73-87chevytrucks.com
General Site Info => General Discussion => Topic started by: Layne on January 04, 2010, 11:39:12 pm
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I know this isn't a 73-87, but you guys are who I turn to when I'm stuck. Here is the situation: 88 gmc sierra 350 700r4. First bought it in sept. Test drove it and it was fine. Bought it, and drove home and I get a dtc. 43/44/45. So: New knock sensor, new O2 sensor, new esc, new cap, rotor, plugs, and ign module. Cleaned up some grounds. It started out as a kind of chugging at steady throttle. I've been throwing it in neutral at stoplights and holding the gas because it won't idle. The other day, I thought it was the IAC so I put one in it. Well, today I thought I'd go to Taco Bell and it did the same stuff, except when I got into my driveway. I sat there and lightly held my foot on the gas and it would bounce between 1000 and 1500 rpm. shook the whole truck and I thought she was going to blow up. Little more pedal pressure and 2000 is fine. Then my cab smelled like sulphur. I think I might replace my tps, but I'm tired of shotgunning parts at it. I know I rambled a bit, so if anything needs clarifying, let me know. I really appreciate the help. Thanks
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I'm thinking cat due to the sulpher smell
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EGR carbon buildup
http://www.2carpros.com/topics/egr.htm
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The diaphragm moves freely, should I Remove a vac line and spray carb and choke cleaner in there? I'm thinking th e cats seen better days, too. I'm planning on either replacing it or "cleaning" it out...
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I've found the best tool to use for "cleaning" cats is a torch - gets 'em real clean
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LOL! I C&C'd the little vacuum line to the EGR. Went down to shell, and as soon as it warmed up, it was doing it again. I put 15 bucks in the tank and C&C'd the line again. Ran AWESOME! It was sputtering a little, so when I got home, I seafoamed it and cleaned that line again. Took it around the block with my foot in the radiator and it seems to be doing better. I think I'm going to carb and choke it every so often to clean as much as I can. No CEL either ;D ;D
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Pull the vacuum hose off the EGR valve and see what it does. The EGR sol is probably stuck open.
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Theres no difference. Wheres the solenoid at? I pressed the diaphragm in and it killed the truck.
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The vacuum hose goes to the EGR valve from the EGR solenoid. There should be no vacuum at the EGR valve when you check it. If ok Pop the valve off and block it off. If it checks ok move onto checking your fuel pressure.
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Vile, do you mean take the EGR off the intake manifold and put a plate on it temporarily?
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just take the vac hose off and plug it. then test drive it.
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K will do. It seems to happen intermittently if that helps narrow it down any
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WOW WOW!!! Running like a top! No backfires, stumbling or chugging! She got a little grouchy with me at stoplight or too, but I didn't have to put it in neutral or "2 foot it". The idle dropped down to around 400 at some stops though. So it's prolly the egr solenoid?
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If you plugged it and it runs better, that is your problem.
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I plugged the vac line to the egr, so the egr is bad, or the solenoid?
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More than likely the solenoid is stuck.
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How long can I drive this way? I'll be getting a sol on fri (payday)
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doesn't hurt it at all, you can drive like that for years
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Ok. Thanks for all the help guys! Appreciate it.
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also now what you need to do is narrow it down a little more, plug the vacuum line back in and unplug the electrical plug from the Solenoid, and see if it comes back, If so the sol is bad, if it still runs good, the computer is telling the solenoid to open for some reason and you need to figure out why.
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All right. Going to drive through and I'll see what happens.
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Kids and I went to Wendy's, about a mile of driving. Plugged in my vac line and unplugged the solenoid electrical connector. Well, my favorite light came on, but she ran GOOD! Anyways, after we came out, I fired it up, and we had idling probs, and it died while I was in motion, which it's never done before. After I fired it up again, we made it home without any problem whatsoever.
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Just checked my dtc's... No code 32 which is what I was thinking. I'm still getting a 43/44/45. Would that be related to my egr sol?
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There should be NO VACUUM at the EGR. If the EGR sticks open because the solenoid is allowing vacuum to hold the EGR open even slightly you will set multiple eroneous DTC's. If you unplug the vacuum hose to the EGR and your problem goes away replace the solenoid. If the EGR itself is sticking open replace the valve.
