TheGr8erG00d

iTrader: (2)

Hey
I'll start out with some background (more or less a life story of my car). I picked up an 89 Iroc Z 5.0 this past February and this thing has been a nightmare (although I love the car anyway). I had to replace the tank, pump, a few lines, etc and the car ran solid for a month before more fuel issues came up. The car spent the last month in the shop (don't have my own garage down here to work in and efi is new to me) getting work off and on and is finally running. That said, it's got a new distributor (old one was absolute toast), new plug wires, another new pump, new pulsator, three new injectors, and a new ecm. They set the timing on it, but I've noticed it's got a little bit of a backfire out the pipes when I let go of the throttle. On a 20 year old car, I normally wouldn't give it a lot of thought, except that it WAS NOT doing this before I had to take it in and get it back to running again. It's really mild, but I'd still like to try and figure it out and I'm not taking back into the place I had this work done in. In the end, I found where I was losing fuel myself (blew out my pulsator), not them, and when they gave my car back, half the brackets and other items they moved to check my wiring and such were still out of place with screws missing. I'm simply not messing with them again if I don't have to.

I've got a timing light on the way, should get it around Thursday, which is fine as I'll be at a jobsite in Oklahoma until then, so I can check it myself. I suspect that maybe they didn't unplug the ESC/EST wire, whichever one it is (the white and brown one) before changing it. Maybe it's also possible they set it top dead center rather than 6 degrees off (it seems a lot of TGO guys reccommend that setting, not sure if that's the stock one or what)

I also read that it could be air leaking in through an intake gasket? Not sure, but we pulled that off to change out three bad injectors I had and I wasn't there when they put it back on so it's hard to say if they replaced the gaskets or if that would really even cause something like this. This is why I prefer to do my own work when I can.

Anyway, I was wondering if anyone had any pointers over tuning my car, checking/adjusting the timing, etc. It seems to be running well once again, although it doesn't quite have as much ooph as it did before I took it in. Granted, it is a 5.0 with and automatic, but it had a little more pull before. It also has a really mild stumble sometimes under light throttle that goes away with just a little throttle, (again since taking it to the shop). I'll check the timing once I get my light, although this isn't actually something I've done before. What else can anyone share with me? I've changed out radiators, pumps, and other minor things when I've had to, but otherwise, my experience is still pretty limited.

ahankins32984

if they replaced the distributor then they should have set the timing back to stock settings mine had the same problem before i did a plugs and wire change before i reset my timing and it made a world of difference!!!

ahankins32984

and you say that it backfires into the pipes??? which pipes are you referring too??

TheGr8erG00d

iTrader: (2)

I know they should have done it, but I really do not think they put the time into it based on 1) I've found a lot of poorly done/forgotten things under the hood and 2) this back fire, although very mild, was not there before. It was a very smooth growl off the throttle before, now it pops once ir twice after taking off the throttle. You can hear it from the tail pipes.

TheGr8erG00d

iTrader: (2)

Bump.

Any tuning advice would be welcome.

ahankins32984

tuning i would start with setting timing correctly alot of times that is a small issue with these cars that is a easy fix that causes alot of what it sounds like your having!!

ahankins32984

as well I would have the exhaust system checked out due to the backfiring before it causes a even bigger problem

ASE doc

A few things can cause the report in the exhaust on decel. One is a leaky injector, another is worn exhaust valve guides, one is an exhaust leak, another is retarded timing. Since you are experiencing reduced power, I would start with timing.

TheGr8erG00d

iTrader: (2)

I got my timing light today, so I'll get onto it tomorrow. In the meantime, I've been changing out burnt out plugs, like one of my grounds, the hot wire to the high hvac fan, the plug to my ac compressor, etc. Why are these so notorious for being burned out on these cars? It's almost kind of unnerving...

ASE doc

Hmm. I haven't noticed that it's that common. You might want to look for poor connections that are causing the motors and coils to draw high current.

