armygreen87

Have a 1989 5.7 tpi iroc. When the symptoms first started it would just missing for a minute randomly over 30 minutes of driving and then drive normal again. Then one day it would start missing so bad it would bog down like it was running on less cylinders and the sound coming from the exhaust changed like a deep sounding lawn mower lol. U could definitely hear the miss. At first when it would do this, I would just put it in neutral and pull over and rev it some til the sound went back to normal and drive off again with normal power. But the last time it happened It died after about 10 to 15 seconds of the missing and bogging. It would crank several times right after and run for two seconds of me pumping the gas and then die. Waited for it to cool and cranked it up and drove it home just 3 miles away. What could be the problem? I have thought ignition coil or distributor but would these give me a code?

armygreen87

Update: I just replaced ICM, distributor cap and rotor, ignition coil. Still bogs. I let it idle for a few a then came back and pushed on the gas in idle and the engine bogs down while the rpms go down. Want to point out my idle is way too high and no matter where I position the TPS, it still acts the same. The idle is not steady to begin with. ..wavering up and down somewhere between 1200 and 1700. I have recently replaced the IAC and TPS. After idling for a while and unplugging sensors here and there to check for changes, it started overheating. My temp tach doesn't work but coolant started boiling. When I unplugged MAF it almost died so its not causing the bogging. When I unplugged the TPS and went to gas it again, there was no difference, same with the IAC. After gasing, as soon as I let go of the gas the RPMS shoot up above its idle and slowly goes back down to its idle. Injectors all tested above 12 ohms. Might have more than one problem here but any ideas?

nomind

Have you checked it for vacuum leaks?

8Mike9

Was the service light flashing with the miss?

armygreen87

Vacuum came to mind..need to rent something to test it. I didn't go inside to check and see if the engine light was flashing from the MAF since I immediately plugged it back in to keep it from stalling. I'm going to check the oil and see if any coolant is in it. But I was told it wouldn't idle hardly if it were head gaskets. Can I spray something all over to find a vacuum leak without test equipment?

armygreen87

Read that wrong. I think it did the first time it started acting up. Don't remember after that. Been sitting a while now so trying to remember all the details. But yesterday no it didn't do that at all

8Mike9

I don't think you have a vacuum leak, just my opinion.

If the SE light was "dancing to the miss"...it would indicate that the ignition system is not generating spark...or incorrect spark...Are you able to pull the distributor and re install by yourself?

I've an inkling the pickup coil may be at fault, but much easier to see and test while on a bench.

8Mike9

I just re-read your 2nd post...I hadn't noticed the ".idle hunting"


Let's start over

Do this...start car and let it warm up at idle.....once cooled off enough, unplug the IAC valve...let's see if the idle is still hunting/surging and go from there

armygreen87

Okay I will try that tomorrow. I replaced the IAC over the summer thinking it would help the unsteady idle I was having when it was running better than it is now. Didn't change the idle then. Possibly got a faulty one from the parts store or just something else is wrong entirely...

armygreen87

I think I may replace the pickup coil and see it that works. Sounds a lot like my problem. Had a hard time starting the car yesterday...it would sputter and back fire to somewhere up front and not stay cranked. I know I have a leaking header. I found this online http://www.ehow.com/list_5946595_signs-bad-pickup-coil.html#page=0[/URL]

8Mike9

Without reading the link...I can tell you this-may miss one or two things since it's been 15-18 years...but...

If you're agile enough...pull everything out of the dizzy...cap/rotor and reluctor...you should be able to see/view the PU coil around the distributor shaft...and notice a two wire connector.

Now closely look at the PU coil and look for corrosion...replace if you see it...if you don't see corrosion, take an ohm meter and measure in between the connector pins (going to the PU coil) ...GM gives some spec...but IIRC should be spot on at either 600 or 700 ohms-again, been awhile-...also while ohming it out, wiggle the wires and make sure the resistance doesn't change...if the resistance sits tight...should be okay...if not, replace.

In order to replace, you have to pull the dizzy out...knock the roll pin out that holds the drive gear in, slide shaft up and out...and reassemble in reverse order.

But...did you unplug the IAC and see if the idle still hunts?

Trying to determine (in my mind) if IAC is hunting causing the idle hunt...if not...then we can continue with other things to look for

armygreen87

Yes the IAC still hunts. I pulled off distributor cap to change pickup coil. The gear on top under rotor is pretty corroded...last time I buy a car from up north lol. Anyway I didn't think I would have to pull the whole distributor...Might as well buy a new one if I'm going thru all the trouble.

armygreen87

What is that corroded disc piece between the rotor and pickup coil called so I can get it replaced Or is it just a part of the old pickup coil and I won't need it?

eseibel67

While you are changing the pickup coil, replace the corroded pole teeth. It is available complete with shaft. Standard Motor Products part # DG43:

8Mike9

Two things...the PU coil could be causing your miss. but wouldn't be causing the surging.