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Cool. I'm 100% on the sol. Going to get it asap. Thanks guys!
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There should be NO VACUUM at the EGR. If the EGR sticks open because the solenoid is allowing vacuum to hold the EGR open even slightly you will set multiple eroneous DTC's. If you unplug the vacuum hose to the EGR and your problem goes away replace the solenoid. If the EGR itself is sticking open replace the valve.
Did you miss this part?
Plugged in my vac line and unplugged the solenoid electrical connector. Well, my favorite light came on, but she ran GOOD! Anyways
Its not the solenoid. You need to disconnect the battery Or pull the ECM fuse and clear the codes from the computer and start again.
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I don't have any vacuum at the egr. I've unplugged and disconnected the solenoid and it runs good either way. I'll disconnect the batt and see if I get any fresh codes.
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Cool let us know how it turns out.
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The sol took care of about 90% of the issue... It's finicky tho; I think when I was seafoaming like a madman, I may have dislodged a chunk of carbon in the EGR. I can idle most of the time, and at 55 with steady throttle, it still chuggs but I'm not getting whiplash any more. lol. 400 seems super low to me, maybe I can bump the idle up a tad?
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Pull the EGR and check it. The valve could also be sticking open a little.
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Think I can clean the heck out of it? I'm really not in a position to get a new one till tax time. $90 is ridiculous! The one for my citation was $20.
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unplug the coolant temp sensor next to the thermostat. see how that does.
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That happened to my old s-10 twice. Made it run rich though- lots of black smoke, and I used to joke with my friends though town that it'd do 30 without touching the gas. I'll give that a shot though.
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You can try cleaning it and lubing the pintle. Unplugging the Coolant sensor will make it run rich and set a dtc.
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tpo much computer crap an garbage what happened to the good old days when all ya needed was a carb distributor and gas to make em go thats why i got rid of my glorified computer on wheels... i got 2 screws that replaces 900 on sensors
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K5- I know where you're coming from, man. Tbi is about my limit lol. It's sposed to be in the 30's this week, and I'll get that egr off and clean it. I can't get motivated if it's cold out. lol. What do you think, though? Hose it down with C&C cleaner, then PB it? I was reading around and it says not to clean these as it can be bad for the diaphragm.
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It's not very dirty in there. I've cleaned the ports and I'm currently soaking the valve in C&C cleaner. There was no solid wall of carbon blocking something as I thought there would be. This truck has AIR. Would that be a concern?
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Is there a way to raise the idle in a tbi??? I soaked the egr in cleaner for a whole day and it never died! Not even once. My concern is that I have the same problem, only it's minute compared to earlier. You can hear it chug, but you can't feel it anymore and as far as I care that's fine. It's seems that at a stop in drive, it'll run at 400, then when I gas it, it hesitates. I think if I can bump the idle up to 8-900 like it should be I wouldn't have a problem anymore. Any suggestions, guys?
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You obviously got a problem man. Raising the idle really isn't the way to deal with it
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Don't mess with the idle. The IAC controls the idle speed. Check the TPS. Do you have a volt meter? If not unplug the tps and drive it. See what it does. Just remember to clear the DTC
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Sounds like I've got a violent cam in there... It was great till it got to closed loop (or open- forgot which one) then it'd drive, but as soon as I was off the gas, she was a shaking. Think we got it zeroed in on the tps?
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Got a new tps on! It's getting better... Now she'll stay at 600 for a minute, then it's like it gets confused and it'll bounce between 300-1000 before it settles down at 500 rpm. Do I have to adjust the tps???
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Yes .55V with the throttle closed. I hate seeing you throwing parts at it.
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I hate seeing you throwing parts at it.
That makes two of us. I've only got the MAP and the ECT :D... All the input I've gotten has been a step for the better, and I appreciate it. It doesn't die anymore which is good. One a side note, I went out of town today, and we did the whole whiplash chugging again. If I hold steady, it chugs then I'll blip the throttle and steady again, we're fine.
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Vile, is that Key On Engine Off when I test the TPS? Got a fresh code for ya... 44. Why is my O2 reading lean? I was out in the garage a minute ago and I ran the truck; it was fine till it warmed up. Then it stumbled maybe 4 or 5 times, then it idled fine. Just out of the blue- stumble, Vroom, stumble, Vroom, ect, ect. Then all is good.
