RFmaster

@kbaer28 any updates????

ImBrandon

Swap in a different ecm. A bad ecm gave me very very similar conditions on my fathers 350 tbi sat for about 2 years. The prom ended up being trashed. Runs smoothly now. Try smacking the ecm you have a couple times to see if it makes it run fine. That's an old time Chevy mechanic trick I learned.

stealthram92z

iTrader: (2)

Hows the car running now? was wondering if your intake bolts might be loose and allowing a vacuum leak, I have seen this before, It happened to me, my 92 RS would run great till you drove it and then it got worse real quick, idle fine then die, replaced the intake gaskets and it has run perfect ever since. Good luck on your car.

Caveman305

iTrader: (8)

i second the ecm, had my RS do the exact same thing a few years ago, to the point that when coming to a stop light i would have to foot brake the car to keep it running, replaced every sensor, full tune up including new distributor, etc. replaced the ECM and never had a problem since.

actually just had a buddy who was having an issue where his TA would idle fine/rev fine in park, once it was put under load the rpm's would hunt(but never come to the point of stalling), we could physically see every sensor related to the problem was new,so i pulled the ecm and was surprised to find it was a recently replaced reman, pulled the ecm from my Iroc and threw it in for the hell of it and the car ran great, my guess is the previous owner didn't unplug the battery before the ecm install and fried the brand new one(or it could have been a dud from the factory)


either way, if all sensor have been checked/replaced i believe the ECM could be the next step

kbaer28

We have had a ton of snow here and have not been able to get the car out to do more testing. Hopefully have some time to work on it soon, as it's supposed to get warm. I have thought about the ecm. Thing I don't like about it, is that they aren't cheap and I don't want to be wrong.

Still a bit confused on why I am getting such high IAC counts..

Is the ecm located above the passenger side footwell?

Caveman305

iTrader: (8)

Yes, drop the pass side under dash panel, it's bolted right under the dash,

There is an ECM test flow chart floating on this site somewhere, if I wasn't on my phone I would link you to it.

Chachi361

im having the same exact issues with my car. I have replaced just about everything u have. I got it to actually run decent enough to get around if I advance the timing to about 25 degrees advanced. the problems started when I added headers, full exhaust and changed the clutch all at once. im thinking that it may be the fuel pump that actually going out now that my car is getting a full load (clutch was slipping). it also runs a little better with the map sensor connector disconnected. I replaced the map with two others and had the same result.

when I connect a timing light the timing seems to retard then advance but barley like 4-8 degrees when going WOT.

any help would greatly be appriciated

ImBrandon

Junkyard ecm is 10$ where I live I'd grab some and check if I were you. Smack the hell outta your current ecm to try to see at least.

Caveman305

iTrader: (8)

Are you disconnecing the est wire while setting timing,

25 degrees is a hell of a lot of advance unless you are reading with the est plugged in, I've only ever needed to go to 6* and that was pushing it

Chachi361

Yes I've been disconnecting the wire before setting timing . If I put it at base timing it won't even drive. Not until the timing is at about 15-20 degrees then it will be drivable but I can't floor it or it just pops out the tb.
I checked the dizzy to make sure it wasn't off a tooth and it isn't. I've tried just about every combination of removing and adding sensors. No luck yet.

I'm gonna go get a ECM today at the pick and pull and see if that solves my problem.

Thanks guys for trying to help out this is my baby a I would hate to leave her parked.

morgsie

iTrader: (1)

It sounds like your off a tooth.

kbaer28

I put a video up of what it is doing to better explain it. This is with the throttle steady that it does the surging. If I were to downshift, it would go away. Runs pretty normal at higher rpms. Is a bit doggy and backfires at lower rpms and does the surging at cruising and 2000ish rpms.


Does this help with any diagnosing?

