Funkwagon455

I'm hoping to get some experienced advise with regards to my '92 Custom Cruiser with a tbi 350 bowtie powerplant. The car drives great, starts up perfect, idles good, mileage is still on par. Once the car is driven to temperature and stopped, if the car sits for more than 10-15 minutes it will surge at idle once started again. The idle will fluctuate between 1400 to 500 rpm for about 45 seconds and then eventually will find itself and settle down. If you attempt to put it in gear before it is cleared, the engine will fall on it's face, and surge hard with no power. It has done this in the past very randomly, but is now a regular basis and I would like to find the remedy. I have read my factory service manual, and troubleshooting charts and have changed parts but am starting to feel like a shotgun mechanic. Thus far I've changed the oxygen sensor, plugs/wires, tps, and fuel filter. The ignition control module, cap,rotor and coil have been replaced more recently repairing an unrelated problem. All parts have been Delco brand. There are no codes displayed on my prom. If you have experienced problems similar to these, and have some good input please enlighten me.

Rickman48

Cold idle solenoid should reset for every start, and idle-up for 30 seconds.
Bet that's it!!

oldsonharmont

You might need to clean the throttle body. Ford used to vent the crankcase fumes back into the throttle body, which would gunk up the metering that controls the idle. The result would be a surging or pulsing idle. Look for the correct cleaner for this job, don't use carb cleaner.

Allan R

Arrrghhhhh! I can feel your pain.

That surging sounds like 2 things you haven't touched yet (sorry to say).
Most common reasons for surging like you describe isn't the TPS, it's the IAC - Idle Air Control. It creates vacuum to compensate for things like AC on, dry steering or accessories that would suck engine rpms to operate. When it's not working right (like sticking) it can easily create this problem.

Chances are really good (I found this from experience on both our cars) that the throttle body is also really carboned up. You can try 'seafoam' to clean it, but what I prefer is to remove the TB, clean it really good with TB cleaner. This will also give you the best option for:
1. Cleaning the throttle plate and TB where the plate seats itself.
2. Cleaning the IAC pintle seat. (Remove the IAC first and clean it too)

If you decide the take of the TB? (recommended for thorough cleaning) Drain some coolant from the rad. There's shared passage for coolant at the bottom of the TB. Otherwise you'll get coolant spill. The rubber gasket can be re-used. Taking the TB off is actually quite easy and logical. The throttle cable comes off it you twist the throttle spring full forward and hold it. The cable slides out sideways - there' a metal tab that holds it in place like on a bicycle brake setup cable. Once you have the TB off, you can remove the IAC and start cleaning. Don't need to remove the TPS.

Don't move the IAC pintle when you're cleaning it. Just spray with TB cleaner and use an old toothbrush to get the crud loose. Spray with more TB cleaner to get the rest of the crud clean. If you do end up moving the pintle, that's ok. There's a 'reset' procedure. [after installed and ready to start car? key to run -not start- for 20 seconds, then 'off' for 10 seconds, then start the car] Problem should be gone. Some IAC circuits need to work for about 20 minutes before they develop the right sensitivity reporting back to the ECM.

While the connectors to the IAC are off, spray them with ELECTRICAL CONTACT cleaner. Do NOT use anything else and do NOT put any dialectic grease on them. Your 92 should have all weather pack connectors - check to see if any are worn. Not likely though.

You can also test the resistance on the 4 pins of the IAC. If you get readings less than 20 ohms, it's defective. IAC's cost new (Delphi) around 70 bucks.

One last thing it could be if this doesn't solve the problem? Cooant temp sender and wiring pigtail. If the idle is really low? Wiggle the wiring pigtail close to the connector to see if there's a break in continuity. If the idle comes back up right away? That's an easy fix. Most auto stores do sell replacement connectors.

Hope one of these things solves your issue. BTW I had similar idle prob with my 1995 98 with the 3800 also. Same basic car - just not in wagon form.

Bluevista

A rear wheel drive 350 V8 powered car is basically the same as a front wheel drive 3800 V6 powered car? There's no shared coolant passage under the TBI on a Chebby V8 BTW.
I agree on checking the idle air control, also the fuel pump for low output pressure and the EGR valve for correct operation, assuming there are no vac leaks anywhere.

You may get some answers on the Impala SS forum, they're a lot more familiar with these engines, lots of members with regular cars and wagons. The chebby truck forums are also a good place for info since most of the LO5 engines were put in trucks. The Longroof forum is a joke, they're resident egomaniac/ bully will tell you in some not so nice words to sell the car and get one with an LT1 so you can have a major new engine and computer problem every day like they do.

