Just did some "routine" stuff to my suburban and she ain't right...help please...

[mountain4x4]

Thats the module. However, if you are low on funds, I have seen entire distributors for pretty cheap. I think you can get one made by Pro Comp Electronics for under $100.

Here's one for $89: http://www.fastengineparts.com/produ...ew.php?id=2233

Just replacing the module doesnt cover the pickup coil, and old distributors can be a PITA to get apart to replace the pickup. You can probably find an ignition coil for under $50, so you can replace all than stuff for under $150. With your truck having over 150K, its not a bad idea.

[Redneck7]

I hear ya. Is that distributor worth a crap? I beleive strongly in the "get what you pay for" adage. Also, for installation (or removal of the old one, whichever it turns out to to be) I have two questions: 1.) what kind of wrench do I need to get to that bolt that holds the distributor. 2.) I don't have a timing light (I'm at my apartment at school...5 hours from home) so what are the chances of the timing being correct after this?
-Ryan

[-=AphiX=-]

your having the same problem that my truck is doing but i just replaced the whole distributor and it still does it at only low idle.

[okeydokey]

hey, a buddy of mine has a '89 tbi 350 truck, im not sure if its the same on the 95, but we replaced a head gasket and retimed it and it had the same problems you are talking about, with his truck there was a wire under the hood above the a/c stuff in the firewall in the harness box. it was a green wire that you had to unhook, and then time the motor with that not pluged in, than hook the wire back up. and BAM problems gone, i dont know if the chiltons book says anuthing about that. a local shop told us about that. i have no idea if this will help at all, especialy seeing how you dont have a timing light.

[guidolyons]

To set the base timing on the 95 TBI should be covered the Haynes or Chilton manual.on my 95 it was a brown wire w/ black stripe under the glove box. Disconnect that to check the base timing. Do not move the distributor with out unhooking this wire, or the computer will keep trying to adjust the timing. You can get to the distributor bolt with an extention and ujoint, but they make a distributor wrench with a 90* bend in it, that makes it easier. If you do remove the distributor you will need a timing light to make sure it is timed properly. Good luck tracking down your problem.

[Redneck7]

yeah, see I had the other half of that...I knew about the wire, but I can't set the timing... would timing make it bog/hesitate only when it's hot though? Me and a friend did a head gasket on an old 4cyl Isuzu and we never got the timing dead on, but it was off throughout the RPM range and hot or cold...my miss is more erratic. It occurs under light acceleration as a bogging or stumbling; Under full throttle acceleration as a surge or hesistation (less violent, but just not a smooth run from low RPM to high) and only when warmed up (5 minutes of driving or so). Cold it will run fine, but I only get 5 minutes of it running fine. Timing could be off since this problem was there when I bought it, so the previous owner could have screwed it up, but I think it would run funny hot or cold. I'm considering purchasing a new distributor and ignition coil and seeing if that works, but if it doesn't fix anything then I'm going to be at the end of my budget for the month with the truck...which sucks...so I'd like to have a pretty clear idea of what it is before I spend money.
-Ryan

[mountain4x4]

You can have the module tested and look at the pickup coil to see if it looks burnt before you replace the distributor. If you do replace it, then just buy a new ig coil as well just to be safe.

If you are very careful to install a new distributor just the same as the old one, it should run, but listen for knock and retard it if it does. It may take some trial and error, but you can get the feel of where it runs best without a timing light. I'd try to find one though, its much better to use one.

I have no idea about the quality of those cheap parts, I recommend Chevy or MSD as your best source. But the cheap one is 1/3 the price of MSD, the Chevy dealer is probably over $200.

The other thing to check is your temp sensor, forgot about that...

[-=AphiX=-]

for my 98 350 it was $600 with tax from the dealer for a complete new distributor last summer.

so where did you say that wire was?

[Redneck7]

Wire to disable the computer's control over the timing? Either under the dash on the passenger's side or on the firewall. From what I understand startin in 96 or 97 it wasn't possible for an everyday joe to adjust the timing...needed special computer tools and there is no wire.
-Ryan

[Redneck7]

Alright, anyone have any thoughts? Here's what I have: A hesitation was happening when I bought it, but not until warmed up. So, I replaced the plugs, wires, rotor cap/button, air filter and fuel filter, somewhere along the way I screwed up the MAP sensor. The screwed up MAP sensor put the computer into a default fuel map which turned out to be really rich and foulled my plugs. Replaced the plugs, fixed the MAP sensor and now the hesitation is back (with a vengence). SO, in summary, it was gone when the computer was not reading from the MAP (and perhaps ignoring other sensors) and running from default fuel maps and it also doesn't appear until you get a couple of minutes into your trip. If it was the distributor as has been suggested, then why would the PCM running on default maps cure it? Also, what would temperature have to do with anything?
-Ryan

[Cat Box]

maybe its a bad egr valve that sticks and causes to much exhaust into the intake charge. that could be why when its idleing it runs for crap but at speed its ok.they just covered this problem in hot rod a couple of months ago.