Chachi361

going to the you pull it to get a ecm and abunch or proms. kbaer im gonna grab a bunch so if u need one ill gladly send one to you in the mail for free. i really hope this can solve our problem

RFmaster

Do not pull EPROMs from ECM's - grab the whole ECM. Depending on application EPROM from one ECM may not be compatible with another ECM from a different vintage or application. IRC, 1989 F-body, auto, used ECM with service part number 1228746 with BCC codes ANTS; ANTT; AXKS; AXKT

BTW Rock auto has 89 F-body ECM for about $72 (+$50 core) and shipping.

//RF

kbaer28

Chachi - That would be awesome. I have checked at many, many salvage yards in the area and nobody has one. Only ones I can find are on ebay and they are in the $100 dollar range. However, let me know what you paid for it and how much shipping is and I will paypal you some money or send you a check. I don't need it for free. Let me know and thanks!

kbaer28

RF - After watching the video, do you suspect ECM?

kbaer28

Does p/n 1228746 come with the Eprom or does that need to be purchased separately?

RFmaster

Hard to tell - honestly I have only seen one true ECM failure. In that particular case ECM would never perform POST and when placed into diagnostic mode would give me code 53. Swapping EPROM did not solve the problem. Swapping with another ECM took care of it completely.

In your case - it could be the culprit. This is one is one of those weird ones. So, swapping-in a good known ECM is probably a good idea at this stage.

Depending on the supplier service ECM's may or may not come with EPROM installed. You should ask. It is easy to transfer from one to another.

//RF

freaky

if you find you need to replace the ecm i would up grade to the ebl flash .

kbaer28

My frustration level with this is getting pretty high.

Today I decided to just try to guess at it, so I started to unhook sensors, drive it, and see if it would change. I tried the O2, IAC, and EST. Most just made it worse, but it still had the exact same chugging at cruise that is shown in the video, with random backfiring and sputtering, missing occasionally under idle.

I took the ecm out, removed the eprom, put it back in, hit the ecm a few times, no change. Now it is showing the egr code, but the egr wouldn't cause the chugging would it?

I looked in the chilton manual for testing the egr and it said to rev it up until vacuum is seen on a gauge, then remove the vacuum hose and engine should rev up. It doesn't. There is vacuum going to the egr but rpms don't change with hose is removed and the diaphragm never moves. No matter what the rpms are at. If I hook up a vacuum pump to the egr, it does move, but when running it never opens, at least in park. That said, I still don't think even a nonfunctioning egr would cause my running issues. Or am I wrong?

Should I just pull the trigger on an ECM from rockauto? Or are there other thoughts?

kbaer28

Grrr.. New ECM.. Same problem.

New O2 sensor.. No change..

I might be giving up on this soon and taking it to a shop..

Any other thoughts?

Chachi361

I'm really starting to think its a weak fuel pump

RFmaster

It looks like your EGR is either stuck or EGR valve diaphragm is blown. Usually a partially stuck open EGR screws up idle quality - rough idle, stumble of idle. An EGR valve stuck in open will cause a lean mixture - this may explain stumble during cruise.

Hmmmmm. Just thinking here - swapping ECM did not change anything.

Yank EGR off and clean out EGR passages with carb cleaner and barrel style brush. Next, EGR should be tested with hand held vacuum pump. With vacuum applied EGR inlet you must see diaphragm move. If does not EGR should be replaced. An 'oscillating' EGR going from 100% open to fully closed at slow rate may be the cause for stumbles during steady driving. This maybe due to malfunctioning EGR solenoid which is controlled by ECM. EGR solenoid provides controlled amount of vacuum that reaches EGR valve and bleeds vacuum from EGR diaphragm when ECM disables EGR operation. Worth a look.

//RF

kbaer28

Chachi - I know what you mean, but I have driven it with the fuel pressure gauge hooked up, idling, under load, cruising, and it stays solid at 12 PSI. I tried the gauge on other cars and it works so I think the fuel pump can be ruled out.

RF - I will pull the EGR again and take a better look. With the engine off, I hooked up a vacuum pump and the diaphragm does move and stay in place. When vacuum is removed, it goes back. I t'd a vacuum gauge between the solenoid and the EGR and under idle, no vacuum, when you rev it up, there is definitely vacuum. I don't remember the number exactly, but I think it was around 15 in/hg. But when the engine is running and vacuum is present to the egr, the diaphragm does not move, ever. Unless it does when in gear, but I cannot check that. It's like the vacuum inside the intake is too strong to let the egr open, even when vacuum is present, is that normal?