Funkwagon455

Thanks for all of the advise, I'd not mentioned that 15 months ago I'd changed the intake manifold gasket due to a coolant leak, at that time I had changed the EGR, temperature probe and the plastic vacuum manifold. I'd also thoroughly cleaned the throttle body and all connections as well as grounds. I had changed the EGR at that time due to the very intermittant problem as well as the "might as well" mindset due to age and mileage. The air idle control valve was my next attempt, but as I had mentioned I'm getting weary of changing parts and spending money on items to no avail. I'll swing by the parts house this week sometime to get it and get it installed. If it remedies the problem I'll do a followup post. Again, Thanks for the help.

J-(Chicago)

Check that it is not "Icing up" as well. I remember that being a problem, but that was probably the units before 1992.

Basically the tbi and top of the intake would cake up with ice crystals from the alcohol and solvents being misted into the intake.

Didn't matter if it was 100 degrees outside or not. On long drives, it would eventually start freezing.

Funkwagon455

Well, I changed the air idle control valve last night and it is still exhibiting the same symptoms as before...... Icing is not an issue, especially here in north Texas in April, the radiant engine heat alone would prohibit any formation. According to what I've read thus far the MAF is the next likely fix......loading some more shells.....

Allan R

Drat! Sorry Allan H, I got carried away with it being a 92 CC and didn't read bowtie special. Duhhhh.

Ok the IAC didn't solve the problem. Is this problem only when it starts from delayed warm start? I'd seriously check out the coolant sensor wires at that pigtail. That's what my low idle ended up being on my 95 3800. I know your's is a 350 now, but continuity in the wires could be a problem.

I seriously doubt you have a vacuum leak, or the car would run with a higher idle all the time. You said your fuel mpg is good, so it's not likely the MAP or the o2 sensors. If you suspect a bad MAF, try tapping it to see whether the engine stumbles. If it does = bad sensor. Also if you unplug the MAF and start the engine the ECM will compensate. If the engine runs better without the MAF hooked up, the sensor is likely kaput. Try the tests first before running to the parts store.

Allan R

Any updates on this?

Funkwagon455

Stand by Allen, I have been busy all weekend with yard/trimming trees burning brush, working on the coupe, and my wife's Grand Wagoneer. All this coupled with two kids in baseball, and dealing with taxes. I hope to have a chance to get by the parts house today to get a temperature sensor for the ECM, I did not realize it had a second coolant sensor specifically for the ECM until I did some more investigation in the Service Manual.

Allan R

No worries, just checking.

Funkwagon455

Well, I installed the ECM temp sensor tonight, and discovered that the pigtail is different. I hope to acquire the correct pigtail for the updated sensor tomorrow.. Thanks for your patience

Funkwagon455

Well, to provide some closure to this issue, I can solidly conclude that the IAC solenoid was in fact that component that fixed this problem. I can only imagine that it took several heat cycles to seat the plunger and operate correctly. She is behaving much better now and makes the drivability much better. Thanks so much to all that provided their expertise on this thread.

Allan R

You're welcome. One thing I was reading a while ago and it slipped my mind. Can't remember what brand it was that the IAC was changed on, but they said - take it for at least a 20 to 30 minute drive varying from 30 - 60 mph to help the IAC re acquaint itself with the ECM.

Glad you got the problem solved. Enjoy your CC

oldjimh

Hi guys. New here, have two 92 Custom Cruisers.

One of them just developed intermittent surge at idle, and at low throttle cruise.

I think it's vacuum related not fuel because applying throttle stops the surge and it has plenty of fuel for brisk acceleration.

Suggestions? Where's that Air Idle Solenoid?

thanks, old jim

Allan R

It's on the passenger side of the throttle body just ahead of where the EGR is on a 305. Undo the Electrical connectors, and then it unscrews with a wrench. If yours has never been changed it's likely time for either a clean or replace.

oldjimh

Thanks ! Was poking around there today and it's mighty dusty (Arizona car).
Will get after it in the morning.

Allan R

Consider taking it to a car wash and pressure washing the engine. Pre-soak it with degreaser first and let it sit for 5 minutes, then rinse. You can blow it dry at home with your air compressor. Working on clean engines is much nicer than working on crap.

oldjimh

thanks guys
indeed it was packed with black carbon. Cleaned it, sprayed cleaner into hole where it goes until clean liquid ran out onto throttle plate. Q tip comes out clean now.
Will test drive in a little while - but what i got out of there sure justifies the symptom.
Can't wait to get home where my GM manuals are.

thanks again,

old jim himself

oldjimh

Well after cleaning the IAC i still had the symptom. So went to Oreilly and examined a new one. Its pintle moved , but not easily. I'd been afraid to push that hard on my old one, so took the new one home. Sure enough mine was frozen solid.