[damn-northerner]

First time posting...

My 99 3/4 suburban (150,000+ miles) acts the same way, i went through the fuel filter, fuel pressure test with engine warm and cold, replaced injectors and rail (5 of 8 were leaking around the o-rings). Replaced wires, plugs, cap and rotor - still the rough idle. Recently i was told that the timing chain may need replaced, i don't know how to verify this though - before tearing everything else off - if anyone else knows this might be helpful to you, definately for me.

[MrWillys]

Originally Posted by mountain4x4

Also check the distributor bearings, if theyre bad, replace the distributor.

Do you mean bushings? If there's a distributor with real live bearings i want one.

[Redneck7]

well its not really the idle thats rough (that was the problem it was having with the bad MAP sensor, it would idle crappy until the computer threw a CEL and defaulted to stored fuel maps). Its more at low RPMs under load...I guess I'll just have to go through and as I can afford it just start replacing everything until it disappears. I was just hoping (or I guess I'm still hoping) that someone can pinpoint it from what I know about it and have posted.
-Ryan

[MrWillys]

First, you need one of these:
http://www.autocheckup.net/Merchant2...tegory_Code=RF
This will allow you to check a multitude of devices.
After reading through this thread I've noticed you haven't set the timing yet. Todays computer controlled timing maps are very complicated. When you were in limp home mode it defaulted to about 28 degrees total timing, and a set fuel map. Now that your back running correctly it could be a timing issue. I would also check the TPS, IAC, and check if it's going closed loop. This will tell you if the O2 is good. It's possible that it's an injector and they are very hard to diagnose. You can check them with an ohm meter, or i really like to just feel them while operating.
It might be a simple as the O2 being bad which would not allow closed loop and not adjusting for fuel properly. I will point out that the computer never adjusts timing. It has a set map it use's based on vacuum and that's it. No memory or changes to the spark map like the fuel map does.
I'd really try to borrow a scanner, or buy one. You never say it wasn't worth it. I use one on my brandnew corvette because my wife can't put the gas cap on right. it really freaks you out when you get a check engine in a brandnew car.
Good luck

[Redneck7]

Appreciate it Mr. Willys...I think I'm going to just take it back up to my mechanic and explain it to him and see what he suggests and then go from there.
-Ryan

[Redneck7]

EGR valve was code one, then something about MAP reading incorrectly...which is probably either an old code or something related to the EGR valve...least thats what he tells me. Hopefully it'll be fixed tomorrow.
-Ryan

[-=AphiX=-]

let me know so that i have an idea where to start on mine

[-=AphiX=-]

let me know so that i have an idea where to start on mine

[Redneck7]

I have a phantom miss. EGR was bad, but it didn't fix it. Everything else checks out. Wave patterns on the ignition control module/pickup/etc were fine. No idea what it is. He's going to use used parts off of a good 350 to try and pinpoint it. I'll keep you updated.
-Ryan

[trkklr77]

get it yet??

[SKY-SCRAPER]

you'r timing is computer controled so check you'r #5-#7 and #1-#8 plug sets they are really close to the same and will cause this problem

[Redneck7]

Kinda got it. Replaced fuel pressure regulator, EGR, plugs, wires, fuel filter, air filter, MAP sensor, cap, rotor button, changed the oil, changed the gas, fixed a leaking something in the TBI unit. Still has an occaisional hesitation, but after paying for all that, I can live with the occaisional hesitation until my wallet recovers. I drove her 5 hours today (~300miles) in mildly hilly terrain and only noticed a stumble/hesitation at all when I was accelerating just enough to get up a hill and instead of shifting out of overdrive it would just jerk a little...so I'd get into the gas a little more, she would downshift, and all was well. Pretty much decided I hate automatics (my first in 5 vehicles).
-Ryan

[johny5]

dam , im having the same problem, with my 89 burb .lucky for me i have an other dead 350 to pull parts off of, i have messed with timing , it helped a little , changed MAP also tps and injectors , nexted i will change distributor.
, i'll post up when its solved..... john

[johny5]

well after all that (injector, tps, map sensor did solve the no start issue) changing the plug wires cleaned up 95% of the hesitaion up.