As mentioned before, you very well could have a vacuum leak...check the connection from the MAF to the TB, inspect for cracks/splits/etc. another area to look at is where the vacuum line is connected to the brake booster.

In all areas you suspect a vacuum leak, use a safe approach...mix up some laundry detergent (about 1/8-1/4 cup) in a spray bottle and shake vigorously (warm water helps) until completely dissolved, the adding the detergent increases the viscosity of the water, plus allows the liquid to "sit" longer in an area...what this shold do when you spray the solution on a leak, it should seal it temporarily and the idle should smooth out/stabilize for a brief second.

Safer than using flammable sprays/etc.

Plus can give your engine that "smells lemon fresh" scent

8Mike9

The reluctor...above might be a good solution for you to just replace the whole shaft.

armygreen87

so I have the distributor out and may just replace the whole thing. while I was removing things to get distributor out, I found a solenoid type thing mounted under the ignition coil. Can u tell me what this is? Looked like it linked to the EGR on one side and the a two prong wire coming from the other end. On the same side as the plug are two more holes further apart with nothing plugged in but looks like something goes there. I would post a pic but i couldn't figure out how to shrink the mpeg to be posted on here.

When I removed distributor and spun the drive gear by hand, the teeth on the reluctor were not catching like I think they should, kept on spinning with little resistance so yeah that part must be bad. I found what looks to be a nice distributor on ebay ( link below). Will this work for my car, assuming it's basically stock? Thanks for any help. http://pages.ebay.com/motors/link/?n...d=141114444082

eseibel67

That is the EGR solenoid. It supplies vacuum to EGR valve when the ECM calls for it. The one nipple is supposed to be open, it's a fresh air vent. It should have tiny foam "filter" on it.

The distributor shaft should spin freely. There's nothing that should "catch".

Distributor in the ebay listing is wrong for your car. You need a "small cap" type without vacuum advance. Your timing advance is controlled by the ECM.

MikailLoewen

Mine was doing the same thing. No codes or anything. Turns out the catalytic convertor was clogged, took it off and now it runs perfectly.

jjcuff1

I had same thing. TUrns out it was a week old advance auto coil. It cranked but nothing. I checked spark over and over and replaced everything but new coil. Swapped in original one and bam fired up.

Dam cheap parts

armygreen87

This crossed my mind but I found a receipt on where the previous owner replaced it like 2 years ago.

armygreen87

The corroded reluctor tries to catch on the teeth of its surrounding plate which is also corroded. If I could just buy the reluctor and plate that surrounds it and the pickup coil (which I already have) then that should work better at least. I may change the egr solenoid too. No filter was on it and the solenoid cylinder outer casing is breaking away anyway. I will start with these two things and see if I have positive results. Wouldn't hurt as these parts look to be going bad anyway whether they are my main problem or not. Thanks for the help, update you guys in a few days I hope

jjcuff1

Any luck after changing PU coil? My car just died again after swapping in old coil and ut ran for weeks.

I am thinking wither dist pickup or injectors since it does it once it is warmed up. But once cold it does not restart. LAst time I swapped ign coil to old one and it fored up fine. I might try again since the icm cap rotor are all new

valencia88iroc

My Car is doing the same thing. 88 Iroc 5.7 Replaced Distributor entirely new, and still dying out after about 10-15 min. I have no catalytic converter, no mods other than flowmasters. The engine codes indicates bad PROM. Code 51. My mechanic said to replace it, and ECM and go from there. once we know the Prom & ECM are good. We Can See if We Get any New codes. autozone can get me the PROM by 12-27-03 which is in 10 days from now. so I'll keep you guys posted on my progress. I Really Hope it Fixes it!! keeping my fingers crossed!!

86T/A_Ram_Air

have you checked your fuel pressure?

jjcuff1

Well on my story, I went through in detail the ECM code 42 diagnostic and the ECM checked out good. so did the PU (but still looks rusty) and the ignition coil.

all pointed to teh ICM again. I swapped in a new one along with a new coil. I cleaned up the surface of the dist plate and added full thin coat to the ICM and it stuck well and bolted down snug.