TheGr8erG00d

iTrader: (2)

Yeah, I've been digging, but I have noticed a few plugs/connectors that a number of people have had fouled up like the one leading to the high blower. I haven't found anything substantial yet. The car did sit for a while at one point and some of the plugs could have filled with gunk and worked too hard, perhaps. Not really sure. I had to replace the plug to my fuel pump, the ground plug to the coil and distributor, plug on the high blower, and I'm waiting on the one for the AC compressor clutch. My distributor was toast and my fuel pump was working to overcome a clogged fuel filter and that is likely why those two plugs were burnt. The AC clutch had quite a bit of corrosion on it so that may be potential for a plug working too hard. As for the burned up high blower, that one is up for speculation but it's the one I've seen a couple entries for on this site.

On another note, I have my timing light now, just trying to figure out how to use this newfangled thing (digital display, weird/crazy increment/decrement buttons). Glad it has a tach because mine doesn't read correctly (makes it appear to idle around 3,000 or so even though it's around 800). I'll need to find a place that works on gauges around here since I need to get some work on the printed circuit to get my fuel gauge and brights indicator lighting up at night (bulbs are fine).

ASE doc

Sounds like you bought a Ferret Instruments digital advance timing light. They are a little weird since they actually register actual timing when you first activate them. Then you can choose whatever advance you want with the buttons and just zero the marks with the light set at your desired advance setting. Pretty cool really. Just watch the read out because it can change.

TheGr8erG00d

iTrader: (2)

No need, I figured it out. Although now I am puzzled in another fashion...

I checked it and it's currently advanced 8 degrees instead of 6. But, isn't a pop/backfire on decel a characteristic of timing being retarded rather than advanced too far? That was always my understanding and that's what I'm hearing on this thread as well. Would being 2 degrees too advanced make it backfire? I really wouldn't think so.

Given that circumstance, it would seem I should advance it to maybe 10 degrees, but I don't understand why it would be drifting so far from stock timing when everything beneath the hood is stock. It definitely didn't pop at all on decel when I sat and revved it in park/drive a month ago, let alone when it rolled off the factory floor. Oy.

Anywho, I was going to play with it some, but it turns out I don't have a very good wrench or swivel for getting to the bolt locking down the distributor. I managed to get one on it, but then I didn't have any room to turn the wrench. I fought with getting to it with my puny wrench collection and finally gave up for the day.

ASE doc

I have a 9/16" torque extension, which is a little 12 point box end about 2" long with a square drive opposite the box end. It goes on an extension with a ratchet and allows you to get around corners. It's perfect for setting timing on the TPI cars. I like it better than my 9/16" GM timing wrench.

It sounds to me like your problem may not be timing related. You can certainly try setting timing to 10 degrees. As long as you get no pinging, you won't hurt anything and you'll probably get better performance. Another possible cause that I didn't think to mention earlier is timing chain wear. Excessive slack in the chain would allow timing to retard too far on decel.

TheGr8erG00d

iTrader: (2)

Well, I ended up leaving the timing alone (it's raining and probably will for some time and when I'm at my apartment near school I am sans garage). I hadn't even considered that it could be the chain. It seems that the only chains/sprockets I hear about stretching or breaking are around 300,000 miles and I'm only sitting at 93,000. Hell, I don't even know how to check the tension on the chain myself. That's outside my realm.

One of the guys I was talking to said the smog pump was notorious for causing this and that he'd remove it. Can anyone else back up this claim? Not sure off the top of my head whether they test emissions here in town or not, but I'm willing to fix the system, but is there a good way to test it and find out if it is causing the popping/backfire. Is there an easy way to cap off some of the hoses from the diverter valve or some other place and run the car to figure out if it is what is causing the backfiring? And if so, where on earth would I find smog pump parts for replacement, or would it be more realistic to gut the system if it is the problem?

And by the way, thanks for your patience, I do appreciate it.
I love this car, but there always seems to be a gremlin lurking somewhere in it!

