Stalls in gear when warmed up, (changed subject from size of egr solenoid bolt)

 Done cussing out the engineers and cooling off period in progress. I can see the tiny bolt head, but not when I put a wrench anywhere near it. Can't seem to get tool in tiny space and fingers into same space....again....big fat wire loom doesn't move enough to get clearance because tranny fill tube is in its way. Not taking tranny fill tube out to lose lots of tranny fluid for the sake of one bolt. Can't even verify that 7mm is the right size wrench.

Looked at mounting new solenoid in a different location but worried the vacuum lines won't bend or reach to get there. Looked at taking solenoid out of its bracket and putting new one in old bracket but doesn't look promising. Bracket looks to be mounted to intake bolt so I don't want to remove it that way.

Surely someone else has run into this and come up with a solution but I didn't see it listed by using the search function on forum. This is a 93 Caprice with 350 and Cal emissions.

Any helpful suggestions are welcome and wanted, please.

Put new solenoid loose next to old one for now. Was gentle with trying to remove vac lines from old one but gentle didn't work. Just a tiny bit more force and broke the plastic line to egr valve then got connector off . Didn't know it was a double connector for the two lines, now I do. Found some plastic vac line while looking for hose I didn't have and put new line into both connectors for egr valve. Put car back together but will wait for tomorrow to test. Would rather have the new solenoid mounted properly but looks like it is held pretty well in place by other things GM engineers decided to cram into the same small space. Don't see that the bracket is any kind of ground for the solenoid so that shouldn't be an issue, I hope.

Still looking for suggestions to get little bolt off old solenoid, other than that I really need to stick with cars that are 1970 or older!

I'll check it tomorrow for you. I've got a couple LT1s on stands that are easy to get to and to take pics of. I don't remember it being tough to do on the car, though. You did take home plate, off, right?

Not an LT1, did take the air cleaner housing off or I wouldn't have been able to see it at all. Knowing the actual size wrench to use would make it easier to do the 'by feel' thing rather than wondering if I had actually gotten the wrench on the bolt head and just couldn't tell because it was too large. I am looking from the top at a slight angle over the fender and can see just enough of the side of the bolt head to guess at 7mm. Could even be SAE sized instead, like the air cleaner top nuts were a very tight 1/2", would have gone bigger if I hadn't had room to wiggle the socket a little bit on those. Might be able to get a socket on the 7mm with a couple of swivels to get around the wire loom and trans tube, wondering if the wire loom was moved by someone else and not put back in the right location.

The bolt has a 7mm head. It is possible to swap them out. It is bolted to the rear lift ring for the engine, that is held in place by one of the intake manifold bolts. The LO3/5 is relatively easy to work on, but that is a tight spot. The solenoid is not grounded through the bracket. The hot side is "hot in run" and the computer grounds the unit when EGR is called for.

The wire loom is close, but could be pulled away if you unbolt the clamp on the back of the engine. The air cleaner nuts are 13mm. You can bend/twist the bracket a little to gain clearance, if necessary.

Thank you Fred and 13mm is why the 1/2 was snug, 13mm on a 1/2 is always just a little loose feeling to me but works as well. Left new egr solenoid unattached and will take care of that at a later date since it seems pretty secure where it is at. Already filled tank the day before with gas from a station that has never given me a problem, 1/3 tank showing and 12.5 gallons filled it up, now has mostly NON shell gasoline.

Results of test drive yesterday were:
Drove to a parking lot and got there just at time engine warmed up for testing. First 2 or 3 takeoffs at light throttle were kind of iffy but no bucking like before. Then the car was doing fine and I started driving to a store. Drove fine but right when I was almost home and stopped downhill under a train overpass waiting for a light I noticed the warning lights come on. Engine had stalled but with no sputter or jerk. Started right back up and drove last 1/4 mile home feathering the gas pedal at red lights just in case of another stall out.  Gripe and moan and decide it might just have been a one time occurrence so let car sit for a couple hours. Drove in dark with lights on and all was fine, got to store just at warmup and engine stalled just after parking. Tried driving home but car threatened to stall so much that I feathered the gas pedal again and kept rpm up at all stops.