Schurkey

Reasonably certain that the EGR is the positive-backpressure style, it won't open unless the exhaust pressure is above a certain level. A GM service manual would be helpful here.

Makes testing at idle much more difficult.

RFmaster

If it is OE Negative back-pressure EGR valve it can be identified by having a "N" stamped on the top side of the valve after the part number. Positive back-pressure EGR valves will have a "P" stamped on the top side of the valve after the part number. Port EGR valves have no identification stamped after the part number. If you have to replace a valve, compare the stampings to be sure you have the right one.


An incorrect operation of EGR valve can be attributed to:

Too much EGR flow will dilute the a/f mixture and make the engine run rough or stall. Excess flow undermines normal combustion and may result in the following symptoms:

Engine stops after cold start.
Engine stops at idle after deceleration.
Vehicle surges during cruise.
Rough idle.

kbaer28

Well I made a block off plate for the EGR, installed it with some high temp RTV, drove it.. Zero change. Same exact backfiring and surging during cruise.

I thought maybe there was an intake leak or something so I soaked the entire thing with brake cleaner, no change during idle.

Thought maybe it was the alternator. Unhooked all the wiring to it, drove it a bit, no change.

I am at a complete loss here. Any ideas?

RFmaster

Yes, this is getting to be very strange. New ECM did not change anything (I kinda suspected that )

Which takes us back to the fuel and ALDL monitoring....

Do me a favor - make a complete list of changes, parts replaced at this point.

//rf

kbaer28

New cap, rotor, distributor.

New coil.

Rebuilt TBI, all new gaskets, screens, etc in TBI.

New plugs and wires.

New O2 sensor, ECM.

Timing has been adjusted, even tried advancing and retarding to see if balancer had slipped. Same surge at cruise.

FP solid at 12 psi all the time.

EGR removed, block off plate installed.

Car has a slight miss at idle sometimes. Surges at cruise (see video above) and will constantly backfire when warm, quiet, almost soft backfires. Kind of like a putt, putt..

Problem is considerably worse when in closed loop, warm.

I think that's everything..

RFmaster

Hmmmm this is a tough one.

The only thing that I am suspecting at this time is that one (or both) of the two injectors is clogged (internally). The car sat in storage for an extended period of time and it is not uncommon for injectors to accumulate crud in them. It is unusual for a clog to form, but it it is more common for a flow rate to drop off. At idle you'll see BLM being slightly above 128 in the 130 to 134 region as ECM tries to compensate for reduced fuel delivery. During cruise, in a close loop, ECM simply runs out of fuel trim range resulting in a surge. I also would expect to see O2 lean code to be set, but somehow it is not being set.

Due to a slow ALDL update rate capturing BLM drift, is tough if not impossible. So from diagnostic point you are at a handicap. Do not like to offer blind advise - sending someone into a dead end is bad for all.

At this point I would look into sourcing a complete TB, with injectors, from a local JY. I end up stripping down completely, have injectors serviced and flow checked before re-assembling TB. Over the years I end having couple good known units sitting on the shelf only to be pulled when chasing weird problems on other people rides.

//RF

kbaer28

I'll see if I can source a used TB. The injectors sure seem to be coning properly. I'll keep an eye on the BLM and see what it is doing.

Wouldn't unmetered air entering the intake create the same problem? So it still could be something like an intake leak, right? Or am I wrong? I soaked the whole thing with brake cleaner but that doesn't always work. I also don't hear any whistling or anything, but I am going to try the propane test today.

RFmaster

Unmetered air is more of the problem at idle - once you move of away from idle smaller vacuum leak contribution becomes less of an issue. However, fuel starvation will cause lean surges.

Intake manifold can leak from inside of the intake V gulley - You'll never be able to reach it with a spray. Propane enrichment is a good diagnostic method to try....