ASE doc

Hmm. I suppose the air pump could cause exhaust report by injecting air at the manifold on a warm engine. It's supposed to switch to injecting air at the cat within a minute or two after engine is started. You could check this by looking for air flow at the hoses to the manifolds when the engine is warm. If there is air there, the diverter valve is not functioning correctly.

TheGr8erG00d

iTrader: (2)

All right, I'll get right on that and post my results!

TheGr8erG00d

iTrader: (2)

Sigh... no air there. I'm going to put it back up on jacks, start her up, and start feeling for exhaust leaks. Maybe I'll find something.

TheGr8erG00d

iTrader: (2)

Nothin'....

I mean, the car is running well otherwise, I guess I shouldn't obsess over this so much. It just bugs me that it sounded a lot more smooth before I replaced the three injectors and distributor and now... not quite so much. I have no other ideas as to what could make the exhaust pop on decel. Smog is diverting correctly. Timing is actually advanced further to 8 rather than 6. No discernable exhaust leaks. I don't really know how to check/adjust the chain besides really tearing into the car and I don't have the facilities or money to do so, let alone justify doing it as there isn't a good reason for the chain to be loose.

The only other symptom I can think of is that the car sometimes stumbles just a little bit when you touch the throttle but that symptom is not consistently there. Gremlins!



I may just have to concede to "well, it is a 20 year old car" syndrome unless you happen to have any other ideas. Otherwise, I'm just going to stew on it for a while and continue checking things and replacing worn out parts until she purrs exactly like new. I really don't have that much futhrer to go! Thanks for the help.

ASE doc

To check timing chain wear, connect a timig light and watch the timing marks as you snap the throttle. Timing should advance and retard smoothly. If it wobbles around at either end, that's probably timing chain. To pinpoint a loose chain, remove spark plugs and use a breaker handle with a 5/8" socket to turn the crank back and forth while watching the rotor with cap off. The rotor should follow the crank very closely with no more than two degrees of delay. Verify that the dist gear is tight to the cam gear by feeling for slack with your hand.

TheGr8erG00d

iTrader: (2)

All right, I'll try this out. Not sure if I'll get to it today (off to a wedding), but I'll give it a shot when I can. First, I'll need to pick up that torque extension. I'll keep you all updated when I can, take care this weekend.

TheGr8erG00d

iTrader: (2)

I finally found and borrowed the tool I needed to get under the distributor and actually cleaned off the marking plate with the timing marks... the shop had the damn thing RETARDED to 8*!

Still have an occasional pop, but I've gotta reset the computer and let it relearn everything. Holy crap, I can't believe that was the problem.

This is why I try to learn and do everything myself.

TheGr8erG00d

iTrader: (2)

Haven't posted on this thread in a while, thought I'd provide an update. The car is still running strong, but it's still rough on idle. Every once in a long while the car will just stop running, like I turned the car off. It only happens once every one to two months, but it still happens. From what I've read, the EGR valve can make the idle rough once the car warms up? If that's true, I suspect it because I get an EGR code 2 out of every 3 times I take the car out on the highway more than 30 minutes. The vacuum lines are good from what I can tell so sometime I'm going to need to check the valve itself and the solenoid.

My real question, is there any merit to the EGR valve causing idle to roughen up as the car warms up and is it possible that it could make the car die every once in a long while when it's idling? The car runs strong otherwise, it just shakes/rumbles the car at idle, almost like it's missing, once I've warmed the car up, but with the lightest touch of the accelerator the car engine runs smooth until you take your foot off.

Comments, thoughts, rude remarks?

rgarcia63

EGR isn't active during idle any leakage will affect idle to the point of stalling. The most common reason is carbon build up keeping the valve from sealing properly. Again, this only one of several reasons for a rough idle.

TheGr8erG00d

iTrader: (2)

That's kind of what I was thinking may be the case. I'm sure there is plenty of carbon as I'm burning oil on start up.