Decided not to post here until checking today for any vac line breaks or pulled loose from connectors. No such thing, everything looked just like I left it. Checked for codes, still just the one I put in by pulling the map sensor connector off while running. Tried starting car, no start until I gave it gas while cranking and then the service engine light kept up a steady blinking  that never quit!!! Looked down and saw paperclip still jumping the diagnostic connector, another doh! moment, took it out and shut off engine, restarted just fine. Drove fine to freeway on ramp and had to wait at light until engine was warmed up. Drove up ramp and onto freeway with no issues and finally got an open freeway to run the car (91 freeway is usually a parking lot due to construction) at good steady speed so the computer could check egr system and maybe give me a code.

Drove great for a few miles and took an exit uphill with no stalling at stoplight. Got back on freeway just fine and drove to exit before mine and drove through town a while with no problem but the idle felt a little low, took a few stoplights and no stalling. Pulled into parking lot and shut engine off but idle was funny while I was turning it off. Restarted and drove home through town with no problem, drove up and down horseshoe shaped hill road with pretty steep incline and decline then went home with no problem. Temp did go up to first mark on the hill but right back to just before first mark where it always stays while driving. Let idle in gear in driveway and idle started messing up (like a carb loading up) but corrected itself in a few seconds. Shut off engine and checked for any new codes, the map sensor code was gone and only getting the 12 now.

Looks like I have a drivable wagon now, just need to get the coolant leak looked into but it is down to a few drops after driving instead of a puddle under it. I'm also waiting (since Oct 3) for the state to send me the license plates! Checked online and the DMV lists a plate number for the car that doesn't show up as having a smog test linked to it so the number is going to be my new plate unless it got stolen in the mail.

Sure wish I knew how long this car had sat before I bought it, I know the dealer had it sitting at least 6 months trying to get $3000 for it before putting it on ebay at 999.00 no reserve. "Same dealer now has about 3 RoadMasters and a couple of Electra/LeSabre box wagons and a pretty tired Caprice box wagon that they want bigger money for. Not knowing a car's history is always the problem when not buying from the actual owner/driver of the car.

For future reference: On a TBI B-body, if you're unsure of the fastener size, it's almost always (read - 99.99999% of the time) 7, 10, 13, or 15mm.

Always.

Good to know most fasteners are metric, my last car was a stupid mix of both metric and SAE fasteners. When I thought for sure they were SAE it turned out to be metric and vice-versa. That was a 91 Grand Marquis with 5.0L. I don't remember on the car before that, built in Italy Chryslers TC by Maserati so it was probably all metric. Of course all my older stuff was SAE, 60's and 70's Chrysler Dodge or Plymouth.

Some SAE sizes are almost identical to Metric. Example 19mm and 3/4 inch.

Added note on bolt sizes. 94-96 cars used some 5.5mm bolts for numerous parts instead of the 7mm. Two examples are the heater fan, and the fan control module/resistor pack.

Well, drove it today and the problem is back but doesn't buck and doesn't need much gas to keep it running. It's dark and wet so the egr hose gets pulled off tomorrow to see if that still clears the problem or if something else has developed.
I have an 02 sensor in the AC Delco box just waiting, TPS in AC Delco box just waiting and an IAC valve in AC Delco box just waiting but haven't wanted to put them on since the problem didn't really seem like they were the issue. Still have to clean the ground at the thermostat to rule that out, is that open to a water passage on the 5.7TBI???
On the IAC, it comes as 3 pieces in the box, the wire connection part, the spring, the threaded part with the actual cone shaped part that closes/opens the passage. How is that supposed to go together? FSM says to pull old part, measure old rod extended length and push new rod into new valve to match but doesn't say the threaded rod has to be inserted into body of valve. And of course these parts didn't come with new gaskets, WTF is up with that when the gasket is supposed to be replaced with the part.