New one is in. I felt one surge in a thirty minute test dive, right after a start. Maybe computer is re-learning or something.

I think probably it's fixed. Thanks AlanR , i will clean the whole TB when get home .

I replaced throttle position sensor too just because it's 22 years old and has moving parts, and have had trouble with them on other vehicles..

Again, glad to have found you folks. Thanks for the help !

Anybody know if there's a fuel pressure port for a test gage ? I didnt notice one..

old jim

Funkwagon455

I had chased this problem for some time, and had even thought that I had fixed it as stated in my last post on this thread. But in fact the problem had persisted and got increasingly worse every day to the point where I knew I would be stranded if not fixed. You may like to check the flash codes if you have gotten a check engine light, that would help to steer you in the right direction. Ultimately my problem was the the electric fuel pump mounted in the tank. I had replaced it with factory parts several years prior, and was not suspect that it would already be giving up. I ordered another Delco pump from my local parts store with a new pickup sock, and knew when I drove out of the driveway that it was truly fixed. The improvement was drastic. The only way I had determined to pickup the fuel pressure was to remove the fuel filter, cut the quick disconnect tubes from the filter and tap into the fuel system on the passenger side frame rail with soft lines leading to a gauge hanging in the aft passengers window. It is rather unorthodox, and perhaps it seems a bit redneck but it was effective and in the end that is all that matters. The hard lines leading to the tbi proved prohibitive for a tap source for fuel pressure. I hope this helps and that you don't have any further issues. Good luck!

oldjimh

Thanks, Funkwagon. No check engine and it just flashes 12, which i think means it sees the jumper .

Will know more in a few days. Might put in a schrader fitting when have TB out.

Fuel pump, eh ? Could be worse.

thanks .

Funkwagon455

From a maintenance perspective I can't see that installing a schrader would be a bad idea. So long as the tank is less than 1/4 full, it should be an easy job and rather inexpensive as well. Your code flash is normal. Keep us updated, it is always nice to have first hand references.

oldjimh

It surged again this morning.
Gas in it was 3 months old. I filled it with 91 and added a bottle of injector cleaner, drove from Denver to Garden City Kansas which is ~300 miles in direction of home. No further hiccups. Yet.

The IAC solenoid i put in was what Oreilly's had in stock, $45. Plastic. I think i'll mail order a better one.

Never did get a code other than 12, nor Check Engine light.

Will keep you posted.

old jim

Funkwagon455

Did it surge after you had driven it, or on cold start up? If the symptoms are the same with the chain store replacement part as the original part I would suspect that it was not the problem in the first place.

oldjimh

Thanks, and yep - agreed.

White Cruiser made it home from Denver to Arkansas, a little over 900 miles the route we came .. DodgeCity, Wichita.....

Surging is only at or near idle, in gear, warm, lasts a minute or so . Only a nuisance in parking lots. Shifting into neutral it idles beautifully. So quiet i think it's quit and have to look at tach. Idles ~ 500 to 550 in gear,,,

if surging it swings from ~900 to ~100 on tach. Shifting into neutral it jumps to 1100 then settles back to 550. Place back into gear and it's fine.

Got only about 18mpg on the trip - i'm wondering O2 sensor. I think i have a spare from the Blue cruiser, will try to find it.

The surging sounds to me like a closed loop control trouble - computer is chasing something.

I've never had EGR troubles - anybody know its symptom? Seems to me EGR should stay closed at low throttle. I'll look around map sensor hose very carefully - Blue cruiser acted similar but much worse when the chipmunks ate the little hose going to it.

I'm home now, will dig out the manuals and dust off toolbox.

old jim

oldjimh

PS I like your redneck fuel pressure gage. Did same thing on a buddy's dumptruck, a big 6 cyl Ford diesel.

I'm contemplating plumbing in an oil pressure sender into fuel line adjacent filter (so the exposed run of line is short) and wiring it to an electric meter on the dash. No fuel lines in passenger compartment that way.
Why the car companies didn't give you a dashboard fuel pressure readout is a pet peeve of mine - it'd save a lot of tow-ins.

Anybody done this that you know of ? I'd rather copy an existing good idea than have to figure it out.

old jim

Funkwagon455

Your symptoms are almost identical to the problem I had, how many miles on the clock? Only happened after it was at temperature, under a load, once cleared the problem would not return until the next startup after sitting 15-20 minutes. Fuel pump......

oldjimh

Thanks !

Reason i hadn't leapt on fuel pump is it has plenty of capacity to accelerate to highway speed and cruises for hours at 70mph.

