things. Can the ESC cause the system to almost completely stop sparking?