Once I get my license plate with tag I won't have to smog test the car for 2 years so I may just leave the EGR hose off if that clears up the problem. Will that cause any harm to other things? Not used to cars with the EGR setup as complex as this one (valve, solenoid, AIR system in the mix), just EGR valve and a vac hose at the most. Also never had to deal with on O2 sensor or computer problems before (removed lean burn computer from 79 T-top Cordoba and went with simple Chrysler electronic ignition setup).

It probably is not the IAC, so I would not worry about it. If you decide to change the O2 sensor, do it when the engine is cold or warm. It gets pretty hot around the sensor. It can be removed with a open end or crescent wrench. My first inclination is that it is not the O2 sensor.

The bolt for the ground does not go through to the water jacket, but it is close enough to water that I would clean it. Make sure the wires to the lugs have continuity. Allow the engine to cool before removing the stud, so coolant does not flood the area. It is probably 13 or 15mm.

The EGR only works at steady speeds, like those you would drive on a highway. Cap/plug any lines that you pull. The AIR system only works at higher speeds, much like the EGR. Disabling it will probably not affect a smog test. The lack of an EGR will not affect the car in any adverse way. You may get an intermittent CEL for when it is supposed to be working.

I recently read about an issue with aftermarket temp sensors. The OEM AC Delco units may be the only ones that work correctly. The incorrect temp sensor may cause numerous issues like the one you are having.

Advanced Auto has a $10 discount on a $25 purchase code MCM41 for online purchases that you can pick up at the local store. The total for a temp sensor was about $18 with local sales tax. It is good until Dec. 5.

Hey have you checked to see if the little heat exchange hose that goes from the driver side exhaust manifold up to the bottom of the intake is still attached? I know when it's not there it can cause the car to chug at idle. Also I would vac test the egr valve just to rule out that it's not broken.

Fred Kiehl wrote:

The EGR only works at steady speeds, like those you would drive on a highway. Cap/plug any lines that you pull. The AIR system only works at higher speeds, much like the EGR.

Enough of this Fred. Stick to what you know as fact and stop trying to address every question when you aren’t sure of the answer. You are only confusing the issue and making it hard for the person asking to know what is best to do next.

AIR system should only be needed on startup to accelerate converter lightoff. At cruising speeds there is enough flow to sustain the reaction.

Fred Kiehl wrote:

Disabling it will probably not affect a smog test. The lack of an EGR will not affect the car in any adverse way.

Uh, no. Lack of EGR will likely cause a failed NOx reading on the emissions test. That is, if it hasn’t already failed for a check engine light or the visual inspection from any missing or capped lines.

Coming from a state where they don’t even have mandatory safety inspections, you should be more careful when make recommendations to persons in states that have biannual emissions tests.

just me wrote:

On the IAC, it comes as 3 pieces in the box, the wire connection part, the spring, the threaded part with the actual cone shaped part that closes/opens the passage. How is that supposed to go together? FSM says to pull old part, measure old rod extended length and push new rod into new valve to match but doesn't say the threaded rod has to be inserted into body of valve. And of course these parts didn't come with new gaskets, WTF is up with that when the gasket is supposed to be replaced with the part.

Insert the spring over the plunger, then insert the threaded end of the plunger into the housing and wiggle it gently with your fingers until it is fully bottomed in the housing, it will take a while, as it is a slow process.

The IAC uses an O-ring to seal it which is usually reusable. Remove it from the existing IAC and transfer it to the new one. Clean the IAC port to ensure carbon buildup isn’t part of the issue. When restarting the car for the first time after replacing the IAC, turning the key to on and waiting for a minute before proceeding to start should be plenty of time for the ECM to drive the IAC to closed and then back to the default location. If everything is working properly, the car can be started normally from then on.

Going forward, you should also invest in a FSM as it gets cost prohibitive to pay for a professional to diagnose and repair every issue that develops with these cars as the get older.