The oil situation is kind of funny, actually. It used to only burn some after sitting overnight and then never any other time. Then I let some guys work on it when I was stumped and they ran some sort of crud through it while troubleshooting, now it might give a tiny puff on start over night but usually none at all. But if I let it sit only an hour or two, it will cloud out the heavens on start up.

I need to replace those valve seals and clean up my tb, intake, etc. I'm thinking that will do me a world of good.

bignastyIROC-Z

i didnt read everyones reply, but this sounds more like the cam timing is off, or mostly a bent valve.
seen that it dies every once in awhile? when it dies does it shake real bad? did u check ur ing. switch?
i had sorta the same problem and where my car would die out of nowhere and i change tb gasket, cleand tb, testd MAF, finally found that my chip in the ecm was the problem.. was very strange lol. gl man

TheGr8erG00d

iTrader: (2)

ECM is brand new. The random times that it dies, it actually doesn't shake badly. And it happens quite rarely. It starts really smooth and then once it warms up the car shakes a bit, but not violently by any means. Just like a gentle rumble, almost feels like it comes from the back of the car, but it matches what the tach is doing (bumping up and down anywhere from just 5-10 rpms to almost a hundred rpms). I do know I have an egr issue as on any hot day that I do highway driving I get a code for it after I've been maintaining speed for around 20 minutes. So I need to replace it anyway, might as well clean the carbon out of my tb and intake while I have them off.

Since I know it runs smooth for a while before it warms up, it sounds to me like it wouldn't be cam timing or a bent valve because those should be noticeable on start up when the engine is cold too, shouldn't they?

bignastyIROC-Z

well u can tell a bent valve went u drive it, but when its idle and u have the timeing right u really cant tell, also i would check ur spark plug wires if u havnt, alot of time ppl cross #8 with another. carbon build up can be the issue, hopfully it is, if ur cam timing off ull get poping at low rpms.

TheGr8erG00d

iTrader: (2)

This thread has really just become an update on what I've been up to with my car. I guess I can live with that.

I replaced the EGR valve on my car about two weeks ago. Unfortunately, I only pop an EGR code on the highway on warmer days and it's fairly cold now. It'll be a while before I find out if it was the EGR itself throwing the cold.

I read there was a possibility that issues with the EGR could cause poor idle and I was hoping that was the case. However, my idle still isn't smooth. It idles a little higher when it's acting up with the new EGR, I've noticed, but still isn't smooth in the least.

So A) maybe my EGR issue is the solenoid or the sensor, which I probably won't notice until a warmer day when it would normally throw a code as I lack the equipment to test either one unless I get a chance to head back up north to my folks' place.

Or B) it's not the EGR that's effecting my idle.

I've also noticed that if I overly rev my car too soon after start up or if I run it really hard on a (very) spirited drive (alternatively I could drop these juvenile habits, I'm sure ha ha), that it won't want to run if I turn it off right afterward, like it's been flooded (so it's probably flooded, Stephen, derp). Could this point to leaky injectors? Most of the threads on here revolving around leaky injectors say something about hard starts once the car is warm and that's actually when my car starts easiest (cold start in the morning it takes around five seconds to start as opposed to instantly when warm).

I feel like I'm being picky because the car runs great otherwise. I just can't get this idle to smooth out and I'm running out of ideas.

In other news with my car, I need to fix my high blower again. Hopefully I'll get some time to this winter. The blower wire that commonly burns out under the hood has been fixed in the past. Now I need to find the one behind the HVAC which I need to get behind to fix the vac leak responsible for my heater not blowing. Also on the todo list is a weekend to rip my doors apart and regrease and lube the window tracks, locks and latches, and adjust my window heights. On yeah, and my front struts are worn out. And I'm sure something else will wear by the time I have saved up to pay for those, ha.

Until then, good luck everyone with your thirdgen projects.