Still, I would try to make certain that fuel pressure is rock steady under actual driving conditions and injectors are delivering enough fuel to satisfy engine requirements.

//RF

kbaer28

Well, more non-progress.

Went to the junk yard, picked up a rather used TB. Switched over the injectors. Same issue. Used TB had the IAC on it, switched that over, same issue. Also switched over the PCV, no change.

So, it could be that even the injectors I got aren't functioning right, but really, what are the chances?

Oh, and at idle, BLM is rock steady at 128.

When cruising, the O2 voltage does get rather low, in the .1 range but with the sputtering and backfiring it jumps around up to .8 and with the slow computer, it is hard to get a real reading from it.

I was thinking the same thing about bothering more at idle if it was an intake gasket. When cold, it does usually idle high, around 1200 rpm, but when warm it is back in the 700 range.

I tried the propane method, but with all the sputtering and backfiring, dousing the motor with unburned propane frankly, scared me. So that really didn't get me anywhere.

No clue where to go from here.

RFmaster

Un burned propane can be rather dangerous!

Here is my thinking at this time....

If we believe that O2 is reporting correctly (O2 is heated and operating at 600F+, and has not been poisoned or dropped onto ground) then there is extra oxygen present in the exhaust stream as indicated by low O2 voltage readings. The fact that BLM (I presume that INT is also stuck at 128) is rock steady at 128, while engine is idling, indicates that ECM is sitting in open loop. Even during cruise the O2 readings should be operating swinging between 0.8 (rich) and 0.2 (lean) Volts. Therefore, it begs the question what is the source of this extra O2:

1) Vacuum leak on intake side at one or two cylinders intake ports - which results in a lean misfire in one or more cylinders. In the 70 and 80's the common way to diagnose misfiring cylinder was to perform cylinder balance test. Since I play around with older cars I have acquired a compact vintage Sun engine analyzer. Unit has ability to disable ignition firing of a selected cylinder while engine RPM drop is observed. This way a misfiring cylinder can be identified quickly. Later OBD-II PCMs have this capability built in, but require OBD scanner tool capable of enabling this diagnostic function. Most automotive shops got rid of their older automotive analyzers - these shop machines were huge and occupy a valuable floor space!

2) Exhaust leak - this could be from AIR injection system leaking (with stock air injection manifolds it is a common problem), cracked cast iron manifolds, bad exhaust head gasket, leaking joint between header and extension pipe, etc. In most instances these can be heard by their popping sound.

So - do not give up.

//RF

EagleMark

E gas is a magnet for moisture. Everything I have touched in the last few years that sat had a puddle of water in bottom of tank and the fuel itself was a milkey color. Everywhere there was a line of corrision at fuel level.

Draining as much as you can leaves the water and dirt in bottom, I've tried this. QUick check even with new filter now as water is always at bottom and sucked up, it lays in bottom of fuel filter. Pull fuel filter and don't spill fuel, pour it is glass jar and let it settle, water will be on the bottom.

Store vehicles with full tank of non ethanol...

Schurkey

Ehhh...not so much. In fact, it's pretty much a non-issue. The propane isn't supplied in large quantity, it disperses quickly, and there's typically no source of ignition anyway.

That said, my preferred method of tracking down vacuum leaks uses aerosol carb cleaner instead of propane.

Good call.

Agreed.

True, but EASY EASY EASY to duplicate "in the field" using nothing more than a $5 12-volt test light--or a small nail and a jumper wire, and a vacuum gauge.

Connect vacuum gauge to manifold vacuum.

Take the ground clip of the test light, connect to any nearby engine ground; or to the battery negative terminal if close-by. Whatever is handy.

Put a dab of silicone dielectric grease on the pointy end of the 12-volt test light. Slide it BETWEEN the wire and boot of the distributor end of the spark plug wire. DO NOT PUNCTURE THE BOOT, or damage the plug wire insulation. The idea is to get between the boot and the wire, and slide the greased probe in about an inch. The metal of the probe will contact the metal of the spark plug wire terminal, shorting the spark to ground for that cylinder only. That cylinder is prevented from firing.