- J

The issue from the description is a poor idle that allows the engine to stall. No codes are shown. I would not worry about the AIR, the IAC or EGR. They do not fail often, do not throw codes, and the symptoms do not indicate any of them. The IAC is controlling the idle, although it is allowing it to decay. Other than that the engine seems to run reasonably.

From my experience the symptom he is referring to can be caused by a poor ground at the thermostat housing, and/or according to what I have recently read, the temp sensor. The recommended temp sensor is the original AC Delco, because of tolerances. The O2 sensor and computer ground are at the stud by the thermostat. It is not throwing a rich or lean code, so I believe the O2 sensor is good. It is not throwing an EGR code while running, so I would eliminate it as well. The IAC appears to follow the commands of the computer, and the only way to truly check the IAC is to measure the counts. It would be one of the last things I would replace. Cleaning the TBI port and the pintle can improve the function though.

If it is throwing a 13 code, it may indicate the O2 sensor ground at the thermostat. The things that do not throw a code are the IAC, AIR, and EGR (unless the car is travelling over 50 MPH, according to the FSM), a bad ground at the thermostat, and lack of fuel pressure. Pretty much everything else will have a code associated with it. Another issue the FSM brought up was excess back pressure causing an activation of the EGR valve, but unless it is borderline high, you probably can't make speed on the freeway. If it has good acceleration, it is probably not high exhaust back pressure. Often the issue with the LO3/5 is relatively simple. It is not as integrated with the computer as the LT1/L99.

Car still runs/drives well with the vac line pulled off the egr. I think it will stay that way until I get the bug to drive myself crazy again. If the car starts to give me grief with unplugged egr then I might have enough clues to actually figure it out. 2 years from now it MUST be fixed to get it smog checked but I seldom keep a car over 2 years. I used to live in another state in a city with no smog checks at all so most people just blocked off the egr when it gave problems, I actually fixed mine but got rid of the computer that controlled timing.

I tried changing the temp sensor to an AC Delco, and my start symptoms actually got worse. I may put the old one back in.

OK, got the bug again to do something about this problem. I have actually run 50 gallons of gas through the car now and started noticing the rotten egg odor showing up, mpg have run from 11 to 14 so I decided to change out the 02 sensor today. Half way expected to see it coated in white from contamination out of the first gas I put in when I picked up the car but it wasn't. Another case of griping out the GM engineers who decided the sensor had to be directly under the sparkplug wire end but mostly the sensor connector plug in a place where only one hand would fit. Got it out with no problem (sprayed twice a couple of days ahead to loosen threads) put new one in and somehow got the connector back together with just fingers from one hand and no eyes on it. Then I hooked the vac hose to the egr valve again.

While getting the new sensor out of box of parts I noticed the new iac and tps are 'Standard' rather than a/c delco as written in post above. I only change one part at a time so those went back in storage.

Car started up just fine, backed out of driveway with a couple of light bucks that I decided to ignore, and went through town a little while with no bucking at stop signs or lights. Drove to the freeway on a saturday hoping for no traffic. I got my wish and drove a 35 mile circuit from the house and back to the house on 3 freeways to check the car out. It drove fine, had a little less power on the onramp than with the egr unhooked, got off the freeway and didn't have any stalling issues or bucking for a quarter mile then turned into a parking lot and felt a little bucking with very slight pressure on gas pedal that went away when I gave it more gas. I will leave it the way it is and see what it does on the next few drives.
The check engine light stayed off the whole time but I didn't check for codes today.

More test driving today and I am able to see a pattern forming. I get a couple of light bucks (chugging) when first starting out cold or after restart warmed up in a parking lot. Not even close to the severity it had been. First time accelerating on the street after the light bucks and they go away, sometimes come back after pulling off road and just using light pressure on gas pedal again. My driving habit is to give just the slightest pressure on the gas pedal in the parking lot, most people would do much more. This tells me I have a throttle issue, might be mechanical or might be electrical, or just a dirty throttle body. More driving might just narrow it down by changing my normal throttle pressure. I might just clean the throttle body for the heck of it - won't hurt. The initial problem with the car must have been a multiple problem and I really hate diagnosing those, they can be a big B.