I also cleaned up the ignitoin coal brackets, very rusty and I had them finger tight before (maybe a problem) but now sung and tight and fired right up again.


since then I have ran car up to temp 220-230F range for several minutes at idle and drove it around the parking a lot several times for last week or so and still seems ok.

armygreen87

Replaced Ignition coil and complete distributor assembly. No more stalling. But I still got vacuum symptoms. Hesitates when I touch gas and idle surging. No codes. My overheating problem I believe to be the thermostat, currently in the process of flushing the cooling system first and it's actually helping the overheating so far.

armygreen87

I have not checked the pressure... There is a gauge already affixed to the fuel rail... Either it's not working or I have fuel pressure problem because I haven't seen it move yet.

valencia88iroc

replaced the engine computer control and its working great! two days now and no problem. Ill keep you guys posted... oh and it was 79.99 at autozone + $40 for the core.

armygreen87

I can't get it to crank anymore. Not sure where to start now

86T/A_Ram_Air

I'm just going to assume your battery is good. Make sure you have 12 volts at the starter and check your grounds

armygreen87

Just replaced battery a month ago. It was cranking but was getting more difficult each time after I replaced it. I'm going to replace the fuel pump relay And see what that does and if no change then i will check the fuel pressure.

armygreen87

It does turn over and I try 20 times with no change in power or sound. Just won't start up. Before it got to this point it was hard to start and backfired in the engine area and sputtered then died several times before really running. Not sure if that helps determine the issue but worth a try

armygreen87

I took the non-working, affixed pressure Guage off of the fuel rail and left the valve open and tried to crank. Spilled fuel all over so I don't think fuel is my problem

86T/A_Ram_Air

10 lbs of pressure fuel will spill all over the place. You need a gauge.

armygreen87

Ok. Do auto stores sell them I can screw on to the fuel rail like my bad one? I figured if I'm going to spend $50 I want one that can just stay there. Oreillys didn't, not sure about the others.

86T/A_Ram_Air

You can do that. Auto zone might loan them out or summit sells the tester for around 50 or 60 bucks I do believe

armygreen87

So I bought a pressure tester and get 17 psi (key in on position, cause it won't start). When I try turning over the pressure drops to about 10 and goes back up to 17 when I stop turning. Guess I hooked it all up right. Just screw guage on Schrader, no other special steps testing in the "on" position?

86T/A_Ram_Air

You should have like 43 psi key on with a tpi system

armygreen87

Ok Thanks. I will troubleshoot the where my fuel problem is

86T/A_Ram_Air

If I had to guess its either the pump or the the pickup hose on the bottom of the pump or an extremely clogged fuel filter

armygreen87

Going to rule out the fuel filter for now. Replaced it a few months ago right before it started running like crap. Even if it's just a hose, might as well replace pump when I go thru the hassle of dropping the fuel tank.

86T/A_Ram_Air

I agree 100%

rgarcia63

Be sure to reset the TPS to specifications.

armygreen87

Is there a forum on here already where someone describes how they lowered the tank? I have an exhaust pipe running horizontally under it and wonder if I could lower it just enough to reach up to the top of the tank and pull out the pump assembly?

86T/A_Ram_Air

Negative. You have to drop the exhaust totally. And drop the rear as much as possible

armygreen87

How do I know where to set it. I set it in a place where the service light would go back out on the dash and figured that must be good. Now it's not running anymore though.

86T/A_Ram_Air

On the home page of this website there is a tach article section that will answer most of your questions

armygreen87

So I got it cranked and didn't change anything. Running it gets up to 30 psi fuel pressure. I think I hear a hiss when I tap the throttle quickly Immediately letting off, vacuum leak maybe sounds like upper front somewhere but throttle body cleaner not triggering anything. If I give it full petal it hesitates and backfires from the engine area. Had someone try to find the pop backfire sound and he seems to think it's coming from the air duct

jjcuff1

Just seeing this thread after a break and I have gone through some good trouble shooting on mine that might help and sounds similar. Can you recap where you are at? What is new and you are sure works (IE autozone parts can be broken even if new) so I sually double check with old part and go through the EST trouble shooting codes to verify working.

but to your problem above:
Fuel PSI seems low and therefore could be part of lean problem. but it sounds secondary to bigger problem.
Probably still have a vac leak. When you stab the gas you will hear a sucking, maybe hissing as vac spikes then drops to 0 with WOT stab.
The backfire is typically a lean condition as you stab it and let off, creates a hi vac condition, super lean AFR and no fuel creates hot temp condition and the gas ignites in the exhaust or intake.

Why: Your condition I might think is the massive vac leak and maybe bad spark. Check your plugs and wires again for continuity and are they gapped right?
For the manifold. I have mine apart now and reinstalling and same as you had minimal luck with throttle test around the seals but as I removed the uppers I was surprised by the number of loose finger tight bolts and apparent gaps between the surfaces. maybe at idle and warmed up it is ok enough to seal but you start wot and the vac sucks in.

Also the TB on mine was loose and those seals are critical too, check the CCV vac lines or replace mine looked ok but all cracks din my hand as I replaced. probably had cracks throughout them. Also the TB plate on the top is a large seal and gasket it self. remove and check and retighten. Mine had loose bolts as I assume the PO was going to remove or replace before he sold it. Huge vac leak.

then backfire could be the spark, again check the plugs wire gap timing, redo the IAT and TPS settings.

then when all done check the Fuel PSI by powering the pump directly from the G terminal of the ALDL with the car off and vac removed see if it gets 42psi and holds for few minutes at least above 30