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Did you check your fuel pressure?
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Not yet. I'll have to buy that adapter tomorrow.
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Will backprobe the TPS tomorrow, too. Before I load my shotgun to blast some more parts at this- When I replaced my ign module, I broke the little tab on one of the connectors. It still went in, but I have no locking action. Could this have shaken slightly loose and caused all of this?
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good possibility duct tape is cheap
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Man, that doesn't sound like a TPS to me... I know this is really basic but when is the last time the fuel filter has been replaced?
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It's real old. I bought a new one but haven't got it on yet, the flare fittings rounded off when I tried, so I'm at a loss at what to do. I'm getting new tires for it with my tax refund, so I'll probably have them change it out. My tps reads .521 V with KOEO. How do I go about adjusting that?
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Got it set at .555 volts. I'll update when I get my new tires and fuel filter on. Running good enough for now. Thanks for the help guys.
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UPDATE
Got some new shoes, although my Keystone Classics won't fit >:( Fuel filter is in, and I rebuilt my TBI. This ordeal is very faint, and happens when the trucks warm now. BTW- have good fuel psi. An added note- the exhaust manifold donut is rotted away at the downpipe at the pass side and the truck overheats super bad when I'm in the gas. Catalytic converter?
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very likely a clogged cat. Does it seem to lack HP when pushing the gas uphill or anything?
if so, take a hammer and pound the cat a few times to loosen up the rust/carbon.
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Yeah, it seems to be a little sluggish for a 350. It's the last of my concerns now as some one vandalized it last night. >:(
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sorry bout the vandals but yup the cat seams to be the problem with the sulpher smell and all, i would take the flange apart were you said the donut is bad since you have to replace that anyway and run it with open manifolds lol and see how that does
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I'll update asap. She's a driver again, but it's a cold ride. Good thing I'm used to riding my motorcycle in this stuff.
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have you ever done a code readout on it?
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I've never hooked up my scantool to it but I've got a jumper for the aldl. I'm not getting any codes anymore.
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so when your checking codes you get code 12? if anything you should always get code 12 cause it means everything is working... if your not even getting a code that says its passes you might wanna check into a new comp
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Sorry, I just got up for work. Nothing other than 12 is what I meant.
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ok then im stumped not really just means all the sensors and comp are working right... that takes care of that headache....ok ill throw out a few suggestions here.... cat, fuel filter, clogged injector... bad fuel pressure? i dunno much bout computer efi trucks lol... hey wait a minute.... has the cat ever been replaced with a universal cat?? and is there any o2 sensors before the cat or after?
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I'm thinking cat due to the sulpher smell
sorry bout the vandals but yup the cat seams to be the problem with the sulpher smell and all, i would take the flange apart were you said the donut is bad since you have to replace that anyway and run it with open manifolds lol and see how that does
have you tried anything with the cat. would it even give a code since the o2 sensor is before the cat?
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Haven't done anything with the cat yet. I've been sick. I'm not sure, but I think it's directly related to my window situation. New fuel filter, injectors spray good, cat is original.
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ok well im stumped then if the cat and o2 sensors havent ever been changed or moved then i dont really know... i know if you change the cat with a universal and end up moving the o2 sensors to far ahead of the cat or 2 far behind it i know you will run into problems
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What is the truck doing now? you said fuel pressure is good. Did you check it with a gauge?
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Buttita bros checked it with the filter off. they said it was 12psi. It really doesn't do much of anything anymore except chug every once in a great while. It's terrible in cruise, but with a steady pedal, it'll kinda lurch at say 55 then all I do is mash the gas let all the way off as quick as possible and resume 55 mph.
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Is this a 700R4? Is it going into lock up too soon?
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Yeah. I never thought of the trans, but would that cycle on and off repeatedly giving you whiplash?
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If it's really harsh (bucking) and you're sure it's not an ignition system realted misfire I'd be leaning towards your fuel pump. If it's just boggy until you punch it, tighten up the tv cable.
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The plug wires are pretty crusty. I was in the middle of a by the week tune-up when these problems happened. IE week one, plugs, week 2 cap and rotor. I was broke btw. LOL.
Do you think the pump was operable when they checked, and it just acts up when i drive it? You know, one of those little things that when you call on the expert, it wants to work good?