Check the vacuum ports when you are cleaning the TBI, especially the PCV, and the MAP ports.

Did my test drives today only after doing the IAC reset procedure each time before starting, made no difference. Jack Rabbit starts gave NO hint of a problem but trying to drive through a hospital parking lot looking for a space brought out the light bucking again, a blip of the pedal took care of it. Just idling without touching the pedal didn't have any bucking but if I just barely touched the gas pedal I got it. In a carb car that would be when going from idle circuit to running circuit, no ifs-ands-or buts. No blipping the pedal yesterday in the parking lot gave me a stall out one time while making a turn from aisle to aisle. I went to the hospital parking lot everyday to visit my 102 year old grandmother who got transferred out tonight so I won't have that as a testing ground anymore.

Changed the throttle position sensor today and did 1 test drive. Still have a slight dead spot in the gas pedal but NO bucking or jerking, and I had to TRY to find that dead spot this time, smooth from a stop with ordinary pedal pressure to get it moving. The seal on the TPS didn't look in very good condition but was still in one piece and I didn't have another so reused it. I guess it only seals against any fuel that gets past a worn throttle plate rod? I had sprayed the butterflys a couple days ago but that made no difference at all. Everything I replace seems to give a slight improvement so I'll just keep plugging along until I get it sorted out. Computer codes would make the diagnosing so much easier but the car refuses to give me any unless I purposely pull a sensor wire to get one.

The car has gone from wicked bucking to a slight dead spot in the throttle and I don't feel like I have to worry about it dying in an intersection after sitting at a red light. Not quite sure I would trust it with the a/c on so I won't be repairing that yet.

Oh well, dead spot still showing up in parking lots. I'm beginning to wonder if the actual throttle body has a worn spot but will try some fuel system cleaner first. Just have to find a good one that can sit in the tank/lines for a month without dissolving something essential, it will take that long to run a tank out of the car at the rate I drive it. Regular driving on the street is NOT a problem like it was to start with. I won't change the IAC or plugs until that is accomplished.

I usually suggest the hose in the tank that goes between the pump and outgoing tube. It twists when the pump is running, and can open and close a crack depending on the amount of torque put on the hose. It may open when it is not under much load, and close under heavier load. It will not throw a code, but will cause variations in fuel pressure that can cause surging. If you want to measure fuel pressure, get a set of engine bay fuel lines from a 91-92 Cadillac Fleetwood with an LO3/5, or a 93 Fleetwood that has an LO5.

Don't think it's the hose, otherwise the symptoms wouldn't disappear when I take off the vac hose to the EGR valve. Right now the symptom is down to that dead spot at extremely light throttle at parking lot speeds but not at any other time. I keep reading the factory service manual on ALL the sensors/computer/injectors and how they interact and I'll eventually come up with a combo of 2 or more things that do the deed. So far replacing the O2 and TPS have made a huge improvement in drivability to where I am leaving the vac line to EGR hooked up and only think about it when in parking lots. I just don't drive the car enough right now to do a lot of testing so I'm doing a lot of reading and thinking.

Did you remove it from the EGR itself, or from the ERG solenoid?

Pulled off of the EGR itself and all symptoms go away. Already replaced the solenoid in previous post. Drove it today and just let it idle through a parking lot with no problems. Even did the 1-2 shift with no problem at about 10 to 12 mph, hard to read the sweep speedometer that low and took awhile to get that fast on downhill sloped lot with just idling. I think I'm safe assuming the transmission or its adjustments are not a part of the problem. Time to step away from this problem so I can come back to it later with a fresh mindset. Maybe it will even take a hint from the radio problem and just fix itself with more use. Cars that aren't run for long periods can get tempermental and I know this one sat for over 6 months on a dealers lot after they got it at a copart auction and who knows how long at previous owner's house. Noticed that dealer has a OCC now that had been on copart recently for next to nothing and they want over 6 grand so that one will be sitting quite awhile as well.