But i was thinking today , pressure might be low and not delivering what the computer expects it to at idle, maybe there's some arbitrary pwm timing to the tbi that needs good fuel pressure? Will read up on that.


Now i'm feeling lucky to have got home with it. My last fuel pump failure was sudden, without warning and left me stranded.

Meantime If you remember roughly what your rouge*-neck pressure readings were with old and new pump ... ?
*(rouge-neck = unconventional, but too high-class to be termed redneck)


old jim

Funkwagon455

I had built up the connections for tapping a fuel gauge into the fuel filter but did not have a gauge at the time. I had already returned the fuel pressure kit, (which had a huge selection of fittings) and had already committed myself to the pump anyway. If the tank is near empty, it does not take all that long to change the pump. I had exhausted so much time on the problem that when it was finally fixed, I was not curious enough to buy a pressure gauge and open the system back up. Mine ran fine at 70 mph for a long time (weeks), but toward the end it was starting to get a little worse every day. Also realize that the pump is actually cooled by the fuel it is submerged in, if you have a tendency to run your tank low the pump is not being cooled as effectively. I have 234,000 on my cruiser now, this was the second pump I had changed.

oldjimh

Funkwagon Thanks !


You've helped a lot.

This one (White cruiser) turned over 111,000 miles on this trip. It was an elderly Arizona couple's car
so the pump has probably accumulated hours out of proportion to the miles. Blue one has 145K mostly cross country .

This one too is getting worse with time.

Will keep ya posted.

I'll get a junkyard oil pressure sender and electrical connector, and order up a new pump . Where'd you buy your pumps?

old jim

Funkwagon455

The first Delco pump and pickup sock were sourced from GMpartsdirect.com at around $100 seven years ago, the second Delco was sourced from my local O'Rielly auto parts with the sock for around $45. I guess the price has gone down on them. The first one only lasted for about four years, that was why I was so determined that it could not be the problem. Why would you source an oil pressure sender via salvage? They are available new,,...well at least they were when mine died some years back. I drive about 33 miles each way (highway@ 65-70mph) five days a week, so I keep the fluids moving pretty regular. Pound for pound it is the best car I have owned: inexpensive, comfortable, lots of utility payload, safe, looks nice, good fuel economy, reliable and acceptable power for a daily driver. I love the powerhouses as well as the prewar car but this car has served me very well for over ten years. I hope yours does the same for you, I feel that they are grossly underrated.

oldjimh

I bought blue one in 2000 with 56 kmiles. It has been a delight, except for unpredictable electric doorlocks. Biggest repair to date was rear air-inflatable shocks, it has the auto-leveler system.

24 mpg highway , ride like a pullman car, holds immense cargo,,, agreed it's excellent transport. Grandkids LOVE the rear facing third seat. Inexpensive to purchase and with a little elbow grease i'll get > 100K from it. Cost to own will be <3cents/mile. It's almost antique so may go up in value!

as to salvaging an oil pressure sender - i'll need the matching electrical plug to make a fuel pressure sender out of it.

old jim

Funkwagon455

With a new child, I purchased mine in 2001. Sold the '85 GMC Caballero (El Camino), and flew myself, my wife and 4 month old son to Virginia to drive home our '92 50,000 mile Cruiser. The fuel pressure gauge kits are available from most chain auto parts stores for a nominal fee, it is a good option for troubleshooting and zero dollar out of pocket. I will drive it until the wheels fall off, and then replace the spindles and axles and keep on truck'n. I had neglected to mention that my level ride (aka auto air shocks) had began to fail some years ago. I replaced my rear shocks with KYB gas-a-just shocks and added air lift bags to the springs for heavy loads. I left the compressor and bagged the fittings, removed the fuse and pickled the system (just in case). It's not the flashiest and does not have the pedigree of others in our driveway, but certainly has earned my respect.

Aron Nance

Amen, Brothers! Ours is now at 246,000, and still truckin' wonderfully. Miminal mechanical problems, and so far, always surmountable. Love the car, and fabulous for long trips across these wonderful United States!

Funkwagon455

Any progress on this Oldjimh?

oldjimh

Not much that's visible.

I found at scrap metal yard a very good throttle body assembly for 35 cents a pound - cost me $1.05 + 7 cents tax. It has a perfectly good IAC and TPS on it and, what i assume are the two injectors.
I'll use it as a study piece for where to place pressure taps for indication.

No hurry, not yet even finished unpacking from the trip. Rained every day this week.
I' going to take my time and enjoy this one. If i can figure out how to work that digital camera the kids gave me will post pictures.

Thanks for your help - it has been more than you know.

Will keep y'all posted.

thanks - old jim