Read drop in manifold vacuum when the test light is shorting out the spark. Note and compare the drop in vacuum as all cylinders are shorted in turn.

(You can use a tachometer instead of, or in addition to the vacuum gauge, but the tach won't be as easy to read due to normal RPM fluctuations. The vacuum gauge works better than a tach.)

Don't forget that if the diverter valve doesn't switch the AIR from "upstream" (air pumped into the exhaust manifolds in front of the O2 sensor) to "downstream" (air pumped into the catalytic converter behind the O2 sensor) the O2 sensor will provide a false "lean" reading.

kbaer28

Well I did the test light test and found the offending cylinder. When I grounded out #5 there was no change at all in how it ran. So with new plugs, wires, dizzy, rotor, and cap I would think that spark could be ruled out, but what's the best way to test and individual cylinder for spark without causing damage?

So, all cylinders have good compression, the third part of the equation is fuel. I pulled the plug and its black, but not wet.

TBI masters, where do I go from here?

EagleMark

Your lucky you asked for safe! You could always ask someone to hold the wire and start engine. The reaction on their face will tell you if there is spark there... LOL!

Just because you have new parts does not mean they are good...

Safest and easiest way is put a plug on that wire and lay it on ground and start the engine, does it spark?

If not use another old wire and see if it sparks?

Or swap wires and see if miss goes to another cylinder?

kbaer28

That's what I figured the best way was.

Let's say there is spark. What's the next diagnostic step?

one92rs

iTrader: (5)

compression test. maybe pull the plug on that cylinder and make sure it is good. didnt close the gap up on installation. could be a bad plug. put another plug in it and see if it changes. then try another wire. pull the cap off and test the connections with an ohm meter. look for trails in the cap.

kbaer28

Everything is new. Dizzy, coil, wires, plugs, etc. However, I will confirm that cylinder has spark. Compression is good.

Next step?

one92rs

iTrader: (5)

like stated before even if it is new it can be bad. there have been many a people including my self ding a plug upon installation. or even get a bad one. check the cap again. check the wires again and the plug.

Ronny

iTrader: (1)

Same can be said for plug. But i would just buy a spare or find any SP to test.

Cap(s) on SP wire? Check for resistance. Open?

Schurkey

Spark tester. Buy one at a parts store, or online, for under $15. Maybe WAY under, depending on "deals" you find.


This will test everything but the spark plug. Your "black" plug may be fouled or cracked. Plug should be white, just like new. The days of the tan spark plug porcelains are long gone.

Look at the intake runner that feeds that cylinder. Any vacuum hoses connected to it? A vacuum leak into the runner may upset the fuel mixture enough to kill that cylinder. Plug the vacuum hose and plug the nipple, or pinch the hose with a needle-nose vice grip. If the cylinder runs, find what is using that vacuum hose and fix it.

EagleMark

It's TBI, if it were an injector issue you'd have 4 problems on that side. If an injector had a horrible dribble it may effect one or two cylinder more but it would be easy to see injector spray pattern was more a leak then a spray pattern.

Double check firing order since you have all these new parts as well. You can swap 2 wires and have only one plug horrible although the other is still a missfire...

kbaer28

Well..

I checked for spark. Solid spark.

Checked the firing order... Switched up 5 and 7. Swapped back, runs awesome now.

Thank you all for the help. If nothing, I learned a ton about how this engine operates. And I thank you for that.

Bottom line, TGO rocks and I am an idiot....

EagleMark

Fixed it for you!

Your not the first or the last to swap a plug wire during installation...

RFmaster

You are NOT an idiot! Far from that as you have diligently slugged through troubleshooting. As always I am first to admit that we always assume the worst before considering simple checks first. For that I am guilty as charged. Cheers.

//RF

The Wolff

Wow...read this whole thread to the end. I would not feel bad if I were you---we have all done similar before. At the very least, this was a great thread on troubleshooting a miss/stumble---very informative.
Thanks